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Title: The Standard Electrical Dictionary

Author: T. O'Conor Sloane

Release date: September 5, 2008 [eBook #26535]

Most recently updated: January 4, 2021

Language: English

Credits: Produced by Don Kostuch

*** START OF THE PROJECT GUTENBERG EBOOK THE STANDARD ELECTRICAL DICTIONARY ***

STANDARD ELECTRICAL DICTIONARY.

[Transcriber's Notes]

Obvious spelling errors have been corrected. I have not reconciled the

variety of spellings of names and other words. Obvious factual errors,

typographical errors, discoveries made after 1892, and contemporary

(2008) theories and use of words are noted in the text within square

brackets. I have not researched and checked every assertion by the

author.

This book was published 5 years before discovery of the electron. See

the labored and completely inaccurate explanations of aurora and

"energy, atomic". The author and his contemporaries were like fifteenth

century sailors. They had a good idea of their latitude and direction

(Ampere, Kirkoff, Maxwell, Gauss, Faraday, Edison, …), but only the

vaguest notion of their longitude (nuclear structure, electrons, ions).

Altitude (special relativity, quantum theory) was not even imagined.

Some relevant dates:

Franklin's Kite--1752

Faraday's Law of Induction--1831

Maxwell's Equations--1861

Edison's Phonograph--1877

Edison's light bulb--1879

Edison's first DC power station--1882

Michelson-Morley experiment disproving ether--1887

Hertz demonstrates radio waves--1888

Westinghouse first AC power station--1891

This book--1892

Discovery of the electron--1897

Marconi radio signals cross the English Channel--1897

First Vacuum Tube--1904

Special Relativity, photo-electric effect explained with photons--1905

General Relativity: space-time dilation and curvature--1915

Confirmation of general relativity's prediction of the deflection

of starlight by the Sun--1919

Discovery of the proton--1920

Quantum theory--1926

Discovery of neutron--1932

First transistor--1947

Soviet satellite Luna measures solar wind--1959

Edward M. Purcell explains magnetism with special relativity--1963

Purcell's explanation of magnetism as a result of Lorentz contraction of

space along the direction of a current is a welcome relief from the

convoluted descriptions in this book.

Mathematical notation is rendered using "programming" notation.

^       Power--Exponential; A^3 means "A cubed"

*       Multiply

/       Divide

+       Add

-       Subtract

( )     Precedence--Perform before enclosing expression

2E6   Scientific Notation (2,000,000)

A

---------------------

4.452 X 10^12 X t

is rendered as

A / ( 4.452E12 *  t  )

Where the rendering of a mathematical expression is in doubt, an image

of the original text is included.

Here are some definitions absent from the text.

Foucault currents.

Eddy currents.

inspissate

To thicken, as by evaporation.

riband

Ribbon.

sapotaceous

Order Sapotace[ae] of trees and shrubs, including the star apple, the

Lucuma, or natural marmalade tree, the gutta-percha tree (Isonandra),

and the India mahwa, as well as the sapodilla, or sapota, after which

the order is named.

Don Kostuch, MS, Electrical Engineering.

[End Transcriber's notes.]

WORKS OF

T. O'CONOR SLOANE, A.M., E.M., Ph.D.

ARITHMETIC OF ELECTRICITY

A MANUAL OF ELECTRICAL CALCULATIONS

BY ARITHMETICAL METHODS.

Third Edition. Illustrated. $1.00.

It is very useful to that class of readers to whom Algebra is a

comparatively unknown quantity, and will meet its wants

admirably.--Electrical World.

ELECTRICITY SIMPLIFIED.

A POPULAR TREATMENT OF THE SUBJECT.

Illustrated. $1. 00.

We especially recommend it to those who would like to acquire a popular

idea of the subject.--Electric Age.

ELECTRIC TOY MAKING.

FOR AMATEURS.

INCLUDING BATTERIES, MAGNETS, MOTORS, MISCELLANEOUS TOYS,

AND DYNAMO CONSTRUCTION.

Fully Illustrated. $1.00.

THE STANDARD ELECTRICAL DICTIONARY.

A POPULAR DICTIONARY OF WORDS AND TERMS

USED IN THE PRACTICE OF ELECTRICAL ENGINEERING.

BY

T. O'CONOR SLOANE, A.M., E.M., Ph.D.

NEW YORK

GEORGE D. HURST

PUBLISHER

Copyright 1892

by

NORMAN W. HENLEY & CO.

PREFACE

The purpose of this work is to present the public with a concise and

practical book of reference, which it is believed will be appreciated in

this age of electricity. The science has expanded so much that the

limits of what may be termed strictly a dictionary of the present day

would a few years ago have sufficed for an encyclopedia. It follows that

an encyclopedia of electricity would be a work of great size. Yet a

dictionary with adequate definitions, and kept within the closest limits

by the statement of synonyms, and by the consigning of all the

innumerable cross-references to a concise index will be far more than a

mere dictionary in the ordinary sense of the term.

Duplication of matter is to be avoided. This makes many definitions

appear short. Yet, by the assistance of the reader's own general

knowledge, and by referring to the very complete index, almost any

subject can be found treated in all its aspects. There are exceptions to

this statement. So much has been done in the way of mechanical detail,

so many inventions in telegraphy and other branches have sprung into

prominence only to disappear again, or to be modified out of

recognition, that to embody descriptions of many ingenious and

complicated apparatus has been absolutely impossible for want of space.

A word as to the use of the book and the system of its construction may

be given here. Each title or subject is defined once in the text. Where

a title is synonymous with one or more others the definition is only

given under one title, and the others appear at the foot of the article

as synonyms. It may be that the reader is seeking the definition of one

of these synonyms. If so a reference to the index shows him at once what

page contains the information sought for. The use of an index in a work,

necessarily of an encyclopedic form, will be appreciated by all users of

this book.

vi   PREFACE.

Where a title embraces several words, all orders of the words will be

cited in the index. To make the operation of finding references easy

this rule has been carried out very fully.

It is customary to regard electricity as a growing science. It is

unquestionably such, but the multiplication of terms and words is now

not nearly so rapid as it has been, and the time for the compiling of a

work of this character seems most propitious. It is hoped that the

public will indulgently appreciate the labor it has entailed on all

concerned in its production.

SYMBOLS AND ABBREVIATIONS.

adj.

Adjective.

v.

Verb.

q.v.

"Which see.'

/

A mark of division, as A/B, meaning "A divided by B."

./.

The same as above.

[Transcriber's note: / will be substituted for this divide symbol.]

=

A mark of equality, meaning "is equal to."

X

A mark of multiplication, meaning "multiplied by."

[Transcriber's note: * will be substituted for this divide symbol.]

Fractional exponents indicate the roots expressed by their denominators

and the powers expressed by their numerators. Thus, A^1/2 means the

"square root of A;" A^1/3 means the "cube root of A;" B^3/2 means the

"square root of the cube or third power of B."

The use of powers of ten, as 10^10, 10^11, as multipliers, will be found

explained at length in the definition "Ten, Powers of."

vii  STANDARD ELECTRICAL DICTIONARY

A.

Abbreviation for anode, employed in text relating to

electro-therapeutics. It is sometimes written An.

Abscissa.

In a system of plane co-ordinates (see Co-ordinates) the

distance of any point from the axis of ordinates measured parallel to

the axis of abscissas.

In the cut the abscissa of the point a is the line or distance a c.

Fig. 1. AXES OF CO-ORDINATES.

Absolute. adj.

In quantities it may be defined as referring to fixed units of quantity,

and it is opposed to "relative," which merely refers to the relation of

several things to each other. Thus the relative resistance of one wire

may be n times that of another; its absolute resistance might be 5 ohms,

when the absolute resistance of the second wire would be 5/n ohms. A

galvanometer gives absolute readings if it is graduated to read directly

amperes or volts; if not so graduated, it may by "calibration" q. v. be

made to do practically the same thing.

8   STANDARD ELECTRICAL DICTIONARY.

Absolute Measurement.

Measurement based upon the centimeter, gram, and second. (See

Centimeter-Gram-Second System.)

Absolute Temperature.

Temperature reckoned from absolute zero (see "Zero, Absolute"). It is

obtained by adding for the centigrade scale 273, and for the Fahrenheit

scale 459, to the degree readings of the regular scale.

Absorption, Electric.

A property of the static charge. When a Leyden jar is being charged it

dilates a little and the capacity increases, so that it can take a

little more charge for a given potential difference existing between its

two coatings. This phenomenon occurs with other static condensers,

varying in degree with the dielectric. With shellac, paraffin, sulphur

and resin, for instance, the absorption is very slight; with

gutta-percha, stearine, and glass, the absorption is relatively great.

The term is due to Faraday. Iceland spar seems almost or quite destitute

of electric absorption.

A. C. C.

Symbol of or abbreviation for "anodic closure contraction" q. v.

Acceleration.

The rate of change of velocity. If of increase of velocity it is

positive; if of decrease, it is negative. It can only be brought about

by the exercise of force and is used as the measure of or as determining

the unit of force. It is equal to velocity (L/T) imparted, divided by

time (T); its dimensions therefore are L/(T^2). The c. g. s. unit of

acceleration is one centimeter in one second.

[Transcriber's note: The unit of acceleration is "centimeters per second

per second."]

Accumulator.

(a) A term sometimes applied to the secondary or storage battery. (See

Battery, Secondary.)

(b) See Accumulator, Electrostatic

(c) See Accumulator, Water Dropping.

(d) See Wheel, Barlow's

Accumulator, Electrostatic.

Two conducting surfaces oppositely placed, and separated by a

dielectric and arranged for the opposite charging of the two surfaces,

constitute an accumulator, sometimes termed a condenser. As this

arrangement introduces the element of a bound and of a binding charge,

the electrostatic capacity of such is greater than that of either or of

both of its component surfaces. The thinner the dielectric which

separates the conducting surfaces, and the larger the surfaces the

greater is the capacity; or the less will be the potential difference

which a given charge will establish between its two coatings. The nature

of the dielectric also determines its capacity. (See Capacity, Specific

Inductive.)

9  STANDARD ELECTRICAL DICTIONARY.

Fig. 2. SIR WILLIAM THOMSON'S WATER-DROPPING ACCUMULATOR.

Accumulator, Water Dropping.

This is also known as Sir William Thomson's Water-Gravity Electric

Machine. It is an apparatus for converting the potential energy of

falling water drops, due to gravity, into electric energy. Referring to

the illustration, G represents a bifurcated water pipe whose two faucets

are adjusted to permit a series of drops to fall from each. C and F are

two metallic tubes connected by a conductor; E and D are the same. Two

Leyden jars, A and B, have their inner coatings represented by strong

sulphuric acid, connected each to its own pair of cylinders, B to D and

E, and A to F and C. The outer coatings are connected to earth, as is

also the water supply. One of the jars, say A, is charged interiorily

with positive electricity. This charge, C and F, share with it, being in

electric contact therewith. Just before the drops break off from the jet

leading into C, they are inductively charged with negative electricity,

the positive going to earth. Thus a series of negatively excited drops

fall into the metal tube D, with its interior funnel or drop arrester,

charging it, the Leyden jar B, and the tube E with negative electricity.

This excitation causes the other stream of drops to work in the converse

way, raising the positive potential of F and C and A, thus causing the

left-hand drops to acquire a higher potential. This again raises the

potential of the right-hand drops, so that a constant accumulating

action is kept up. The outer coatings of the Leyden jars are connected

to earth to make it possible to raise the potential of their inner

coatings. In each case the drops are drawn by gravity into contact with

objects similarly excited in opposition to the electric repulsion. This

overcoming of the electric repulsion is the work done by gravity, and

which results in the development of electric energy.

10   STANDARD ELECTRICAL DICTIONARY.

Acidometer.

A hydrometer or areometer used to determine the specific gravity of

acid. They are employed in running storage batteries, to determine when

the charging is completed. (See Areometer.)

Aclinic Line.

A terrestrial element; the locus on the earth's surface of no

inclination of the magnetic needle; the magnetic equator. (See Magnetic

Elements.)

Acoustic Telegraphy.

The system of sound-reading in telegraphy, universally used in the Morse

system. The direct stroke of the armature of the electro-magnet and its

"back stroke" disclose to the ear the long and short strokes, dots and

lines, and long and short spaces as produced by the dispatcher of the

message. In the Morse system a special magnet and armature is used to

produce the sound called the "sounder;" in other systems, e. g.,

Steinheil's and Bright's apparatus, bells are used. (See Alphabets,

Telegraphic.)

Acoutemeter.

A Hughes audiometer or sonometer applied to determining the quality of a

person's hearing (See Hughes' Induction Balance,--Audiometer). The

central coil by means of a tuning fork and microphone with battery

receives a rapidly varying current tending to induce currents in the

other two coils. Telephones are put in circuit with the latter and pick

up sound from them. The telephones are applied to the ears of the person

whose hearing is to be tested. By sliding the outer coils back and forth

the intensity of induction and consequent loudness of the sounds in the

telephones is varied. The position when the sounds grow so faint as to

be no longer audible, gives the degree of delicacy of the person's

hearing. By using a single telephone the same apparatus affords a means

of testing the relative capacity of the right and left ears.

11  STANDARD ELECTRICAL DICTIONARY.

Actinic Rays.

The rays of light at the violet end of the spectrum; also the invisible

rays beyond such end, or the ether waves of short periods which most

strongly induce chemical change.

Actinism.

The power possessed by ether waves of inducing chemical change, either

of decomposition or of combination. The violet and ultra-violet end of

the spectrum of white light, generally speaking, represent the most

highly actinic rays.

Actinometer, Electric.

Properly an apparatus for measuring the intensity of light by its action

upon the resistance of selenium. A current produced by fixed

electro-motive force passing through the selenium affects a galvanometer

more or less according to the intensity of the light. It is more

properly an electric photometer. The term has also been applied to a

combination of a thermo-electric pile and galvanometer, the light

falling on the pile affecting the motions of the galvanometer.

Action, Local.

(a) The wasteful oxydation of the zinc in a galvanic battery due to

local impurities and variations in the composition of the zinc. These

act to constitute local galvanic couples which cause the zinc to

dissolve or oxydize, without any useful result. Amalgamation of the zinc

prevents local action. Chemically pure zinc is also exempt from local

action, and can be used in an acid battery without amalgamation. (See

Amalgamation.)

(b) The same term has been employed to indicate the eddy or foucault

currents in dynamo electric machines. (Sec Current, Foucault.)

Activity.

The rate of doing work; the work done per second by any expenditure of

energy. The activity of a horse-power is 550 foot lbs. per second, or

746 volt-coulombs per second. The practical electric unit is the

volt-ampere, often called the watt. (Sec Energy, Electric.)

Adapter.

A screw coupling to engage with a different sized screw on each end; one

of the uses is to connect incandescent lamps to gas-fixtures.

A. D. C.

Abbreviation for Anodic Duration Contraction, q. v.; a term in

electro-therapeutics.

Adherence, Electro-magnetic.

The adherence between surfaces of iron due to elcctro-magnetic

attraction. It has been applied to the driving-wheels of an engine and

rail, whose grip is increased by such action. In one method a deep

groove was cut around the wheel which was wound with a magnetizing coil.

Thus one rim becomes a north and the other a south pole, and the rail

completing the circuit acts as the armature. Such an arrangement

prevents a wheel from sliding. Electro-magnetic adherence has also been

employed to drive friction gear wheels. In one arrangement the two

wheels are surrounded by a magnetizing coil, under whose induction each

attracts the other, developing high adherence between their peripheries.

12  STANDARD ELECTRICAL DICTIONARY.

Fig. 3. ELECTRO-MAGNETIC CAR WHEEL.

Fig. 4. ELECTRO-MAGNETIC FRICTION GEAR.

Admiralty Rule of Heating.

The British Admiralty specifications for the permissible heating of

dynamos. It holds that at the end of a run of six hours no part of the

dynamo under trial shall show a rise of temperature greater than 11º C.

(20º F.) above the temperature of the air surrounding it. This is

thought to be a very stringent and unnecessarily high requirement.

Aerial Conductor.

An electric conductor carried from housetops, poles, or otherwise so as

to be suspended in the air, as distinguished from an underground or

submarine conductor.

Affinity.

The attraction of atoms and in some cases perhaps of molecules for each

other by the force of chemical attraction. When the affinity is allowed

to act or is carried out, a chemical change, as distinguished from a

physical or mechanical change, ensues. Thus if sulphur and iron are each

finely powdered and are mixed the change and mixture are mechanical. If

slightly heated the sulphur will melt, which is a physical change. If

heated to redness the iron will combine with the sulphur forming a new

substance, ferric sulphide, of new properties, and especially

characterized by unvarying and invariable ratios of sulphur to iron.

Such change is a chemical one, is due to chemical affinity, is due to a

combination of the atoms, and the product is a chemical compound.

13  STANDARD ELECTRICAL DICTIONARY.

Agir Motor.

The Anderson and Girdlestone motor. The term "agir" is made up from the

first portions of each name.

Agonic Line.

The locus of points on the earth's surface where the magnetic needle

points to the true north; an imaginary line determined by connecting

points on the earth's surface where the needle lies in the true

geographical meridian. Such a line at present, starting from the north

pole goes through the west of Hudson's Bay, leaves the east coast of

America near Philadelphia, passes along the eastern West Indies, cuts

off the eastern projection of Brazil and goes through the South Atlantic

to the south pole. Thence it passes through the west of Australia, the

Indian Ocean, Arabia, the Caspian sea, Russia and the White sea to the

North Pole. It crosses the equator at 70° W. and 55° E. approximately.

(See Magnetic Elements.)

Synonym--Agone.

[Transcriber's note: The file Earth_Declination_1590_1990.gif provided

by the U.S. Geological Survey (http://www.usgs.gov) is an animation of

the declination of the entire earth.]

Air.

Air is a dielectric whose specific inductive capacity at atmosphere

pressure is taken as 1. It is practically of exactly the same

composition in all places and hence can be taken as a standard. When dry

it has high resistance, between that of caoutchouc and dry paper.

Dampness increases its conductivity.

It is a mixture of oxygen and nitrogen, with a little carbonic acid gas

and other impurities. Its essential composition is:

Oxygen:     (by weight) 23.14     (by volume) 21

Nitrogen:               76.86                 79

The specific inductive capacity varies for different pressures thus:

Approximate   (.001 mm., .0004 inch)   0.94 (Ayrton)

Vacuum

( 5 mm. , .2 inches )

0.9985 (Ayrton)

0.99941 (Boltzman.)

The specific gravity of air under standard conditions 15.5° C (60° F.)

and 760 mm. barometric pressure (30 inches) is taken as unity as a

standard for gases.

[Transcriber's note: Argon accounts for 0.9340%. It was discovered in

1894, two years after this book.]

Air-Blast.

(a) In the Thomson-Houston dynamo an air-blast is used to blow away the

arc-producing spark liable to form between the brushes and commutator.

It is the invention of Prof. Elihu Thomson. The air is supplied by a

positive action rotary blower connected to the main shaft, and driven

thereby. The wearing of the commutator by destructive sparking is thus

prevented.

A drum H H is rotated, being mounted on the axis X of the dynamo. As it

rotates the three vanes are thrown out against the irregular shaped

periphery of the outer case T T. The arrow shows the direction of

rotation. The air is thus sent out by the apertures a a. O is the

oil-cup.

(b) The air-blast has also been used by Prof. Thomson in experiments

with high frequency currents of high potential. By directing a blast of

air against a spark discharge between ball terminals of an alternating

current, the nature of the current was changed and it became capable of

producing most extraordinary effects by induction.

14   STANDARD ELECTRICAL DICTIONARY.

Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO.

Air Condenser.

A static condenser whose dielectric is air. The capacity of an air

condenser in farads is equal to

A / ( 4.452E12 * t )

in which A is the area of one sheet or sum of the areas of one set of

connected sheets in square inches and t is the thickness of the layer of

air separating them.

A convenient construction given by Ayrton consists in a pile of glass

plates P separated by little bits of glass F of known thickness, three

for each piece. Tin-foil T is pasted on both sides of each piece of

glass and the two coatings are connected. The tin-foil on each second

plate is smaller in area than that on the others. The plates are

connected in two sets, each set comprising every second plate. For A in

the formula the area of the set of smaller sheets of tin-foil is taken.

By this construction it will be seen that the glass does not act as the

dielectric, but only as a plane surface for attachment of the tin-foil.

Posts E E keep all in position. One set of sheets connects with the

binding post A, the other with B.

The capacity of any condenser with a dielectric of specific inductive

capacity i is given by the formula:

( i *A^1 ) / ( 4.452E12 * t1 )

The air condenser is used for determining the value of i for different

dielectrics.

Fig. 6. AIR CONDENSER.

15  STANDARD ELECTRICAL DICTIONARY.

Air Gaps.

In a dynamo or motor the space intervening between the poles of the

field magnet and the armature. They should be of as small thickness, and

of as extended area as possible. Their effect is to increase the

magnetic reluctance of the circuit, thereby exacting the expenditure of

more energy upon the field. They also, by crowding back the potential

difference of the two limbs, increase the leakage of lines of force from

limb to limb of the magnet.

Air Line Wire.

In telegraphy the portion of the line wire which is strung on poles and

carried through the air.

Air Pump, Heated.

It has been proposed to heat portions of a mercurial air pump to secure

more perfect vacua, or to hasten the action. Heating expands the air and

thus produces the above effects.

16   STANDARD ELECTRICAL DICTIONARY.

Air Pump, Mercurial.

An air pump operated by mercury. The mercury acts virtually as the

piston, and the actuating force is the weight of the column of mercury,

which must exceed thirty inches in height. There are many types.

Mercurial air pumps are largely used for exhausting incandescent lamp

chambers. (See Geissler Air Pump,--Sprengel Air Pump.)

Air Pumps, Short Fall.

A mercurial air pump in which the fall of mercury or the height of the

active column is comparatively small. It is effected by using several

columns, one acting after the other. A height of ten inches for each

column suffices in some forms. Enough columns must be used in succession

to make up an aggregate height exceeding 30 inches.

Fig. 7. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER.

Fig. 8. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER.

Alarm, Burglar.

A system of circuits with alarm bell extending over a house or

apartments designed to give notice of the opening of a window or door.

As adjuncts to the system the treads of the stairs are sometimes

arranged to ring the bell, by completing a circuit when trod on. Door

mats are also arranged to close circuits in like manner.

17  STANDARD ELECTRICAL DICTIONARY.

For doors and windows switches are provided which are open as long as

the door or window is closed, but which, on being released by opening

the door or windows, automatically close the circuit. The circuit

includes an alarm bell and battery, and the latter begins to ring and

continues until stopped, either by the closing of the door or by a

switch being turned. The connections are sometimes so contrived that the

reclosing of the door or window will not stop the bell from ringing.

The cuts show various switches for attachment to doors and windows. It

will be seen that they normally keep the circuit closed, and that it is

only open when pressure, as from a closed door, is brought upon them. In

the case of a door a usual place for them is upon the jamb on the hinge

side, where they are set into the wood, with the striking pin

projecting, so that as the door is closed the pin is pressed in, thus

breaking the circuit.

Sometimes the connections are arranged so as to switch on the electric

lights if the house is entered. Special annunciators showing where the

house has been entered are a part of the system. A clock which turns the

alarm on and off at predetermined hours is also sometimes used.

The circuits may be carried to a central station or police station. One

form of burglar alarm device is the Yale lock switch. This is a contact

attached to a Yale lock which will be closed if the wrong key is used,

completing a circuit and ringing a bell.

Fig. 9. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER.

Alarm, Electric.

An appliance for calling attention, generally by

ringing a bell. It is used to notify of water-level in boilers or tanks,

of entrance of a house, or of other things as desired. It is evident

that any number of alarms could be contrived.

18   STANDARD ELECTRICAL DICTIONARY.

Alarm, Fire and Heat.

An alarm for giving notice of the existence of a conflagration. Such are

sometimes operated by a compound bar thermostat (see Thermostat), which

on a given elevation of temperature closes a circuit and rings an

electric bell. Sometimes the expansion of a column of mercury when

heated is used. This, by coming in contact with one or two platinum

points, completes a circuit, and rings the bell.

The identical apparatus may be used in living rooms, greenhouses.

factories and elsewhere, to give an alarm when the temperature rises or

falls beyond predetermined limits.

Alarm, Overflow.

An alarm to indicate an overflow of water has been suggested on the

lines of a contact completed by water, or of the elements of a battery

which would be made active by water. Thus two sheets of metal might be

separated by bibulous paper charged with salt. If these sheets were

terminals of a circuit including a bell and battery, when water reached

them the circuit would be closed and the bell would ring. It was also

proposed to use one copper and one zinc sheet so as to constitute a

battery in itself, to be thrown into action by moisture. These contacts

or inactive batteries could be distributed where water from an overflow

would be most likely to reach them.

Alarm, Water Level.

An alarm operated by a change of water level in a tank or boiler. By a

float a contact is made as it rises with the water. Another float may be

arranged to fall and close a contact as the level falls. The closing of

the contacts rings an electric bell to notify the attendant in charge.

Alcohol, Electrical Rectification of.

A current of electricity passed through impure alcohol between zinc

electrodes is found to improve its quality. This it does by decomposing

the water present. The nascent hydrogen combines with the aldehydes,

converting them into alcohols while the oxygen combines with the zinc

electrode.

Alignment.

The placing in or occupying of the same straight line. The bearings of a

shaft in dynamos, engines, and other machinery have to be in accurate

alignment.

Allotropy.

The power of existing in several modifications possessed by some

substances, notably by chemical elements. Instances of the allotropic

state are found in carbon which exists as charcoal, as graphite

(plumbago or black lead), and as the diamond. All three are the same

elemental substance, although differing in every physical and electrical

property.

19   STANDARD ELECTRICAL DICTIONARY.

Alloy.

A mixture, produced almost universally by fusion, of two or more metals.

Sometimes alloys seem to be chemical compounds, as shown by their having

generally a melting point lower than the average of those of their

constituents. An alloy of a metal with mercury is termed an amalgam. An

important application in electricity is the use of fusible alloys for

fire alarms or for safety fuses. German silver is also of importance for

resistance coils, and palladium alloys are used for unmagnetizable

watches. An alloy of wrought iron with manganese is almost

unmagnetizable, and has been proposed for use in ship building to avoid

errors of the compass.

Alloys or what are practically such can be deposited by electrolysis in

the electro- plater's bath. We give the composition of some alloys

interesting to the electrician.

Solder:   Lead   1 part   Tin   2 parts

"      "       "    1  "

"      "       "    2  "

German Silver: Copper, 2 parts; Nickel, 1 part;

Zinc, 1 part (used for resistances).

Platinum, Silver Alloys: Platinum, 1 part;

silver, 2 parts (used for resistances.)

Palladium alloys for watch springs. (See Palladium.)

Alphabet, Telegraphic.

The combinations of sounds, of dots and dashes marked on paper, of

right-hand and left-hand deflections of a needle, of bells of different

notes, or of other symbols by which a fixed combination is expressed for

each character of the alphabet, for numerals, and for punctuation. While

the code is designed for telegraphic uses it can be used not only for

the conveyance of signals and messages by the electrical telegraphs, but

also by any semaphoric or visual system, as by flashes of light,

movements of a flag or even of the arms of the person signalling.

In the English and continental needle telegraphy in which the message is

transmitted by the movements of an index normally vertical, but

oscillating to one side or the other under the influence of the current,

the latter being controlled by the transmitter of the message, the left

hand swings of the needle are interpreted as dots, the right hand as

dashes.

This system enables one alphabet to be translated into the other, or

virtually one alphabet answers for both Morse and needle transmitters.

There are two principal telegraphic alphabets, the American Morse and

the International codes. They are very similar, their essential

distinction being that spaces are used in the American code, while they

are excluded from the International code.

In the American Morse system the message is now universally received by

sound. (See Sounder--Sound Reading.)

20   STANDARD ELECTRICAL DICTIONARY.

The two codes or telegraphic alphabets are given here.

THE INTERNATIONAL ALPHABET.

Parenthesis,             - . - - . -

Understand,              ... - .

I don't understand,      ..-- ....--..

Wait,                    .-. . .

Erase,                   ...   ...   ...

Call signal,             -.-.-.-

End of message,          .-.-.-.

Cleared out all right,   .-..-..-.

A  .-    L  .-..  W  .--

B  -...  M  --    X  -..-

C  -.-.  N  -.    Y  -.--

D  -..   O  ---   Z  --..

E  .     P  .--.

F  ..-.  Q  --.-  Ch ----

G  --.   R  .-.   Ä  .-.-

H  ....  S  ...   Ö  ---.

I  ..    T  -     Ü  ..--

J  .---  U  ..-   É  ..-..

K  -.-   V  ...-  Ñ  --.--

NUMERALS

1  .----  4  ....-  8  ---..

2  ..---  5  .....  9  ----.

3  ...--  6  -....  0  -----

7  --...

[Transcriber's note: The original image of the dot/dash pattern is somewhat

ambiguous. Since there may be differences from contemporary specifications,

the original image is included.]

[Image of page 20: THE INTERNATIONAL ALPHABET.]

21  STANDARD ELECTRICAL DICTIONARY.

PUNCTUATION, ETC.,

Period (.)         ...   ...

Comma (,)          .-.-.-

Query(?)           ..--..

Exclamation (!)    --..--

Apostrophe (')     .----.

Hyphen (-)         -....-

Fresh paragraph,   .-.-..

Inverted commas,   -..-.

THE AMERICAN ALPHABET.

A  .-       L  ----(Continuous)  W  .--

B  -...     M  --                X  .-..

C  ..s.     N  -.                Y  ..s..

D  -..      O  .s.               Z  ….

E  .        P  .....

F  .-.      Q  ..-.              Ch ----

G  --.      R  .s..              Ä  .-.-

H  ....     S  ...               Ö  ---.

I  ..       T  -                 Ü  ..--

J  - . - .  U  ..-               É  ..-..

K  -.-      V  ...-              Ñ  --.--

NUMERALS

1  .--.    4  ....-     8  -....

2  ..-..   5  ---       9  -..-

3  ...-.   6  ... ...   0  -----(Continuous)

7  --..

[Transcriber's Note: The "s" in the American Code indicates a "space". I

leave the following to the reader's imagination. See the original

image.]

Comma (,)

Semicolon (;)

Colon (:)

Colon Dash (:~)

Period (.)

Interrogation (?)

Exclamation (!)

Dash (-)

Hyphen (-)

Pound Sterling (£)

Shilling Mark ( )

[Image of page 21: THE AMERICAN ALPHABET.]

22   STANDARD ELECTRICAL DICTIONARY.

[Transcriber's Note: I leave these to the reader's imagination. See the

following original image.]

Dollars ($)

Decimal Point (.)

Cents (c)

Paragraph ()

Pence (d.)

Fractional Mark (--)

Capitalized Letter

Italics or Underline

Colon followed by Quotation :"

Parenthesis (   )

Brackets [   ]

Quotation Marks " "

Quotation within a Quotation " ' ' "

[Image of page 22: THE AMERICAN ALPHABET.]

The principal differences in the two codes are the use of spaces in the

American code, such being excluded from the International code. This

affects the letters C, R, Y, & Z.

The following diagram, due to Commandant Perian, enables the letter

corresponding to an International code sign to be rapidly found with the

exception of R.

<- dot       start         dash   ->

/                           \

E                             T

/          \                /             \

I              A             N                M

/    \          /    \        /    \         /      \

S      U        R      W       D      K       G       O

/  \    / \     / \    /  \    /  \     /  \    /  \    /  \

H   V   F   U   L   A   P   J   B   X   C   Y   Z    Q  Ô   CH

Fig. 10. Diagram for translating the Morse Alphabet.

In order to find what letter corresponds to a given sign, starting from

the top of the diagram, each line is traced down to a bifurcation,

taking the right hand line of each bifurcation for a dash, and the left

hand line for a dot, and stopping when the dots and dashes are used up.

Thus, for example,

the signal -.- -   leads us to the letter d,

the signal - - - - to the letter j and so on.

23  STANDARD ELECTRICAL DICTIONARY.

Alternating. adj.

Term descriptive of a current changing periodically in

direction. (See Current, Alternating.)

Synonyms--Oscillatory--periodic--undulatory--harmonic.

Alternating Current Arc.

The arc produced by the alternating current. It presents several

peculiarities. With an insufficient number of alternations per second it

goes out. As the carbons wear away equally it is adopted for such lamps

as the Jablochkoff candle, (see Candle, Jablochkoff). As no crater is

formed the light is disseminated equally both up and down. For this

reason to get full downward illumination a reflector is recommended.

Alternating Current System.

A system of electric distribution employing the alternating current. For

transmission in the open air or in conduits a high potential circuit is

used, from 1,000 to 10,000 volts being maintained at the central

station. Two leads unconnected at the end lead from the station. Where

current is desired a converter or transformer (see Converter) is placed,

whose primary is connected to the two leads bridging the interval

between them. From the secondary the house leads are taken with an

initial potential in some cases of 50 volts. The converters are thus all

placed in parallel. By law or insurance rules the converters are

generally kept outside of buildings. Where no secondary current is taken

from the converters very little primary current passes them on account

of their counter-electromotive force. As more secondary current is taken

the primary increases and this accommodation of one to the other is one

of the interesting and valuable features. Street lamps are sometimes

connected in series. Each lamp in such case is in parallel with a small

coil with iron core. While the lamp is intact little current passes

through the coil. If the lamp is broken, then the converter impedes the

current by its spurious resistance, q. v., just enough to represent and

replace the resistance of the extinguished and broken lamp filament.

(See Meter, Alternating Current; Motor, Alternating Current.)

Alternation.

The change in direction of a current. The number of such changes is

expressed as number of alternations; thus a current may have a frequency

of 500 or 20,000 alternations per second.

[Transcriber's note: One alternation per second is now called one hertz.]

Alternation, Complete.

A double alternation; a change from one direction

to the other and back again to the original phase. A symbol derived from

its graphic representation by a sine curve is used to indicate it. The

symbol is  ~

24   STANDARD ELECTRICAL DICTIONARY.

Alternative Path.

A second path for a current appearing as a disruptive

discharge. Where two paths are offered the discharge, as it is of

alternating or oscillatory type, selects the path of least

self-induction. Thus a thick bar of copper, with no air gap, may be

abandoned by the current in favor of a small iron wire with an air gap,

but which has less self-induction.

The lightning arresters, q. v., for the protection of telegraph offices

are sometimes based on these principles. A path of very high resistance

but of small self-induction is offered between the line and the earth.

This the lightning discharge selects in preference to the instruments

with their iron cores, as the latter are of very high self-induction.

Alternator.

A dynamo electric generator supplying an alternating current. (See

Dynamo, Alternating Current.)

Synonym--Alternating current generator or dynamo.

Alternator, Constant Current.

An alternating current dynamo supplying a current of unvarying virtual

amperage. Alternators of this type are constructed with an armature of

high self-induction. Sometimes fine winding contained in deep peripheral

notches in the core-discs is employed to magnify the self-induction.

Such generators are employed for series lighting, especially

arc-lighting.

Aluminum.

A metal; one of the elements; symbol: Al.

Atomic weight: 27.4. Equivalent: 9.13. Valency: 3.

Specific gravity: 2.6. It is a conductor of electricity.

Relative resistance annealed, (Silver = 1)  1.935

Specific resistance at 0ºC (32°F.)    2.912 microhms

Resistance of a wire at 0ºC  (32°F.)

a) 1 foot long, weighing 1 grain,     0.1074 ohms.

b) 1 foot long, 1/1000 inch thick,   17.53     "

c) 1 meter long, weighing 1 gram,     0.0749   "

d) 1 meter long, 1 millimeter thick   0.03710  "

Resistance of a 1-inch cube at 0ºC (32°F.) 1.147 microhms

Electro-chemical equivalent.    .0958 (hydrogen == .0105)

25  STANDARD ELECTRICAL DICTIONARY.

Amalgam.

(a) A combination or alloy in which one of the constituents is mercury.

Usually the term is applied to an alloy of a single metal with mercury.

Some metals readily form amalgams; such metals are: Gold, zinc, silver,

lead and others; some, such as platinum and iron, form amalgams only

under exceptional circumstances.

(b) The word is also applied to compositions for application to the

cushions of frictional electric machine in which cases it is often a

misnomer. True amalgams used for this purpose are made as follows:

(a) Tin, 1 part;  Zinc, 1 part;  Mercury, 2 parts (Kienmayer).

(b) Tin, 2 parts; Zinc, 3 parts.

(c) Tin, 3 parts; Zinc, 5 parts; Mercury, 4 parts.

(d) Zinc, 1 part: Mercury, 4 parts; Mercury, 9 parts.  [sic]

The tin, if such is used, (formula a, b and c) is first melted, the zinc

is added in successive portions. The mercury, which must be heated, is

slowly poured into the melted alloy after removal of the latter from the

fire, and the mixture, while making, is constantly stirred. It is kept

stirred or rubbed in a mortar until cold. Sometimes it is poured into

water and kept in constant agitation until cold. It is thus obtained in

a granular condition, and is pounded in a mortar until reduced to

powder. It must be dried and kept in tightly stopped bottles and is

applied to the cushions after they have been greased. It is to be

noticed that it is said that alloy (d) requires no pulverization beyond

constant rubbing in a mortar as it cools. Sometimes the amalgam is

shaken about in a wooden tray with chalk while cooling. The action of

amalgams is not very clearly understood. Some claim that there is a

chemical action, others that they simply act as conductors, others that

they are more highly negative to the glass than the leather of the

cushions.

Graphite or sulphide of tin (mosaic gold) are sometimes used to coat the

cushions; it is these that are sometimes incorrectly called amalgams.

Amalgamation.

The application of mercury to a metal with which it forms an amalgam, or

with which it amalgamates. Battery zincs are amalgamated in two ways. In

the immersion method, the plate is dipped into an acid solution of

mercuric chloride or nitrate. The latter is best. In the direct

application method the plate is first wet all over with dilute acid and

a little mercury is dropped upon it and is rubbed over the surface with

a rag or, what is better, with a piece of galvanized iron. A very little

mercury answers the purpose. The whole surface of the plate should be

left as bright as silver. (See Action, Local.)

Amber.

Amber is a fossil resin, supposed to be a product of the extinct Pinites

Succinifer and other coniferous trees. Most of it is gathered on the

shores of the Baltic between Koenigsberg and Memel. It is also found in

small pieces at Gay Head, Mass., and in New Jersey green sand. It is

found among the prehistoric remains of the Swiss Lake dwellers. When

rubbed with a cloth it becomes excited with negative electricity. The

Greek word for it is electron, which gave the name electricity to the

modern science. Thales of Miletus, 600 B. C., and Theophrastus, about

300 B. C., both mention its electric properties or power of attracting

small objects when rubbed.

26   STANDARD ELECTRICAL DICTIONARY.

Ammeter.

The commercial name for an ampere-meter, an instrument designed

to show by direct reading the number of amperes of current which are

passing through a circuit.

A great variety of ammeters have been invented, based on different

principles. The definitions following this one give some idea of the

lines of construction followed.

Synonym--Ampere meter.

Ammeter, Ayrton's.

A direct reading instrument for measuring current intensity.

A solenoid receives the current. In the axis of the solenoid an iron

tube is suspended by a long spiral spring that passes down within it,

and the upper end of which spring is fastened to the glass top of the

instrument. The tube is provided with proper guides so as to maintain a

vertical position, and is free to rotate. Its upper end carries an

index.

The whole operates as a magnifying device. A slight longitudinal

displacement of the tube causes it to rotate through a considerable

angle by the action of the spring. By properly proportioning the parts,

the angle of displacement of the index is directly proportional to the

current between 15º and 270º angular displacement.

The same instrument is wound for use as a volt-meter.

Its principal fault is its restricted range.

Ammeter, Commutator.

A commutator ammeter is one whose windings consist of separate strands,

each of any desired number of turns, and provided with a commutating

attachment for throwing them into series or into parallel as desired.

The essential condition is that all the wires shall be of equal

resistance and of equal number of turns. Such an instrument can be used

for heavy or light currents. Two sets of graduations are marked on its

scale if it is a calibrated instrument. (See Calibration.) Commutator

volt-meters are constructed on the same principle.

Ammeter, Cunynghame's.

A modification of the Siemens' electro-dynamometer. (See

Electro-dynamometer, Siemens'.) An electro-magnet with very massive core

is excited by the current. As the core is of small reluctance the

strength of the magnet is nearly proportional to the current strength.

Between the poles of the magnet a soft iron armature or induced magnet

is pivoted. It carries a pointer so adjusted that when the axis of the

soft iron magnet is at an angle of about 30º with the line joining the

poles of the electro-magnet the pointer will indicate zero.

The soft iron armature is so massive that the magnetism induced in it is

proportional to the strength of the electro-magnet. Hence the couple

exerted by the electro-magnet on the pivoted armature will be

proportional to the square of the current.

The armature is retained in place by a spiral spring lying in line with

its axis of rotation. The instrument is operated as a zero reading

instrument. The current is passed through it. The needle is deflected;

it is brought back to zero by turning a milled head which twists the

spring. The current will be proportional to the square root of the angle

of displacement of the milled head. A scale with index is provided,

giving directly the square roots of the angle over which the pointer is

moved.

The same instrument is wound for use as a volt-meter.

27  STANDARD ELECTRICAL DICTIONARY.

Ammeter, Eccentric Iron Disc.

This ammeter comprises a cylindrical electro-magnet excited by the

current to be measured. A disc of iron free to rotate is suspended on

pivots below it. A piece is cut off the disc at one part of its

periphery so as to give more metal to one side than to the other. In its

zero position this portion of the disc swings towards the magnet. As the

latter is more and more excited the other or more projecting portion of

the disc turns towards it, being attracted like an armature, and moves

against the force of gravity, the disc rotating. An index attached to

the disc swings over the face of a graduated scale. The disc is so

counterpoised that in its natural position the index points to zero.

Ammeter, Electro-magnetic.

An ammeter depending for its working upon the action of an

electro-magnet, which is excited by the current to be measured.

Ammeter, Gravity.

An ammeter whose hand or index is drawn into the zero position by

gravity, and whose displacement therefrom is produced by the action of

the current to be measured.

Fig. 11. GRAVITY SOLENOID AMMETER.

Ammeter, Magnetic Vane.

A fixed plate of soft iron is placed within a coil. Facing it is a

second disc free to move or swing on an axis. When the field is excited

the two repel each other because like polarity is induced in each, and

the motion of the movable disc indicates the strength of the current.

The same instrument is wound for high resistance and constitutes a

Magnetic Vane Voltmeter.

28   STANDARD ELECTRICAL DICTIONARY.

Ammeter, Magnifying Spring.

A solenoid ammeter in which a spiral spring is used to convert the

longitudinal motion of the armature or movable core into a rotary motion

(see Ammeter, Ayrton's) and magnify the apparent range of motion.

Ammeter, Permanent Magnet.

An ammeter with a magnetic field produced by a permanent magnet.

Ammeter, Solenoid.

An ammeter in which the attraction, when a current is passing through

it, exerted by a hollow coil of wire upon an iron bar or tube in line

with its axis, is utilized to indicate the strength of current. The bar

is drawn into the coil to different extents proportional to the

attraction. As an example see Ammeter, Ayrton's, and cut of Gravity

Ammeter.

Ammeter, Spring.

An ammeter in which the part moved by the current is controlled or

brought to the zero position by a spring.

Ammeter, Steel Yard.

A solenoid ammeter in which the solenoid core is suspended vertically

from the short end of a steel yard fitted with a sliding weight. The

current passes through the solenoid coil and attracts or draws downwards

the coil. A sliding weight is moved in and out on the long steel-yard

arm which is graduated for amperes. In use the weight is slid out until

the arm is in equipose; the divisions give the amperes.

Fig. 12. STEEL YARD AMMETER.

29  STANDARD ELECTRICAL DICTIONARY.

Ammunition Hoist, Electric.

An apparatus for use on ships for hoisting ammunition to the guns by an

electric elevator. The characteristic feature of it is that a constant

motion of the switch or handle is required to keep it in action. If the

operator is shot so as to be incapacitated from taking charge of the

switch, the hoist stops until another is assigned to it.

Amperage.

Current intensity expressed in amperes, as an amperage of ten amperes.

Ampere.

The practical unit of electric current strength. It is the measure of

the current produced by an electro-motive force of one volt through a

resistance of one ohm. In electric quantity it is the rate of one

coulomb per second. It is one-tenth the absolute C. G. S. unit of

current strength. Its best analogy is derived from water. Assuming the

electric current to be represented by a current of water, the pressure,

head, or descent producing such current would be the electro-motive

force. The current might be measured in gallons (or other unit) passed

per second. In the analogy these gallons would be coulombs. But it might

be measured by reference to a standard stream, as for instance, the

stream which would pass through a hole an inch square under a given

head, say six inches of water. This unit is the miner's inch, and is the

exact analogy of the ampere. A current of water may flow at the rate of

so many miner's inches, just as a current of electricity may flow at the

rate of so many amperes. In neither case it will be noted is there any

reference to time. "An ampere per second" is a redundant expression, and

means no more than "an ampere"; an "ampere-second," on the other hand,

is a coulomb. The number of coulombs passed per second gives the amperes

of current.

For value of ampere, see Coulomb.

[Transcriber's note: The SI definition of an ampere: A current in two

straight parallel conductors of infinite length and negligible

cross-section, 1 metre apart in vacuum, would produce a force equal to

2E-7 newton per metre of length.]

Fig. 13. THE MINER'S INCH AS AN ANALOGY FOR THE AMPERE.

30   STANDARD ELECTRICAL DICTIONARY.

Ampere, Arc.

A conductor bent into the arc of a circle, and employed in measuring the

electric current by the electric balance.

Ampere-currents.

The currents assumed to be the cause of magnetism. (See Magnetism,

Ampere's Theory of.)

Ampere-feet.

The product of amperes of current by the length, in feet, of a conductor

passing such current. It may be in empiric calculations of dynamo or

motor construction, but is little used. One ampere-foot is a current of

one ampere passing through one foot length of a conductor, or one-tenth

ampere through ten feet, and so on.

Ampere-hour.

The quantity of electricity passed by a current of one ampere in one

hour. It is used by electric power and lighting companies as the unit of

energy supplied by them, because they maintain a constant potential

difference in their leads, so that only the amperes and hours need

measuring or recording to give the energy, viz. : volt-ampere-hours.

The same unit is applied to batteries to indicate their potential

energy, because they also are assumed to be of constant voltage or

electro-motive force.

Ampere-meters.

The product of amperes of current by the length, in meters, of a

conductor carrying such current. One ampere-meter is a current of one

ampere passing through one meter of a conductor.

The term must not be confused with the identically spelled Ampere-meter,

a synonym for Ammeter.

Ampere-minute.

The quantity of electricity passed by a current of one ampere in one

minute; sixty coulombs.

Ampere Ring.

A conductor forming a ring or circle used in electric balances for

measuring currents. (See Balance, Ampere.)

Ampere-second.

The quantity of electricity passed by a current of one ampere in one

second; the coulomb, q. v.

Amperes, Lost.

In a shunt or compound-wound dynamo, part of the total amperes of

current produced in the armature coils go through the shunt, and hence,

do not appear in the outer circuit. S. P. Thompson has proposed the term

"lost amperes" for this portion of the current.

Ampere's Memoria Technica.

An expression of the effect of a current on a magnetic needle. If we

imagine the observer in the line of the current and facing the magnetic

needle, the current entering by his feet and leaving by his head, the

north pole is deflected to his left.

31  STANDARD ELECTRICAL DICTIONARY.

Ampere-turns.

The amperes of current supplied to a magnet coil multiplied by the

number of turns the current makes in the coil. If the coil is wound two

or three in parallel, the virtual turns by which the amperes are

multiplied are one-half or one-third the actual turns of wire.

Synonym--Ampere Windings.

Ampere-turns, Primary.

The ampere-turns in the primary coil of an induction coil or

transformer.

Ampere-turns, Secondary.

The ampere-turns in the secondary coil of an induction coil or

transformer.

Amplitude of Waves.

Waves are distinguished by length and amplitude. The latter, in the case

of transverse waves, such as those of water and of the ether, correspond

with and measure the height from lowest to highest point, or from valley

to summit of the waves in question. In the case of longitudinal waves,

such as those of the air, due to sounding bodies, the ratio of degree of

rarefaction to degree of condensation existing in the system is the

amplitude. The latter can be graphically represented by a sinuous line,

such as would represent the section of a transverse wave. Ether waves

are produced by heated bodies and by electro-magnetic impulses, as in

the discharge of the Leyden jar.

The amplitude of a wave, other things being equal, is the measure of its

intensity. Thus, the louder a sound the greater is the amplitude of the

system of waves to which it is due. The same applies to ether waves,

whether they are perceived in the electro-magnetic, light, or

heat-giving modification. As the amplitude of ether waves cannot be

accurately known, amplitude is a relative term and is not stated

generally in any absolute unit.

Analogous Pole.

One of the elements of a pyro-electric crystalline substance, such as

tourmaline. When heated, such bodies acquire electrical properties. If

of such crystalline form that they are differently modified at the ends

of their crystalline axis, by hemihedral modifications, the ends may be

differently affected. One end may show positive electricity when the

temperature is rising, and negative when falling. Such end is then

called the analogous pole. The opposite end presents, in such cases, the

opposite phenomena; becoming negative when the temperature is rising,

and becoming positive when it is falling; such end is called the

antilogous pole.

Analysis.

The determination of the elements of a case. It may be chemical, and

consist in finding what a substance consists of; it may be mathematical,

and consist in determining the unknown quantities in a problem; or it

may belong to other branches of science. The term has a very extended

application. Where the constituents are only determined in kind it is

called qualitative analysis; where their quantity or percentage is

ascertained it is called quantitative analysis.

32   STANDARD ELECTRICAL DICTIONARY.

Analysis, Electric.

Chemical analysis by electrolytic methods. (See Electrolytic  Analysis.)

Analyzer, Electric.

An apparatus used in investigations on electric ether waves. It consists

of a series of parallel metallic wires. When the electric waves have

been polarized, the analyzer will only permit them to go through it

intact, when the plane of vibration of the waves is parallel to its

wires.

Anelectrics.

(a) Bodies which do not become electrified by friction; a term

introduced by Gilbert, now little used, as all bodies develop

electricity under proper conditions by contact action; the reverse of

idioelectrtics.

(b) Also a conductor of electricity, the reverse of a dielectric, q. v.

(See Conductor.)

It will be seen that Gilbert's anelectrics were, after all, the same as

the modern anelectrics, i.e., conductors.

Anelectrotonus.

A term used in medical electricity or electro-therapeutics to indicate

the deceased functional activity induced in a nerve by the proximity of

the anode of an active electric circuit completed through the nerve. The

converse of Kathelectrotonus.

Angle of Declination.

The angle of error of the magnetic needle or compass, measuring the

extent of its deviation from the meridian in any locality. It is the

angle between the plane of the magnetic axis of a magnetic needle free

to take its natural position, and the geographical meridian, the needle

being counterpoised if necessary, so as to hold an absolutely horizontal

position. The deviation is expressed as being east or west, referring

always to the north pole. (See Magnetic Elements.)

Synonym--Variation of the Compass.

[Transcriber's note:  See Agonic Line.]

Angle of the Polar Span.

In a dynamo or motor the angle subtended by the portion of a pole piece

facing the armature, such angle being referred to the centre of the

cross-section of the armature as its centre.

33   STANDARD ELECTRICAL DICTIONARY.

Angular Velocity.

The velocity of a body moving in a circular path, measured with

reference to the angle it passes over in one second multiplied by the

radius and divided by the time. A unit angle is taken (57°.29578 =

57° 17' 44".8 nearly) such that it is subtended by a portion of the

circumference equal in length to the radius. Hence, the circumference,

which is 360°, is equal to 2*PI*unit angle, PI being equal to 3.1416--.

"Unit angular velocity" is such as would in a circle of radius = 1

represent a path = 1, traversed in unit time = 1 second. If the radius

is r and the angle passed over is theta, the distance is proportional to

r*theta; if this distance is traversed in t seconds the angular velocity

is theta / t. The angular velocity, if it is multiplied by r, theta

expressing a distance, will give the linear velocity. The dimensions of

angular velocity are an angle (= arc / radius) / a Time = (L/L)/T =

(T^-1).

The velocity expressed by the rate of an arc of a circle of unit radius,

which arc subtends an angle of 57° 17' 44".8, such arc being traversed

in unit time, is unit angular velocity.

Animal Electricity.

Electricity, notably of high tension, generated in the animal system, in

the Torpedo, Gymnotus and Silurus. The shocks given by these fish are

sometimes very severe. The gymnotus, or electric eel, was elaborately

investigated by Faraday. It has the power of voluntarily effecting this

discharge. There is undoubtedly some electricity in all animals. The

contact of the spinal column of a recently killed frog with the lumbar

muscles produces contraction, showing electric excitement. Currents can

be obtained from nerve and muscle, or from muscle sides and muscle cut

transversely, in each case one thing representing positive and the other

negative elements of a couple.

Angle of Inclination or Dip.

The angle which the magnetic axis of a magnet, which magnet is free to

move in the vertical plane of the magnetic meridian, makes with a

horizontal line intersecting such axis. To observe it a special

instrument, the dipping compass, inclination compass, dipping needle, or

dipping circle, as it is called, is used. (See Elements, Magnetic,

--Dipping Needle,--Compass, Inclination.)

Angle of Lag.

The angle expressing the displacement of the magnetic axis of the

armature core of a dynamo in the direction of its rotation. (See Lag.)

Lag is due to the motion of the armature core.

Angle of Lead.

The angle expressing the displacement in the direction of rotation of

the armature of a dynamo which has to be given the brushes to compensate

for the lag. (See Lag.) This is positive lead. In a motor the brushes

are set the other way, giving a negative angle of lead or angle of

negative lead.

Anion.

The electro-negative element or radical of a molecule, such as oxygen,

chlorine or the radical sulphion. (See Ions.) It is the portion which

goes to the anode, q.v., in electrolytic decomposition.

34   STANDARD ELECTRICAL DICTIONARY.

Anisotropic. (adj.)

Unequal in physical properties, as in conduction and specific inductive

capacity, along various axes or directions. An anisotropic conductor is

one whose conductivity varies according to the direction of the current,

each axis of crystallization in a crystalline body marking a direction

of different conductivity. An anisotropic medium is one varying in like

manner with regard to its specific inductive capacity. In magnetism an

anisotropic substance is one having different susceptibilities to

magnetism in different directions. The term is applicable to other than

electric or magnetic subjects.

Synonym--AEolotropic.

Annealing, Electric.

Annealing by the heat produced by the passage of the electric current

through the body to be annealed. The object is clamped or otherwise

brought into a circuit, and a current strong enough to heat it to

redness, or to the desired temperature is passed through it.

Annunciator.

An apparatus for announcing a call from any place to another, as from a

living-room to an office in a hotel, or for announcing the entering of

any given room or window in a building protected by a burglar alarm.

A usual system comprises for each annunciator an electro-magnet. Its

armature is normally held away from its poles by a spring, and when in

that position a latch connected to the armature holds a little shutter.

When by a push-button or other device a current is sent through a

circuit which includes the electro-magnet the armature is attracted,

this releases the latch and the shutter drops. In dropping it displays a

number, letter or inscription which indicates the locality of the

push-button or other circuit-closing device. Often annunciators are

connected in circuit with a bell.

Fig. 14. ANNUNCIATOR.

35  STANDARD ELECTRICAL DICTIONARY.

Annunciator Clock.

A clock operating an annunciator by making contact at determined times.

Annunciator Drop.

The little shutter which is dropped by some forms of annunciators, and

whose fall discloses a number, character or inscription, indicating

whence the call was sent.

Fig. 15. DROP ANNUNCIATOR.

Fig. 16. ANNUNCIATOR DETACHING MECHANISM.

Annunciator, Gravity Drop.

An annunciator whose operations release shutters which fall by gravity.

Annunciator, Needle.

A needle annunciator is one whose indications are given by the movements

of needles, of which there is usually a separate one for each place of

calling.

Annunciator, Swinging or Pendulum.

An annunciator which gives its indications by displacing from its

vertical position a pendulum or vertically suspended arm.

36   STANDARD ELECTRICAL DICTIONARY.

Anodal Diffusion.

A term in electro-therapeutics; the introduction of a medicine into the

animal system by using a sponge-anode saturated with the solution of the

drug in question. On passing a current the desired result is secured by

cataphoresis, q. v.

Anode.

The positive terminal in a broken metallic or true conducting circuit;

the terminal connected to the carbon plate of a galvanic battery or to

its equivalent in case of any other generator. In general practice it is

restricted to the positive terminal in a decomposition or electrolytic

cell, such as the nickel anode in a nickel-plating bath or the anode of

platinum in a gas voltameter. It is the terminal out of or from which

the current is supposed to flow through the decomposition cell. In

electro-therapeutics the term is used simply to indicate the positive

terminal. In an electrolytic cell the electro-negative substance or

anion goes to the anode. Hence, it is the one dissolved, if either are

attacked. The nickel, copper or silver anodes of the electroplater

dissolve in use and keep up the strength of the bath. The platinum anode

in a gas voltameter is unattacked because the anion cannot act upon it

chemically.

Anodic Closure Contraction.

A physiological change in a living subject produced by the closing of

the electric current; the muscular contraction which takes place beneath

the anode applied to the surface of the body when the circuit is closed,

the kathode being applied elsewhere; it is due, presumably, to direct

action on the motor nerve. It is a term in electro-therapeutics. It is

the converse of anodic opening contraction, q. v. An abbreviation A. C.

C. is often used to designate it.

Anodic Duration Contraction.

A term in electro-therapeutics. On the opening or closing of an electric

circuit, the anode of which is placed over a muscle, a contraction is

observed (see Anodic Closure Contraction--Anodic Opening Contraction).

The above term is used to designate the duration of such contraction. An

abbreviation A. D. C. is often used to designate it.

Anodic Opening Contraction.

The converse of Anodic Closure Contraction, q. v.; it is the contraction

of living muscle beneath or near the anode where the circuit, including

such anode and the body in its course, is closed; a physiological

phenomenon observed in electro-therapeutics to which branch of science

the term belongs. An abbreviation A. O. C. is often used to designate

it.

Anodic Reactions.

A term in electro-therapeutics; the diagnosis of disease by the actions

of the tissue near the anode of a circuit.

Anti-Induction Conductor.

A conductor constructed to avoid induction effects in the conducting

element. Many kinds have been made. A tubular metal shield or envelope

which may be grounded will protect an enclosed conductor to some extent.

Or the conductor may be a double wire twisted around itself, one branch

being used for the regular and the other for the return circuit, thus

constituting a closed metallic circuit. The inductive effects are due to

interrupted or varying currents in neighboring wires and circuits. Many

anti-induction conductors have been invented and patented.

37  STANDARD ELECTRICAL DICTIONARY.

Anti-magnetic Shield.

In general terms a hollow screen of soft iron designed to protect any

mass of steel behind or enclosed by it from magnetization by any magnet

near it, such as a dynamo field magnet. This it does by concentrating

the lines of force within its own mass, so that the space within it or

enclosed by it is comparatively free from lines of force. It is often

applied to watches, and is virtually an iron case in which they are

enclosed.

Antimony.

A metal, one of the elements, atomic weight, 122:

equivalent, 40.6 and 24.4; valency, 3 and 5;

specific gravity, 6.8.

It is a conductor of electricity.

Relative resistance, compressed (silver = 1), 23.60

Specific resistance,   35.50 microhms.

Resistance of a wire,

(a) 1 foot long, weighing 1 grain,       3.418 ohms.

(b) 1 foot long, 1/1000 inch thick,    213.6     "

(c) 1 meter long, weighing 1 gram,       2.384   "

(d) 1 meter long. 1 millimeter thick,    0.4521  "

Resistance of a 1-inch cube,   13.98 microhms.

Approximate percentage resistance per degree C.

(1.8º F. at 20º C. 88º F.)   0.389 per cent.

Elcctro-chemical equivalent (hydrogen = .0105)  .2560

(See Thermo-Electric Series.)

Anvil.

An intermittent contact, or "make and break" of the current is sometimes

produced by directly pressing a key down upon a metallic surface, the

two being terminals of the circuit. The surface or stud on which such

pressure is produced is called the anvil. The ordinary telegraph key,

which makes a contact by the pressure of the operator's fingers does it

by making a contact between a contact piece upon the front end of the

key and the anvil. In the induction coil the anvil is also found. Thus

in the cut representing the end of an induction coil and its circuit

breaker in which O and O' and P and P' represent the secondary circuit

terminal connections A is the core of soft iron wires, h is the anvil;

the hammer when resting upon it so as to be in contact closes the

circuit. When the current coming from the primary to the post i, passes

through the hammer and anvil h, and emerges by m, it magnetizes the

core; this attracts the hammer, which is made of or is armed with a mass

of iron. This breaks the circuit. The hammer falls at once on the anvil,

again making the circuit, and the action is repeated with great

rapidity. Hammer and anvil or key and anvil connections should be made

of platinum.

Fig. 17. INDUCTION COIL CIRCUIT BREAKER.

38   STANDARD ELECTRICAL DICTIONARY.

A. O. C.

Abbreviation for Anodic Opening Contraction, q. v.

Aperiodic. adj.

In an oscillating apparatus, or in the oscillating member of apparatus,

the fact of having no reference to time of vibration; dead-beat.

Synonym. Dead-beat.

39  STANDARD ELECTRICAL DICTIONARY.

Fig. 18. ARAGO'S DISC.

Arago's Disc.

An apparatus consisting of a disc of copper mounted horizontally, or on

a vertical spindle, and so arranged as to be susceptible of rapid

rotation. Immediately over it, and best with a pane of glass

intervening, a magnetic needle is mounted on a pivot directly over the

axis of the disc. If the disc is rotated the lines of force of the

magnet are cut by it, and consequently currents are produced in the

copper. These currents act upon the needle and cause it to rotate,

although quite disconnected. It is advisable for the needle to be strong

and close to the disc, which should rotate rapidly.

Arc v.

To form a voltaic arc.

Arc, Compound.

A voltaic arc springing across between more than two electrodes.

Arc, Metallic.

The voltaic arc produced between terminals or electrodes of metal. The

characteristics of such arc as contrasted with the more usual arc

between carbon electrodes are its greater length for the same

expenditure of energy, its flaming character and characteristic colors

due to the metals employed. It is sometimes, for the latter reason, used

in spectroscopic investigations.

Arc Micrometer.

A micrometer for measuring the distance between the electrodes of a

voltaic arc.

Arc, Simple.

A voltaic arc produced, as usual, between only two electrodes.

40   STANDARD ELECTRICAL DICTIONARY.

Arc, Voltaic.

The voltaic arc is the arc between two carbon electrodes slightly

separated, which is produced by a current of sufficient strength and

involving sufficient potential difference. The pencils of carbon are

made terminals in a circuit. They are first placed in contact and after

the current is established they are separated a little. The current now

seems to jump across the interval in what sometimes appears an arch of

light. At the same time the carbon ends become incandescent. As regards

the distance of separation with a strong current and high electro-motive

force, the arc may be several inches long.

The voltaic arc is the source of the most intense heat and brightest

light producible by man. The light is due principally to the

incandescence of the ends of the carbon pencils. These are differently

affected. The positive carbon wears away and becomes roughly cupped or

hollowed; the negative also wears away, but in some cases seems to have

additions made to it by carbon from the positive pole. All this is best

seen when the rods are slender compared to the length of the arc.

It is undoubtedly the transferred carbon dust which has much to do with

its formation. The conductivity of the intervening air is due partly,

perhaps, to this, but undoubtedly in great measure to the intense

heating to which it is subject. But the coefficient of resistance of the

intervening air is so much higher than that of any other part of the

circuit that an intense localization of resistance occurs with

corresponding localization of heating effect. This is the cause of the

intense light. Thus if the carbons are but 1/32 of an inch apart as in a

commercial lamp the resistance may be 1.5 ohms. The poor thermal

conductivity of the carbon favors the concentration of heat also. The

apparent resistance is too great to be accounted for by the ohmic

resistance of the interposed air. A kind of thermoelectric effect is

produced. The positive carbon has a temperature of about 4,000° C.

(7,232° F.), the negative from 3,000° C. (5,432° F.) to 3,500° C.

(6,322° F.). This difference of temperature produces a

counter-electro-motive force which acts to virtually increase the

resistance of the arc. The carbon ends of an arc can be projected with

the lantern. Globules are seen upon them due to melted silica from the

arc of the carbon.

Fig. 19. EXPERIMENTAL APPARATUS FOR PRODUCING THE VOLTAIC ARC.

41  STANDARD ELECTRICAL DICTIONARY.

Areometer.

An instrument for determining the specific gravity of a fluid. It

consists of an elongated body ballasted so as to float vertically and

provided with a mark or a scale. It floats deeper in a light than in a

heavy liquid. If it carries but one mark weights are added until that

mark is reached, when the weights required give the specific gravity. Or

the scale may give the reading directly based upon the depth to which it

sinks. Areometers are often made of glass, ballasted with shot or

mercury enclosed in their bottom bulb as shown. They are used in

regulating battery solutions, and in watching the charging and

discharging of storage batteries.

Fig. 20. AREOMETER

Fig. 21. BEAD AREOMETER

Areometer, Bead.

A tube of glass containing beads of different specific gravities. It has

apertures at top and bottom. When immersed in a liquid, the same fills

it, and the specific gravity within certain limits, depending on the

factors of the beads, is shown by the beads which float and those which

sink. It is used for storage batteries and other purposes where acids

and solutions have to be tested.

Argyrometry.

The method of ascertaining the weight and inferentially the thickness of

an electroplater's deposit of silver. It is done by weighing the article

before and after plating.

Arm.

The four members of a Wheatstone bridge, q. v., are termed its arms.

Referring to the diagram of a bridge, P, Q, R, S, are the arms.

Fig. 22. DIAGRAM OF WHEATSTONE'S BRIDGE.

Armature.

(a.) A mass or piece of iron or steel, or a collection of pieces of iron

designed to be acted on by a magnet. While nickel or cobalt might be

used, they rarely or never are except in experimental apparatus. The

armature of a permanent horse shoe magnet is simply a little bar of soft

iron. When the magnet is not in use it is kept in contact with the poles

with the idea of retaining its magnetism. It is then said to be used as

a keeper. A bar magnet does not generally have an armature. The armature

is also used to exhibit the attraction of the magnet.

Sometimes an armature is made of steel and is permanently magnetized.

Such an armature, termed a polarized armature, is repelled when its like

poles are opposed to like poles of the magnet and otherwise is attracted

with force due to the sums of the magnetism. If the magnet is

sufficiently powerful depolarization of the armature may ensue when like

poles are opposed to like poles. Polarized armatures are used in various

appliances, magneto generators, telegraphic instruments and others.

(b) In a dynamo or Motor the mass of laminated iron or of wire which

carries the coils of insulated wires which are caused to rotate in the

field of force of the field magnets in order to establish and maintain

potential difference with its accompanying current, or which rotates

under the effects of a current in a motor. (See Dynamo Electric

Generator.)

The work of the armature core is twofold. It acts as a portion of the

magnetic circuit, conducting the lines of force, and by virtue of its

high permeability or multiplying power concentrating a number of the

lines of force through its own substance. To enable it to act with

efficiency in this direction it should be made of iron of the highest

permeability, and should approach as closely as possible to the armature

cores consistent with leaving space for the wire winding. It next acts

as a support for the wires which are to be swept through the field of

force. Thus it acts both to establish a strong field and then acts as a

carrier for the wires which are to be cut by the wires in question. In

connection with this subject the different definitions under Armature,

Dynamo, Commutator, Induction and similar topics may be consulted.

(c) See Armature of Influence Machine.

(d) See Armature of Leyden Jar or Static Condenser.

42   STANDARD ELECTRICAL DICTIONARY.

Armature, Bar.

An armature in a dynamo or motor whose winding is made up of conductors

in the form of bars, round, rectangular and of other sections. This type

of armature conductor is objectionable as Foucault currents are produced

in it. It is found best to laminate or subdivide low resistance armature

windings.

[Transcriber's Note: Foucault currents are also called eddy currents.]

Armature, Bipolar.

An armature in which two poles are induced by the field. A bipolar field

magnet produces a bipolar armature.

Armature Bore.

The cylindrical space defined by the pole pieces of a dynamo or motor

within which the armature rotates.

Synonym--Armature Chamber.

43  STANDARD ELECTRICAL DICTIONARY.

Armature, Closed Coil.

An armature for a motor or dynamo, the ends of all of whose coils are

united, so as to be in one closed circuit all the way around.

Fig. 23. CLOSED COIL GRAMME RING ARMATURE.

Armature Coil, or Coils.

The insulated wire wound around the core of the armature of an electric

current generator or motor.

Armature Core.

The central mass of iron on which the insulated wire, to be rotated in

the field of an electric current generator or motor, is wound. (See

Dynamo-electric Machine and Motor, Electric.)

Armature, Cylinder.

An armature of the Gramme ring type, but longer in the axial direction,

so that its core resembles a long hollow cylinder, the wire being wound

inside and outside as in the Gramme ring. (See Gramme Ring.)

Armature, Disc.

(a) An armature of a dynamo electric machine or motor in which the coils

are wound so as to be flat and are carried on the face of a disc forming

the core or part of the core of the armature. S. P. Thompson treats it

as a modified drum armature extended radially, the outer periphery

corresponding to the back end of the drum. The poles of the field are

generally placed to face the side or sides of the disc.

(b) Another type of disc armature has its wire wound on bobbins arranged

around the periphery of a disc.

In disc armatures there is often no iron core, their thinness enabling

this to be dispensed with.

44   STANDARD ELECTRICAL DICTIONARY.

Fig. 24. DISC ARMATURE OF FRITSCHE MACHINE.

Fig. 25. PLAN OF WINDING PACINOTTI'S DISC ARMATURE.

Armature, Discoidal Ring.

In a dynamo an armature of the shape of a ring of considerable radial

depth of section as compared to its axial depth. It is generally made of

iron ribbon or thin band wound to the proper size.

Synonym--Flat Ring Armature.

45 STANDARD ELECTRICAL DICTIONARY.

Armature, Drum.

An armature for a dynamo or motor, consisting of a cylinder of iron

preferably made up of discs insulated from each other by thin shellacked

paper, or simply by their oxidized surfaces, and wound with wire

parallel to the axis where it lies on the cylindrical periphery and

crossing the heads approximately parallel to the diameter. It operates

practically on the same principle as a Gramme Ring Armature. (See Gramme

Ring.)

Synonym--Cylindrical Armature.

Armature Factor.

The number of conductors on an armature, counted or enumerated all

around its external periphery.

Armature, Hinged.

An armature pivoted to the end of one of the legs of an electro-magnet

so as to be free to swing and bring its other end down upon the other

pole.

Fig. 26. HINGED ARMATURES OF CLUB-FOOT ELECTRO MAGNETS.

Armature, Hole.

An armature whose core is perforated to secure cooling.

Synonym--perforated Armature.

Armature, Intensity.

An armature wound for high electro-motive force. A term little used at

the present time.

Armature Interference.

A limit to the ampere turns permissible on a given armature is found in

the increase of cross magnetizing effect, q. v., the increased lead

necessitated, and the growth of the demagnetizing power. All such

perturbing effects are sometimes expressed as armature interference.

46   STANDARD ELECTRICAL DICTIONARY.

Armature, Load of.

The circumflux, q. v., of the armature, or the ampere turns of the same.

The maximum load which can be carried by an armature without sparking is

directly proportional to the radial depth of core and to the length of

the gap, and inversely proportional to the breadth of the polar span.

Armature, Multipolar.

An armature in which a number of poles greater than two is determined by

the field. A multipolar field is employed for its production.

Armature, Neutral.

An armature of a magnet or telegraph relay which is not polarized or

magnetized.

Synonym--Non-polarized Armature--Neutral Relay Armature.

Armature of Influence Machine.

Pieces of paper pasted on the stationary plate of an electric machine of

the Holtz type.

Armature of Leyden Jar or Static Condenser.

The inner and outer tin-foil coatings of a Leyden jar or other

condenser.

Armature, Open Coil.

An armature of a dynamo or motor on which the coils are not joined in

one closed circuit, but have their ends or some of them separated, and

connected each to its own commutator bar or each set to their own bar.

Fig. 27. OPEN COIL RING ARMATURE.

47  STANDARD ELECTRICAL DICTIONARY.

Armature, Pivoted.

An armature for an electro-magnet mounted on a pivot, which is at right

angles to the yoke or parallel with the legs of the magnet, so as to be

free to rotate. When the magnet is excited the armature is drawn into

line or approximately so with its base or yoke. The system is used in

some telegraph apparatus.

Armature Pockets.

Spaces or recesses in armatures provided for the reception of the coils.

Armature, Polarized.

An armature made of steel or having a steel core to which permanent

magnetism has been imparted. Such are used in some forms of magneto

current generators, and in telegraphic instruments. (See Relay,

Polarized.)

Armature, Pole.

An armature having coils wound on separate poles projecting radially all

around the periphery of its central hub or disc, or projecting

internally from a ring-like frame, their ends facing the field magnet.

Synonym--Radial Armature.

Armature, Quantity.

An armature of a dynamo or motor wound for current of large quantity.

The term is now but little used.

Armature-Reactions.

When an armature is running in an active dynamo a series of

reactions is established, the more important of which are:

I. A tendency to cross-magnetize the armature.

II. A tendency to spark at the brushes.

III. A tendency for the armature current to demagnetize on account of

the lead which has to be given to the brushes.

IV. Variations in the neutral points as more or less current is taken

from the machine.

V. Heating of armature, both core and conductors, and of pole pieces,

which heating is due to Foucault currents.

Armature, Revolving, Page's.

An early form of motor. The field is produced by a permanent magnet.

Above its poles is a soft iron armature wound with a coil of insulated

wire. A two-part commutator with contact springs conveys the current to

the coil. The whole is so arranged that the polarity of the armature, as

induced by the coil, through which a current is passed, is reversed as

its ends sweep by the poles of the magnet. Then it is repelled from the

poles and swings through 180° to have its polarity reversed and to go

through the next 180°, and so on. Thus it rotates at a very high rate of

speed.

In the cut showing the elevation A, B, is the armature;  f, g, the

springs or brushes; h, the commutator with its sections o, i. In the

section of the commutator W, W, designate the springs or brushes, A, the

vertical spindle carrying the armature and commutator, and S, S, the

commutator sections.

48   STANDARD ELECTRICAL DICTIONARY.

Fig. 28. PAGE'S REVOLVING ARMATURE.

Fig. 29. SECTION OF COMMUTATOR OF PAGE'S REVOLVING ARMATURE.

W, W, Brushes; A, Spindle; S, S, Armature Segments.

Armature, Ring.

An armature whose core is in the shape of a ring, as the Gramme Ring

Armature. (See Figs. 23 & 27.)

49  STANDARD ELECTRICAL DICTIONARY.

Armature, Rolling.

(a) An armature for a permanent horseshoe magnet consisting of a

straight cylinder of soft iron on which a heavy wheel is mounted. When

the legs of the magnet are inclined downward and the bar is laid across

them it rolls down to the poles, across their ends, and back up the

under side. It is merely a magnetic toy or illustrative experiment.

Synonym--Wheel Armature.

(b) Another form consists of little bars of iron with brass discs

attached to the ends. On placing two of these together and bringing the

poles of a magnet near them, as shown, they become magnetized with like

polarity by induction and repel each other, rolling away in opposite

directions.

Fig. 30. ROLLING OR WHEEL ARMATURE.

Fig. 31. ROLLING ARMATURES.

Armature, Shuttle.

The original Siemens' armature, now discarded. The core was long and

narrow, and its cross section was nearly of the section of an H. The

grooves were wound full of wire, so that the whole formed almost a

perfect cylinder, long and narrow comparatively. (See Winding Shuttle.)

Synonym--Siemens' Old Armature--Girder Armature--H Armature.

Fig. 32. SHUTTLE OR H ARMATURE.

Armature, Spherical.

An armature of a dynamo which is wound on a spherical core, so as to be

almost a sphere. It is employed in the Thomson-Houston dynamo, being

enclosed in a cavity nearly fitting it, formed by the pole pieces.

Armature, Stranded Conductor.

A substitute for bar-armatures in which stranded copper wire conductors

are substituted for the solid bar conductors, to avoid Foucault

currents. (See Armature, Bar.)

50   STANDARD ELECTRICAL DICTIONARY.

Armature, Unipolar.

An armature of a unipolar dynamo. (See Dynamo Unipolar.)

Armor of Cable.

The metal covering, often of heavy wire, surrounding a telegraph or

electric cable subjected to severe usage, as in submarine cables.

Synonym--Armature of Cable.

Arm, Rocker.

An arm extending from a rocker of a dynamo or motor, to which arm one of

the brushes is attached. (See Rocker.) Ordinarily there are two arms,

one for each brush.

Articulate Speech.

Speech involving the sounds of words. It is a definition which has

acquired importance in the Bell telephone litigations, one contention,

concerning the Bell telephone patent, holding that the patentee did not

intend his telephone to transmit articulations, but only sound and

music.

Astatic. adj.

Having no magnetic directive tendency due to the earth's magnetism.

Examples are given under Astatic Needle; Circuit, Astatic; and

Galvanometer Astatic.

Fig. 33. NOBILI'S PAIR.

FIG. 34. VERTICAL PAIR ASTATIC COMBINATION.

Astatic Needle.

A combination of two magnetic needles so adjusted as to

have as slight directive tendency as possible. Such a pair of needles

when poised or suspended will hardly tend to turn more to one point of

the compass than another. The combination is generally made up of two

needles arranged one above the other, with their poles in opposite

directions. This combination is usually called Nobili's pair. If of

equal strength and with parallel magnetic axes of equal length they

would be astatic. In practice this is very rarely the case. A resultant

axis is generally to be found which may even be at right angles to the

long axis of the magnets, causing them to point east and west. Such a

compound needle requires very little force to turn it one way or the

other. If one of the needles is placed within a coil of insulated wire a

feeble current will act almost as strongly to deflect the system as if

the other was absent, and the deflection will only be resisted by the

slight directive tendency of the pair of needles. This is the basis of

construction of the astatic galvanometer. Sometimes coils wound in

opposite directions and connected in series, or one following the other,

surround both needles, thus producing a still greater effect of

deflection.

Other astatic needles are shown in the cuts below. [Figures 33 to 35.]

51  STANDARD ELECTRICAL DICTIONARY.

FIG. 35. SIMPLE ASTATIC NEEDLE.

Asymptote.

A line continuously approached by a curve, but which the curve, owing to

its construction or nature of curvature, can never touch, be tangent to,

or intersect.

Atmosphere.

(a) A term applied to the atmospheric pressure as a practical unit of

pressure equal to 15 lbs. to the square inch as generally taken. It is

really about 14.7 lbs. per square inch, or 1,033 grams per square

centimeter.

(b) Air, q. v.

Atmosphere Residual.

The atmosphere left in a vessel after exhaustion. The term may be

applied to any gas. In an incandescent lamp after flashing the residual

atmosphere consists of hydro-carbons.

Atmospheric Electricity.

The electricity of the atmosphere, rarely absent, but often changing in

amount and sign. Benjamin Franklin, in a memoir published in 1749,

indicated the method of drawing electricity from the clouds by pointed

conductors. In June, 1752, he flew a kite and by its moistened cord drew

an electric spark from the clouds, confirming his hypothesis that

lightning was identical with the disruptive discharge of electricity. To

observe electricity in fine weather a gold-leaf or other electroscope

may be connected to the end of a long pointed insulated conductor. The

electricity during thunderstorms can be shown by a similar arrangement,

or burning alcohol or tinder gives an ascending current of warm air that

acts as a conductor. Quite elaborate apparatus for observing and

recording it have been devised. Atmospheric electricity is usually

positive, but occasionally negative. When the sky is cloudless it is

always positive, increasing with the elevation and isolation of the

place. In houses, streets, and under trees no positive electricity can

be found. In the Isle of Arran, Scotland, a rise of 24 to 48 volts per

foot of increase in elevation was found by Sir William Thomson. At

sunrise the electrification of the air is feeble, it increases towards

noon and decreases again to reach a second maximum a few hours after

sunset. It increases with the barometric pressure generally. In cloudy

weather it is sometimes negative and the sign often changes several

times in the same day. In a thunderstorm the changes in sign and

potential are very rapid. The cause of atmospheric electricity is far

from clear. Tait attributes it to a contact effect between air and water

vapor, Solmeke to friction of water vesicles against ice particles in

the upper atmosphere, he first showing that the two may coexist. The

cause of the enormous increase of potential producing lightning is

attributed to the decreased capacity due to the change of water from

cloud vesicles to drops, thus diminishing the electrostatic capacity of

the water in question. (See Lightning.)

52   STANDARD ELECTRICAL DICTIONARY.

Atom.

The ultimate particle or division of an elementary substance; the

smallest part that can exist in combination, and one which cannot exist

alone. An elementary substance is composed of molecules just as truly as

a compound one, but the atoms in the molecule of an elementary substance

are all precisely alike. Hence atoms are the units of chemistry, they

have to do with combinations, but the physical unit, the smallest

particle of matter that can have an independent existence, is the

molecule. The two are often confounded, especially by writers of a few

years ago, so that by "atom" the molecule is often meant. There is

nothing to be said of their size or mass. All such calculations refer to

the molecule, q. v., often spoken of and called the atom.

[Transcriber's note: Yet to be discovered: electron--1897 (5 years),

proton--1920 (28 years), neutron--1932 (30 years), quark--1961 (69 years).]

Atomic Attraction.

The attraction of atoms for each other, in virtue of which they combine

into molecules; chemical affinity, q. v., treats principally of this,

although molecular attraction also plays a part in it.

Atomic Heat.

The product of the atomic weight of a substance by its specific heat.

This product is approximately the same, 6.4; this approximation is so

close that it is of use in determining the valency and atomic weights of

substances. The atomic weight of a substance therefore represents the

approximate number of gram-calories required to raise one gram-atom, q.

v., of such substance through 1° C. (1.8° F.)

Atomicity.

The quantivalence or valency of the atoms; the number of combination

bonds, or bonds of affinity, possessed by the atoms of any substance.

Thus two atoms of hydrogen combine with one atom of oxygen, and three of

oxygen with one of sulphur, forming saturated compounds. Therefore,

taking hydrogen as of single atomicity or a monad, oxygen is of double

atomicity or a dyad, and sulphur is of six-fold atomicity, or a hexad.

The elements are thus classified into seven orders of atomicities, thus:

1, Monads or Univalent elements,   Hydrogen, etc.

2, Dyads or Bivalent        "      Oxygen, etc.

3, Triads or Trivalent      "      Nitrogen, etc.

4, Tetrads or Quadrivalent  "      Lead, etc.

5, Pentads or Quinquivalent "      Phosphorous, etc.

6, Hexads or Sexivalent     "      Chromium, etc.

7, Heptads or Septivalent   "      Chromium, etc.

The same element often possesses several atomicities. Barium is

generally a dyad, sometimes a tetrad; nitrogen acts as a monad, dyad,

triad, tetrad and pentad. The familiar electrolysis of water, giving two

volumes of hydrogen to one of oxygen, is one of the illustrations of the

theory indicating that two atoms of hydrogen are combined with one of

oxygen.

53  STANDARD ELECTRICAL DICTIONARY.

Atomic Weight.

The number expressing the relative weight of the atom of any substance,

that of hydrogen being generally taken as unity. This is the universal

system, although any other element might be taken as the basis of the

system. The whole theory of atomic weights is based on the

indivisibility of the atom and on the theory of atomicity, q. v. (See

Equivalents.)

[Transcriber's note: The standard is now the isotope carbon-12 as

exactly 12.]

Attraction.

The tendency to approach and adhere or cohere, shown by all forms of

matter. It includes gravitation, cohesion, adhesion, chemical affinity

and other forms, and is opposed by repulsion, and is sometimes overcome

by it, although it may be assumed to be always present. See the

different kinds of attractions under their titles: Atomic Attraction,

Electro-magnetic Attraction and Repulsion, Electro Static Attraction and

Repulsion, Electro-dynamic Attraction and Repulsion; Magnetic Attraction

and Repulsion; Molar Attraction.

Audiometer.

An apparatus for obtaining a balance of induction from two coils acting

upon a third. The third is placed between the other two and is free to

move towards either. A scale is provided to show the extent of its

movement. A varying or interrupted current being passed through the two

outer coils, the preponderating current will produce the most induction

if the central coil is equidistant. It can always be moved to such a

point that there will be no inductive effect, one counteracting the

other. Thus its position measures the relative induction. A telephone is

in circuit with the intermediate coil and is used to determine when its

position is such that no current is induced in it. It is sometimes used

as a direct test of hearing. (See Hughes' Induction Balance.)

Synonym--Acoutemeter.

Aura, Electrical.

The blast of air produced at highly electrified points.

Aurora.

A luminous display seen in the northern heavens in the northern

hemisphere, where it is the Aurora Borealis, and seen in the southern

heavens in the southern hemisphere, where it is called Aurora Australis,

or indifferently for either, the Aurora Polaris. It takes the form of

pale luminous bands, rays and curtains varying in color. Near the poles

they are very numerous. A French commission observed 150 auroras in 200

days. Their height is variously estimated at from 90 to 460 miles; they

are most frequent at the equinoxes and least so at the solstices. There

is a secular variation also, they attain a maximum of occurrence every

11 years together with sun spots, with a minimum 5 or 6 years after the

maximum. There is also a period of 60 years, coincident with

disturbances in the earth's magnetism. Various attempts have been made

to account for them. They have a constant direction of arc with

reference to the magnetic meridian (q. v.) and act upon the magnetic

needle; in high latitudes they affect telegraph circuits violently.

There is a strong probability that they represent electric currents or

discharges. De la Rive considers them due to electric discharges between

the earth and atmosphere, which electricities are separated by the

action of the sun in equatorial regions. According to Balfour Stewart,

auroras and earth currents.(q. v.) may be regarded as secondary currents

due to small but rapid changes in the earth's magnetism. The subject is

very obscure. Stewart treats the earth as representing the magnetic core

of an induction coil, the lower air is the dielectric, and the upper

rarefied and therefore conducting atmosphere is the secondary coil. This

makes the aurora a phenomenon of induced currents. Then the sun may be

regarded as the instigator of the primary changes in the earth's lines

of force representing the primary of an induction coil.

[Transcriber's note: Solar wind, streams of electrons and protons,

interacting with the earth's magnetic field causes aurora. Neither

electrons (1897) nor protons (1920) were known in 1892. The Soviet

satellite Luna first measured the solar wind in 1959. Even today

increased understanding of solar and auroral phenomenon continues.]

54   STANDARD ELECTRICAL DICTIONARY.

Austral Pole.

The north pole of the magnet is thus called sometimes in France; the

austral pole of a magnet is the one which points towards the north polar

regions As unlike magnetic poles attract each other, it is but rational

to call the north-seeking pole of the magnet the south or Austral Pole.

In the same nomenclature the south pole of a magnet, or the

south-seeking pole, is called the Boreal Pole.

A. W. G.

Abbreviation for American Wire Gauge, q. v.

Axis, Electric.

The electric axis of a pyroelectric crystal, such as a tourmaline

crystal; the line connecting the points of greatest pyroelectric

excitability.

Axis of Abscissa.

In a system of rectilinear, or right angle co-ordinates, the horizontal

axis. (See Co-ordinates.)

Synonym--Axis of X.

Axis of Ordinates.

In a system of rectilinear right angle co-ordinates, the vertical axis.

(See Co-ordinates.)

Synonym--Axis of Y.

Azimuth.

The angle between the plane of the meridian and the plane of an azimuth

circle, q. v.

Azimuth Circle.

A great circle, whose plane passes through the zenith or point of the

heavens directly overhead; any great circle in whose plane the vertical

at the point of observation is included.

Each celestial body has or determines an azimuth circle.

55  STANDARD ELECTRICAL DICTIONARY.

B.

(a) Abbreviation for Baumé, a hydrometer scale. (See Baumé.) Thus 10º B.

means "ten degrees Baumé."

(b) Symbol for the coefficient of induced magnetization, or the number

of lines per square centimeter induced in a magnetic circuit or in any

specified part of it.

B. A.

Abbreviation for British Association. It is prefixed to standards fixed

by the committee of the British Association for the Advancement of

Science. Thus the B. A. ohm means the British Association ohm, a measure

of resistance which is equal to the resistance of a column of mercury

104.9 centimeters long and one square millimeter area of cross-section.

(See Ohm.)

Back Induction.

A demagnetizing force produced in a dynamo armature when a lead is given

the brushes. The windings by such setting of the brushes are virtually

divided into two sets, one a direct magnetizing set, the other a cross

magnetizing set. The latter have a component due to the obliqueness of

the neutral line, which component is demagnetizing in its action.

Back Shock or Stroke of Lightning.

A lightning stroke received after the main discharge of the lightning,

and caused by a charge induced in neighboring surfaces by the main

discharge. The discharge affects the evenness of distribution of

surrounding surfaces so that a species of secondary discharge is

required to make even the distribution, or to supply charge where needed

to bind an opposite one. The effects are much lese severe as a rule than

those of the main charge, although the back stroke has caused death. The

back stroke is sometimes felt a considerable distance from the place of

the original lightning stroke.

Synonym--Return Stroke.

Back Stroke.

(a) In telegraphy the return stroke of the lever in a telegraph sounder,

striking the end of the regulating screw with a sound distinct from that

which it produces on the forward stroke as it approaches the magnet

poles. It is an important factor in receiving by ear or sound reading.

(b) See Back Shock or Stroke of Lightning.

Balance.

(a) Wheatstone's Bridge, q. v., is sometimes termed the Electric

Balance.

(b) A suspension or torsion balance is one which includes a filament or

pair of filaments to whose lower end or ends are attached a horizontal

indicator often called a needle, or a magnetic needle. (See Torsion

Balance.)

(c) See Induction Balance, Hughes'.

(d) For Thermic Balance, see Bolometer.

(e) See Balance, Ampere.

56   STANDARD ELECTRICAL DICTIONARY.

Balance, Ampere.

A class of electrical measuring instruments due to Sir William Thomson

may be grouped under this head.

The instrument is a true balance or scales such as used for weighing. It

is supported by a torsional wire support in place of knife edges. At

each end it carries a circle of wire through which the current to be

tested is passed. The torsional wire support enables the current to be

carried to these wire rings. Above and below each of these rings are two

similar rings, also connected so as to receive the current. They are so

connected that the current shall go through them in opposite senses.

When a current passes, therefore, one of these rings repels and one

attracts the balanced ring.

The extent of this action measures the intensity of the current. A

sliding weight moving along a graduated scale on the balance is used to

bring the balance beam into equilibrium when the current is passing. The

degree of displacement of this weight gives the strength of the current

in amperes.

These balances are made for different currents. Thus there is a

centi-ampere balance, deka-ampere balance and others, as well as an

ampere balance.

Balata.

A gum used as an insulating material. It is the inspissated juice of a

sapotaceous tree, the bullet tree, Mimusops globosa, of tropical

America, from the Antilles to Guiana. It is intermediate in character

between caoutchouc and gutta percha. It is superior to gutta percha in

some respects, being very slightly acted on by light.

Synonym--Chicle.

B. & S.. W. G.

Abbreviation for Brown & Sharpe Wire Gauge; the regular American Wire

Gauge. (See Wire Gauge, American.)

Barad.

An absolute or fundamental unit of pressure, equal to one dyne per

square centimeter.

Barometer.

An apparatus for measuring the pressure exerted by the atmosphere. It

consists, in the mercurial form, of a glass tube, over 31 inches long,

closed at one end, filled with mercury and inverted, with its open end

immersed in a cistern of mercury. The column falls to a height

proportional to the pressure of the atmosphere from 30 to 31 inches at

the sea level. The "standard barometer" is a height of the mercury or of

the "barometric column" of 30 inches or 760 centimeters, measured from

the surface of the mercury in the cistern.

The column of mercury is termed the barometric column. Above it in the

tube is the Torricellian vacuum.

[Transcriber's note: More accurately, 29.92 inches of mercury or 14.696

PSI.]

Bars of Commutators.

The metal segments of a commutator of a dynamo or motor. They are made

of bars of copper, brass or bronze insulated from one another. (See

Commutator.)

Synonyms--Segments, Commutator Segments, Commutator Bars.

57 STANDARD ELECTRICAL DICTIONARY.

Bath.

(a) In electro-plating the solution used for depositing metal as

contained in a vat or tank; as a silver, copper, or nickel bath used for

plating articles with silver, copper, or nickel respectively.

(b) In electro-therapeutics a bath with suitable arrangements,

electrodes and connections for treating patients with electricity. It is

termed an electric bath or electro-therapeutic bath.

Bath, Bipolar Electric.

In electro-therapeutics a bath in which the electrodes are both immersed

in the water. The patient placed between them receives part of the

discharge. The electrodes are large copper plates, termed shovel

electrodes.

Bath, Electric Shower.

An electro-medical shower bath. The patient is placed on a metallic

stove or support connected to one of the electric terminals. Water

slightly alkaline is showered upon him. The other electrode is in

connection with the water. The rain of drops and streamlets is the

conductor of the current or discharge.

Bath, Multipolar Electric.

An electro-medical bath with a number of electrodes instead of two.

Bath, Stripping.

In electro-plating a solution used for dissolving and thus removing the

plating from any object. The stripping bath is of the same general type

as the plating bath for the same metal as the one to be dissolved. The

object to be "stripped" is made the anode of a plating circuit, and as

the current acts the old plating is attacked and dissolves, leaving the

body of the article bare. It is simply the operation of plating

reversed. The same term is applied to baths acting by simple solution.

Stripping baths are described under the different metals as Silver Bath,

Stripping--Gold Bath, Stripping.

Bath, Unipolar Electric.

An electro-medical bath, in which only one electrode connects with the

water of the bath. The second electrode is supported above the bath. The

patient touches this while in the water whenever electric action is

desired.

FIG. 36. THREE WIRE MOULDING OR BATTEN.

FIG. 37. TWO WIRE MOULDING OR BATTEN.

58   STANDARD ELECTRICAL DICTIONARY.

Batten.

A strip of wood grooved longitudinally for holding wires in wiring

apartments for electric light or power. In use they are fastened to the

wall, grooves inward, or else grooves outward, with the wires lying in

the grooves and covered with the covering strip. For two wire work each

batten contains two grooves; for the three wire system it contains three

grooves.

Synonym--Moulding.

Battery.

A combination of parts or elements for the production of electrical

action. The term is principally applied to voltaic batteries, but there

are also magnetic batteries, batteries of Leyden jars, and other

combinations, described in their places, which come under this category.

[Transcriber's note: A group of similar items such as questions,

machines, parts, guns, or electric cells.]

Battery, Acetic Acid.

A battery whose active solution or excitant is acetic acid or vinegar.

This acid has been used by Pulvermacher in his medical battery, as being

a substance found in every household in the form of vinegar. It is now

but little used.

Battery, Alum.

A battery using as excitant a solution of alum. This battery has had

some application for electric clocks, but only to a limited extent.

Fig. 38. BALLOON OR FLASK BATTERY.

Battery, Aluminum.

A battery in which aluminum is the negative plate and aluminum sulphate

the excitant. It is mounted like the gravity battery. Its electro-motive

force is 0.2 volt.

59  STANDARD ELECTRICAL DICTIONARY.

Battery, Bagration.

A battery with zinc and carbon electrodes immersed in earth sprinkled

with sal ammoniac (ammonium chloride). The copper is preferably first

immersed in sal ammoniac solution and dried, until a green layer is

formed on its surface.

The battery is highly praised for its constancy by De la Rive, but may

be regarded as obsolete.

Battery, Balloon.

A form of gravity battery into whose centre a globular flask, B, is

inverted, which is filled before inversion with copper sulphate, of

which 2 lbs. are used, and water, so as to remain full. This acts as a

reservoir of copper sulphate, which it constantly supplies. The glass

jar is closed with a perforated wooden cover.

Battery, Banked.

(a) A battery arranged to feed a number of separate circuits.

(b) A battery connected in parallel or in multiple arc.

Battery, Bichromate.

A battery with amalgamated zinc and carbon plates, with an exciting

fluid composed of sulphuric acid, water, and potassium bichromate. For

formula of such solutions see Electropoion Fluid--Kookogey's

Solution--Poggendorff's Solution--Trouvé's Solution--Delaurier's

Solution, and others. (See Index.)

Battery, Bunsen.

A two fluid porous cell battery. The negative plate is carbon, the

positive plate, amalgamated zinc. The depolarizer is nitric acid or

electropoion fluid, q.v., in which the carbon is immersed. The last

named depolarizer or some equivalent chromic acid depolarizing mixture

is now universally used.  The excitant is a dilute solution of sulphuric

acid. Originally the carbon was made cylindrical in shape and surrounded

the porous cups, in which the zinc was placed. This disposition is now

generally reversed. The electro-motive force is 1.9 volts. The

depolarizing solution is placed in the compartment with the carbon. The

excitant surrounds the zinc.

Fig. 39. BUNSEN'S BATTERY.

60   STANDARD ELECTRICAL DICTIONARY.

Battery, Cadmium.

A battery in which cadmium is the negative plate, sulphate of cadmium

solution the excitant and depolarizer, and zinc the positive plate.

Electro-motive force, .31 volt or about one third of a Daniell cell. It

is mounted like a gravity battery.

Battery, Callan.

A modification of Grove's battery. Platinized lead is used for the

negative plate, and as a depolarizer a mixture of 4 parts concentrated

sulphuric acid, 2 parts of nitric acid, and 2 parts of a saturated

solution of potassium nitrate. (See Battery, Grove's.)

Battery, Camacho's.

A battery with carbon negative and amalgamated zinc positive electrodes.

The carbon is contained in a porous cup, packed with loose carbon.

Electropoion or other fluid of that type serves as excitant and

depolarizer, and is delivered as shown from cell to cell by syphons.

Fig. 40. CAMACHO'S BATTERY.

Battery, Carré's.

A Daniell battery for whose porous cup a vessel or species of sack made

of parchment paper is substituted. The battery has been used for

electric light, and has been run for 200 successive hours, by replacing

every 24 hours part of the zinc sulphate solution by water.

61  STANDARD ELECTRICAL DICTIONARY.

Battery, Cautery.

A battery used for heating a platinum wire or other conductor used for

cauterization in electro-therapeutics. The term is descriptive, not

generic.

Battery, Chloric Acid.

A battery of the Bunsen type in which an acidulated solution of

potassium chlorate is used as depolarizer.

Battery, Chloride of Lime.

A battery in which bleaching powder is the excitant. The zinc electrode

is immersed in a strong solution of salt, the carbon in a porous vessel

is surrounded with fragments of carbon and is packed with chloride of

lime (bleaching powder). There is no action on open circuit. It has to

be hermetically sealed on account of the odor. Its electro-motive force

is--initial, 1.65 volts; regular, 1.5 volts.

Synonym--Niaudet's Battery.

Battery, Chromic Acid.

Properly a battery in which chromic acid is used as a depolarizer. It

includes the bichromate battery. (See Battery, Bichromate.)

Battery, Closed Circuit.

A battery adapted by its construction to maintain a current on a closed

circuit for a long time without sensible polarization. The term is

merely one of degree, for any battery becomes exhausted sooner or later.

As examples the Grove, Bunsen or Daniell batteries may be cited.

62   STANDARD ELECTRICAL DICTIONARY.

Fig. 41. COLUMN BATTERY.

Battery, Column.

The original Volta's pile. It consists of a series of compound circular

plates, the upper or lower half, A, copper; the other, Z, of zinc.

Between each pair of plates some flannel or cloth, u, u, is laid, which

is saturated with dilute acid. As shown in the cut, the parts are laid

up in two piles, connected at the top with a bar, c, c, and with vessels

of acidulated water, b, b, as electrodes. The great point in setting it

up is to be sure that no acid runs from one disc of flannel to the next

over the outside of the plates, as this would create a short circuit.

The plates are best compound, being made up of a zinc and a copper plate

soldered together. They may, however, be separate, and merely laid one

on the other. In such case great care must be taken to admit no acid

between them.

Volta's pile is no longer used, except occasionally. Trouvé's blotting

paper battery (see Battery, Trouvé's) is a relic of it, and the same is

to be said for Zamboni's dry pile.

It rapidly polarizes, the flannel retains but little acid, so that it is

soon spent, and it is very troublesome to set up. Great care must be

taken to have the cloth discs thoroughly saturated, and wrung out to

avoid short circuiting by squeezing out of the acid.

Battery, D'Arsonval's.

A battery of the Bunsen type, differing therefrom in the solutions. As

excitant in which the zinc electrode is immersed, the following solution

is used:

Water, 20 volumes;

Sulphuric Acid (purified by shaking with a little olive or similar oil),

1 volume;

hydrochloric acid, 1 volume.

As polarizer in which the carbon is immersed the following is used:

Nitric acid, 1 volume;

hydrochloric acid, 1 volume;

water acidulated with 1/20th sulphuric acid, 2 volumes.

Battery, de la Rue.

A battery with zinc positive and silver negative electrode; the

depolarizer is silver chloride; the excitant common salt or ammonium

chloride. The cut shows one of its forms of construction.

The right hand portion of the cut, Fig. 42, shows the zinc perforated at

C for the connection from the next silver plate. The next to it is the

negative electrode of silver around which a mass of silver chloride is

cast in cylindrical form. A is a parchment paper cylinder with two holes

near its top, through which the silver wire of the negative electrode is

threaded, as shown in B. A solution of 23 parts ammonium chloride in

1,000 parts of water is the approved excitant. Its electro-motive force

is 1.03 volts.

The jars are closed with paraffin.

Fig. 42. DE LA RUE'S BATTERY.

63   STANDARD ELECTRICAL DICTIONARY.

Battery, Dry.

(a) A form of open circuit battery in which the solutions by a mass of

zinc oxychloride, gypsum, or by a gelatinous mass such as gelatinous

silica, or glue jelly, are made practically solid. Numbers of such have

been patented, and have met with considerable success.

(b) Zamboni's dry pile, q. v., is sometimes termed a dry battery.

Battery, Element of.

A term applied sometimes to a single plate, sometimes to the pair of

plates, positive and negative, of the single couple.

Battery, Faradic.

A term applied, not very correctly however, to apparatus for producing

medical faradic currents. It may be an induction coil with battery, or a

magneto-generator worked by hand.

Battery, Ferric Chloride.

A battery of the Bunsen type, in which a solution of perchloride of iron

(ferric chloride) is used for the depolarizing agent. A little bromine

is added with advantage. The depolarizing agent recuperates on standing,

by oxidation from the oxygen of the air.

Battery, Fuller's.

A battery of the Bunsen type. The zinc plate is short and conical, and

rests in the porous jar into which some mercury is poured. An insulated

copper wire connects with the zinc. A plate of carbon is in the outer

jar. The solutions are used as in the Bunsen battery.

Synonym--Mercury Bichromate Battery.

Battery, Gas.

(a) A battery whose action depends on the oxidation of hydrogen as its

generating factor. It was invented by Grove. Plates of platinum are

immersed in cups of dilute acid, arranged as if they were plates of zinc

and carbon, in an ordinary battery. Each plate is surrounded by a glass

tube sealed at the top. The plates are filled with acid to the tops.

Through the top the connection is made. A current from another battery

is then passed through it, decomposing the water and surrounding the

upper part of one set of plates with an atmosphere of oxygen and of the

other with hydrogen. Considerable quantities of these gasses are also

occluded by the plates. On now connecting the terminals of the battery,

it gives a current in the reverse direction of that of the charging

current.

This battery, which is experimental only, is interesting as being the

first of the storage batteries.

(b) Upward's Chlorine Battery and any battery of that type (see Battery,

Upward's,) is sometimes termed a gas battery.

64   STANDARD ELECTRICAL DICTIONARY.

Battery Gauge.

A pocket or portable galvanometer for use in testing batteries and

connections.

Battery, Gravity.

A battery of the Daniell type, in which the porous cup is suppressed and

the separation of the fluids is secured by their difference in specific

gravity. A great many forms have been devised, varying only in details.

The copper plate, which is sometimes disc shaped, but in any case of

inconsiderable height, rests at the bottom of the jar. Near the top the

zinc plate, also flat or of slight depth, is supported. As exciting

liquid a strong solution of copper sulphate lies at the bottom of the

jar. This is overlaid by a solution of zinc sulphate, or sodium

sulphate, which must be of considerably less specific gravity than that

of the copper sulphate solution. In charging the jar one-tenth of a

saturated solution of zinc sulphate mixed with water is sometimes used

as the upper fluid. This may be first added so as to half fill the jar.

The strong solution of copper sulphate may then be added with a syphon

or syringe underneath the other so as to raise it up. From time to time

copper sulphate in crystals are dropped into the jar. They sink to the

bottom and maintain the copper sulphate solution in a state of

saturation.

Fig. 43. GRAVITY BATTERY OF THE TROUVÉ-CALLAUD TYPE.

If the battery is left on open circuit the liquids diffuse, and metallic

copper precipitates upon the zincs. This impairs its efficiency and

creates local action. As long as the battery is kept at work on closed

circuit work but little deposition, comparatively speaking, occurs.

From time to time, in any case, the zinc plates are removed and scraped,

so as to remove the copper which inevitably forms on their surface. Care

must be taken that the zinc sulphate solution, which is constantly

increasing in strength, does not get so strong as to become of as high

specific gravity as the copper sulphate solution. From time to time some

of the upper solution is therefore removed with a syphon or syringe and

replaced with water. An areometer is useful in running this battery.

65  STANDARD ELECTRICAL DICTIONARY.

Battery, Grenet.

A plunge battery with zinc positive and carbon negative electrodes.

Electropoion or other chromic acid or bichromate solution is used as

depolarizer and excitant. The zinc plate alone is plunged into and

withdrawn from the solution.

Fig. 44. GRENET'S BATTERY.

Fig. 45. GROVE'S BATTERY.

Battery, Grove's.

A two fluid galvanic battery. A porous cup has within it a riband of

platinum, which is the negative plate; amalgamated zinc in the outer jar

is the positive plate. Dilute sulphuric acid (10 per cent. solution) is

placed in the outer jar, and strong nitric acid (40° B.) as a

depolarizer in the porous cups. Its E. M. F. is 1.96 volts.

It is objectionable, as it gives off corrosive nitrous fumes. These are

produced by the oxidation of the nascent hydrogen by the nitric acid, by

the following reaction:

3 H + H N O3 = 2 H2 O + N O. There are other reactions, one of which

results in the formation of ammonia by the reduction of the nitric acid

radical by the hydrogen. Ammonium can be detected in the spent liquids.

66   STANDARD ELECTRICAL DICTIONARY.

Battery, Hydrochloric Acid.

A battery in which hydrochloric acid is used as the excitant. Many

attempts have been made to use this acid in batteries, but the volatile

nature of the acid causes the production of so much odor with corrosive

fumes that it has never come into use.

Battery, Lead Chloride.

A battery of the lead sulphate type in which lead chloride is the

depolarizer. It has had no extended use.

Battery, Lead Sulphate.

A battery similar to Marié Davy's battery or the gravity battery, but

using lead sulphate as depolarizer and excitant. Lead, copper or tin is

the material of the negative plate. Becquerel used the lead sulphate as

a solid cylindrical mass surrounding a lead rod 1/5 to 1/4 inch in

diameter. One part of common salt may be mixed with 5 parts of the lead

sulphate. The electro-motive force is about 0.5 volt. The resistance is

very high.

Battery, Leclanché.

An open circuit battery with porous cup. In the outer jar is a zinc rod;

a carbon plate is placed in the porous cup. The latter is packed with a

mixture of clean powdered manganese binoxide as depolarizer, and

graphite in equal volumes. A strong solution of ammonium chloride (sal

ammoniac) is placed in the outer jar. It is only used on open circuit

work. Its electromotive force is 1.48 volts, when not polarized.

The reaction is supposed to be about the following:

2 N H4 Cl + 2 Mn O2 + Zn = Zn Cl2 + 2 N H3 + H2 0 + M2 O3

The battery rapidly weakens on open circuit, but quickly recuperates.

There is another form of this battery, termed the agglomerate battery.

(See Battery, Leclanché Agglomerate.)

Fig. 46. LECLANCHÉ BATTERY.

Battery, Leclanché Agglomerate.

A form of the Leclanché in which the porous jar is suppressed. Cakes

made of a mixture of carbon, 52 parts; manganese binoxide, 40 parts; gum

lac, 5 parts; potassium bisulphate, 3 parts, compressed at 300

atmospheres, at a temperature of 100° C. (212° F.), are fastened by

India rubber bands or otherwise against the carbon plate. These

constitute the depolarizer. Various shapes are given the carbon and

depolarizing agglomerates.

Battery, Local.

A battery supplying a local circuit (see Circuit. Local). The current is

governed by the relay situated on the main line and operated by its

current.

Battery, Main.

The battery used in operating the main line. It is usually applied to

telegraphy. Its function is then to supply current for working relays,

which in turn actuate the local circuits.

Main and local circuits and batteries are also used in the automatic

block system of railroad signalling.

67  STANDARD ELECTRICAL DICTIONARY.

Battery, Marié Davy's.

A two fluid porous cup battery with carbon negative plate, zinc positive

plate, and mercury sulphate, a nearly insoluble salt, as depolarizer and

excitant. Mercurous or mercuric sulphates have been used in it. Its

electromotive force is 1.5 volts. The local action and waste, owing to

the slight solubility of the mercury compounds, is very slight. If used

on close circuit it becomes polarized. It is also subject under extreme

circumstances to reversal of polarity, zinc becoming deposited upon the

carbon, and there forming a positive electrode.

In using the cells in series the level of liquid in all must be the

same, otherwise the cell in which it is lowest will become polarized and

exhausted.

Modifications of this battery on the lines of the gravity battery have

been constructed.

Synonym--Sulphate of Mercury Battery.

Battery, Maynooth's.

A battery of the Bunsen type, with cast iron negative plate. The iron

takes the passive form and is not attacked.

Battery, Medical.

A term applied very indiscriminately to medical current generators, and

to medical induction coils, or to any source of electricity, static or

current, for medical application.

68   STANDARD ELECTRICAL DICTIONARY.

Battery, Meidinger's.

A variety of Daniell cell of the gravity type. The plates are

cylindrical. The zinc plate lies against the upper walls of the vessel.

The copper plate of smaller diameter rests on the bottom. A large tube,

with an aperture in its bottom, is supported in the centre and is

charged with copper sulphate crystals. The cup is filled with a dilute

solution of Epsom salts (magnesium sulphate) or with dilute sulphuric

acid.

Battery Mud.

A deposit of mud-like character which forms in gravity batteries and

which consists of metallic copper precipitated by the zinc. It indicates

wasteful action.

Battery, Multiple-connected.

A battery connected in parallel, all the positive plates being connected

to one electrode, and all the negative to another.

Battery, Nitric Acid.

A battery in which nitric acid is used as the excitant. Owing to its

cost and volatility this acid has been but little used in batteries,

other than as a depolarizer. In Grove's battery (see Battery, Grove's)

it has been thus used.

Battery of Dynamos.

A number of dynamos may be arranged to supply the same circuit. They are

then sometimes termed as above, a Dynamo Battery. They may be arranged

in series or in parallel or otherwise combined.

Battery of Leyden Jars.

To produce the quantity effect of a single large Leyden jar with a

number of small ones they are often connected in parallel and termed a

battery. In such case the inner coatings are all connected by regular

bar conductors, and the outside coatings are also all in connection.

They are conveniently placed in a box or deep tray whose inner surface

is lined with tinfoil, with an outside connection for grounding, etc.

The cascade, q. v., arrangement is not so generally termed a battery.

Battery, Open Circuit.

A battery adapted for use in open circuit work. Its main requirement is

that it shall not run down, or exhaust itself when left on open circuit.

The Leclanché battery is very extensively used for this work. Its action

is typical of that of most open circuit batteries. It is without any

action on open circuit. It is very quickly exhausted on closed circuit,

but recuperates or depolarizes quite soon when on open circuit. It is

always in condition for a momentary connection, but useless for steady

work.

Battery, Oxide of Copper.

A battery with zinc positive and iron negative electrodes. The excitant

is a 30 or 40 per cent. solution of sodium or potassium hydrate (caustic

soda or caustic potash). The depolarizer is copper oxide. In action the

copper is gradually reduced to the metallic state. The iron element is

often the containing vessel. The battery is practically inactive on open

circuit.

Its electro-motive force varies from .75 to .90 volt. To prevent the

formation of sodium or potassium carbonate the cell should be closed, or

else the liquid should be covered with mineral oil.

Synonyms--Lalande & Chaperon Battery--Lalande-Edison Battery.

69  STANDARD ELECTRICAL DICTIONARY.

Battery, Peroxide of Lead.

A battery in which peroxide of lead (lead binoxide) is the depolarizer.

It is a sort of predecessor of the present secondary battery.

Battery, Platinized Carbon.

A modification of Smee's battery, in which platinized carbon is used for

the negative plates. Before polarization the E. M. F. is equal to that

of Smee's battery. Polarization reduces its electro-motive force

one-half.

Battery, Plunge.

A battery whose plates are mounted so as to be immersed in the battery

cups or cells, when the battery is to be used, and withdrawn and

supported out of the cups when not in use. The object is to prevent

wasting of the plates by standing in the solution. It is a construction

generally used with sulphuric acid--chromic acid solution and

amalgamated zinc and carbon plates.

Battery, Pneumatic.

A battery arranged to have air blown through the solution to assist

diffusion and depolarization. It is a construction applied to chromic

acid or bichromate batteries.

Battery, Primary.

A battery in which the current is supplied by the solution of one of the

plates by the solution. The term distinguishes it from a secondary or

storage battery.

Battery, Pulvermacher's Electro-Medical.

In this battery, the electrodes were zinc and copper wires wound upon

small pieces of wood. Dilute vinegar was used as the excitant, because

it could be found in every household. Formerly the battery had great

success. It is now little used.

Battery, Sal Ammoniac.

Batteries in which a solution of ammonium chloride is the excitant; they

are very extensively used on open circuit work. (See Battery,

Leclanché.)

The crystals formed in these batteries have been analyzed and found to

consist of ammonium zinc chloride, 3 Zn Cl2, 8 N H3, 4 H20.

Battery, Salt, or Sea Salt.

Batteries in which a solution of sodium chloride or common salt is the

excitant, have been largely used, especially for telegraphic purposes.

The Swiss telegraphs use a carbon-zinc combination with salt and water

as the excitant. The batteries are sometimes mounted as plunge

batteries. They are exhausted by short circuiting after some hours, but

recuperate on standing. The zinc is not amalgamated.

70   STANDARD ELECTRICAL DICTIONARY.

Battery, Sand.

A battery whose cells are charged with sand saturated with dilute acid.

It prevents spilling of acid. It is now practically obsolete.

Fig. 47. SECONDARY BATTERY.

Battery, Secondary.

A voltaic battery whose positive and negative electrodes are formed or

deposited by a current from a separate source of electricity by

electrolysis. On disconnection the battery is ready to yield a current,

in the reverse direction of that of the charging current. The usual type

has lead plates on one of which lead binoxide and on the other of which

spongy lead is formed. The lead binoxide seems to be the negative

element, and it also acts as the depolarizer. The spongy lead is the

positive electrode. The solution is dilute sulphuric acid of specific

gravity 1.17. The action consists first in the oxidation of the spongy

lead. The hydrogen set free by the reaction, and which by electrolytic

transfer goes to the other plate, reduces the lead binoxide to

protoxide. The sulphuric acid then attacks the oxides and converts the

oxides into sulphates.

The charging process consists in sending a current in the reverse

direction through the battery. If there are several cells they are

arranged in series, so that each one receives the same intensity of

current. An electrolytic decomposition takes place, the lead sulphate on

one plate is reduced to metallic lead, and that on the other plate is

oxidized to lead binoxide. It is then ready for use.

71  STANDARD ELECTRICAL DICTIONARY.

The plates in a lead plate battery are of very large area per cell, and

are placed close together. Sometimes, as in Planté's battery, large flat

plates are laid together with a separating insulator between them, and

are then rolled into a spiral. Sometimes, the most usual arrangement,

the plates are in sets, the positive and negative ones alternating, and

each cell containing a number of plates.

To secure a good quantity of active material, the plates are sometimes

perforated, and the perforations are filled with oxide of lead. This

gives a good depth of material for the charging current to act on, and

avoids the necessity for a tedious "forming," q. v.

The electro-motive force of such a battery per cell is 2 volts. Its

resistance may only be one or two-hundredths of an ohm. An intense

current of many amperes can be supplied by it, but to avoid injuring the

cell a current far less than the maximum is taken from it.

To charge it, a slightly greater electro-motive force, the excess being

termed spurious voltage, is required.

Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY.

72   STANDARD ELECTRICAL DICTIONARY.

Battery, Secondary, Plante's.

Plante's secondary battery is one of the earlier forms of storage

battery, but has had much success. Two lead plates, large in area and

close together but not touching, are "formed," by exposure to an

electrolyzing current of electricity in one direction, while they are

immersed in dilute sulphuric acid. This converts the surface of one

plate into binoxide. The cell is then allowed to discharge itself almost

completely, when the charging current is again turned on. This process

is repeated over and over again, until the surfaces of the plates are

considerably attacked, one plate, however, being maintained in a state

of oxidation. After a few days of this operation a period of rest is

allowed between the reversals, which sets up a local action on the

oxidized plate, between the metallic lead of the plate, and its coating

of binoxide. This causes the lead to be attacked, under the influence of

the local couple, and sulphate of lead is formed, which, ultimately, by

the charging current is converted into peroxide. These operations

produce an exceedingly good battery. The process described is termed

forming.

The plates separated by strips of insulating material are generally

wound into a double spiral.

Battery, Siemens' and Halske's.

A Daniell battery of peculiar shape. The copper, C, is at the bottom of

the glass jar, A. The inner jar, K, has the form of a bell, and supports

a mass of paper pulp, which is dampened with sulphuric acid. The zinc,

Z, rests on top of the mass of pulp. The battery is very durable, but of

high resistance.

Battery, Sir William Thomson's.

A form of Daniell battery, of the gravity type. The receptacles are

shallow wooden trays lined with lead. A thin plate of copper rests on

the bottom. The zinc plate is of gridiron shape, and rests on wooden

blocks which support it in a horizontal position above the copper. One

tray is placed on top of the other, the upper tray resting on the

corners of the zinc plate which rise above the level of the top of the

flat vessel. Thus connection is assured without wires or binding posts.

It is charged like a gravity battery. The density of the zinc sulphate

solution should be between 1.10 and 1.30. The circuit must be kept

closed to prevent deposition of metallic copper on the zinc. The entire

disposition of the battery is designed to reduce resistance.

Battery, Skrivanow.

A pocket battery of the De la Rue type, with a solution of 75 parts

caustic potash in 100 parts of water as the excitant. The silver

chloride is contained in a parchment paper receptacle. Its

electro-motive force is 1.45 to 1.5 volts.

Battery, Smee's.

A single fluid combination, with zinc positive plate, and a plate of

silver, coated with platinum black, for the negative plate. The finely

divided platinum affords a surface from which the hydrogen bubbles

instantly detach themselves, thus preventing polarization. The liquid is

a mixture of one part sulphuric acid to seven parts of water. For the

negative plate silver-plated copper, coated with platinum black, is

used. Electromotive force, .47 volt.

Fig. 49. SMEE'S BATTERY.

73  STANDARD ELECTRICAL DICTIONARY.

Fig. 50. SPIRAL BATTERY, OR HARE'S DEFLAGRATOR.

Battery, Spiral.

A battery whose plates of thin zinc and copper are wound into a spiral

so as to be very close, but not touching. Dilute sulphuric acid is the

excitant. It is now practically obsolete.

Synonyms--Calorimeter--Hare's Deflagrator.

Battery, Split.

A battery of a number of voltaic cells, connected in series, with their

central portion grounded or connected to earth. This gives the ends of

opposite potentials from the earth, and of difference therefrom equal to

the product of one-half of the number of cells employed, multiplied by

their individual voltage.

Battery Solutions, Chromic Acid.

A number of formulae have been proposed for these solutions. (See

Electropoion Fluid--Kookogey's Solution--Poggendorff's Solution--

Trouvé's Solution--Delaurier's Solution--Chutaux's Solution--Dronier's

Salt--Tissandier's Solution.)

Battery, Trough.

A battery whose elements are contained in a trough, which is divided by

cross-partitions so as to represent cups. A favorite wood for the trough

is teak, which is divided by glass or slate partitions. Marine glue or

other form of cement is used to make the joints tight. For porous cup

divisions plates of porous porcelain or pottery are placed across,

alternating with the impervious slate partitions.

Battery, Trouvé's Blotting Paper.

A battery of the Daniell type in which the solutions are retained by

blotting paper. A considerable thickness of blotting paper lies between

the two plates. The upper half of the thickness of the blotting paper is

saturated with a solution of zinc sulphate, on which the zinc plate

rests.

The lower half of the paper is saturated with copper sulphate solution,

and this rests upon the copper plate.

Fig. 51. TROUVÉ'S BLOTTING PAPER BATTERY.

74   STANDARD ELECTRICAL DICTIONARY.

Battery, Tyer's.

A modification, as regards the positive element, of Smee's battery, q.

v. The bottom of the battery jar contains a quantity of mercury in which

pieces of zinc are thrown, and this constitutes the positive element.

A ball of zinc at the end of an insulated copper wire affords the

connection with the zinc and mercury. Its great advantage is that the

smallest scraps of zinc can be used in it, by being dropped into the

mercury. The negative plate is platinized silver; the exciting liquid,

dilute sulphuric acid.

Fig. 52. TYER'S BATTERY.

75  STANDARD ELECTRICAL DICTIONARY.

Fig. 53. SECTION OF UPWARD'S BATTERY.

Fig. 54. ELEVATION OF UPWARD'S BATTERY.

Battery, Upward's.

A primary voltaic cell, the invention of A. Renée Upward. Referring to

the cuts, the positive plate. Z, is of cast zinc; it is immersed in

water, in a porous cup, B. Outside of the porous cup and contained in

the battery jar are two carbon plates, C, C, connected together. The

rest of the space between the porous cup and battery jar is packed with

crushed carbon, and the top is cemented. Chlorine gas is led by a pipe,

D, into the outer cell. It diffuses through the fine carbon, dissolves

in the water, and so finds its way to the zinc, which it attacks,

directly combining therewith, and forming zinc chloride (Zn + 2 Cl = Zn

Cl 2). Such of the chlorine as is not absorbed finds its way by an outlet

tube, E, to the next cell. Arrangements are provided for generating

chlorine gas as required. The high specific gravity of the gas is

utilized in regulating its distribution through the cells. The

electro-motive force of the cell is 2.1 volts. A cell 11.5 by 5.5 inches

and 12.5 inches deep has a resistance of 0.2 ohm.

An overflow pipe, F, with faucet, T, is supplied to withdraw the

solution of zinc chloride as it accumulates.

76   STANDARD ELECTRICAL DICTIONARY.

Battery, Varley's.

A Daniell battery of the Siemens' and Halske's type (see Battery,

Siemens' and Halske's), in which zinc oxide is substituted for the paper

pulp of the other battery. It has been very little used.

Battery, Volta's.

The original acid battery. It has a negative electrode of copper, a

positive electrode of zinc; the excitant is sulphuric acid diluted with

sixteen times its volume of water. It rapidly polarizes, and is very

little used.

Battery, Voltaic or Galvanic.

An apparatus for converting chemical energy directly into electric

energy. This is as broad a definition as can well be given. The general

conception of a battery includes the action of electrolysis, a solution

in the battery acting upon one of two conducting electrodes immersed in

such fluid, which dissolves one of them only, or one more than the

other. The best way to obtain a fundamental idea of a battery is to

start with the simplest. Dilute sulphuric acid dissolves neither pure

zinc nor copper. But it has a far stronger affinity for the first named

metal. If now we immerse in dilute acid two plates, one of pure zinc,

and one of copper, no action will be discernible. But if the plates are

brought in contact with each other a stream of bubbles of hydrogen gas

will escape from the surface of the copper and the zinc will dissolve.

By applying proper tests and deductions it will be found that the copper

and zinc are being constantly charged with opposite electricities, and

that these are constantly recombining. This recombination produces what

is known as an electric current.

To constitute a battery the zinc and copper plates must be connected

outside of the solution. This connection need not be immediate. Any

conductor which touches both plates will bring about the action, and the

current will pass through it.

The easiest way to picture the action of a battery is to accept the

doctrine of contact action. In the battery the molecules of water are

pulled apart. The hydrogen molecules go to the copper, the oxygen

molecules go to the zinc, each one, leaving its contact with the other,

comes off charged with opposite electricity. This charges the plates,

and the continuous supply of charge and its continuous discharge

establishes the current.

The accumulation of hydrogen acts to stop the action by polarization.

Its own affinity for oxygen acts against or in opposition to the

affinity of the zinc for the same element, and so cuts down the action.

A depolarizer of some kind is used in acid batteries for this reason. As

such depolarizer has only to act upon one plate, in most batteries it is

usual to surround such plate only, as far as it is possible, with the

depolarizer. The solution which dissolves the zinc is termed the

excitant or exciting solution.

To this concrete notion of a voltaic battery the different modifications

described here may be referred. Zinc, it will be seen, forms the almost

universally used dissolved plate; carbon or copper forms the most usual

undissolved plate; sulphuric acid in one form or another is the most

usual excitant.

The solution in a voltaic battery is electrolyzed (see Electrolysis).

Hence the solutions must be electrolytes. The sulphuric acid and other

ingredients play a secondary role as imparting to the battery fluids

this characteristic.

It is not necessary to have electrodes of different substances, the same

metal maybe used for both if they are immersed in different solutions

which act differentially upon them, or which act with more energy on one

than on the other. Such are only of theoretical interest.

77  STANDARD ELECTRICAL DICTIONARY.

Battery, Water.

A voltaic battery, whose exciting fluid is water. They are used for

charging quadrant electrometer needles and similar purposes. They

polarize very quickly and are of high resistance. Hence very small

plates in large number can be used without impairing their advantage.

Rowland's water battery dispenses with cups and uses capillarity

instead. The zinc and platinum or copper plates of a couple are placed

very close together, while the couples are more distant. On dipping into

water each couple picks up and retains by capillarity a little water

between its plates, which forms the exciting fluid. Many hundred couples

can be mounted on a board, and the whole is charged by dipping into

water and at once removing therefrom. It then develops its full

potential difference.

Fig. 55. SECTION OF WOLLASTON BATTERY.

Fig. 56. PLATES OF WOLLASTON'S BATTERY.

78   STANDARD ELECTRICAL DICTIONARY.

Battery, Wollaston.

The original plunge battery is attributed to Wollaston. He also invented

the battery known by his name, having the disposition shown in the cut,

of zinc Z, surrounded by a thin sheet of copper C; o, o', o", are the

terminals and B, B, the battery jars. Dilute sulphuric acid is used for

exciting fluid.

B. A. U.

Abbreviation for British Association unit, referring generally to the B.

A. unit of resistance.

B. A. Unit of Resistance.

The original ohm used under that name previous to 1884. The Paris

committee of that year recommended as a practical unit what is known as

the legal ohm. (See Ohm, Legal.)

1  Legal Ohm                 =  1.0112      B. A. Units of Resistance.

1  B. A. Unit of Resistance  =   .9889      Legal Ohms.

1  B. A. Unit of Resistance  =   .98651E9   C. G. S. units.

B. E. adj.

British Engineering, a qualification of a set of units, the B. E. units,

having for base the foot and pound. The term is but little used.

Beaumé Hydrometer.

A hydrometer graduated on the following principle:

The zero point corresponds to the specific gravity of water for liquids

heavier than water. A solution of 15 parts of salt in 85 parts of water

corresponds in specific gravity to 15° B., and between that and zero

fifteen equal degrees are laid out. The degrees are carried down below

this point.

The zero points for liquids lighter than water correspond to the

specific gravity of a solution of 10 parts of salt in 90 parts of water.

The specific gravity of water is taken as 10° B. This gives ten degrees

which are continued up the scale.

Becquerel's Laws of Thermoelectricity.

These are stated under the heads, Law of Intermediate Metals and Law of

Successive Temperatures, q. v.

Bed Piece.

In a dynamo or motor the frame carrying it, including often the

standards in which the armature shaft is journaled, and often the yoke

or even entire field magnet core.

Bell, Automatic Electric.

A bell which rings as long as the circuit is closed, having a circuit

breaker operated by its own motion. (See Bell, Electric.)

Synonyms--Trembling Bell--Vibrating Bell.

Bell, Call.

A bell operated by electricity, designed to call attention, as to a

telephone or telegraphic receiver. (See Bell, Electric.)

79  STANDARD ELECTRICAL DICTIONARY.

Bell Call.

A calling device for attracting the attention of any one, consisting of

some type of electric bell.

Bell, Circular.

A gong-shaped bell, whose clapper and general mechanism is within its

cavity or behind it.

Bell, Differentially Wound.

An electric bell, whose magnet is wound differentially so as to prevent

sparking.

Fig. 57. AUTOMATIC ELECTRIC BELL.

Bell, Electric.

A bell rung by electricity. Generally it is worked by a current exciting

an electro-magnet, attracting or releasing an armature which is attached

to the vibrating or pivoted tongue of the bell. It may be worked by a

distant switch or press-button, q. v., ringing once for each movement of

the distant switch, etc., or it may be of the vibrating bell type as

shown in the cut. When the current is turned on in this case it attracts

the armature. As this moves towards the poles of the magnet it breaks

the circuit by drawing the contact spring, q. v., away from the contact

point, q. v. This opens the circuit, to whose continuity the contact of

these two parts is essential. The hammer, however, by its momentum

strikes the bell and at once springs back. This again makes the contact

and the hammer is reattracted. This action continues as long as the

circuit is closed at any distant point to which it may be carried. The

ordinary vibrating bell is a typical automatic circuit breaker, q. v.,

this type keeping up the ringing as long as the circuit is closed. Other

bells have no electric contact and simply ring once every time the

circuit is closed. Others worked by an alternating current ring once for

each change of direction of current.

80   STANDARD ELECTRICAL DICTIONARY.

Bell, Electro-mechanical.

A bell which has its striking train operated by a spring or descending

weight, and which train is thrown into action by the release of a detent

or equivalent action by the closing of an electric circuit. It rings for

any given time after being started.

Bell, Indicating.

A bell which by drop-shutter or other indicator connected in circuit

with it, indicates its number or other designation of its call.

Bell, Magneto.

An electric bell operated by the alternating current from a magneto

generator. It has a polarized armature and no circuit breaker. The

armature is attracted first in one direction and then in the other, as

the current alternates and reverses the polarity of the electro-magnet.

Bell, Relay.

A bell operated by a relay circuit.

Bias.

In polarized relay the adjustment of the tongue to lie normally against

one or the other contact. (See Relay, Polarized.)

81   STANDARD ELECTRICAL DICTIONARY.

Fig. 58. RESISTANCE COILS SHOWING BIFILAR WINDING.

Bifilar Winding.

The method followed in winding resistance coils to prevent them from

creating fields of force. The wire is doubled, and the doubled wire

starting with the bend or bight is wound into a coil. The current going

in opposite senses in the two lays of the winding produces no field of

force.

Binary Compound.

A chemical compound whose molecule contains only two elements, such as

water (H2 0), lead oxide (Pb 0), and many others.

Binding.

In a dynamo or motor armature the wire wound around the coils to secure

them in place and prevent their disturbance by centrifugal action.

Fig. 59. DOUBLE BINDING POST.

Fig. 60. BINDING POST, ENGLISH PATTERN.

FIG. 61. WOOD SCREW BINDING POST.

Binding Posts or Screws.

Arrangements for receiving the loose end of a wire of an electric

circuit, and securing such end by a screw. Several constructions are

used, as shown here. Sometimes the wire is passed through a hole, and a

screw tapped in at right angles to the hole is screwed down upon the

wire. Sometimes the wire is clamped between two shoulders, one on the

screw, the other on the post. The screw is often a flat-headed thumb

screw or has a milled edge. Sometimes the screw has a slot and is turned

by a screw-driver.

Several openings are often provided in the same post for different

wires.

Binnacle.

The case containing a mariner's compass on shipboard. It is enclosed

completely; it has a glass side or window through which the compass can

be seen, and is provided with one or two lamps arranged to light the

card, while showing as little light as possible outside.

82   STANDARD ELECTRICAL DICTIONARY.

Bioscopy, Electric.

The diagnosis of life and death by the action of the animal system when

subjected to an electric current or electrification.

Bismuth.

A metal, one of the elements, atomic weight, 210 ; equivalent, 70;

valency, 3; specific gravity, 9.9. It is a conductor of electricity.

Relative Resistance, compressed, (silver = 1)   87.23

Specific Resistance,   131.2 microhms

Resistance of a wire

(a) 1 foot long,  weighing 1 grain,     18.44   ohms

(b) 1 foot long,  1/1000 inch thick,   789.3  "

(c) 1 meter long, weighing 1 gram,      12.88   "

(d) 1 meter long, 1 millimeter thick,    1.670   "

Resistance of a 1-inch cube   51.65   microhms

Electro chemical equivalent,   .7350  (Hydrogen = .0105)

(See Thermo-electric Series.)

Figs. 62, 63. INCANDESCENT WIRE FUSE.  ABEL'S PATENT.

Fig. 64.  VON EBNER'S FRICTIONAL ELECTRIC MACHINE FOR

EXPLODING ELECTRIC FUSES OR DETONATORS.

Bi-telephone.

A pair of telephones arranged with a curved connecting arm or spring, so

that they can be simultaneously applied to both ears. They are

self-retaining, staying in position without the use of the hands.

83  STANDARD ELECTRICAL DICTIONARY.

Blasting, Electric.

The ignition of blasting charges of powder or high explosives by the

electric spark, or by the ignition to incandescence (red or white heat)

of a thin wire immersed in or surrounded by powder. Special influence or

frictional electric machines or induction coils are used to produce

sparks, if that method of ignition is employed. For the incandescent

wire a hand magneto is very generally employed. (See Fuse, Electric.)

The cuts, Figs. 62 and 63, show one form of incandescent wire fuse. The

large wires are secured to the capsule, so that no strand can come upon

the small wire within the cavity.

The cut, Fig. 64, shows a frictional electric machine for igniting spark

fuses.

Bleaching, Electric.

Bleaching by agents produced or made available by the direct action of

electricity. Thus if a current under proper conditions is sent through a

solution of common salt (sodium chloride), the electrodes being close

together, the salt is decomposed, chlorine going to one pole and sodium

hydrate to the other. The two substances react upon each other and

combine, forming sodium hypochlorite, which bleaches the tissue immersed

in its solution.

Block System.

A system of signalling on railroads. The essence of the system consists

in having signal posts or stations all along the road at distances

depending on the traffic. The space between each two signal posts is

termed a block. From the signal posts the trains in day time are

signalled by wooden arms termed semaphores, and at night by lanterns.

The arms may be moved by hand or by automatic mechanism depending in

part on electricity for carrying out its functions. Thus in the

Westinghouse system the semaphores are moved by pneumatic cylinders and

pistons, whose air valves are opened and shut by the action of solenoid

magnets, q. v. The current of these magnets is short circuited by

passing trains, so as to let the valves close as the train passes the

signal post. The block system causes the semaphore to be set at "danger"

or "caution," as the train enters the next block. Then the following

train is not allowed to enter the block until the safety signal is

shown. The Westinghouse system provides for two semaphores on a post,

one indicating "danger" as long as the train is on the next block; the

other indicating "caution" as long as the train is on the next two

blocks. The rails form part of the circuit, their joints being bridged

by copper wire throughout the block, and being insulated where the

blocks meet.

Block Wire.

In the block system a wire connecting adjacent block-signal towers or

semaphore poles.

Blow-pipe.

A name sometimes given to an electric experiment illustrating the

repulsion of electrified air particles from a point held at high

relative potential. A metallic point, placed on the prime conductor of

an electric friction or influence machine, becomes highly electrified,

and the air becoming excited is repelled and acts upon the candle flame.

If the candle is placed on the conductor and a point held towards it the

repulsion is still away from the point.

84   STANDARD ELECTRICAL DICTIONARY.

Blow-pipe, Electric Arc.

A name sometimes given to devices for using the voltaic arc to produce

local heating effects. The directive action of the magnet may be used to

force out the arc like a blow-pipe flame, or a blast of air may be

directly applied for the same purpose.

Blue-stone.

A trade name for crystallized copper sulphate, used in Daniell's and

gravity batteries.

Boat, Electric.

A boat propelled by electricity. The electricity drives a motor which

actuates a screw propeller. The current is generally supplied by a

storage battery. When used on rivers charging stations are established

at proper places. When the boat is used as a tender or launch for a

steam ship, such as a war-vessel, the battery is charged by a plant on

board the ship. From their noiselessness electric boats are peculiarly

available for nocturnal torpedo operations, and the universal equipment

of modern war-ships with electric lightning and power plants makes their

use possible at all points. This type is often termed an electric

launch, and most or all electric boats fall under this category.

Bobbins.

A spool of wood or other material wound with insulated wire. In a

tangent galvanometer the bobbin becomes a ring, with a channel to

receive the winding. As the ring is not infinitely large compared to the

needle the tangent law is not absolutely fulfilled. It is most

accurately fulfilled (S. P. Thomson) when the depth of the groove or

channel in the radial direction bears to the breadth in the axial

direction the ratio of square root of 3 to the square root of 2 or

approximately 11 : 9

Body Protector.

A metallic short circuit connected with the wrists and lower legs of the

human body, so that if by accident an active circuit is grounded by the

hands and body of the workman wearing it, most of the current will pass

through the wire conductors, thus avoiding the vital organs of the body.

Boiler Feed, Electric.

An apparatus by which an electric current acting on an electro-magnet,

or other equivalent device, opens the water supply when the water level

in a boiler sinks too low, and cuts off the water supply as the water

level rises.

Boiling.

In secondary batteries the escape of hydrogen and oxygen gas when the

battery is charged. The bubbling of the escaping gases produces the

effect of boiling.

85  STANDARD ELECTRICAL DICTIONARY.

Boll.

An absolute, or c. g. s., unit of momentum; a gram moving at the rate of

one centimeter per second; a gram-kine (see Kine); a unit proposed by

the British Association.

Bolometer.

An apparatus for detecting small amounts of radiant energy (radiant

heat, so called). A coil suspended by a fine wire or filament so as to

be free to rotate under the effect of force is made up of two parallel

and equal wires, insulated from each other, but connected so that

parallel currents sent through them go in opposite direction through

each. This coil is hung in a strong electro-magnetic field produced by a

large coil surrounding it. When a current passes through the suspended

coil no effect will follow, because the oppositely wound portions

counteract each other exactly. In the circuit with one half of the

suspended coil is an exceedingly thin strip of platinum wire. The other

half of the coil has no strips. Both halves unite after leaving the

coil. If now the strip of platinum is heated its conductivity is

affected and its half of the coil receives less current than the other

half. This disturbs the balance and the coil swings through a small arc.

This apparatus may be made very sensitive, so that an increase of

temperature of 1/1400º F., 9/70000°C. (1/14000º F.) will be perceptible.

Another construction takes the form of a Wheatstone Bridge, q. v., in

whose arms are introduced resistances consisting of bands of iron, .5

Millimeter wide (.02 inches), .004 millimeter (.00016 inch) thick, and

folded on themselves 14 times so as to make a rectangular grating, 17 x

12 millimeters (.68 x .48 inch). The least difference of heat applied to

the grating affects the galvanometer.

Synonym-Thermic Balance.

Boreal Pole.

The south pointing pole of the magnet. (See Austral Pole.)

Bot.

A colloquial expression for the English Board of Trade unit of

Electrical Supply. It is formed of the initials of the words "Board of

Trade." (See Unit, Board of Trade.)

Box Bridge.

A constriction of Wheatstone's Bridge in which the necessary resistance

coils are contained in a single box with plugs for throwing the coils in

and out of circuit, and connections to bring the coils into the

different arms of the system. The cut shows a box bridge. Connections

for the galvanometer, battery wires, and terminals of the unknown

resistance are provided, by which its resistances and the connections

are brought into the exact relations indicated in the conventional

diagram of Wheatstone's bridge. (See Wheatstone's Bridge.)

Referring to the cut, the battery wire, say from the zinc plate,

connects at A1, thereby reaching A, its true connecting point. To B1 one

end of the galvanometer circuit or lead is attached, thereby reaching B,

its true connecting point. To C are connected the other end from the

galvanometer and one end of the unknown resistance. The other end of the

unknown resistance, and the other end of the battery wire, in this case

from the carbon plate, connect to D. At G is an infinity plug, as it is

called. When out it breaks the circuit.

In use after the connections are made the key is depressed and the

galvanometer observed. The resistance is changed until no action of the

galvanometer is produced by closing the circuit when the ratio of the

resistances of the arms gives the proportion for calculating the unknown

resistances.

Synonym--Commercial Wheatstone Bridge, or commercial form of same.

Fig. 65. TOP OF BOX BRIDGE.

86   STANDARD ELECTRICAL DICTIONARY.

Boxing the Compass.

Naming the thirty-two points of the compass in order, and in sequence to

any point called out at random. There are many exercises in the relative

sailing points and bearings that come under the same head. Thus the

direction of two given points being given by names of the compass

points, it may be required to state the number of points intervening.

Brake, Electro-magnetic.

A brake to stop a wheel from rotating. It comprises a shoe, or sometimes

a ring, which by electro-magnetic attraction is drawn against the

rotating wheel, thus preventing it from turning, or tending to bring it

to rest. (See Electro-magnet, Annular.)

Fig. 66. ELECTRIC BRAKE.

87  STANDARD ELECTRICAL DICTIONARY.

Branch.

A conductor branching from a main line. Sometimes the term is restricted

to a principal conductor, from which current is distributed.

Branch Block.

In electric wiring of buildings, a block of porcelain or other material

with grooves, holes and screws for the connection of branch wires to a

main wire. Its functions are not only to afford a basis for connecting

the wires, but also to contain safety fuses. As when a branch wire is

taken off, fuses have to be put in its line, the branch block carries

these also. One end of each fuse connects with a main wire, the other

end connects with one of the wires of the branch leader or wire.

Porcelain is a favorite material for them, as the fusing or "blowing

out" of the safety fuses cannot set it on fire.

Branch Conductor.

A parallel or shunt conductor.

Brazing, Electric.

Brazing in which the spelter is melted by means of electricity; either

current incandescence or the voltaic arc may be used. It is identical in

general with electric welding. (See Welding, Electric.)

Branding, Electric.

A system of branding in which the heat of electrically ignited or

incandescent conductors is used to produce or burn in the marks upon the

surface. For the alternating current a small transformer is connected to

or forms part of the tool.

88   STANDARD ELECTRICAL DICTIONARY.

Brassing.

The deposition of a coating of brass by electrolysis. The plating bath

contains both copper and zinc. As anode a plate of brass is used. The

operation must be constantly watched. The deposition of both metals goes

on simultaneously, so  that a virtual alloy is deposited. By changing

the depth of immersion of the anode the color of the deposit is varied.

As a formula for a brassing bath the following are typical. They are

expressed in parts by weight.

(a) For iron and steel.

I.

Sodium Bisulphate,                 200

Potassium Cyanide, 70 per cent.,   500

Sodium Carbonate,                1,000

Water,                           8,000

II.

Copper Acetate,                    125

Zinc Chloride,                     100

Water,                           2,000

Add the second solution to the first.

(b) For zinc.

I.

Sodium Bisulphate,                 700

Potassium Cyanide, 70 per cent., 1,000

Water,                          20,000

II.

Copper Acetate,                    350

Zinc Chloride,                     350

Aqua Ammoniae,                     400

Water,                           5,000

Add the second solution to the first.

Use a brass anode; add more zinc to produce a greenish color; more

copper for a red color. A weak current gives a red color; a strong

current lightens the color. The battery power can be altered, a larger

or smaller anode can be used, or a copper or zinc anode can be used to

change the color of the deposit. The bath may vary from 1.036 to 1.100

sp. gr., without harm.

Break.

A point where an electric conductor is cut, broken, or opened by a

switch or other device, or simply by discontinuity of the wires.

Break-down Switch.

A switch used in the three-wire system to provide for the discontinuance

of the running of one of the dynamos.

By connecting the positive and negative bus wires to one terminal of the

active dynamo, and the neutral bus wire to the other terminal, one

dynamo will supply the current and the system operates like a two-wire

system, but can only be used for half its normal capacity.

Breaking Weight.

The weight which, applied in tension, will break a prism or cylinder, as

an electric current conductor.

89  STANDARD ELECTRICAL DICTIONARY.

Breath Figures, Electric.

If a conductor is electrified and placed upon a piece of glass, it will

electrify the glass in contact with it by conduction or discharge. On

removing the conductor the glass remains electrified. The localized

electrification is shown by breathing gently on the glass, when a

species of image of the conductor is produced by the condensed moisture.

A coin is often used for conductor.

Breeze, Electric.

A term in medical electricity, used to designate the silent or brush

discharge of high tension electricity. As an instance of its employment,

the electric head bath (see Bath, Electric Head,) may be cited. The

patient forming one electrode, being insulated and connected to one of

the conductors, the other conductor, on being brought near his person,

discharges into his body.

Bridge.

(a) A special bar of copper connecting the dynamos to the bus wire, q. v.,

in electric lighting or power stations.

(b) Wheatstone's bridge, q. v., and its many modifications, all of which

may be consulted throughout these pages.

British Association Bridge.

The type of Wheatstone bridge used by the committee of the association

in determining the B. A. ohm; the meter bridge, q. v.

Broadside Method.

A method of determining the magnetic moment of a magnet. The magnet, n,

s, under examination is fixed so that it is at right angles to the

magnetic meridian, M, R, which passes through its own center and that of

a compass needle. From the deflection of the latter the moment is

calculated.

Fig. 67. BROADSIDE METHOD.

Bronzing.

In electro-plating the deposition of a mixture or virtual alloy of

copper and tin. In general manipulation it resembles the operation of

depositing gold and silver alloy, or of brassing.

For bronzing the following bath is recommended:

Prepare each by itself (a) a solution of copper phosphate and (b) a

solution of stannous chloride in a solution of sodium pyrophosphate. For

a, dissolve recently precipitated copper phosphate in concentrated

solution of sodium pyrophosphate. For b, add to a saturated solution of

sodium pyrophosphate solution of stannous chloride as long as the

precipitate which is formed dissolves. Of these two solutions add to a

solution of sodium pyrophosphate which contains about 1.75 oz. of the

salt to the quart, until the precipitate appears quickly and of the

desired color. For anodes use cast bronze plates. Sodium phosphate must

be added from time to time; if the deposit is too light add copper

solution, if too dark add tin solution. (W. T. Brannt.)

90   STANDARD ELECTRICAL DICTIONARY.

Brush.

In electric current generators and motors, the pieces of copper or other

material that bear against the cylindrical surface of the commutator are

thus termed. Many different constructions have been employed. Some have

employed little wheels or discs bearing against and rotating on the

surface of the commutator. A bundle of copper strips is often employed,

placed flatwise. Sometimes the same are used, but are placed edgewise.

Wire in bundles, soldered together at their distant ends have been

employed. Carbon brushes, which are simply rods or slabs of carbon, are

used with much success.

Synonym--Collecting Brush.

Brush, Carbon.

A brush for a dynamo or motor, which consists of a plate or rod of

carbon, held in a brush holder and pressed against the commutator

surface.

Brushes, Adjustment of.

In electric current generators and motors, the brushes which bear upon

the commutator when the machine is in action need occasional adjustment.

This is effected by shifting them until sparking between them and the

commutator is nearly or quite suppressed.

Fig. 68. BRUSH HOLDER.

Brushes, Lead of.

In a dynamo electric generator, the lead or displacement in advance of

or beyond the position at right angles to the line connecting the poles

of the field magnet, which is given the brushes. In a motor the brushes

are set back of the right angle position, or are given a negative lead.

(See Lag.)

91  STANDARD ELECTRICAL DICTIONARY.

Brush Holders.

The adjustable (generally) clutch or clamps for holding the commutator

brushes of a dynamo, which keep them in contact with the commutator, and

admit of adjustment by shifting backward and forward of the brushes to

compensate for wear. They are connected to and form part of the rocker,

q. v. By rotating the latter the brush-holders and brushes are carried

in one direction or other around the commutator, so as to vary the lead

as required.

Brush, Pilot.

A third brush, used for application to different parts of a revolving

armature commutator to determine the distribution of potential

difference between its different members. (See Curve of Distribution of

Potential in Armature.) One terminal of a volt-meter is connected to one

of the regular brushes, A, of a dynamo; the other to a third brush, p,

which is pressed against different portions of the commutator of the

dynamo. The readings of the volt-meter are plotted in a curve of

distribution of potential.

Fig. 69. PILOT BRUSH.

Brush, Rotating.

Brushes for taking off the current from dynamo commutators, or giving

current connection to motors, whose ends are in the form of rollers

which rotate like little wheels, and press against the commutator

surface.

Brush, Third.

A third brush is sometimes provided in a dynamo for regulating purposes.

Applied to a series machine it adjoins one of the regular brushes and

delivers its current to a resistance, to whose further end the regular

circuit is connected. By a sliding connection the resistance is divided

between the third brush circuit and the regular circuit, and by varying

the position of this contact regulation is obtained.

It is to be distinguished from the pilot brush used for determining the

characteristic of the commutator, although based on the same general

principles.

Fig. 70. THIRD BRUSH REGULATION.

92   STANDARD ELECTRICAL DICTIONARY.

Brush, Wire Gauze.

A collecting or commutator brush for a dynamo or motor, which brush is

made of wire gauze rolled up and compressed into shape.

Buckling.

The bending up and distortion of secondary battery plates. It is largely

due to over-exhausting the batteries. Where the E. M. F. is never

allowed to fall below 1.90 volt it is far less liable to occur.

Bug.

Any fault or trouble in the connections or working of electric

apparatus.

Bug Trap.

A connection or arrangement for overcoming a "bug." It is said that the

terms "bug" and "bug trap" originated in quadruplex telegraphy.

Bunsen Disc.

In photometry, the Bunsen Disc is a piece of paper upon whose centre a

spot is saturated with melted paraffin, or a ring of paraffined surface

surrounds an untouched central spot. If placed in such a position that

it receives an equal illumination on each side, the spot almost

disappears. It is used on the bar photometer. (See Photometer, Bar.)

Synonym--Grease Spot.

93  STANDARD ELECTRICAL DICTIONARY.

Buoy, Electric.

A buoy for use to indicate channels or dangers in harbors and elsewhere,

which carries an electric light, whose current is supplied by cable from

shore. It has been proposed to use glass tubes exhausted of air and

containing mercury, which, as moved by the waves, would produce a

luminous effect. A fifty-candle power incandescent lamp is an approved

source of light.

Burner, Electric Gas.

A gas burner arranged for the flame to be lighted by electricity. It

takes a great variety of forms. In some cases a pair of terminals are

arranged near the flame or a single terminal is placed near the metal

tip, the latter forming one of the terminals. The spark is generally

produced by an induction coil, or a spark coil. The gas may first be

turned on and the spark then passed. Sometimes the turning of the gas

cock of an individual burner makes and breaks a contact as it turns, and

thereby produces simultaneously with the turning on of the gas a spark

which lights it.

Another form is wholly automatic. A pair of electro-magnets are attached

below the base of the burner, one of which, when excited, turns on the

gas, and the other one when it is excited turns it off. At the same time

a spark is produced with the turning on of the gas so that it is

lighted. Thus, by use of a automatic burner, a distant gas burner can be

lighted by turning an electric switch. An out-door lamp may be lighted

from within a house.

The increasing use of electric incandescent lamps, lighted by the

turning of a switch, tends to displace electric gas burners. The latter

have been classified into a number of types depending on their

construction.

Burners are sometimes connected in series with leads from an induction

coil. Then the gas is turned on all at once, and a succession of sparks

passed until the gas is all lighted. The ignition is practically

instantaneous.

Button, Push.

A species of switch which is actuated by the pressure of a button. In

its normal position the button is pressed outwards by a spring, and the

circuit is open. When pressed inwards, it closes the circuit. When

released it springs backward and opens the circuit again.

They are principally used for ringing bells. If the latter are of the

automatic type, they ring as long as the button is pressed.

For door-bells and room-bells, the button often occupies the center of a

rosette of wood or bronze or other ornamental piece. Sometimes, as shown

in the cut, they are constructed for use on floors to be pressed by the

foot. The general principle of their construction is shown, although the

method of making the contact varies.

Synonym--Press Button.

Fig. 71. FLOOR PUSH BUTTON.

94   STANDARD ELECTRICAL DICTIONARY.

Burning.

(a) In a dynamo, the production of shifting and temporary arcs between

the commutator and brushes, which arcs produce heat enough to injure the

parts in question.

(b) In electro-plating, a defect due to too strong a current in

proportion to the strength of solution and area of electrodes. This

gives a black or badly-colored deposit.

Bus Rod.

A copper conductor used in electric lighting or power stations, to

receive the current from all the dynamos. The distributing leads are

connected to the bus wires.

In the three-wire system there are three; in the two-wire system there

are two bus wires.

The name is undoubtedly derived from "omnibus."

The bus wires may be divided into positive, negative, and, in the

three-wire system, neutral bus wires.

Synonyms--Omnibus Rod, Wire, or Bar--Bus Bar, or Wire.

Buzzer.

An electric alarm or call produced by a rapid vibration of electric make

and break mechanism, which is often magnified by enclosure in a

resonating chamber, resembling a bell, but which is not struck or

touched by the vibrating parts. Sometimes a square wooden box is used as

resonator.

Fig. 72. BUZZER.

95  STANDARD ELECTRICAL DICTIONARY.

B. W. G.

Abbreviation for Birmingham Wire Gauge. (See Wire Gauge, Birmingham.)

C.

(a) Abbreviation for Centigrade, as 100 C., meaning 100 Centigrade. (See

Centigrade Scale.)

(b) A symbol of current or of current strength. Thus in the expression

of Ohm's law C = E/R. C indicates current strength or intensity, not in

any fixed unit, but only in a unit of the same order in which E and R

are expressed; E Indicating electro-motive force and R resistance.

Cable.

(a) Abbreviation for Cablegram, q. v.

(b) v. It is also used as a verb, meaning to transmit a message by

submarine cable.

(c). An insulated electric conductor, of large diameter. It often is

protected by armor or metallic sheathing and may be designed for use as

an aerial, submarine, subterranean or conduit cable. A cable often

contains a large number of separately insulated conductors, so as to

supply a large number of circuits.

Cable, Aerial.

A cable usually containing a large number of separately insulated wires,

and itself insulated. It is suspended in the air. As its weight is

sometimes so great that it could not well sustain it, a suspending wire

is in such cases carried along with it, to which it is suspended by

cable hangers, q. v.

Cable Box.

A box for receiving underground cable ends and connecting the separate

wires of the cable to air-line wires. It is often mounted on a pole,

which forms the starting point of the air-line portion of the system.

Cable, Bunched.

A cable containing a number of separate and individual conductors. In

some forms it consists virtually of two or more small cables laid

tangent to each other and there secured. Thus each in section represents

two or more tangent circles with the interstice solidly filled with the

metal sheathing.

Cable, Capacity of.

The electrostatic capacity of a cable. A cable represents a Leyden jar

or static condenser. The outer sheathing or armor, or even the more or

less moist coating, if it is unarmored, represents one coating. The wire

conductors represent the other coating, and the insulator is the

dielectric.

The capacity of a cable interferes with its efficiency as a conductor of

broken or interrupted currents, such as are used in telegraphy or

telephoning. As each impulse or momentary current is sent into the line,

it has to charge the cable to at least a certain extent before the

effects of the current are perceptible at the other end. Then the cable

has to discharge itself. All this creates a drag or retardation.

The capacity of a cable is used to determine the locality of breaks in

the continuity of the conductors. The capacity per unit of length being

accurately known, it is obvious that, if the conductor breaks without

disturbance of the insulator, the distance of the break from the end can

be ascertained by determining the capacity of the cable from one end.

This capacity will be in proportion to the capacity of a mile, a knot or

any fixed unit, as the distance to the break is to the length used as

standard.

96   STANDARD ELECTRICAL DICTIONARY.

Cable Core.

The conductors of a cable. They are generally copper wire. In a

telephone cable they may be very numerous and insulated from each other.

In ocean cables they may be a group of bare wires twisted or laid

together. Sometimes the conductors are arranged for metallic circuits,

each pair being distinguished by special colored windings.

Cable, Duplex.

A cable containing two wires, each with separate insulation, so as to be

virtually two cables, laid and secured parallel and side by side.

Cable, Flat.

A cable, flat in shape, so as to lie closely against a wall or ceiling.

Cablegram.

A message which has been transmitted or is to be transmitted by a

submarine cable. It is sometimes called a cable.

Cable Grip.

A grip for holding the end of a cable, when the cable is to be drawn

into a conduit in a subway. It is an attachment to provide the cable

with an eye or loop. Its end is a split socket and embraces the end of

the cable, and is secured thereto by bolts driven through the cable end.

In drawing a cable into a conduit a capstan and rope are often used, and

the rope is secured to the cable end by the grip.

Fig. 73. CABLE HANGER, CABLE, AND SUSPENDING WIRE.

Fig. 74. CABLE HANGER, OPEN.

Cable Hanger.

When a heavy electric cable is suspended from poles it often would be

unsafe to trust to its longitudinal strength to support or sustain its

own weight unless the poles were very near together. In such case an

auxiliary or sustaining wire is run along with it, and by clips or

hangers the cable is connected thereto at as frequent intervals as seem

desirable. The contrivance may take the form of a strip of metal

surrounding the cable and carrying a hook or eye through which the

supporting wire passes.

Synonym--Cable Clip.

97  STANDARD ELECTRICAL DICTIONARY

Cable Hanger Tongs.

Tongs for attaching cable hangers, q.v. They have long handles so as to

be worked from the ground at the middle of a span.

Cable, Suspending Wire of.

A wire by which an aerial cable is in part or entirely suspended. The

cable, being incapable of sustaining its own weight, is secured by clips

or hangers to a wire, strong from pole to pole immediately above it.

(See Cable Hanger.)

Cable Tank.

A tank in which a submarine cable is coiled away on board a cable-laying

ship, or in the factory on shore for the purpose of testing or

watching its insulation. Sometimes, in order to test it under pressures

approximating to those it will be subjected to in practice, the tank is

closed and the portion of cable within it is subjected to hydraulic

pressure. This represents the pressure it will be exposed to in deep

water.

Calamine.

A mineral; zinc silicate; formula Zn2 Si 03, crystalline system,

Orthorhombic; specific gravity, 3.16-3.9.

The crystals often show strong pyroelectric properties.

Calibration.

The determination by experiment or calculation of the value of the

readings of an instrument, such as a galvanometer or eudiometer. Thus if

a tangent galvanometer has its circle graduated in degrees, a table of

the value of tangents corresponding to every reading occurring in

practice would represent a calibration by calculation. A determination

of the current required to produce each deflection would be a

calibration in the more usual sense. Calibration is generally absolute,

as referring to some fixed unit, but it may be relative, as between two

things both of unknown absolute value.

Calibration, Absolute.

The determination of the absolute value of currents producing given

deflections in a galvanometer, or in other instruments the determination

of corresponding values, as the instrument may be a magnetometer,

quadrant electrometer, or other apparatus.

Calibration, Invariable.

Calibration applicable to specially constructed galvanometers, which is

unaffected by the proximity of masses of iron or field magnets. Such

galvanometers must have a constant controlling field. Such is given by a

powerful permanent magnet, whose field is practically unaffected by the

causes named. Or else, in place of a controlling field, a spring maybe

used to which the needle is attached, and which tends to hold it in one

position.

98   STANDARD ELECTRICAL DICTIONARY.

Calibration, Relative.

The determination of the law connecting the various indications of an

instrument, such as the deflections of the needle of a galvanometer,

with the relative causes; in the case of a galvanometer, the strength of

the currents or the electro-motive forces producing them directly or

indirectly.

Call Bell.

A bell rung by pressing a button or otherwise to call the attention of a

person in a distant place. They can be classified into a great variety

of types according to their uses or construction.

Call Button.

A push button used for ringing a call bell, sounding a buzzer, working

an annunciator and for similar purposes. (See Push Button.)

Synonym--Push Button.

Calling Drop.

In a telephone exchange or telegraph office a drop shutter annunciator,

which falls to call the attention of the operator, notifying him that

the line connected to such drop is to be connected to some other

circuit.

Calorie or Calory.

A practical unit of heat. There are two calories, respectively called

the great and the small calorie, or the kilogram and the gram calorie.

The first is the quantity of heat required to raise the temperature of

one kilogram of water one degree centigrade. The second is the quantity

of heat required to raise the temperature of one gram of water one

degree centigrade.

Calorimeter.

An apparatus for measuring the quantity of heat evolved or produced by

or under different conditions. Dulong's water calorimeter consists of a

water jacket, and by the increase of temperature of the water and

enclosing vessels the amount of heat produced by anything in the inner

vessels is determined. The amount of ice a heated body will melt is

sometimes made the basis of a calorimeter. The expansion of a fluid, as

water, may be used. In the calorimeter shown in the cut the heat

produced in a conductor by the passage of an electric current is caused

to heat water whose temperature is shown by a thermometer immersed

therein. The increase of temperature and the weight of the water give

the basis for a determination of the heat produced by the current.

Knowing the resistance of the conductor immersed, the watts can be

calculated. This gives the bases for the determination of the

heat-equivalent of electric energy. This is but an imperfect

calorimeter, as it constantly would lose heat by the surrounding

atmosphere, and would cease to operate as a calorimeter when the water

was as hot as the wire normally would be, for then it would not absorb

all the heat.

Fig. 75. CALORIMETER.

99 STANDARD ELECTRICAL DICTIONARY.

Candle.

The generally accepted unit of illuminating power; there are

three kinds in use as standards. (See Candle, Decimal--Candle, German

Standard--Candle, Standard.)

Candle, Concentric.

An electric candle of the Jablochkoff type, having a small solid carbon

inside of an outside tubular carbon, the space between being filled with

refractory material corresponding to the colombin, q. v., of the

ordinary type. The arc springs across from one carbon to the other.

Candle, Debrun.

An arc lamp with approximately parallel carbons. A transverse priming

connects their bases, and the arc starting there at once flies out to

the end.

Candle, Decimal.

A standard of illuminating power, proposed to the Congress of

Electricians of 1889 by Picou. It is one-twentieth of a Viole, or almost

exactly one standard candle. (See Viole's Standard of Illuminating

Power.)

Candle, Electric.

An arc lamp regulated by simple gravity, or without any feed of the

carbons or special feeding apparatus, generally for the production of an

arc light of low intensity. This definition may be considered too

elastic, and the word may be restricted to parallel carbon lamps in

which the arc springs across from carbon to carbon. For the latter class

an alternating current is used to keep the carbons of equal length. They

are but little used now. Various kinds have been invented, some of which

are given here.

Candle, German Standard.

A standard of illuminating power used in Germany. It is a paraffin

candle, 6 to the pound, 20 millimeters diameter; flame, 56 millimeters

high; rate of consumption, 7.7 grams per hour. Its value is about two

per cent. lower than the English standard candle.

100   STANDARD ELECTRICAL DICTIONARY.

Candle Holder.

A clamp for holding electric candles of the Jablochkoff type. The ones

shown in the cut designed for Jablochkoff  candles comprise a pair of

metallic clamps, each member insulated from the other, and connected as

terminals of the circuit. When the candle is placed in position the

metal pieces press against the carbons of the candle and thus convey the

current. Below each member of the clamps is a binding screw for the line

wire terminals.

Fig. 76. JABLOCHKOFF CANDLE HOLDERS.

Fig. 77. JABLOCHKOFF CANDLE.

Candle, Jablochkoff.

An arc lamp without regulating mechanism, producing an arc between the

ends of parallel carbons. It consists of two parallel rods of carbon,

between which is an insulating layer of non-combustible material called

the colombin. Kaolin was originally employed for this part; later, as

the fusion of this material was found to short- circuit the arc, a

mixture of two parts of calcium sulphate and one of barium sulphate was

used. The carbons are 4 millimeters (.16 inch) thick, and the colombin

is 3 millimeters (.12 inch) wide and two-thirds as thick. A little slip

of carbon is placed across the top, touching both carbons to start the

arc. Once started the candle burns to the end, and cannot be restarted

after ignition, except by placing a short conductor across the ends, as

at first. The Jablochkoff candle may now be considered as virtually

extinct in this country. In France at one time a great number were in

use.

To keep the carbons of equal length an alternating current must always

be used with them. Special alternating combinations were employed in

some cases where a direct current had to be drawn upon.

Candle, Jamin.

An arc lamp with approximately parallel carbons, one of which oscillates

and is controlled by an electro-magnet and armature. A coil of wire is

carried around the carbons to keep the arc steady and in place. The

frame and wire coils have been found unsatisfactory, as causing a

shadow.

Candle Power.

The amount of light given by the standard candle. The legal English and

standard American candle is a sperm candle burning two grains a minute.

It should have burned some ten minutes before use, and the wick should

be bent over and have a red tip. Otherwise its readings or indications

are useless. A sixteen candle power lamp means a lamp giving the light

of sixteen candles. The candle power is a universal unit of illuminating

power.

101  STANDARD ELECTRICAL DICTIONARY.

Candle Power, Rated.

The candle power of arc lamps is always stated in excess of the truth,

and this may be termed as above. A 2000 candle power lamp really gives

about 800 candles illumination.

Synonym--Nominal Candle Power.

Candle Power, Spherical.

The average candle power of a source of light in all directions. An arc

lamp and an incandescent lamp vary greatly in the intensity of light

emitted by them in different directions. The average of a number of

determinations at various angles, the lamp being moved about into

different positions, is taken for the spherical candle power.

Candle, Standard.

A standard of illuminating power. Unless otherwise expressed the English

standard sperm candle is indicated by this term. (See Candle Power.)

Candle, Wilde.

An arc lamp with approximately parallel carbons. One of the carbons can

rotate through a small arc being pivoted at its base. This oscillation

is regulated by an electro-magnet at its base, and the carbons touch

when no current is passing. They separate a little when the current

passes, establishing an arc. The regulation is comparable to that of a

regular arc lamp.

Fig. 78. WILDE CANDLE.

Caoutchouc.

India rubber; a substance existing in an emulsion or solution in the

juice of certain trees and vines of the tropics, whence it is obtained

by coagulation and drying. The name "rubber" is due to the fact that one

of its earliest uses was for erasing pencil marks by rubbing. It has a

very high value as an insulator. The unworked crude rubber is called

virgin gum; after working over by kneading, it is termed masticated or

pure gum rubber; after mixture with sulphur and heating, it is termed

vulcanized rubber. If enough sulphur is added it becomes hard, and if

black, is termed ebonite; if vermilion or other pigment is also added to

produce a reddish color, it is termed vulcanite. The masticated gum

dissolves more or less completely in naphtha (sp. gr., .850) benzole,

turpentine, chloroform, ether and other similar liquids.. The resistance

per centimeter cube of "Hooper's" vulcanized India rubber, such as is

used in submarine cables is 1.5E16 ohms. The specific inductive capacity

of pure India rubber is 2.34--of vulcanized 2.94 (Schiller).

Synonyms--India Rubber--Rubber.

102   STANDARD ELECTRICAL DICTIONARY.

Capacity, Dielectric.

The capacity of a dielectric in retaining an electrostatic charge; the

same as Specific Inductive Capacity. 'The number expressing it is

sometimes called the dielectric constant. (See Capacity, Specific

Inductive.)

Capacity, Electric, or Electrostatic.

The relative capacity of a conductor or system to retain a charge of

electricity with the production of a given difference of potential. The

greater the charge for a given change of potential, or the less the

change of potential for a given charge the greater the capacity. The

measure of its capacity is the amount of electricity required to raise

the potential to a stated amount. The unit of capacity is the farad, q.

v. Electric capacity is comparable to the capacity of a bottle for air.

A given amount of air will raise the pressure more or less, and the

amount required to raise its pressure a stated amount might be taken as

the measure of capacity, and would be strictly comparable to

electrostatic charge and potential change. The capacity, K, is obviously

proportional to the quantity, Q, of the charge at a given potential, E,

and inversely proportional to the potential, E, for a given quantity, Q,

or,

(1) K == Q/E

and

(2) Q = K * E,

or, the quantity required to raise a conductor by a given potential is

equal to the capacity of the conductor or system multiplied by the rise

of potential. The capacity of a conductor depends upon its environments,

such as the nature of the dielectric surrounding it, the proximity of

oppositely charged bodies and other similar factors. (See

Dielectric-Condenser-Leyden jar.)

The dimensions of capacity are found by dividing a quantity of

electricity by the potential produced in the conductor by such

quantity.

Quantity ( ((M^.5)*(L^1.5)) / T ) / potential ( ((M^.5)*(L^.5)) / T ) = L.

Capacity, Instantaneous.

The capacity of a condenser when connected only for an instant to a

source of electricity. This is in contrast to electric absorption (see

Absorption, Electric), and is capacity without such absorption taking

part in the action.

103  STANDARD ELECTRICAL DICTIONARY.

Capacity of a Telegraph Conductor.

The electric capacity of a telegraphic conductor is identical in quality

with that of any other conductor. It varies in quantity, not only for

different wires, but for the same wire under different environments, as

the wire reacting through the surrounding air or other dielectric upon

the earth, represents one element of a condenser, the earth, in general,

representing the other. Hence, a wire placed near the earth has greater

capacity than one strung upon high poles, although the wires may be

identical in length, material and diameter. The effect of high capacity

is to retard the transmission of intermitting signals. Thus, when--as in

the Morse system--a key is depressed, closing a long telegraph current

and sending a signal into a line, it is at least very probable that a

portion of the electricity travels to the end of the wire with the

velocity of light. But as the wire has to be charged, enough current to

move the relay may not reach the end for some seconds.

Capacity of Polarization of a Voltaic Cell.

The relative resistance to polarization of a voltaic cell, measured by

the quantity of electricity it can supply before polarization. A

counter-electromotive force may be developed, or the acid or other

solution may become exhausted. The quantity of electricity delivered

before this happens depends on the size and type of cell and other

factors.

Capacity, Residual.

When two insulated conductors are separated by a dielectric, and are

discharged disruptively by being connected or nearly connected

electrically, on removing the discharger it is found that a slight

charge is present after a short interval. This is the residual charge.

(See Charge, Residual.) Shaking or jarring the dielectric facilitates

the complete discharge. This retaining of a charge is a phenomenon of

the dielectric, and as such, is termed residual capacity. It varies

greatly in different substances. In quartz it is one-ninth what it is in

air. Iceland spar (crystalline calcite) seems to have no residual

capacity. The action of shaking and jarring in facilitating a discharge

indicates a mechanical stress into which the electrostatic polarization

of the conductor has thrown the intervening dielectric.

Capacity, Specific Inductive.

The ratio of the capacity of a condenser when its plates are separated

by any substance to the capacity of the same condenser when its plates

are separated by air.

A static accumulator consists of two conducting surfaces separated by an

insulator. It is found that the capacity of an accumulator for an

electric charge, which varies with or may be rated by the potential

difference to which its conductors will be brought by the given charge,

varies with the nature of the interposed dielectric, and is proportional

to a constant special to each substance. This constant is the specific

inductive capacity of the dielectric.

The same condenser will have a higher capacity as the dielectric is

thinner, other things being equal. But different dielectrics having

different specific inductive capacities, the constant may be determined

by ascertaining the relative thicknesses of layers having the same total

inductive capacity. The thicker the layer, the higher is its specific

inductive capacity.

Thus it is found that 3.2 units thickness of sulphur have the same total

inductive capacity as 1 unit thickness of air. In other words, if

sulphur is interposed between two conducting plates, they may be

separated to over three times the distance that would be requisite to

retain the same capacity in air. Hence, sulphur is the better

dielectric, and air being taken as unity, the specific inductive

capacity of sulphur is 3.2.

104   STANDARD ELECTRICAL DICTIONARY.

The specific inductive capacity of a dielectric varies with the time and

temperature. That of glass rises 2.5 per cent. between 12° C. (53.6° F.)

and 83° C. (181.4° F.). If a condenser is discharged disruptively, it

retains a small residual charge which it can part with later. If a

metallic connection is made between the plates, the discharge is not

instantaneous. Vibration shaking and jarring facilitate the complete

discharge. All this shows that the charge is a phase of the dielectric

itself, and indicates a strained state into which it is brought.

The following table gives the specific inductive capacity of various

substances:

Specific Inductive Capacity.

Substance                                         Specific

Inductive   Authority

Capacity.

Vacuum, air at about 0.001 millimeters pressure   0.94 about  Ayrton

Vacuum, air at about 5 millimeters                0.9985      Ayrton

0.99941     Boltzmann

Hydrogen at about 760 millimeters pressure        0.9997      Boltzmann

0.9998      Ayrton

Air at about 760 millimeters pressure             1.0         Taken as the

standard

Carbon Dioxide at about 760 millimeters pressure  1.000356    Boltzmann

1.0008      Ayrton

Olefiant Gas at about 760 millimeters pressure    1.000722    Boltzmann

Sulphur Dioxide at about 760 millimeters pressure 1.0037      Ayrton

Paraffin Wax, Clear                               1.92        Schiller

1.96        Wüllner

1.977   Gibson and Barclay

2.32        Boltzmann

Paraffin Wax, Milky                               2.47        Schiller

India Rubber, Pure                                2.34        Schiller

India Rubber, Vulcanized                          2.94        Schiller

Resin                                             2.55        Boltzmann

Ebonite                                           2.56        Wüllner

2.76        Schiller

3.15        Boltzmann

Sulphur                                           2.88 to 3.21  Wüllner

3.84        Boltzmann

Shellac                                           2.95 to 3.73  Wüllner

Gutta percha                                      4.2

Mica                                              5

Flint Glass, Very light                           6.57        J. Hopkinson

Flint Glass, Light                                6.85        J. Hopkinson

Flint Glass, Dense                                7.4         J. Hopkinson

Flint Glass, Double extra dense                  10.1         J. Hopkinson

105  STANDARD ELECTRICAL DICTIONARY.

Capacity, Unit of.

The unit of capacity is the capacity of a surface which a unit quantity

will raise to a unit potential. The practical unit is the surface which

a coulomb will raise to one volt, and is called the farad, q. v.

Capacity, Storage.

In secondary batteries the quantity of electrical current which they can

supply when charged, without undue exhaustion. It is expressed in

ampere-hours. The potential varies so little during the discharge that

it is assumed to be constant.

Capillarity.

The reaction between liquid surfaces of different kinds or between

liquid and solid surfaces due to surface tension. Its phenomena are

greatly modified by electric charging, which alters the surface tension.

Capillarity is the cause of solutions "creeping," as it is termed. Thus

in gravity batteries a crust of zinc sulphate often formed over the edge

of the jar due to the solution creeping and evaporating. As a liquid

withdraws from a surface which it does not wet, creeping as above is

prevented by coating the edge with paraffin wax, something which water

does not moisten. It also causes the liquids of a battery cell to reach

the connections and injure them by oxidation. The solutions creep up in

the pores of the carbons of a battery and oxidize the clamps. To give

good connections a disc of platinum or of lead is used for the contact

as not being attacked. Another way is to dip the upper ends of the dry

and warm carbons into melted paraffin wax, or to apply the wax to the

hot carbons at the top, and melt it in with a hot iron.

106   STANDARD ELECTRICAL DICTIONARY.

Carbon.

(a) One of the elements; atomic weight, 12. It exists in three

allotropic modifications, charcoal, graphite and diamond. In the

graphitic form it is used as an electric current conductor, as in

batteries and for arc lamp, electrodes and incandescent lamp filaments.

It is the only substance which conducts electricity and which cannot be

melted with comparative ease by increase of current. (See Resistance.)

(b) The carbon plate of a battery or rod of an arc lamp. To secure

greater conductivity in lamp carbons, they are sometimes plated with

nickel or with copper.

(c) v. To place carbons in arc lamps. This has generally to be done once

in twenty-four hours, unless the period of burning is very short.

Carbon, Artificial.

For lamps, carbons and battery plates carbons are made by igniting,

while protected from the action of the air, a mixture of carbon dust and

a cementing and carbonizable substance. Lamp black may be added also.

Powdered coke or gas carbon is mixed with molasses, coal tar, syrup, or

some similar carbonaceous liquid. It is moulded into shape. For lamp

carbons the mixture is forced from a vessel through a round aperture or

die, by heavy pressure, and is cut into suitable lengths. For battery

plates it may be simply pressed into moulds. The carbons are ignited in

covered vessels and also covered with charcoal dust, lamp black or its

equivalent. They are heated to full redness for some hours. After

removal and cooling they are sometimes dipped again into the liquid used

for cementing and reignited. Great care in securing pure carbon is

sometimes necessary, especially for lamps. Fine bituminous coal is

sometimes used, originally by Robert Bunsen, in 1838 or 1840;

purification by different processes has since been applied; carbon from

destructive distillation of coal tar has been used. The famous Carré

carbons are made, it is said, from 15 parts very pure coke dust, five

parts calcined lamp-black, and seven or eight parts sugar--syrup mixed

with a little gum. Five hours heating, with subsequent treatment with

boiling caramel and reignition are applied. The latter treatment is

termed "nourishing." Napoli used three parts of coke to one of tar.

Sometimes a core of different carbon than the surrounding tube is

employed.

107  STANDARD ELECTRICAL DICTIONARY.

The following are the resistances of Carré's carbons per meter (39.37

inches):

Diameter in     Diameter in  Resistance in Ohms.

Millimeters.    Inches.      @ 20° C. (98° F.)

1           .039           50.000

2           .078           12.5

3           .117            5.55

4           .156            3.125

5           .195            2.000

6           .234            1.390

8           .312             .781

10           .390             .5

12           .468             .348

15           .585             .222

18           .702             .154

20           .780             .125

At high temperatures the resistance is about one-third these amounts. A

layer of copper may increase the conductivity one hundred times and

prolong the duration 14 per cent. Thus a layer of copper 1/695

millimeter (1/17300 inch) thick increases the conductivity 4.5 times; a

coating 1/60 millimeter (1/1500 inch) thick increases the conductivity

one hundred and eleven times.

Carbon, Cored.

A carbon for arc lamps with a central core of softer carbon than the

exterior zone. It fixes the position of the arc, and is supposed to give

a steadier light.

Synonym--Concentric Carbon.

Carbon Holders.

In arc lamps, the fixed clamps for holding the ends of the carbons.

Carbonization.

The igniting in a closed vessel, protected from air, of an organic

substance so as to expel from it all the constituents except part of

the carbon; destructive distillation. (See Carbonized Cloth.)

Carbonized Cloth.

Cloth cut in discs and heated in vessels protected from the air, until

reduced to carbon. The heating is sometimes conducted in vacuo. They are

placed in a pile in a glass or other insulating tube, and offer a

resistance which can be varied by pressure. The greater the pressure the

less will be the resistance, and vice versa.

Carbon Dioxide.

A compound gas, CO2. It is composed of

Carbon, 12 parts by weight.

Oxygen. 32  "

Specific gravity, 1.524 (Dulong and Berzelins).

Molecular weight, 44.

It is a dielectric of about the resistance of air. Its specific

inductive capacity at atmospheric pressures is

1.000356 (Boltzmann).

1.0008 (Ayrton).

Synonyms--Carbonic Acid--Carbonic Acid Gas.

108   STANDARD ELECTRICAL DICTIONARY

Carbon, Volatilization of.

In arc lamps the heat is so intense that it is believed that part of the

carbon is volatilized as vapor before being burned or oxidized by the

oxygen of the air. The same volatilization may take place in

incandescent lamps which are overheated.

Carcel.

The standard of artificial illumination used in France. It is the light

yielded by a standard lamp burning 42 grams (648 grains) of colza oil

per hour, with a flame 40 millimeters (1.57 inch) in height. One carcel

is equal to 9.5 to 9.6 candles.

Carcel Lamp.

The lamp giving the standard of illuminating power. The wick is

cylindrical, giving an Argand or central draft flame. It is woven with

75 strands, and weighs 3.6 grams (55.5 grains) per decimeter (3.9

inches) of length. The chimney is 29 centimeters (11.3 inches) high, 47

millimeters (1.88 inch) in diameter at the bottom, contracting just

above the wick to 34 millimeters (1.36 inch).

Carcel Gas Jet.

A standard Argand gas burner, made with proper rating to give the light

of a definite number of carcels illuminating power. Cognizance must be

taken of the quality of the gas as well as of the burner used.

Carrying Capacity.

In a current conductor, its capacity for carrying a current without

becoming unduly heated. It is expressed in amperes. (See Wire Gauge,

American.)

Cascade.

The arrangement of Leyden jars in series on insulating supports, as

described below.

Cascade, Charging and Discharging Leyden Jars In.

An arrangement of Leyden jars in series for the purpose of charging and

discharging. They are placed on insulating supports, the inner coating

of one connected with the outer coating of the next one all through the

series. The actual charge received by such a series, the outer coating

of one end jar being grounded, and the inner coating of the other being

connected to a source of high potential, or else the same being

connected to electrodes of opposite potentials is no greater than that

of a single jar, but a much higher potential difference can be developed

without risk of perforating the glass of a jar. The difference of

potential in each jar of the series is equal to the total potential

difference divided by the number of jars. The energy of discharge is

equal to the same fraction of the energy of a single jar charged with

the same quantity.

[Transcriber's note: The equal distribution of potential assumes all the

jars have the same capacity. The charge on all jars is the same since

they are in series.]

109  STANDARD ELECTRICAL DICTIONARY.

Case-hardening, Electric.

The conversion of the surface of iron into steel by applying a proper

carbonaceous material to it while it is heated by an electric current.

It is a superficial cementation process.

Cataphoresis.

Electric osmore; the transfer of substances in solution through porous

membranes under the influence probably of electrolysis, but without

themselves being decomposed.

Cautery, Electric.

An electro-surgical appliance for removing diseased parts, or arresting

hemorrhages, taking the place of the knife or other cutting instrument.

The cautery is a platinum wire heated to whiteness by an electric

current, and when in that condition used to cut off tumors, stop the

flow of blood and parallel operations. The application is painful, but

by the use of anaesthetics pain is avoided, and the healing after the

operation is greatly accelerated.

The heated wire of the cautery can be used for cutting operations in

many cases where excision by a knife would be almost impracticable.

Synonyms--Galvano-cautery--Galvano-caustry--Galvano-electric,

do.--Galvano-thermal, do.

C. C.

A contraction of cubic centimeter. It is often written in small letters,

as 100 c.c., meaning 100 cubic centimeters.

Cell, Constant.

A cell which yields a constant and uniform current under unvarying

conditions. This implies that neither the electro-motive force or the

resistance of the cell shall vary, or else that as the electro-motive

forces run down the resistance shall diminish in proper proportion to

maintain a constant current. There is really no constant cell. The

constancy is greatest when the external resistance is high in proportion

to the internal resistance.

Cell, Electrolytic.

A vessel containing the electrolyte, a liquid decomposable by the

current, and electrodes, arranged for the passage of a decomposing

current. The voltameter, q. v., is an example.

Cell, Standard Voltaic.

A cell designed to be a standard of electro-motive force; one in which

the same elements shall always be present under the same conditions, so

as to develop the same electro-motive force. In use the circuit is

closed only for a very short time, so that it shall not become altered

by polarization or exhaustion.

Cell, Standard Voltaic, Daniell's.

A zinc-copper-copper sulphate couple.

Many forms are used. Sometimes a number of pieces of blotting paper are

interposed between two plates, one of copper--the other of zinc. The

paper next the copper is soaked in copper sulphate solution, and those

next the zinc in zinc sulphate solution, of course before being put

together. Sometimes the ordinary porous cup combination is employed. The

cut shows a modification due to Dr. Fleming (Phil. Mag. S. 5, vol. xx,

p. 126), which explains itself. The U tube is 3/4-inch diameter, and 8

inches long. Starting with it empty the tap A is opened, and the whole U

tube filled with zinc sulphate solution, and the tap A is closed. The

zinc rod usually kept in the tube L is put in place, tightly corking up

its end of the U tube. The cock C is opened, which lowers the level of

the solution in the right-hand limb of the U tube only. The tap B is

opened and the copper sulphate solution is run in, preserving the line

of separation of the two solutions. The copper rod is taken out of its

tube M, and is put in place. India rubber corks are used for both rods.

As the liquids begin to mix the mixture can be drawn off at C and the

sharp line of demarcation re-established. In Dr. Sloane's standard cell

two test tubes are employed for the solutions and a syphon is used to

connect them.

Oxidation of the zinc lowers the E. M. F.; oxidation of the copper

raises it. With solutions of equal sp. gr. the E. M. F. is 1.104 volts.

If the copper sulphate solution is 1.100 sp. gr. and the zinc sulphate

solution 1.400 sp. gr., both at 15° C. (59°F.), the E. M. F. will be

1.074 volt. Clean pure zinc and freshly electrolyzed copper should be

used.

Fig. 79 STANDARD DANIELL CELL--FLEMING'S FORM.

110   STANDARD ELECTRICAL DICTIONARY.

Cell, Standard Voltaic, Latimer Clark's.

A mercury and zinc electrode couple with

mercurous sulphate as excitant and depolarizer. The positive

element is an amalgam of zinc, the negative is pure mercury. Each

element, in a representative form, the H form, is contained in a

separate vessel which communicate by a tube. Over the pure mercury some

mercurous sulphate is placed. Both vessels are filled to above the level

of the connecting tube with zinc sulphate solution, and kept saturated.

It is tightly closed or corked. The E. M. F. at 15° C (59° F.) is 1.438.

Temperature correction

(1 -  (.00077 *(t - 15° C) ) )

t being expressed in degrees centigrade (Rayleigh). A diminution in

specific gravity of the zinc solution increases the E. M. F. The cell

polarizes rapidly and the temperature coefficient is considered too

high.

Fig. 80. LATIMER CLARK'S STANDARD CELL.

111   STANDARD ELECTRICAL DICTIONARY.

Cements, Electrical.

A few cements find their use in electrical work. Marine glue,

Chatterton's compound, and sealing wax may be cited.

Centi-.

Employed as a prefix to indicate one-hundredth, as centimeter, the

one-hundredth of a meter; centi-ampere, the one-hundredth of an ampere.

Centigrade-scale.

A thermometer scale in use by scientists of all countries and in general

use in many. The temperature of melting ice is 0º; the temperature of

condensing steam is 100° ; the degrees are all of equal length. To

reduce to Fahrenheit degrees multiply by 9 and divide by 5, and add 32

algebraically, treating all readings below 0º as minus quantities. For

its relations to the Reamur scale, see Reamur Scale. Its abbreviation is

C., as 10º C., meaning ten degrees centigrade.

Centimeter.

A metric system unit of length; one-hundredth of a meter; 0.3937 inch.

The absolute or c. g. s. unit of length.

Centimeter-gram-second System.

The accepted fundamental or absolute system of units, called the C. G.

S. system. It embraces units of size, weight, time, in mechanics,

physics, electricity and other branches. It is also called the absolute

system of units. It admits of the formation of new units as required by

increased scope or classification. The following are basic units of the

system :

Of length, centimeter;

of mass, gram;

of time, second:

of force, dyne:

of work or energy, erg.

See Dyne, Erg., and other units in general.

112   STANDARD ELECTRICAL DICTIONARY.

Central Station Distribution or Supply.

The system of supplying electric energy in current form from a main

generating plant to a district of a number of houses, factories, etc. It

is in contrast with the isolated plant system in which each house or

factory has its own separate generating installment, batteries or

dynamos.

Centre of Gravity.

A point so situated with respect to any particular body, that the

resultant of the parallel attracting forces between the earth and the

several molecules of the body always passes through it. These are

resultants of the relative moments of the molecules. If a body is

suspended, as by a string, the centre of gravity always lies vertically

under its point of suspension. By two trials the point of intersection

of plumb lines from the point of suspension being determined the centre

of gravity is known. The vertical from the point of support coincides

with the line of direction.

Centre of Gyration.

The centre of gyration with respect to the axis of a rotating body is a

point at which if the entire mass of the body were concentrated its

moment of inertia would remain unchanged. The distance of this point

from the axis is the radius of gyration.

Centre of Oscillation.

The point referred to in a body, suspended or mounted to swing like a

pendulum, at which if all the mass were concentrated, 1t would complete

its oscillations in the same time. The distance from the axis of support

to this point gives the virtual length of the pendulum which the body

represents.

Centre of Percussion.

The point in a suspended body, one free to swing like a pendulum, at

which an impulse may be applied, perpendicular to the plane through the

axis of the body and through the axis of support without shock to the

axis. It is identical with the centre of oscillation, q. v., when such

lies within the body.

Centrifugal Force.

The force which draws a body constrained to move in a curved path away

from the centre of rotation. It is really due to a tangential impulse

and by some physicists is called the centrifugal component of tangential

velocity. It has to be provided against in generator and motor

armatures, by winding them with wire or bands to prevent the coils of

wire from spreading or leaving their bed upon the core.

113  STANDARD ELECTRICAL DICTIONARY.

Centrifugal Governor.

The usual type of steam-engine governor. The motion of the engine

rotates a system of weights, which are forced outward by centrifugal

force, and are drawn inwards by gravity or by springs. Moving outwards

they shut off steam, and moving inwards they admit it, thus keeping the

engine at approximately a constant speed. The connections between them

and the steam supply and the general construction vary widely in

different governors.

C. G. S.

Abbreviation or symbol for Centimeter-gram-second, as the C. G. S.

system. (See Centimeter-gram-second System.) It is sometimes expressed

in capitals, as above, and sometimes in small letters, as the c. g. s.

unit of resistance.

Chamber of Incandescent Lamp.

The interior of the bulb of an incandescent lamp. (See Lamp,

Incandescent.)

Fig. 81. CHARACTERISTIC CURVE OF A DYNAMO.

FIG. 82. DROOPING CHARACTERISTIC.

Characteristic Curve.

A curve indicating the variations in electro-motive force developed

during the rotations of the armature of a dynamo or other generator of

E. M. F. The term as used in the electrical sense is thus applied,

although the indicator diagram of a steam engine may be termed its

characteristic curve, and so in many other cases. As the amperes taken

from a series generator are increased in number, the E. M. F. rises, it

may be very rapidly up to a certain point, and thereafter more slowly.

To construct the curve coordinates, q. v., are employed. The resistance

of the dynamo and of the outer circuit being known, the current

intensity is measured. To obtain variations in electro-motive force the

external resistance is changed. Thus a number of ampere readings with

varying known resistance are obtained, and for each one an

electro-motive force is calculated by Ohm's law. From these data a curve

is plotted, usually with volts laid off on the ordinate and amperes on

the abscissa.

By other methods other characteristic curves may be obtained, for which

the titles under Curve may be consulted.

114   STANDARD ELECTRICAL DICTIONARY.

Characteristic, Drooping.

A characteristic curve of a dynamo which indicates a fall in voltage

when an excessive current is taken from the dynamo in question. It is

shown strongly in some Brush machines, and is partly due to the

arrangements for cutting out two of the coils as they approach the

neutral line. It is an advantage, as it protects from overheating on

short circuit.

Characteristic, External.

In a dynamo the characteristic curve in which the relations of volts

between terminals to amperes in the outer circuit are plotted. (See

Curve, External Characteristic.)

Characteristic, Internal.

A characteristic curve of a shunt dynamo, in which the relations of

volts to amperes in the shunt circuit is plotted.

Characteristics of Sound.

Of interest, electrically, as affecting the telephone, they comprise:

(1) Pitch, due to frequency of vibrations.

(2) Intensity or loudness, due to amplitude of waves of sound.

(3) Quality or timbre, the distinguishing characteristics of any

specific sound due to overtones, discords, etc., by which the sound is

recognizable from others. The telephone is held by the U. S. courts to

be capable of reproducing the voice by means of the undulatory current.

(See Current, Undulatory.)

Charge.

The quantity of electricity that is present on the surface of a body or

conductor. If no electricity is supplied, and the conductor is connected

to the earth, it is quickly discharged. A charge is measured by the

units of quantity, such as the coulomb. The charge that a conductor can

retain at a given rise of potential gives its capacity, expressible in

units of capacity, such as the farad. A charge implies the stretching or

straining between the surface of the charged body, and some

complimentary charged surface or surfaces, near or far, of large or

small area, of even or uneven distribution.

Charge. v.

(a) To introduce an electrostatic charge, as to charge a condenser.

(b) To decompose the elements of a secondary battery, q. v., so as to

render it capable of producing a current. Thus, a spent battery is

charged or recharged to enable it to do more work.

Synonyms--Renovate--Revivify--Recharge.

115  STANDARD ELECTRICAL DICTIONARY.

Charge, Bound.

A charge of electricity borne by the surface of a body so situated with

reference to another oppositely charged body, that the charge is

imperceptible to ordinary test, will not affect an electroscope nor

leave the surface if the latter is connected to the earth. To discharge

such a body it must be connected to its complimentarily charged body.

The bound charge was formerly called dissimulated or latent electricity.

(See Charge, Free.)

The charge or portion of a charge of a surface which is neutralized

inductively by a neighboring charge of opposite kind. The degree of

neutralization or of binding will depend on the distance of the two

charged surfaces from one another and on the electro-static nature of

the medium intervening, which must of necessity be a dielectric. A

charge not so held or neutralized is termed a free charge. Thus a

surface may be charged and by the approach of a surface less highly

charged may have part of its charge bound. Then if connected to earth.

it will part with its unbound or free charge, but will retain the other

until the binding surface is removed, or until the electricity of such

surface is itself bound, or discharged, or until connection is made

between the two surfaces. Thus a body may have both a bound and a free

charge at the same time.

Charge, Density of.

The relative quantity of electricity upon a given surface. Thus a

charged surface may have an evenly distributed charge or one of even

density, or an unevenly distributed charge or one of uneven density. In

a thunderstorm the earth has a denser charge under the clouds than

elsewhere.

Synonym--Electrical Density.

Charge, Dissipation of.

As every body known conducts electricity, it is impossible so to

insulate a surface that it will not lose its charge by leakage. An

absolute vacuum might answer, and Crookes in a high vacuum has retained

a charge against dissipation for years. The gradual loss is termed as

above.

Charge, Distribution of.

The relation of densities of charge on different parts of a charged

body. On a spherical conductor the charge is normally of even

distribution; on other conductors it is unevenly distributed, being of

greatest density at points, edges, and parts of smallest radius of

curvature. Even distribution can also be disturbed by local induction,

due to the presence of oppositely charged bodies.

116   STANDARD ELECTRICAL DICTIONARY.

Charge, Free.

The charge borne by an insulated body, independent of surrounding

objects. Theoretically it is an impossibility. A charge always has its

compliment somewhere in surrounding objects. As a matter of convenience

and convention, where the complimentary charge is so distributed that

its influence is not perceptible the charge is called a free charge. If

connected to earth the free charge will leave the body. If the body is

connected with an electroscope the free charge will affect the same.

(See Charge, Bound.)

Charge, Residual.

When a Leyden jar or other condenser is discharged by the ordinary

method, after a few minutes standing a second discharge of less amount

can be obtained from it. This is due to what is known as the residual

charge. It seems to be connected in some way with the mechanical or

molecular distortion of the dielectric. The jarring of the dielectric

after discharge favors the rapidity of the action, diminishing the time

required for the appearance of the residual charge. The phenomenon, it

will be seen, is analogous to residual magnetism. This charge is the

reciprocal of electric absorption and depends for its amount upon the

nature of the dielectric. (See Absorption, Electric, and Capacity,

Residual.)

Synonym--Electric Residue.

Chatterton's Compound.

A cement used for cementing together layers or sheets of gutta percha,

and for similar purposes in splicing telegraph cables. Its formula is:

Stockholm Tar,   1 part.

Resin,           1 part.

Gutta Percha,    3 parts.

All parts by weight.

Chemical Change.

When bodies unite in the ratio of their chemical equivalents, so as to

represent the satisfying of affinity or the setting free of thermal or

other energy, which uniting is generally accompanied by sensible heat

and often by light, as in the ignition of a match, burning of a candle,

and, when the new compound exhibits new properties distinct from those

of its components, a chemical combination is indicated. More definitely

it is a change of relation of the atoms. Another form of chemical change

is decomposition, the reverse of combination, and requiring or absorbing

energy and producing several bodies of properties distinct from those of

the original compound. Thus in a voltaic battery chemical combination

and decomposition take place, with evolution of electric instead of

thermal energy.

Chemical Equivalent.

The quotient obtained by dividing the atomic weight, q. v., of an

element by its valency, q. v. Thus the atomic weight of oxygen is 16,

its valency is 2. its chemical equivalent is 8. It is the weight of the

element corresponding to a unit weight of hydrogen, either as replacing

it, or combining with it. In electro-chemical calculations the chemical

equivalent is often conveniently used to avoid the necessity of dividing

by the valency when atomic weights are used. The latter is really the

better practice. The atomic weights in the old system of chemical

nomenclature were chemical equivalents.

117  STANDARD ELECTRICAL DICTIONARY.

Chemical Recorder.

A form of telegraphic recorder in which the characters, often of the

Morse alphabet or some similar one, are inscribed on chemically prepared

paper by decomposition affecting the compound with which the paper is

charged. In the original chemical recorder of Bain, the instrument was

somewhat similar to the Morse recorder, except that the motionless

stylus, S, always pressing against the paper was incapable of making any

mark, but being of iron, and the paper strip being impregnated with

potassium ferrocyanide, on the passage of a current a stain of Prussian

blue was produced where the stylus touched the paper. The current passes

from the line by way of the iron stylus, through the paper, and by way

of a brass surface, M, against which the paper is held and is pressed by

the stylus, to the earth. This recorder is extremely simple and has no

part to be moved by the current. The solution in which the paper is

dipped contains a mixture of potassium ferrocyanide and ammonium

nitrate. The object of the latter is to keep the paper moist. In recent

recorders a solution of potassium iodide has been used, which gives a

brown stain of free iodine, when the current passes. This stain

disappears in a few days.

Fig. 83. BAIN'S TELEGRAPH EMPLOYING CHEMICAL RECORDER.

In the cut, R is the roll of paper, B is a tank of solution with roll,

W1, for moistening the paper; M is the brass surface against which the

stylus, S, presses the paper, P P; W, W are feed rollers; T is the

transmitting key, and zk the battery; Pl, Pl are earth plates. The

apparatus is shown duplicated for each end.

118   STANDARD ELECTRICAL DICTIONARY.

Chemistry.

The science treating of atomic and molecular relations of the elements

and of chemical compounds of the same.

Chimes, Electric.

An apparatus employed to illustrate the principles of the electrostatic

charge, involving the ringing of bells by electrostatic attraction and

repulsion. It is used in connection with a frictional, or influence

electric machine. Two bells are employed with a button or clapper

suspended between them. One bell is connected to one of the prime

conductors, q. v., of the machine. The other insulated therefrom is

connected to earth, or if an influence machine is used, to the other

prime conductor. The clappers are hung by a silk thread, so as to be

entirely insulated. On working the machine the bells become oppositely

excited. A clapper is attracted to one, then when charged is repelled

and attracted to the other, it gives up its charge and becoming charged

with similar electricity to that of the bell it touches, is repelled and

attracted to the other, and this action is kept up as long as the

excitement continues, the bells ringing continuously.

Fig. 84. ELECTRIC CHIMES.

Chronograph, Electric.

An apparatus for indicating electrically, and thereby measuring, the

lapse of time. The periods measured may be exceedingly short, such as

the time a photographic shutter takes to close, the time required by a

projectile to go a certain distance, and similar periods.

A drum rotated with even and known velocity may be marked by a stylus

pressed upon it by the action of an electro-magnet when a key is

touched, or other disturbance. Then the space between two marks would

give the period elapsing between the two disturbances of the circuit. As

it is practically impossible to secure even rotation of a drum, it is

necessary to constantly measure its rate of rotation. This is effected

by causing a tuning-fork of known rate of vibration to be maintained in

vibration electrically. A fine point or bristle attached to one of its

arms, marks a sinuous line upon the smoked surface of the cylinder. This

gives the basis for most accurately determining the smallest intervals.

Each wave drawn by the fork corresponds to a known fraction of a second.

For projectiles, the cutting of a wire opens a circuit, and the opening

is recorded instead of the closing. By firing so as to cut two wires at

a known distance apart the rate is obtained by the chronograph.

Synonym--Chronoscope.

119  STANDARD ELECTRICAL DICTIONARY.

Chutaux's Solution.

A solution for bichromate batteries. It is composed as follows:

Water,                1,500 parts

Potassium bichromate,   100 parts

mercury bisulphate,     100 parts

66° sulphuric acid,      50 parts.

Circle, Galvanic or Voltaic.

A term for the voltaic circuit; obsolete.

Fig. 85. MAGIC CIRCLE.

Circle, Magic.

A form of electro-magnet. It is a thick circle of round iron and is used

in connection with a magnetizing coil, as shown, to illustrate

electro-magnetic attraction.

120   STANDARD ELECTRICAL DICTIONARY.

Circuit.

A conducting path for electric currents properly forming a complete path

with ends joined and including generally a generating device of some

kind. Part of the conduction may be true and part electrolytic. (See

Electrolytic Conduction.) The term has become extended, so that the term

is often applied to any portion of a circuit conveniently considered by

itself. The simplest example of a complete circuit would be a circular

conductor. If rotated in the earth's field so as to cut its lines of

force a current would go through it, and it would be an electric

circuit. Another example is a galvanic battery with its ends connected

by a wire. Here the battery generates the current which, by electrolytic

conduction, goes through the battery and by true conduction through the

wire. For an example of a portion of a circuit spoken of as "a circuit"

see Circuit, Astatic.

Circuit, Astatic.

A circuit so wound with reference to the direction of the currents

passing through it that the terrestrial or other lines of force have no

directive effect upon it, one member counteracting the other. It may be

produced by making the wire lie in two closed curves, A and B, each

enclosing an equal area, one of identical shape and disposition with the

other, and with the current circulating in opposite directions in each

one. Thus each circuit represents a magnetizing turn of opposite

polarity and counteracting each other's directive tendency exhibited in

a field of force with reference to an axis a c. Another form of astatic

circuit is shown in Fig. 86. The portions C, D, lying on opposite sides

of the axis of rotation a c, are oppositely acted on by the earth's

directive force as regards the direction of their rotation.

Figs. 86 and 87. ASTATIC CIRCUITS.

Circuit, Branch.

A circuit dividing into two or more parts in parallel with each other.

121  STANDARD ELECTRICAL DICTIONARY.

Circuit Breaker.

Any apparatus for opening and closing a circuit is thus termed, but it

is generally applied to automatic apparatus. A typical circuit breaker

is the hammer and anvil of the induction coil. (See Induction Coil;

Anvil.) Again a pendulum connected to one terminal of a circuit may

swing so as to carry a point on its lower end through a globule of

mercury as it swings, which globule is connected to the other terminal.

A great many arrangements of this character have been devised.

Synonym.--Contact Breaker.

Circuit Breaker, Automatic.

A circuit breaker worked by the apparatus to which it is attached, or

otherwise automatically. (See Induction Coil; Anvil; Bell, Electric.)

Circuit Breaker, File.

A coarsely cut file, forms one terminal of an electric circuit, with a

straight piece of copper or steel for the other terminal. The latter

terminal drawn along the teeth makes and breaks the contact once for

every tooth. The movable piece should have an insulated handle.

Circuit Breaker, Mercury.

A circuit breaker which may be identical in principle, with the

automatic circuit breaker of an induction coil, but in which in place of

the anvil, q. v., a mercury cup is used, into which the end of a wire

dips and emerges as it is actuated by the impulses of the current. Each

dip makes the contact, which is broken as the wire springs back. The

mercury should be covered with alcohol to protect it from oxidation.

Circuit Breaker, Pendulum.

A circuit breaker in which a pendulum in its swing makes and breaks a

contact. It may be kept in motion by clockwork, or by an electro-magnet,

attracting intermittently an armature attached to its rod, the

magnet circuit being opened and closed by the pendulum or circuit

breaker itself. A mercury contact may be used with it.

Fig. 88. PENDULUM CIRCUIT BREAKER.

122   STANDARD ELECTRICAL DICTIONARY.

Circuit Breaker, Tuning Fork.

A circuit breaker in which a tuning fork makes and breaks the circuit.

Each vibration of one of the prongs in one direction makes a contact,

and the reverse vibration breaks a contact. The adjustment is

necessarily delicate, owing to the limited amplitude of the motion of

the fork. The fork is kept in vibration sometimes by an electro-magnet,

which is excited as the circuit is closed by the fork. One leg of the

fork acts as the armature of the magnet, and is attracted according to

its own natural period.

Circuit Breaker, Wheel.

A toothed wheel with a spring bearing against its teeth. One terminal of

a circuit connects with the wheel through its axle, the other connects

with the spring. When the wheel is turned the circuit is opened and

closed once for each tooth. The interstices between teeth on such a

wheel may be filled with insulating material, giving a cylindrical

surface for the contact spring to rub on.

Fig. 89--TOOTHED WHEEL CIRCUIT BREAKER.

Circuit, Closed.

A circuit whose electric continuity is complete; to make an open circuit

complete by closing a switch or otherwise is to close, complete, or make

a circuit.

Synonyms--Completed Circuit--Made Circuit.

Circuit, Compound.

A circuit characterized by compounding of generating or receiving

devices, as including several separate batteries, or several motors, or

other receiving devices. It is sometimes used to indicate a circuit

having its battery arranged in series. It should be restricted to the

first definition.

123  STANDARD ELECTRICAL DICTIONARY.

Circuit, Derived.

A partial circuit connected to two points of another circuit, so as to

be in parallel with the portion thereof between such two points; a shunt

circuit.

Synonyms--Shunt Circuit--Derivative Circuit--Parallel Circuit.

Circuit, Electric, Active.

A circuit through which a current passes. The circuit itself need only

be a conducting ring, or endless wire. Generally it includes, as part of

the circuit, a generator of electro-motive force, and through which

generator by conduction, ordinary or electrolytic, the same current goes

that passes through the rest of the circuit. One and the same current

passes through all parts of a series circuit when such current is

constant.

A current being produced by electro-motive force, and electromotive

force disappearing in its production in an active circuit, there must be

some source of energy which will maintain electromotive force against

the drain made upon it by the current.

The simplest conception of an active electric circuit is a ring or

endless conductor swept through a field of force so as to cut lines of

force. A simple ring dropped over a magnet pole represents the

simplification of this process. In such a ring a current, exceedingly

slight, of course, will be produced. In this case there is no generator

in the circuit. An earth coil (see Coil, Earth,) represents such a

circuit, with the addition, when experimented with, of a galvanometer in

the circuit.

In practice, a circuit includes a generator such as a battery or dynamo,

and by conductors is led through a continuous path. Electric lamps,

electrolytic cells, motors and the like may be included in it.

The term "circuit" is also applied to portions of a true circuit, as the

internal circuit, or external circuit. A certain amount of elasticity is

allowed in its use. It by no means necessarily indicates a complete

through circuit.

Circuit, Electrostatic.

(a) A circuit through which an electrostatic or high tension discharge

takes place. It is virtually an electric circuit.

(b) The term is applied also to the closed paths of electrostatic lines

of force.

Circuit, External.

The portion of a circuit not included within the generator.

Circuit, Grounded.

A circuit, one of whose members, the return circuit, is represented by

the earth, so that the earth completes the circuit. In telegraphy each

end of the line is grounded or connected to an earth-plate, q. v., or to

the water or gas-pipes, and the current is assumed to go through the

earth on its return. It really amounts to a discharging at one end, and

charging at the other end of the line. The resistance of the earth is

zero, but the resistance of the grounding or connection with the earth

may be considerable.

Synonyms--Ground Circuit--Earth Circuit--Single Wire Circuit.

[Transcriber's note: The resistance of the earth is high enough that

large power system return currents may produce dangerous voltage

gradients when a power line is shorted to the ground. Don't walk near

downed lines!]

124   STANDARD ELECTRICAL DICTIONARY.

Circuit Indicator.

A pocket compass, decomposition apparatus, galvanometer or other device

for indicating the condition of a wire, whether carrying a current or

not, and, if carrying one, its direction, and sometimes roughly

indicating its strength.

Circuit, Internal.

The portion of an electric circuit included within the generator.

Circuit, Line.

The portion of a circuit embracing the main line or conductor, as in a

telegraph circuit the line carried on the poles; distinguished from the

local circuit (see Circuit, Local,) in telegraphy.

Circuit, Local.

In telegraphy, a short circuit with local generator or battery included,

contained within the limits of the office or station and operated by a

relay, q. v. This was the original local circuit; the term is applicable

to any similar arrangement in other systems. Referring to the cut, the

main line circuit includes the main battery, E, Key, P, Relay, R, ground

plates, G, G1. The relay magnet opens and closes the local circuit with

its local battery, L, and sounder magnet, H, with its armature, B. The

minor parts, such as switches, are omitted.

Fig. 90. LOCAL CIRCUIT OF TELEGRAPH SYSTEM.

Circuit, Local Battery.

A local circuit worked by and including a local battery in its course.

125   STANDARD ELECTRICAL DICTIONARY.

Circuit, Loop.

A minor circuit introduced in series into another circuit by a cut-out,

or other device, so as to become a portion of the main circuit.

Circuit Loop Break.

A supporter or bracket with two arms for carrying insulators. Its use is

to enable a loop connection to be introduced into a line which is cut,

so as to enable the connection of the ends of the loop to be made, one

to each end of the through wire, which ends are attached, one to each of

the two insulators.

Circuit, Main.

The circuit including the main line and apparatus supplied by the main

battery, as distinguished from the local circuit. (See Circuit, Local.)

Circuit, Main Battery.

The main circuit, including the main or principal battery in its course.

Circuit, Metallic.

A circuit in which the current outside the generator, or similar parts,

is carried on a metallic conductor; a circuit without any ground

circuit. The including of a galvanic battery or electro plating bath

would not prevent the application of the term; its essential meaning is

the omission of the earth as the return circuit.

Circuit, Negative Side of.

The side of a circuit opposite to the positive side. (See Circuit,

Positive Side of) It is defined as the half of a circuit leading to the

positive terminal of the generator.

Circuit, Open.

A circuit with its continuity broken, as by disconnecting a wire from

the battery, or opening a switch; a broken circuit is its synonym. To

open a switch or disconnect or cut the wire is termed opening or

breaking the circuit.

Synonyms--Incomplete Circuit--Broken Circuit.

Circuit, Positive Side of.

This side is such that an observer standing girdled by the current with

his head in the positive side or region, would see the current pass

around him from his right toward his left hand. It is also defined as

the half of the circuit leading to the negative terminal of the

generator.

Circuit, Recoil.

The portion of a parallel circuit presenting an alternative path, q. v.,

for a disruptive discharge.

Circuit, Return.

(a) The part of a circuit extending from the generator to the extreme

point in general, upon which no apparatus is placed. In telegraph

systems the ground generally forms the return circuit. The distinction

of return and working circuit cannot always be made.

(b) It may also be defined as the portion of a circuit leading to the

negative terminal of the generator.

126   STANDARD ELECTRICAL DICTIONARY

Circuits, Forked.

Circuits starting in different paths or directions from one and the same

point.

Circuit, Simple.

A circuit containing a single generator, and single receiver of any

kind, such as a motor or sounder, with a single connecting conductor. It

is also used to indicate arrangement in multiple arc, but not generally,

or with approval.

Circuits, Parallel.

Two or more conductors starting from a common point and ending at

another common point are termed, parallel circuits, although really but

parts of circuits. If of equal resistance their joint resistance is

obtained by dividing the resistance of one by the number of parallel

circuits. If of unequal resistance r, r', r" , etc., the formula for

joint resistance, R, of two is

R = ( r * r' ) / ( r + r' )

This resistance may then be combined with a third one by the same

formula, and thus any number may be calculated.

Synonym--Shunt Circuit.

Circuit, Voltaic.

Properly a circuit including a conductor and voltaic couple.

It is also applied to the electric circuit, q. v., or to any circuit

considered as a bearer of current electricity.

Circular Units.

Units of area, usually applied to cross sectional area of conductors, by

whose use area is expressed in terms of  circle of unit diameter,

usually a circular mil, which is the area of a circle of one-thousandth

of an inch diameter, or a circular millimeter, which is the area of a

circle of one millimeter diameter. Thus a wire one-quarter of an inch

in diameter has an area of 250 circular mils; a bar one centimeter in

diameter has an area of ten circular millimeters.

[Transcriber's Note: Area is the diameter squared. A 1/4 inch wire has

62500 circular mils of area. A one centimeter (10 millimeter) wire has

100 circular millimeters of area. Actual area = circular mils * (PI/4).]

Circumflux.

The product of the total number of conductor turns on the armature of a

dynamo or motor, into the current carried thereby. For two pole machines

it is equal to twice the armature ampere-turns; for four pole machines

to four times such quantity, and so on.

Clamp.

The appliance for grasping and retaining the end of the rod that holds a

carbon in the arc lamp.

Clark's Compound.

A cement used for the outside of the sheath of telegraph cables.

Its formula is:

Mineral Pitch,   65 parts.

Silica,          30 parts.

Tar,              5 parts.

All parts by weight.

127  STANDARD ELECTRICAL DICTIONARY.

Cleats.

A support; a short block of wood, grooved transversely, for holding

electric wires against a wall. For the three wire system three grooves

are used. The entire wiring of apartments is sometimes done by the

"cleat system," using cleats instead of battens, q. v., or mouldings.

The cleats are secured against the wall with the grooves facing it, and

the wires are introduced therein.

Fig. 91. TWO WIRE CLEAT.

Fig. 92. THREE WIRE CLEAT.

Cleat, Crossing.

A cleat with grooves or apertures to support wires which cross each

other. Two or three grooves are transverse, and on the under side, as

above; one groove is longitudinal and on the upper side.

Cleavage, Electrification by.

If a mass of mica is rapidly split in the dark a slight flash is

perceived. Becquerel found that in such separation the two pieces came

away oppositely charged with electricity. The splitting of mica is its

cleavage.

Clock, Controlled.

In a system of electric clocks, the clocks whose movements are

controlled by the current, regulated by the master or controlling clock.

Synonym--Secondary Clock.

Clock, Controlling.

In a system of electric clocks the master clock which controls the

movements of the others, by regulating the current.

Synonym--Master Clock.

Clock, Electric Annunciator.

A clock operating any form of electric annunciator, as dropping

shutters, ringing bells, and the like. It operates by the machinery

closing circuits as required at any desired hour or intervals.

128   STANDARD ELECTRICAL DICTIONARY.

Clock, Electrolytic.

A clock worked by the electrolytic deposition and resolution of a

deposit of metal upon a disc. It is the invention of Nikola Tesla. A

metallic disc is mounted on a transverse axis, so as to readily rotate.

It is immersed in a vessel of copper sulphate. A current is passed

through the bath, the terminals or electrodes being near to and facing

the opposite edges of the disc, so that the line connecting the

electrodes lies in the plane of the disc. If a current is passed through

the solution by the electrodes, copper is deposited on one side of the

disc, and as it rotates under the influence of the weight thus

accumulated on one side, the same metal as it is brought to the other

side of the disc is redissolved. Thus a continuous rotation is

maintained. The cause of the deposition and solution is the position of

the disc; one-half becomes negative and the other positive in their

mutual relations.

Clock, Self-winding Electric.

A clock which is wound periodically by an electric motor and battery.

Clockwork, Feed.

In arc-lamps the system of feeding the carbon or carbons by clockwork

whose movements are controlled by the resistance of the arc. This system

is employed in the Serrin, and in the Gramme regulators, among others.

The carbons, if they approach, move clockwork. The movement of this is

stopped or freed by an electro-magnet placed in shunt around the arc

and carbons.

Cloisons.

Partitions or divisions; applied to the winding of electro-magnets and

coils where the winding is put on to the full depth, over single

sections of the core, one section at a time, until the whole core is

filled up.

Closure.

The closing or completion of a circuit by depressing a key or moving a

switch.

Clutch.

In arc lamps a device for the feed of the upper carbons. In its simplest

form it is simply a plate or bar pierced with a hole through which the

carbon passes loosely. The action of the mechanism raises or lowers one

end of the plate or bar. As it rises it binds and clutches the carbon,

and if the action continues it lifts it a little. When the same end is

lowered the carbon and clutch descend together until the opposite end of

the clutch being prevented from further descent, the clutch approaches

the horizontal position and the rod drops bodily through the aperture.

The cut shows the clutches of the Brush double carbon lamp. In practice

the lifting and releasing as regulated by an electro-magnet are so very

slight that practically an almost absolutely steady feed is secured. A

similar clutch is used in the Weston lamp.

129  STANDARD ELECTRICAL DICTIONARY.

Clutch, Electro-magnetic.

A clutch or appliance for connecting a shaft to a source of rotary

motion while the latter is in action. In one form a disc, in whose face

a groove has been formed, which groove is filled with a coil of wire, is

attached to the loose wheel, while the shaft carries a flat plate to act

as armature. On turning on the current the flat plate is attached,

adheres, and causes its wheel to partake of the motion of the shaft.

Contact is made by brushes and collecting rings.

In the cut, A A is the attracted disc; the brushes, B B, take current to

the collecting rings, C. The magnetizing coil is embedded in the body of

the pulley, as shown.

Fig. 93. CLUTCH OF BRUSH LAMP.

Fig. 94. ELECTRO-MAGNETIC CLUTCH.

130   STANDARD ELECTRICAL DICTIONARY.

Coatings of a Condenser or Prime Conductor.

The thin conducting coatings of tinfoil, gold leaf or other conducting

substance, enabling the surface to receive and part with the electric

charge readily. Without such a coating the charge and discharge would be

very slow, and would operate by degrees only, as one part of a

non-conducting surface might be densely charged and another part be

quite devoid of sensible charge.

Code, Cipher.

A code of arbitrary words to designate prearranged or predetermined

words, figures or sentences. The systems used in commerce have single

words to represent whole sentences or a number of words of a sentence.

This not only imparts a degree of secrecy, but makes the messages much

shorter. Codes are used a great deal in cable transmission.

Code, Telegraphic.

A telegraphic alphabet. (See Alphabets, Telegraphic.)

Coefficient.

In algebra, the numerical multiplier of a symbol, as in the expression

"5x," 5 is the coefficient. In physics, generally a number expressing

the ratio or relation between quantities, one of which is often unity,

as a standard or base of the set of coefficients. Thus the coefficient

of expansion by heat of any substance is obtained by dividing its volume

for a given degree of temperature by its volume at the standard

temperature as 0º C., or 32º F. This gives a fraction by which if any

volume of a substance, taken at 0º C., or at whatever may be taken as

the basic temperature, is multiplied, the expanded volume for the given

change of temperature will be obtained as the product. A coefficient

always in some form implies the idea of a multiplier. Thus the

coefficient of an inch referred to a foot would be 1/12 or .833+,

because any number of inches multiplied by that fraction would give the

corresponding number of feet.

[Transcriber's note: 1/12 is 0.0833+]

Coefficient, Economic.

In machinery, electric generators, prime motors and similar structures,

the number expressing the ratio between energy absorbed by the device,

and useful, not necessarily available, work obtained from it. It is

equal to work obtained divided by energy absorbed, and is necessarily a

fraction. If it exceeded unity the doctrine of the conservation of

energy would not be true. The economic coefficient expresses the

efficiency, q. v., of any machine, and of efficiencies there are several

kinds, to express any one of which the economic coefficient may be used.

Thus, let W--energy absorbed, and w = work produced ; then w/W is the

economic coefficient, and for each case would be expressed numerically.

(See Efficiency, Commercial--Efficiency, Electrical--Efficiency of

Conversion.)

The distinction between useful and available work in a dynamo is as

follows: The useful work would include the work expended by the field,

and the work taken from the armature by the belt or other mechanical

connection. Only the latter would be the available work.

131  STANDARD ELECTRICAL DICTIONARY.

Coercive or Coercitive Force.

The property of steel or hard iron, in virtue of which it slowly takes

up or parts with magnetic force, is thus termed ("traditionally";

Daniell). It seems to have to do with the positions of the molecules, as

jarring a bar of steel facilitates its magnetization or accelerates its

parting, when not in a magnetic field, with its permanent or residual

magnetism. For this reason a permanent magnet should never be jarred,

and permitting the armature to be suddenly attracted and to strike

against it with a jar injures its attracting power.

Coercive force is defined also as the amount of negative magnetizing

force required to reduce remnant magnetism to zero.

By some authorities the term is entirely rejected, as the phenomenon

does not seem directly a manifestation of force.

Coil and Coil Plunger.

A device resembling the coil and plunge, q. v., except that for the

plunger of iron there is substituted a coil of wire of such diameter as

to enter the axial aperture of the other, and wound or excited in the

same or in the opposite sense, according to whether attraction or

repulsion is desired.

Coil and Plunger.

A coil provided with a core which is free to enter or leave the central

aperture. When the coil is excited, the core is drawn into it. Various

forms of this device have been used in arc lamp regulators.

Synonym--Sucking coil.

Fig. 95. COIL AND COIL PLUNGER OF MENGIES ARC LAMP.

Fig. 96. COIL AND PLUNGER EXPERIMENT.

132   STANDARD ELECTRICAL DICTIONARY.

Coil and Plunger, Differential.

An arrangement of coil and plunger in which two plungers or one plunger

are acted on by two coils, wound so as to act oppositely or

differentially on the plunger or plungers. Thus one coil may be in

parallel with the other, and the action on the plunger will then depend

on the relative currents passing through the coils.

Coil, Choking.

A coil of high self-induction, used to resist the intensity of or

"choke" alternating currents. Any coil of insulated wire wound around

upon a laminated or divided iron core forms a choking coil. The iron

coil is usually so shaped as to afford a closed magnetic circuit.

A converter or transformer acts as a choking coil as long as its

secondary is left open. In alternating current work special choking

coils are used. Thus for theatrical work, a choking coil with a movable

iron core is used to change the intensity of the lights. It is in

circuit with the lamp leads. By thrusting in the core the self-induction

is increased and the current diminishes, lowering the lamps; by

withdrawing it the self-induction diminishes, and the current increases.

Thus the lamps can be made to gradually vary in illuminating power like

gas lights, when turned up or down.

Synonyms--Kicking Coil--Reaction Coil.

Fig. 97. DIFFERENTIAL COILS AND PLUNGERS.

Fig. 98. BISECTED COILS.

133    STANDARD ELECTRICAL DICTIONARY.

Coils, Bisected.

Resistance coils with connections at their centers, as shown in the

diagram. They are used for comparing the resistances of two conductors.

The connections are arranged as shown in the coil, each coil being

bisected. For the wires, movable knife-edge contacts are employed. The

principle of the Wheatstone bridge is used in the method and

calculations.

Coil, Earth.

A coil of wire mounted with commutator to be rotated so as to cut the

lines of force of the earth's magnetic field, thereby generating

potential difference. The axis of rotation may be horizontal, when the

potential will be due to the vertical component of the earth's field, or

the axis may be horizontal, when the potential will be due to the

vertical component, or it may be set at an intermediate angle.

Synonym--Delezenne's Circle.

Fig. 99. DELEZENNE'S CIRCLE OR EARTH COIL.

Coil, Electric.

A coil of wire used to establish a magnetic field by passing a current

through it. The wire is either insulated, or so spaced that its

convolutions do not touch.

Coil, Flat.

A coil whose windings all lie in one plane, making a sort of disc, or an

incomplete or perforated disc.

Coil, Induction.

A coil in which by mutual induction the electromotive force of a portion

of a circuit is made to produce higher or lower electro-motive force, in

an adjoining circuit, or in a circuit, part of which adjoins the

original circuit, or adjoins part of it.

An induction coil comprises three principal parts, the core, the primary

coil and the secondary coil. If it is to be operated by a steady

current, means must be provided for varying it or opening and closing

the primary circuit. A typical coil will be described.

134   STANDARD ELECTRICAL DICTIONARY.

The core is a mass of soft iron preferably divided to prevent extensive

Foucault currents. A cylindrical bundle of soft iron wires is generally

used. Upon this the primary coil of reasonably heavy wire, and of one or

two layers in depth, is wrapped, all being carefully insulated with

shellac and paper where necessary. The secondary coil is wrapped upon or

over the primary. It consists of very fine wire; No. 30 to 36 is about

the ordinary range. A great many turns of this are made. In general

terms the electro-motive force developed by the secondary stands to that

of the primary terminals in the ratio of the windings. This is only

approximate.

The greatest care is required in the insulating. The secondary is

sometimes wound in sections so as to keep those parts differing greatly

in potential far from each other. This prevents sparking, which would

destroy the insulation.

A make and break, often of the hammer and anvil type, is operated by the

coil. (See Circuit Breaker, Automatic.) As the current passes through

the primary it magnetizes the core. This attracts a little hammer which

normally resting on an anvil completes the circuit. The hammer as

attracted is lifted from the anvil and breaks the circuit. The soft iron

core at once parts with its magnetism and the hammer falls upon the

anvil again completing the circuit. This operation goes on rapidly, the

circuit being opened and closed in quick succession.

Every closing of the primary circuit tends to produce a reverse current

in the secondary, and every opening of the primary circuit tends to

produce a direct current in the secondary. Both are of extremely short

duration, and the potential difference of the two terminals of the

secondary may be very high if there are many times more turns in the

secondary than in the primary.

The extra currents interfere with the action of an induction coil. To

avoid their interference a condenser is used. This consists of two

series of sheets of tin foil. Leaves of paper alternate with the sheets

of tin-foil, the whole being built up into a little book. Each sheet of

tin-foil connects electrically with the sheet next but one to it. Thus

each leaf of a set is in connection with all others of the same set, but

is insulated from the others. One set of leaves of tin-foil connects

with the hammer, the other with the anvil. In large coils there may be

75 square feet of tin-foil in the condenser.

The action of the condenser is to dispose of the direct extra current.

When the primary circuit is opened this current passes into the

condenser, which at once discharges itself in the other direction

through the coil. This demagnetizes the core, and the action intensifies

and shortens the induced current. The condenser prevents sparking, and

in general improves the action of the coil.

Many details enter into the construction of coils, and many variations

in their construction obtain. Thus a mercury cup into which a plunger

dips often replaces the anvil and hammer.

135   STANDARD ELECTRICAL DICTIONARY.

The induction coil produces a rapid succession of sparks, which may

spring across an interval of forty inches. The secondary generally ends

in special terminals or electrodes between which the sparking takes

place. A plate of glass, two inches in thickness, can be pierced by

them. In the great Spottiswoode coil there are 280 miles of wire in the

secondary, and the wire is about No. 36 A.W.G.

Fig. 100. VERTICAL SECTION OF INDUCTION COIL.

Fig. l01. PLAN OF INDUCTION COIL CONNECTIONS.

Induction coils have quite extended use in electrical work. They are

used in telephone transmitters, their primary being in circuit with the

microphone, and their secondary with the line and receiving telephone.

In electric welding, and in the alternating current system they have

extended application. In all these cases they have no automatic circuit

breaker, the actuating current being of intermittent or alternating

type.

136   STANDARD ELECTRICAL DICTIONARY.

In the cuts the general construction of an induction coil is shown. In

the sectional elevation, Fig. 100, A, is the iron core; B is the primary

of coarse wire; C is a separating tube, which may be of pasteboard; D is

the secondary of fine wire; E, E are the binding posts connected to the

secondary; H, H are the heads or standards; K, K are the terminals of

the primary; F is the vibrating contact spring; G, a standard carrying

the contact screw; J is the condenser with wires, L, M, leading to it.

Referring to the plan, Fig. 101, H represents the primary coil; B and A

are two of the separate sheets of the condenser, each sheet with

projecting ears; G, G are the heads of the coil; the dark lines are

connections to the condenser. One set of sheets connects with the

primary coil at C, and also with the vibrating spring shown in plan and

in the elevation at F. The other set of sheets connects with the post,

carrying the contact screw. The other terminal of the primary runs to a

binding post E. F, in the plan is a binding post in connection with the

standard and contact screw.

Coil, Induction, Inverted.

An induction coil arranged to have a lower electro-motive force in the

secondary than in the primary. This is effected by having more

convolutions in the primary wire than in the secondary. Such coils in

practice are used with the alternating current and then do not include a

circuit breaker or condenser. They are employed in alternating current

system and in electric welding. (See Welding, Electric--Converter.)

In the cut an inverted coil, as constructed for electric welding is

shown. In it the primary coil is marked P; the secondary, merely a bar

of metal, is marked E, with terminals S, S; the heavy coils, I, of iron

wire are the core; K is a screw for regulating the clamps; J, Z is a

second one for the same purpose, while between D and D' the heat is

produced for welding the bars, B, B', held in the clamps, C, C'. It will

be seen how great may be the difference in turns between the single

circle of heavy copper rod or bar which is the secondary of the coil,

and the long coil of wire forming the primary.

Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING.

137   STANDARD ELECTRICAL DICTIONARY.

Coil, Induction, Telephone.

An induction coil used in telephone circuits. It is placed in the box or

case near the transmitter. The primary is in circuit with the

microphone. The secondary is in circuit with the line and receiving

telephone. In the Bell telephone apparatus the primary of the induction

coil is wound with No. 18 to 24 A. W. G. wire to a resistance of 1/2

ohm; the secondary, with No. 36 wire to a resistance of 80 ohms. The

Edison telephone induction coil was wound with similar wires to a

resistance of 3 to 4 ohms and of 250 ohms respectively.

Coil, Magnetizing.

A coil of insulated wire for making magnets; and for experimental uses;

it has a short axis and central aperture of as small size as consistent

with the diameter of the bar to be magnetized, which has to pass through

it readily. The wire may be quite heavy, 2 or 3 millimeters (.08--.12

inch) thick, and is cemented together with carpenter's glue, or with

shellac or ethereal solution of gum copal. In use it is passed over the

bar a few times while a heavy current is going through it. It is used

for magic circles also. (See Circle, Magic.)

Fig. 103. MAGNETIZING COIL.

Coil, Resistance.

A coil constructed for the purpose of offering a certain resistance to a

steady current. This resistance may be for the purpose of carrying out

quantitative tests, as in Wheatstone bridge work (see Wheatstone's

Bridge), or simply to reduce the intensity of a current. For the first

class of work the coils are wound so as to prevent the creation of a

magnetic field. This is effected by first doubling the wire without

breaking it, and then starting at the bend the doubled wire, which is

insulated, is wound on a bobbin or otherwise until a proper resistance

is shown by actual measurement. The coils are generally contained or set

in closed boxes with ebonite tops. Blocks of brass are placed on the

top, and one end from one coil and one end from the next connect with

the same block. By inserting a plug, P, so as to connect any two blocks,

which have grooves reamed out for the purpose, the coil beneath will be

short circuited. German silver, platinoid or other alloy, q. v., is

generally the material of the wire. A great object is to have a wire

whose resistance will be unaffected by heat.

138   STANDARD ELECTRICAL DICTIONARY.

Fig. 104. RESISTANCE COILS AND CONNECTIONS, SHOWING PLUG.

Coil, Rhumkorff.

The ordinary induction coil with circuit breaker, for use with original

direct and constant current, is thus termed. (See Coil, Induction.)

Synonym--Inductorium.

Coil, Ribbon.

A coil made of copper ribbon wound flatwise, often into a disc-like

shape, and insulated by tape or strips of other material intervening

between the successive turns.

Coils, Compensating.

Extra coils on the field magnets of dynamos or motors, which coils are

in series with the armature windings for the purpose of keeping the

voltage constant. In compound wound machines the regular series-wound

coil is thus termed. In a separately excited dynamo a coil of the same

kind in circuit with the armature may be used as a compensator.

Coils, Henry's.

An apparatus used in repeating a classic experiment in electro-magnetic

induction, due to Prof. Henry. It consists in a number of coils, the

first and last ones single, the intermediate ones connected in pairs,

and one of one pair placed on the top of one of the next pair. On

opening or closing the circuit of an end coil the induced effect goes

through the series and is felt in the circuit of the other end coil.

Prof. Henry extended the series so as to include seven successive

inductions, sometimes called inductions of the first, second, third and

other orders. Frequently ribbon coils (see Coil, Ribbon,) are used in

these experiments.

Coils, Sectioned.

A device for prolonging the range of magnetic attraction. It consists of

a series of magnetizing coils traversed by an iron plunger. As it passes

through them, the current is turned off the one in the rear or passing

to the rear and turned into the next one in advance. The principle was

utilized in one of Page's electric motors about 1850, and later by

others. The port-electric railroad, q. v., utilizes the same principle.

139  STANDARD ELECTRICAL DICTIONARY.

Collecting Ring.

In some kinds of generators instead of the commutator a pair of

collecting rings of metal, insulated from the machine and from each

other, are carried on the armature shaft. A brush, q. v., presses on

each, and the circuit terminals connect to these two brushes. Such rings

are employed often on alternating current generators, where the current

does not have to be changed or commuted. Collecting rings with their

brushes are used also where a current has to be communicated to a

revolving coil or circuit as in the magnetic car wheel, the cut of which

is repeated here. The coil of wire surrounding the wheel and rotating

with it has to receive current. This it receives through the two

stationary brushes which press upon two insulated metallic rings,

surrounding the shaft. The terminals of the coil connect one to each

ring. Thus while the coil rotates it constantly receives current, the

brushes being connected to the actuating circuit.

Fig. 105. MAGNETIC CAR WHEEL SHOWING

COLLECTING RINGS AND BRUSHES.

Collector.

(a) A name for the brush, q. v., in mechanical electric generators, such

as dynamos, a pair of which collectors or brushes press on the

commutator or collecting rings, and take off the current.

(b) The pointed connections leading to the prime conductor on a static

machine for collecting the electricity; often called combs. The points

of the combs or collectors face the statically charged rotating glass

plate or cylinder of the machine.

Colombin.

The insulating material between the carbons in a Jablochkoff candle or

other candle of that type. Kaolin was originally used. Later a mixture

of two parts calcium sulphate (plaster of Paris) and one part barium

sulphate (barytes) was substituted.

The colombin was three millimeters (.12 inch) wide, and two millimeters

(.08 inch) thick. (See Candle, Jablochkoff.)

Column, Electric.

An old name for the voltaic pile, made up of a pile of discs of copper

and zinc, with flannel discs, wet with salt solution or dilute acid,

between each pair of plates.

140   STANDARD ELECTRICAL DICTIONARY.

Comb.

A bar from which a number of teeth project, like the teeth of a comb. It

is used as a collector of electricity from the plate of a frictional or

influence electric machine; it is also used in a lightning arrester to

define a path of very high resistance but of low self-induction, for the

lightning to follow to earth.

Communicator.

The instrument by which telegraph signals are transmitted is sometimes

thus termed.

Commutator.

In general an apparatus for changing. It is used on electric current

generators, and motors, and on induction coils, and elsewhere, for

changing the direction of currents, and is of a great variety of types.

Synonym--Commuter (but little used).

Fig. 106. DYNAMO OR MOTOR COMMUTATOR.

Commutator Bars.

The metallic segments of a dynamo or motor commutator.

Commutator, Flats in.

A wearing away or lowering in level of one or more metallic segments of

a commutator. They are probably due in many cases to sparking, set up by

periodic springing in the armature mounting, or by defective commutator

connections.

Commutator of Current Generators and Motors.

In general a cylinder, formed of alternate sections of conducting and

non-conducting material, running longitudinally or parallel with the

axis. Its place is on the shaft of the machine, so that it rotates

therewith. Two brushes, q. v., or pieces of conducting material, press

upon its surface.

141  STANDARD ELECTRICAL DICTIONARY.

As a part of electric motors and generators, its function is to collect

the currents produced by the cutting of lines of force so as to cause

them all to concur to a desired result. The cut shows the simplest form

of commutator, one with but two divisions. Its object may be to enable a

current of constant direction to be taken from a rotating armature, in

which the currents alternate or change direction once in each rotation.

It is carried by the shaft A of the armature and rotates with it. It

consists of two leaves, S S, to which the terminals of the armature are

connected. Two springs, W W, the terminals of the outer circuit, press

against the leaves. The springs which do this take off the current. It

is so placed, with reference to the springs and armature, that just as

the current changes in direction, each leaf changes from one spring to

the other. Thus the springs receive constant direction currents. The

changing action of this commutator appears in its changing the character

of the current from alternating to constant. Were two insulated

collecting rings used instead of a commutator, the current in the outer

circuit would be an alternating one. On some dynamos the commutator has

a very large number of leaves.

Taking the Gramme ring armature, there must be as many divisions of the

commutator as there are connections to the coils. In this case the

function of the commutator is simply to lessen friction, for the brushes

could be made to take current from the coils directly outside of the

periphery of the ring.

Commutator, Split Ring.

A two-division commutator for a motor; it consists of two segments of

brass or copper plate, bent to arcs of a circle, and attached to an

insulating cylinder. They are mounted on the revolving spindle, which

carries the armature, and acts as a two part commutator. For an example

of its application, see Armature, Revolving, Page's. (See also Fig.

107.)

Fig. 107. SECTION OF SPLIT RING COMMUTATOR, WITH BRUSHES.

Compass.

An apparatus for utilizing the directive force of the earth upon the

magnetic needle. It consists of a circular case, within which is poised

a magnetized bar of steel. This points approximately to the north, and

is used on ships and elsewhere to constantly show the direction of the

magnetic meridian. Two general types are used. In one the needle is

mounted above a fixed "card" or dial, on which degrees or points of the

compass, q. v., are inscribed. In the other the card is attached to the

needle and rotates with it. The latter represents especially the type

known as the mariner's compass. (See Compass, Mariner's--Compass,

Spirit, and other titles under compass, also Magnetic Axis--Magnetic

Elements.) The needle in good compasses carries for a bearing at its

centre, a little agate cup, and a sharp brass pin is the point of

support.

Compass, Azimuth.

A compass with sights on one of its diameters; used in determining the

magnetic bearing of objects.

142   STANDARD ELECTRICAL DICTIONARY.

Compass Card.

The card in a compass; it is circular in shape, and its centre coincides

with the axis of rotation of the magnetic needle; on it are marked the

points of the compass, at the ends generally of star points. (See

Compass, Points of the.) It may be fixed, and the needle may be poised

above it, or it may be attached to the needle and rotate with it.

Compass, Declination.

An instrument by which the magnetic declination of any place may be

determined. It is virtually a transit instrument and compass combined,

the telescope surmounting the latter. In the instrument shown in the

cut, L is a telescope mounted by its axis, X, in raised journals with

vernier, K, and arc x, for reading its vertical angle, with level n. The

azimuth circle, Q, R, is fixed. A vernier, V is carried by the box, A,

E, and both turn with the telescope. A very light lozenge-shaped

magnetic needle, a, b, is pivoted in the exact centre of the graduated

circles, Q R, and M. The true meridian is determined by any convenient

astronomical method, and the telescope is used for the purpose. The

variation of the needle from the meridian thus determined gives the

magnetic declination.

FIG. 108. DECLINATION COMPASS.

Compass, Inclination.

A magnetic needle mounted on a horizontal axis at its centre of gravity,

so as to be free to assume the dip, or magnetic inclination, when placed

in the magnetic meridian. It moves over the face of a vertical graduated

circle, and the frame also carries a spirit level and graduated

horizontal circle. In use the frame is turned until the needle is

vertical. Then the axis of suspension of the needle is in the magnetic

meridian. The vertical circle is then turned through 90° of the horizon,

which brings the plane of rotation of the needle into the magnetic

meridian, when it assumes the inclination of the place.

143  STANDARD ELECTRICAL DICTIONARY.

Compass, Mariner's.

A compass distinguished by the card being attached to and rotating with

the needle. A mark, the "lubber's mark" of the sailors is made upon the

case. This is placed so that the line connecting it, and the axis of

rotation of the card is exactly in a plane, passing through the keel of

the ship. Thus however the ship may be going, the point of the card

under or in line with the "lubber's mark," shows how the ship is

pointing. The case of the mariner's compass is often bowl-shaped and

mounted in gimbals, a species of universal joint, so as to bc always

horizontal. (See Compass, Spirit-Gimbals.)

FIG. 109. MARINER'S COMPASS.

Compass, Points of the.

The circle of the horizon may bc and is best referred to angular

degrees. It has also been divided into thirty-two equiangular and named

points. A point is 11.25°. The names of the points are as follows:

North, North by East, North North-east, North-east by North, North-east,

North-east by East, East North-east, East by North, East, East by South,

East South-east, South-east by East, South-east, South-east by South,

South South-east, South by East, South, South by West, South South-west,

South-west by South, South-west, South-west by West, West South-west,

West by South, West, West by North, West North-west, North-west by West,

North-west, North West by North, North North-west, North by West. They

are indicated by their initials as N. N. W., North North-west, N. by W.,

North by West.

Compass, Spirit.

A form of mariner's compass. The bowl or case is hermetically sealed and

filled with alcohol or other nonfreezing liquid. The compass card is

made with hollow compartments so as nearly to float. In this way the

friction of the pivot or point of support is greatly diminished, and the

compass is far more sensitive.

Compass, Surveyor's.

A species of theodolite; a telescope with collimation lines, mounted

above a compass, so as to be applicable for magnetic surveys. Its use is

to be discouraged on account of the inaccuracy and changes in

declination of the magnetic needle.

144   STANDARD ELECTRICAL DICTIONARY.

Compensating Resistances.

In using a galvanometer shunt the total resistance of the circuit is

diminished so that in some cases too much current flows through it; in

such case additional resistance, termed as above, is sometimes

introduced in series. The shunt in parallel with the galvanometer is

thus compensated for, and the experimental or trial circuit does not

take too much current.

Complementary Distribution.

Every distribution of electricity has somewhere a corresponding

distribution, exactly equal to it of opposite electricity; the latter is

the complimentary distribution to the first, and the first distribution

is also complimentary to it.

Component.

A force may always be represented diagrammatically by a straight line,

terminating in an arrow-head to indicate the direction, and of length to

represent the intensity of the force. The line may always be assumed to

represent the diagonal of a parallelogram, two of whose sides are

represented by lines starting from the base of the arrow, and of length

fixed by the condition that the original force shall be the diagonal of

the parallelogram of which they are two contiguous sides; such lines are

called components, and actually represent forces into which the original

force may always be resolved. The components can have any direction.

Thus the vertical component of a horizontal force is zero; its

horizontal component is equal to itself. Its 450 component is equal to

the square root of one-half of its square.

Condenser.

An appliance for storing up electrostatic charges: it is also called a

static accumulator. The telegraphic condenser consists of a box packed

full of sheets of tinfoil. Between every two sheets is a sheet of

paraffined paper, or of mica. The alternate sheets of tinfoil are

connected together, and each set has its own binding post. (See

Accumulator, Electrostatic.)

Condenser, Sliding.

An apparatus representing a Leyden jar whose coatings can be slid past

each other. This diminishes or increases the facing area, and

consequently in almost exactly similar ratio diminishes or increases the

capacity of the condenser.

Conductance.

The conducting power of a given mass of specified material of specified

shape and connections. Conductance varies in cylindrical or prismatic

conductors, inversely as the length, directly as the cross-section, and

with the conductivity of the material. Conductance is an attribute of

any specified conductor, and refers to its shape, length and other

factors. Conductivity is an attribute of any specified material without

direct reference to its shape, or other factors.

Conduction.

The process or act of conducting a current.

145  STANDARD ELECTRICAL DICTIONARY.

Conductivity.

The relative power of conducting the electric current possessed by

different substances. A path for the current through the ether is opened

by the presence of a body of proper quality, and this quality, probably

correlated to opacity, is termed conductivity. There is no perfect

conductor, all offer some resistance, q. v., and there is hardly any

perfect non-conductor. It is the reverse and reciprocal of resistance.

Conductivity, Specific.

The reciprocal of specific resistance. (See Resistance--Specific.)

Conductivity, Unit of.

The reciprocal of the ohm; it is a more logical unit, but has never been

generally adopted; as a name the title mho (or ohm written backwards)

has been suggested by Sir William Thomson, and provisionally adopted.

Conductivity, Variable.

The conductivity for electric currents of conductors varies with their

temperature, with varying magnetization, tension, torsion and

compression.

Conductor.

In electricity, anything that permits the passage of an electric

current. Any disturbance in the ether takes the form of waves because

the ether has restitutive force or elasticity. In a conductor, on the

other hand, this force is wanting; it opens a path through the ether and

a disturbance advances through it from end to end with a wave front, but

with no succession of waves. This advance is the beginning of what is

termed a current. It is, by some theorists, attributed to impulses given

at all points along the conductor through the surrounding ether, so that

a current is not merely due to an end thrust. If ether waves preclude a

current on account of their restitutive force, ether waves cannot be

maintained in a conductor, hence conductors should be opaque to light,

for the latter is due to ether waves. This is one of the more practical

every day facts brought out in Clerk Maxwell's electromagnetic theory of

light. The term conductor is a relative one, as except a vacuum there is

probably no substance that has not some conducting power. For relative

conducting power, tables of conductivity, q. v., should be consulted.

The metals beginning with silver are the best conductors, glass is one

of the worst.

[Transcriber's note: See "ether" for contemporary comments on this now

discarded concept.]

Conductor, Anti-Induction.

A current conductor arranged to avoid induction from other lines. Many

kinds have been invented and made the subject of patents. A fair

approximation may be attained by using a through metallic circuit and

twisting the wires composing it around each other. Sometimes concentric

conductors, one a wire and the other a tube, are used, insulated, one

acting as return circuit for the other.

Conductor, Conical.

A prime conductor of approximately conical shape, but rounded on all

points and angles. Its potential is highest at the point.

146   STANDARD ELECTRICAL DICTIONARY.

Conductor, Imbricated.

A conductor used in dynamo armatures for avoiding eddy currents, made by

twisting together two or more strips of copper.

Conductor, Prime.

A body often cylindrical or spherical in shape, in any case with no

points or angles, but rounded everywhere, whose surface, if the

conductor itself is not metallic, is made conducting by tinfoil or gold

leaf pasted over it. It is supported on an insulating stand and is used

to collect or receive and retain static charges of electricity.

Conductors, Equivalent.

Conductors of identical resistance. The quotient of the length divided

by the product of the conductivity and cross-section must be the same in

each, if each is of uniform diameter.

Conjugate. adj.

Conjugate coils or conductors are coils placed in such relation that the

lines of force established by one do not pass through the coils of the

other. Hence variations of current in one produce no induced currents in

the other.

Connect. v.

To bring two ends of a conductor together, or to bring one end of a

conductor in connection with another, or in any way to bring about an

electrical connection.

Connector.

A sleeve with screws or other equivalent device for securing the ends of

wires in electrical contact. A binding-post, q. v., is an example.

Sometimes wire spring-catches are used, the general idea being a device

that enables wires to be connected or released at will without breaking

off or marring their ends. The latter troubles result from twisting

wires together.

Consequent Poles.

A bar magnet is often purposely or accidentally magnetized so as to have

both ends of the same polarity, and the center of opposite polarity. The

center is said to comprise two consequent poles. (See Magnet,

Anomalous.)

Conservation of Electricity.

As every charge of electricity has its equal and opposite charge

somewhere, near or far, more or less distributed, the sum of negative is

equal always to the sum of positive electrical charges. For this

doctrine the above title was proposed by Lippman.

Contact Breaker.

Any contrivance for closing a circuit, and generally for opening and

closing in quick succession. An old and primitive form consisted of a

very coarsely cut file. This was connected to one terminal, and the

other terminal was drawn over its face, making and breaking contact as

it jumped from tooth to tooth. (See Circuit Breaker--do. Automatic,

etc.--do. Wheel-do. Pendulum.)

147   STANDARD ELECTRICAL DICTIONARY.

Contact, Electric.

A contact between two conductors, such that a current can flow through

it. It may be brought about by simple touch or impact between the ends

or terminals of a circuit, sometimes called a dotting contact, or by a

sliding or rubbing of one terminal on another, or by a wheel rolling on

a surface, the wheel and surface representing the two terminals.

There are various descriptions of contact, whose names are

self-explanatory. The term is applied to telegraph line faults also, and

under this, includes different descriptions of contact with neighboring

lines, or with the earth.

Contact Electricity.

When two dissimilar substances are touched they assume different

electric potentials. If conductors, their entire surfaces are affected;

if dielectrics, only the surfaces which touch each other. (See Contact

Theory.)

Contact Faults.

A class of faults often called contacts, due to contact of the conductor

of a circuit with another conductor. A full or metallic contact is where

practically perfect contact is established; a partial contact and

intermittent contact are self-explanatory.

Contact Point.

A point, pin or stud, often of platinum, arranged to come in contact

with a contact spring, q. v., or another contact point or surface, under

any determined conditions.

Contact Potential Difference.

The potential difference established by the contact of two dissimilar

substances according to the contact theory, q. v.

Contact Series.

An arrangement or tabulation of substances in pairs, each intermediate

substance appearing in two pairs, as the last member of the first, and

first member of the succeeding pair, with the statement of the potential

difference due to their contact, the positively electrified substance

coming first. The following table of some contact potentials is due to

Ayrton and Perry:

CONTACT SERIES.

Difference of Potential in Volts.

Zinc--Lead        .210

Lead--Tin         .069

Tin--Iron         .313

Iron--Copper      .146

Copper--Platinum  .238

Platinum-Carbon   .113

The sum of these differences is 1.089, which is the contact potential

between zinc and carbon.

Volta's Law refers to this and states that--

The difference of potential produced by the contact of any two

substances is equal to the sum of the differences of potentials

between the intervening substances in the contact series.

It is to be remarked that the law should no longer be restricted to or

stated only for metals.

148   STANDARD ELECTRICAL DICTIONARY.

Contact-spring.

A spring connected to one lead of an electric circuit, arranged to press

against another spring, or contact point, q. v., under any conditions

determined by the construction of the apparatus. (See Bell,

Electric--Coil, Induction.)

Contact Theory.

A theory devised to explain electrification, the charging of bodies by

friction, or rubbing, and the production of current by the voltaic

battery. It holds that two bodies, by mere contact become oppositely

electrified. If such contact is increased in extent by rubbing together,

the intensity of their electrification is increased. This

electrification is accounted for by the assumption of different kinetic

energy, or energy of molecular motion, possessed by the two bodies;

there being a loss and gain of energy, on the two sides respectively,

the opposite electrifications are the result. Then when separated, the

two bodies come apart oppositely electrified.

The above accounts for the frictional production of electricity. In the

voltaic battery, a separation of the atoms of hydrogen and oxygen, and

their consolidation into molecules occurs, and to such separation and

the opposite electrification of the electrodes by the oxygen and

hydrogen, the current is attributed, because the hydrogen goes to one

electrode, and the oxygen to the other, each giving up or sharing its

own charge with the electrodes to which it goes. If zinc is touched to

copper, the zinc is positively and the copper negatively electrified. In

the separation of hydrogen and oxygen, the hydrogen is positively and

the oxygen negatively electrified. In the battery, the current is due to

the higher contact difference of oxygen and hydrogen compared to that

between zinc and copper. It will be seen that the two contact actions in

a battery work against each other, and that the current is due to a

differential contact action. The zinc in a battery is electrified

negatively because the negative electrification of the oxygen is greater

in amount than its own positive electrification due to contact with the

copper.

Contractures.

A muscular spasm or tetanus due to the passage of a current of

electricity; a term in electro-therapeutics.

Controlling Field.

The magnetic or electro-magnetic field, which is used in galvanometers

to control the magnetic needle, tending to restore it to a definite

position whenever it is turned therefrom. It may be the earth's field or

one artificially produced.

Controlling Force.

In galvanometers and similar instruments, the force used to bring the

needle or indicator back to zero. (See Controlling

Field--Electro-Magnetic Control--Gravity Control--Magnetic

Control--Spring Control.)

149   STANDARD ELECTRICAL DICTIONARY.

Convection, Electric.

The production of blasts or currents of air (convection streams) from

points connected to statically charged conductors. The term is sometimes

applied to electric convection of heat. (See Convection of Heat,

Electric.)

Convection, Electrolytic.

The resistance of acidulated water as a true conductor is known to be

very, almost immeasurably, high. As an electrolytic, its resistance is

very much lower. Hence the current produced between immersed electrodes

is theoretically almost null, unless the difference of potential between

them is high enough to decompose the liquid. Yet a feeble current too

great for a true conduction current is sometimes observed when two

electrodes with potential difference too low to cause decomposition are

immersed in it. Such a current is termed an electrolytic convection

current. It is supposed to be due to various causes. Some attribute it

to the presence of free oxygen from the air, dissolved in the water with

which the hydrogen combines. Others attribute it to the diffusion of the

gases of decomposition in the solution; others assume a partial

polarization of the molecules without decomposition. Other theories are

given, all of which are unsatisfactory. The term is due to Helmholtz.

Convection of Heat, Electric.

The effect of a current upon the distribution of heat in an unevenly

heated conductor. In some, such as copper, the current tends to equalize

the varying temperatures; the convection is then said to be positive, as

comparable to that of water flowing through an unequally heated tube. In

others, such as platinum or iron, it is negative, making the heated

parts hotter, and the cooler parts relatively cooler.

The effect of the electric current in affecting the distribution of heat

in unequally heated metal (Thomson's effect. q. v.), is sometimes so

termed. If a current passes through unequally heated iron it tends to

increase the difference of temperature, and the convection is negative;

in copper it tends to equalize the temperature, and the convection is

positive.

Converter.

An induction coil used with the alternating current for changing

potential difference and inversely therewith the available current. They

generally lower the potential, and increase the current, and are placed

between the primary high potential system that connects the houses with

the central station, and the secondary low potential system within the

houses. A converter consists of a core of thin iron sheets, wound with a

fine primary coil of many convolutions, and a coarse secondary coil of

few convolutions. The ratio of convolutions gives the ratio of maximum

potential differences of their terminals between the primary and

secondary coils. The coil may be jacketed with iron to increase the

permeance. (See Alternating Current System.)

Fig. 110. FERRANTI'S CONVERTER OR TRANSFORMER.

Fig. 111.   SWINBURNE'S HEDGEHOG TRANSFORMER.

150   STANDARD ELECTRICAL DICTIONARY.

Co-ordinates, System of.

A system for indicating the position of points in space by reference to

fixed lines, intersecting at a determined and arbitrary point 0, termed

the origin of co-ordinates. In plane rectangular co-ordinates two lines

are drawn through the origin, one horizontal, termed the axis of

abscissas, or axis of X. All distances measured parallel to it, if

unknown, are indicated by x, and are termed abscissas. The other axis is

vertical, and is termed the axis of ordinates, or axis of Y. All

distances measured parallel to it, if unknown, are indicated by y and

are termed ordinates. Thus by naming its abscissa and ordinate a point

has its position with reference to the axes determined, and by

indicating the relation between a point, line or curve, and a system of

abscissas and ordinates, the properties of a line or curve can be

expressed algebraically. Co-ordinates may also be inclined to each other

at any other angles, forming oblique co-ordinates; relations may be

expressed partly in angles referred to the origin as a centre, giving

polar co-ordinates. For solid geometry or calculations in three

dimensions, a third axis, or axis of Z, is used, distances parallel to

which if unknown are indicated by z.

Fig. 112. AXES OF CO-ORDINATES.

151   STANDARD ELECTRICAL DICTIONARY.

Cooling Box.

In a hydroelectric machine, q. v., a conduit or chest through which the

steam passes on its way to the nozzles. Its object is to partially

condense the steam so as to charge it with water vesicles whose friction

against the sides of the nozzles produces the electrification .

152   STANDARD ELECTRICAL DICTIONARY.

Copper.

A metal; one of the elements. Symbol, Cu; atomic weight, 63.5;

equivalent, 63.5 and 31.75; valency, 1 and 2; specific gravity, 8.96.

It is a conductor of electricity, whose conductivity is liable to

vary greatly on account of impurities.

Annealed.   Hard drawn.

Relative resistance (Silver = 1),     1.063      1.086

Specific resistance,                  1.598      1.634 microhms.

Resistance of a wire at 0° C. (32° F.),

Annealed.     Hard Drawn.

(a) 1 foot long, weighing 1 grain,     .2041  ohms   .2083  ohms.

(b) 1 foot long, 1/1000 inch thick,   9.612   "     9.831    "

(c) 1 meter long, weighing 1 gram,     .1424  "      .1453   "

(d) 1 meter long, 1 millimeter thick,  .02034 "      .02081  "

microhm.   microhm.

Resistance of 1 inch cube at 0°C. (32° F.)   .6292     .6433

Percentage of resistance change,

per 1° C. (1.8° F.) at about 20° C. (68° F.) = 0.388 per cent.

Electro-chemical Equivalent (Hydrogen = .0105)   Cuprous  .6667

Cupric   .3334

In electricity it has been very extensively used as the negative plate

of voltaic batteries. It has its most extensive application as

conductors for all classes of electrical leads.

Copper Bath.

A solution of copper used for depositing the metal in the electroplating

process. For some metals, such as zinc or iron, which decompose copper

sulphate solution, special baths have to be used.

The regular bath for copper plating is the following:

To water acidulated with 8 to 10 percent. of sulphuric acid as much

copper sulphate is added as it will take up at the ordinary temperature.

The saturated bath should have a density of 1.21. It is used cold and is

kept in condition by the use of copper anodes, or fresh crystals may be

added from time to time.

For deposition on zinc, iron, tin and other metals more electropositive

than copper, the following baths may be used, expressed in parts by

weight:

Tin

Iron and Steel.   Cast Iron

Cold     Hot.     and Zinc.   Zinc.

Sodium Bisulphate,    500     200         300      100

Potassium Cyanide,    500     700         500      700

Sodium Carbonate,    1000     500         ---      ---

Copper Acetate,       475     500         350      450

Aqua Ammoniae,        350     300         200      150

Water,               2500    2500        2500     2500

These are due to Roseleur.

153  STANDARD ELECTRICAL DICTIONARY.

Copper Stripping Bath.

There is generally no object in stripping copper from objects. It can be

done with any of the regular copper baths using the objects to be

stripped as anode. The danger of dissolving the base itself and thereby

injuring the article and spoiling the bath is obvious.

Cord Adjuster.

A device for shortening or lengthening the flexible cord, or flexible

wire supplying the current, and by which an incandescent lamp is

suspended. It often is merely a little block of wood perforated with two

holes through which the wires pass, and in which they are retained in

any desired position by friction and their own stiffness.

Fig. 113. FLEXIBLE CORD ADJUSTER.

Cord, Flexible.

A pair of flexible wire conductors, insulated lightly, twisted together

and forming apparently a cord. They are used for minor services, such as

single lamps and the like, and are designated according to the service

they perform, such as battery cords, dental cords (for supplying dental

apparatus) and other titles.

Core.

(a) The conductor or conductors of an electric cable. (See Cable Core.)

(b) The iron mass, generally central in an electro-magnet or armature,

around which the wire is coiled. It acts by its high permeance to

concentrate or multiply the lines of force, thus maintaining a more

intense field. (See Armature--Magnet, Electro--Magnet, Field--Core,

Laminated). In converters or transformers (See Converter) it often

surrounds the wire coils.

Core-discs.

Discs of thin wire, for building up armature cores. (See Laminated

Core.) The usual form of core is a cylinder. A number of thin discs of

iron are strung upon the central shaft and pressed firmly together by

end nuts or keys. This arrangement, it will be seen, gives a cylinder as

basis for winding the wire on.

Core-discs, Pierced.

Core-discs for an armature of dynamo or motor, which are pierced around

the periphery. Tubes of insulating material pass through the peripheral

holes, and through these the conductors or windings are carried. The

conductors are thus embedded in a mass of iron and are protected from

eddy currents, and they act to reduce the reluctance of the air gaps.

From a mechanical point of view they are very good. For voltages over

100 they are not advised.

Synonym--Perforated Core-discs.

154   STANDARD ELECTRICAL DICTIONARY.

Core-discs, Segmental.

Core-discs made in segments, which are bolted together to form a

complete disc or section of the core. The plan is adopted principally on

large cores. The discs thus made up are placed together to form the core

exactly as in the case of ordinary one piece discs.

Fig. 114. PIERCED OR PERFORATED CORE-DISC.

Core-discs, Toothed.

Core-discs of an armature of a dynamo or motor, which discs are cut into

notches on the periphery. These are put together to form the armature

core, with the notches corresponding so as to form a series of grooves

in which the wire winding is laid. This construction reduces the actual

air-gaps, and keeps the wires evenly spaced. Distance-pieces of

box-wood, m, m, are sometimes used to lead the wires at the ends of the

armature.

Fig. 115. TOOTHED CORE-DISC.

Core, Laminated.

A core of an armature, induction coil or converter or other similar

construction, which is made up of plates insulated more or less

perfectly from each other. The object of lamination is to prevent the

formation of Foucault currents. (See Currents, Foucault.) As insulation,

thin shellacked paper may be used, or sometimes the superficial

oxidation of the plates alone is relied on. The plates, in general, are

laid perpendicular to the principal convolutions of the wire, or

parallel to the lines of force. The object is to break up currents, and

such currents are induced by the variation in intensity of the field of

force, and their direction is perpendicular to the lines of force, or

parallel to the inducing conductors.

A core built up of core discs is sometimes termed a tangentially

laminated core. Made up of ribbon or wire wound coil fashion, it is

termed a radially laminated core.

155  STANDARD ELECTRICAL DICTIONARY.

Core Ratio.

In a telegraph cable the ratio existing between the diameter of the

conducting core and the insulator. To get a ratio approximately accurate

in practical calculations, the diameter of the core is taken at 5 per

cent. less than its actual diameter. The calculations are those

referring to the electric constants of the cable, such as its static

capacity and insulation resistance.

Core, Ribbon.

For discoidal ring-shaped cores of armatures, iron ribbon is often used

to secure lamination and prevent Foucault currents.

Synonym--Tangentially Laminated Core.

Core, Ring.

A core for a dynamo or motor armature, which core forms a complete ring.

Core, Stranded.

In an electric light cable, a conducting core made up of a group of

wires laid or twisted together.

Core, Tubular.

Tubes used as cores for electro-magnets. For very small magnetizing

power, tubular cores are nearly as efficient as solid ones in straight

magnets, because the principal reluctance is due to the air-path. On

increasing the magnetization the tubular core becomes less efficient

than the solid core, as the reluctance of the air-path becomes

proportionately of less importance in the circuit.

Corpusants.

The sailors' name for St. Elmo's Fire, q. v.

Coulomb.

The practical unit of quantity of electricity. It is the quantity passed

by a current of one ampere intensity in one second. It is equal to 1/10

the C. G. S. electro-magnetic unit of quantity, and to 3,000,000,000 C.

G. S. electrostatic units of quantity. It corresponds to the

decomposition of .0935 milligrams of water, or to the deposition of

1.11815 milligrams of silver.

[Transcriber's note: A coulomb is approximately 6.241E18 electrons. Two

point charges of one coulomb each, one meter apart, exerts a force of

900,000 metric tons.]

Coulomb's Laws of Electrostatic Attraction and Repulsion.

1. The repulsions or attractions between two electrified bodies are in

the inverse ratio of the squares of their distance.

2. The distance remaining the same, the force of attraction or repulsion

between two electrified bodies is directly as the product of the

quantities of electricity with which they are charged.

156   STANDARD ELECTRICAL DICTIONARY.

Counter, Electric.

A device for registering electrically, or by electro-magnetic machinery,

the revolutions of shafts, or any other data or factors.

Counter-electro-motive Force.

A potential difference in a circuit opposed to the main potential

difference, and hence, resisting the operation of the latter, and

diminishing the current which would be produced without it. It appears

in electric motors, which, to a certain extent, operate as dynamos and

reduce the effective electro-motive force that operates them. It

appears in the primary coils of induction coils, and when the secondary

circuit is open, is almost equal to the main electro-motive force, so

that hardly any current can go through them under such conditions. It

appears in galvanic batteries, when hydrogen accumulates on the copper

plate, and in other chemical reactions. A secondary battery is charged

by a current in the reverse direction to that which it would normally

produce. Its own potential difference then appears as a

counter-electro-motive force.

Synonym--Back Electro-motive Force.

Counter-electro-motive Force of Polarization.

To decompose a solution by electrolysis, enough electro-motive force is

required to overcome the energy of composition of the molecule

decomposed. A part of this takes the form of a counter-electromotive

force, one which, for a greater or less time would maintain a current in

the opposite direction if the original source of current were removed.

Thus in the decomposition of water, the electrodes become covered, one

with bubbles of oxygen, the others with bubbles of hydrogen; this

creates a counter E. M. F. of polarization. In a secondary battery, the

working current may be defined as due to this cause.

Synonym--Back Electro-motive Force of Polarization.

Couple.

Two forces applied to different points of a straight line, when opposed

in direction or unequal in amount, tend to cause rotation about a point

intermediate between their points of application and lying on the

straight line. Such a pair constitute a couple.

Couple, Voltaic or Galvanic.

The combination of two electrodes, and a liquid or liquids, the

electrodes being immersed therein, and being acted on differentially by

the liquid or liquids. The combination constitutes a source of

electro-motive force and consequently of current. It is the galvanic or

voltaic cell or battery. (See Battery, Voltaic--Contact

Theory--Electro-motive Force--Electro-motive Series.)

Coupling.

The joining of cells of a galvanic battery, of dynamos or of other

devices, so as to produce different effects as desired.

157  STANDARD ELECTRICAL DICTIONARY

Couple, Astatic.

An astatic couple is a term sometimes applied to astatic needles, q.v.

C. P.

(a) An abbreviation of or symbol for candle power, q. v.

(b) An abbreviation of chemically pure. It is used to indicate a high

degree of purity of chemicals. Thus, in a standard Daniell battery, the

use of C. P. chemicals may be prescribed or advised.

Crater.

The depression that forms in the positive carbon of a voltaic arc. (See

Arc, Voltaic.)

Creeping.

A phenomenon of capillarity, often annoying in battery jars. The

solution, by capillarity, rises a little distance up the sides,

evaporates, and as it dries more creeps up through it, and to a point a

little above it. This action is repeated until a layer of the salts may

form over the top of the vessel. To avoid it, paraffine is often applied

to the edges of the cup, or a layer of oil, often linseed oil, is poured

on the battery solution,

Crith.

The weight of a litre of hydrogen at 0º C. (32º F.), and 760 mm. (30

inches) barometric pressure. It is .0896 grams. The molecular weight of

any gas divided by 2 and multiplied by the value of the crith, gives the

weight of a litre of the gas in question. Thus a litre of electrolytic

gas, a mixture of two molecules of hydrogen for one of oxygen, with a

mean molecular weight of 12, weighs (12/2) * .0896 or .5376 gram.

Critical Speed.

(a) The speed of rotation at which a series dynamo begins to excite its

own field.

(b) In a compound wound dynamo, the speed at which the same potential is

generated with the full load being taken from the machine, as would be

generated on open circuit, in which case the shunt coil is the only

exciter. The speed at which the dynamo is self-regulating.

(c) In a dynamo the rate of speed when a small change in the speed of

rotation produces a comparatively great change in the electro-motive

force. It corresponds to the same current (the critical current) in any

given series dynamo.

Cross.

(a) A contact between two electric conductors; qualified to express

conditions as a weather cross, due to rain, a swinging cross when a wire

swings against another, etc.

(b) vb. To make such contact.

Cross-Connecting Board.

A special switch board used in telephone exchanges and central telegraph

offices. Its function is, by plugs and wires, to connect the line wires

with any desired section of the main switchboard. The terminals of the

lines as they enter the building are connected directly to the

cross-connecting board.

158   STANDARD ELECTRICAL DICTIONARY.

Cross Connection.

A method of disposing of the effects of induction from neighboring

circuits by alternately crossing the two wires of a metallic telephone

circuit, so that for equal intervals they lie to right and left, or one

above, and one below.

[Transcriber's note: Also used to cancel the effect of variations in the

ambient magnetic field, such as solar activity.]

Crossing Wires.

The cutting out of a defective section in a telegraph line, by carrying

two wires from each side of the defective section across to a

neighboring conductor, pressing it for the time into service and cutting

the other wire if necessary.

Cross-magnetizing Effect.

A phase of armature interference. The current in an armature of a dynamo

or motor is such as to develop lines of force approximately at right

angles to those of the field. The net cross-magnetizing effect is such

component of these lines, as is at right angles to the lines produced by

the field alone.

Cross-over Block.

A piece of porcelain or other material shaped to receive two wires which

are to cross each other, and hold them so that they cannot come in

contact. It is used in wiring buildings, and similar purposes. (See

Cleat, Crossing.)

Cross Talk.

On telephone circuits by induction or by contact with other wires sound

effects of talking are sometimes received from other circuits; such

effects are termed cross talk.

Crucible, Electric.

A crucible for melting difficultly fusible substances, or for reducing

ores, etc., by the electric arc produced within it. Sometimes the

heating is due more to current incandescence than to the action of an

arc.

Fig. 116. ELECTRIC FURNACE OR CRUCIBLE.

Crystallization, Electric.

Many substances under proper conditions take a crystalline form. The

great condition is the passage from the fluid into the solid state. When

such is brought about by electricity in any way, the term electric

crystallization may be applied to the phenomenon. A solution of silver

nitrate for instance, decomposed by a current, may give crystals of

metallic silver.

159     STANDARD ELECTRICAL DICTIONARY.

Cup, Porous.

A cup used in two-fluid voltaic batteries to keep the solutions separate

to some extent. It forms a diaphragm through which diffusion inevitably

takes place, but which is considerably retarded, while electrolysis and

electrolytic convection take place freely through its walls. As

material, unglazed pottery is very generally used.

In some batteries the cup is merely a receptacle for the solid

depolarizer. Thus, in the Leclanché battery, the cup contains the

manganese dioxide and graphite in which the carbon electrode is

embedded, but does not separate two solutions, as the battery only uses

one. Nevertheless, the composition of the solution outside and inside

may vary, but such variation is incidental only, and not an essential of

the operation.

Current.

The adjustment, or effects of a continuous attempt at readjustment of

potential difference by a conductor, q. v., connecting two points of

different potential. A charged particle or body placed in a field of

force tends to move toward the oppositely charged end or portion of the

field. If a series of conducting particles or a conducting body are held

so as to be unable to move, then the charge of the field tends, as it

were, to move through it, and a current results. It is really a

redistribution of the field and as long as such redistribution continues

a current exists. A current is assumed to flow from a positive to a

negative terminal; as in the case of a battery, the current in the outer

circuit is assumed to flow from the carbon to the zinc plate, and in the

solution to continue from zinc to carbon. As a memoria technica the zinc

may be thought of as generating the current delivering it through the

solution to the carbon, whence it flows through the wire connecting

them. (See Ohm's Law--Maxwell's Theory of Light--Conductor-Intensity.)

[Transcriber's note: Supposing electric current to be the motion of

positive charge causes no practical difficulty, but the current is

actually the (slight) motion of negative electrons.]

Current, After.

A current produced by the animal tissue after it has been subjected to a

current in the opposite direction for some time. The tissue acts like a

secondary battery. The term is used in electro-therapeutics.

Current, Alternating.

Usually defined and spoken of as a current flowing alternately in

opposite directions. It may be considered as a succession of currents,

each of short duration and of direction opposite to that of its

predecessor. It is graphically represented by such a curve as shown in

the cut. The horizontal line may denote a zero current, that is no

current at all, or may be taken to indicate zero electro-motive force.

The curve represents the current, or the corresponding electro-motive

forces. The further from the horizontal line the greater is either, and

if above the line the direction is opposite to that corresponding to the

positions below the line. Thus the current is alternately in opposite

directions, has periods of maximum intensity, first in one and then in

the opposite sense, and between these, passing from one direction to the

other, is of zero intensity. It is obvious that the current may rise

quickly in intensity and fall slowly, or the reverse, or may rise and

fall irregularly. All such phases may be shown by the curve, and a curve

drawn to correctly represent these variations is called the

characteristic curve of such current. It is immaterial whether the

ordinates of the curve be taken as representing current strength or

electromotive force. If interpreted as representing electro-motive

force, the usual interpretation and best, the ordinates above the line

are taken as positive and those below as negative.

Synonyms--Reversed Current--Periodic Currents.

Fig. 117. CHARACTERISTIC CURVE OF ALTERNATING CURRENT.

160   STANDARD ELECTRICAL DICTIONARY.

Current, Atomic.

A unit of current strength used in Germany; the strength of a current

which will liberate in 24 hours (86,400 seconds) one gram of hydrogen

gas, in a water voltameter. The atomic current is equal to 1.111

amperes. In telegraphic work the milliatom is used as a unit, comparable

to the milliampere. The latter is now displacing it.

Current, Charge.

If the external coatings of a charged and uncharged jar are placed in

connection, and if the inner coatings are now connected, after

separating them they are both found to be charged in the same manner. In

this process a current has been produced between the outside coatings

and one between the inner ones, to which Dove has given the name Charge

Current, and which has all the properties of the ordinary discharge

current. (Ganot.)

Current, Circular.

A current passing through a circular conductor; a current whose path is

in the shape of a circle.

Current, Commuted.

A current changed, as regards direction or directions, by a commutator,

q. v., or its equivalent.

Current, Constant.

An unvarying current. A constant current system is one maintaining such

a current. In electric series, incandescent lighting, a constant current

is employed, and the system is termed as above. In arc lighting systems,

the constant current series arrangement is almost universal.

161  STANDARD ELECTRICAL DICTIONARY.

Current, Continuous.

A current of one direction only; the reverse of an alternating current.

(See Current, Alternating.)

Current, Critical.

The current produced by a dynamo at its critical speed; at that speed

when a slight difference in speed produces a great difference in

electro-motive force. On the characteristic curve it corresponds to the

point where the curve bends sharply, and where the electro-motive force

is about two-thirds its maximum.

Current, Daniell/U.S. , Daniell/Siemens' Unit.

A unit of current strength used in Germany. It is the strength of a

current produced by one Daniell cell in a circuit of the resistance of

one Siemens' unit. The current deposits 1.38 grams of copper per hour.

It is equal to 1.16 amperes.

Current, Demarcation.

In electro-therapeutics, a current which can be taken from an injured

muscle, the injured portion acting electro-negatively toward the

uninjured portion.

Current Density.

The current intensity per unit of cross-sectional area of the conductor.

The expression is more generally used for electrolytic conduction, where

the current-density is referred to the mean facing areas of the

electrodes, or else to the facing area of the cathode only.

The quality of the deposited metal is intimately related to the current

density. (See Burning.)

Proper Current Density for Electroplating

Amperes Per Square Foot of Cathode.--(Urquhart.)

Copper, Acid Bath.                               5.0  to 10.0

"       Cyanide Bath,                            3.0  "   5.0

Silver, Double Cyanide,                          2.0  "   5.0

Gold, Chloride dissolved in Potassium Cyanide,   1.0  "   2.0

Nickel, Double Sulphate,                         6.6  "   8.0

Brass, Cyanide,                                  2.0  "   3.0

Current, Diacritical.

A current, which, passing through a helix surrounding an iron core,

brings it to one-half its magnetic saturation, q. v.

Current, Diaphragm.

If a liquid is forced through a diaphragm, a potential difference

between the liquid on opposite sides of the diaphragm is maintained.

Electrodes or terminals of platinum may be immersed in the liquid, and a

continuous current, termed a diaphragm current, may be taken as long as

the liquid is forced through the diaphragm. The potential difference is

proportional to the pressure, and also depends on the nature of the

diaphragm and on the liquid.

162   STANDARD ELECTRICAL DICTIONARY.

Current, Direct.

A current of unvarying direction, as distinguished from an alternating

current. It may be pulsatory or intermittent in character, but must be

of constant direction.

Current, Direct Induced.

On breaking a circuit, if it is susceptible of exercising

self-induction, q. v., an extra current, in the direction of the

original is induced, which is called "direct" because in the same

direction as the original. The same is produced by a current in one

circuit upon a parallel one altogether separated from it. (See

Induction, Electro-Magnetic-Current, Extra.)

Synonym--Break Induced Current.

Current, Direction of.

The assumed direction of a current is from positively charged electrode

to negatively charged one; in a galvanic battery from the carbon or

copper plate through the outer circuit to the zinc plate and back

through the electrolyte to the carbon or copper plate. (See Current.)

[Transcriber's note: Current is caused by the motion of negative

electrons, from the negative pole to the positive. The electron was

discovered five years after this publication.]

Current, Displacement.

The movement or current of electricity taking place in a dielectric

during displacement. It is theoretical only and can only be assumed to

be of infinitely short duration. (See Displacement, Electric.)

Currents, Eddy Displacement.

The analogues of Foucault currents, hypothetically produced in the mass

of a dielectric by the separation of the electricity or by its

electrification. (See Displacement.)

Current, Extra.

When a circuit is suddenly opened or closed a current of very brief

duration, in the first case in the same direction, in the other case in

the opposite direction, is produced, which exceeds the ordinary current

in intensity. A high potential difference is produced for an instant

only. These are called extra currents. As they are produced by

electro-magnetic induction, anything which strengthens the field of

force increases the potential difference to which they are due. Thus the

wire may be wound in a coil around an iron core, in which case the extra

currents may be very strong. (See Induction, Self-Coil, Spark.)

Current, Faradic.

A term in medical electricity for the induced or secondary alternating

current, produced by comparatively high electro-motive force, such as

given by an induction coil or magneto-generator, as distinguished from

the regular battery current.

163   STANDARD ELECTRICAL DICTIONARY.

Current, Foucault.

A current produced in solid conductors, and which is converted into heat

(Ganot). These currents are produced by moving the conductors through a

field, or by altering the strength of a field in which they are

contained. They are the source of much loss of energy and other

derangement in dynamos and motors, and to avoid them the armature cores

are laminated, the plane of the laminations being parallel to the lines

of force. (See Core, Laminated.)

The presence of Foucault currents, if of long duration, is shown by the

heating of the metal in which they are produced. In dynamo armatures

they are produced sometimes in the metal of the windings, especially if

the latter are of large diameter.

Synonyms--Eddy Currents--Local Currents--Parasitical Currents.

Current, Franklinic.

In electro-therapeutics the current produced by a frictional electric

machine.

Current, Induced.

The current produced in a conductor by varying the conditions of a field

of force in which it is placed; a current produced by induction.

Current Induction.

Induction by one current on another or by a portion of a current on

another portion of itself. (See Induction.)

Current Intensity.

Current strength, dependent on or defined by the quantity of electricity

passed by such current in a given time. The practical unit of current

intensity is the ampere, equal to one coulomb of quantity per second of

time.

Current, Inverse Induced.

The current induced in a conductor, when in a parallel conductor or in

one having a parallel component a current is started, or is increased in

strength. It is opposite in direction to the inducing current and hence

is termed inverse. (See Induction, Electro-magnetic.) The parallel

conductors may be in one circuit or in two separate circuits.

Synonyms--Make-induced Current--Reverse-induced Current.

Current, Jacobi's Unit of.

A current which will liberate one cubic centimeter of mixed gases

(hydrogen and oxygen) in a water voltameter per minute, the gases being

measured at 0º C. (32º F.) and 760 mm. (29.92 inches) barometric

pressure. It is equal to .0961 ampere.

Current, Joint.

The current given by several sources acting together. Properly, it

should be restricted to sources connected in series, thus if two battery

cells are connected in series the current they maintain is their joint

current.

Current, Linear.

A current passing through a straight conductor; a current whose path

follows a straight line.

164   STANDARD ELECTRICAL DICTIONARY.

Current, Make and Break.

A succession of currents of short duration, separated by absolute

cessation of current. Such current is produced by a telegraph key, or by

a microphone badly adjusted, so that the circuit is broken at intervals.

The U. S. Courts have virtually decided that the telephone operates by

the undulatory currents, and not by a make and break current. Many

attempts have been made to produce a telephone operating by a

demonstrable make and break current, on account of the above

distinction, in hopes of producing a telephone outside of the scope of

the Bell telephone patent.

[Transcriber's note: Contemporary long distance telephone service is

digital, as this item describes.]

Current-meter.

An apparatus for indicating the strength of current. (See Ammeter.)

Current, Negative.

In the single needle telegraph system the current which deflects the

needle to the left.

Current, Nerve and Muscle.

A current of electricity yielded by nerves or muscles. Under proper

conditions feeble currents can be taken from nerves, as the same can be

taken from muscles.

Current, Opposed.

The current given by two or more sources connected in opposition to each

other. Thus a two volt and a one volt battery may be connected in

opposition, giving a net voltage of only one volt, and a current due to

such net voltage.

Current, Partial.

A divided or branch current. A current which goes through a single

conductor to a point where one or more other conductors join it in

parallel, and then divides itself between the several conductors, which

must join further on, produces partial currents. It produces as many

partial currents as the conductors among which it divides. The point of

division is termed the point of derivation.

Synonym--Derived Current.

Current, Polarizing.

In electro-therapeutics, a constant current.

Current, Positive.

In the single needle telegraph system the current which deflects the

needle to the right.

Current, Pulsatory.

A current of constant direction, but whose strength is constantly

varying, so that it is a series of pulsations of current instead of a

steady flow.

Current, Rectified.

A typical alternating current is represented by a sine curve, whose

undulations extend above and below the zero line. If by a simple two

member commutator the currents are caused to go in one direction, in

place of the sine curve a series of short convex curves following one

another and all the same side of the zero line results. The currents all

in the same direction, become what is known as a pulsating current.

Synonym--Redressed Current.

165  STANDARD ELECTRICAL DICTIONARY.

Current, Rectilinear.

A current flowing through a rectilinear conductor. The action of

currents depending on their distance from the points where they act,

their contour is a controlling factor. This contour is determined by the

conductors through which they flow.

Current Reverser.

A switch or other contrivance for reversing the direction of a

current in a conductor.

Currents, Ampérian.

The currents of electricity assumed by Ampere's theory to circulate

around a magnet. As they represent the maintenance of a current or of

currents without the expenditure of energy they are often assumed to be

of molecular dimensions. As they all go in the same sense of rotation

and are parallel to each other the result is the same as if a single set

of currents circulated around the body of the magnet. More will be found

on this subject under Magnetism. The Ampérian currents are purely

hypothetical and are predicated on the existence of a field of force

about a permanent magnet. (See Magnetism, Ampére's Theory of.)

If the observer faces the north pole of a magnet the Ampérian currents

are assumed to go in the direction opposite to that of a watch, and the

reverse for the south pole.

Figs. 118-119 DIRECTION OF AMPÉRIAN CURRENTS.

Currents, Angular.

Currents passing through conductors which form an angle with each other.

Currents, Angular, Laws of.

1. Two rectilinear currents, the directions of which form an angle with

each other, attract one another when both approach to or recede from the

apex of the angle.

2. They repel one another, if one approaches and the other recedes from

the apex of the angle.

166   STANDARD ELECTRICAL DICTIONARY

Currents, Earth.

In long telegraph lines having terminal grounds or connected to earth

only at their ends, potential differences are sometimes observed that

are sufficient to interfere with their working and which, of course, can

produce currents. These are termed earth-currents. It will be noted that

they exist in the wire, not in the earth. They may be of 40 milliamperes

strength, quite enough to work a telegraph line without any battery.

Lines running N. E. and S. W. are most affected; those running N.W. and

S. E. very much less so. These currents only exist in lines grounded at

both ends, and appear in underground wires. Hence they are not

attributable to atmospheric electricity. According to Wilde they are the

primary cause of magnetic storms, q. v., but not of the periodical

changes in the magnetic elements. (See Magnetic Elements.)

Synonym--Natural Currents.

Current, Secondary.

(a) A current induced in one conductor by a variation in the current in

a neighboring one; the current produced in the secondary circuit of an

induction coil or alternating current converter.

(b) The current given by a secondary battery. This terminology is not to

be recommended.

Current, Secretion.

In electro-therapeutics, a current due to stimulation of the secretory

nerves.

Current Sheet.

(a) If two terminals of an active circuit are connected to two points of

a thin metallic plate the current spreads over or occupies practically a

considerable area of such plate, and this portion of the current is a

current sheet.

The general contour of the current sheet can be laid out in lines of

flux. Such lines resemble lines of force. Like the latter, they are

purely an assumption, as the current is not in any sense composed  of

lines.

(b) A condition of current theoretically brought about by the Ampérian

currents in a magnet. Each molecule having its own current, the

contiguous portions of the molecules counteract each other and give a

resultant zero current. All that remains is the outer sheet of electric

current that surrounds the whole.

Current, Sinuous.

A current passing through a sinuous conductor.

Currents, Multiphase.

A term applied to groups of currents of alternating type which

constantly differ from each other by a constant proportion of periods of

alternation. They are produced on a single dynamo, the winding being so

contrived that two, three or more currents differing a constant amount

in phase are collected from corresponding contact rings. There are

virtually as many windings on the armature as there are currents to be

produced. Separate conductors for the currents must be used throughout.

Synonyms--Polyphase Currents--Rotatory Currents.

167  STANDARD ELECTRICAL DICTIONARY.

Currents of Motion.

In electro-therapeutics, the currents produced in living muscle or

nerves after sudden contraction or relaxation.

Currents of Rest.

In electro-therapeutics, the currents traversing muscular or nervous

tissue when at rest. Their existence is disputed.

Currents, Orders of.

An intermittent current passing through a conductor will induce

secondary alternating currents in a closed circuit near it. This

secondary current will induce a tertiary current in a third closed

circuit near it, and so on. The induced currents are termed as of the

first, second, third and other orders. The experiment is carried out by

Henry's coils. (See Coils, Henry's.)

Currents, Thermo-electric.

These currents, as produced from existing thermo-electric batteries,

are generated by low potential, and are of great constancy. The opposite

junctions of the plates can be kept at constant temperatures, as by

melting ice and condensing steam, so that an identical current can be

reproduced at will from a thermopile.

Thermo-electric currents were used by Ohm in establishing his law. (See

Ohm's Law.)

Current, Swelling.

In electro-therapeutics, a current gradually increasing in strength.

Current, Undulatory.

A current varying in strength without any abrupt transition from action

to inaction, as in the make and break current. The current may be

continually changing in direction (see Current, Alternating), and hence,

of necessity, may pass through stages of zero intensity, but such

transition must be by a graduation, not by an abrupt transition. Such

current may be represented by a curve, such as the curve of sines. It is

evident that the current may pass through the zero point as it crosses

the line or changes direction without being a make and break current.

When such a current does alternate in direction it is sometimes called a

"shuttle current." The ordinary commercial telephone current and the

alternating current is of this type. (See Current, Make and Break.)

Current, Unit.

Unit current is one which in a wire of unit length, bent so as to form

an arc of a circle of unit length of radius, would act upon a unit pole

(see Magnetic Pole, Unit,) at the center of the circle with unit force.

Unit length is the centimeter; unit force is the dyne.

[Transcriber's note: The SI definition of an ampere: A current in two

straight parallel conductors of infinite length and negligible

cross-section, 1 metre apart in vacuum, would produce a force equal to

2E-7 newton per metre of length.]

168   STANDARD ELECTRICAL DICTIONARY.

Current, Wattless.

Whenever there is a great difference in phase in an alternating current

dynamo between volts and current, the true watts are much less than the

product of the virtual volts and amperes, because the the watts are

obtained by multiplying the product of the virtual volts and amperes by

the cosine of the angle of lag (or lead). Any alternating current may be

resolved into two components in quadrature with each other, one in phase

with the volts, the other in quadrature therewith, the former is termed

by S. P. Thompson the Working Current, the latter the Wattless Current.

The greater the angle of lag the greater will be the wattless current.

Curve, Arrival.

A curve representing the rate of rise of intensity of current at the end

of a long conductor when the circuit has been closed at the other end.

In the Atlantic cable, for instance, it would require about 108 seconds

for the current at the distant end to attain 9/10 of its full value. The

curve is drawn with its abscissa representing time and its ordinates

current strength.

Curve, Characteristic.

A curve indicating, graphically, the relations between any two factors,

which are interdependent, or which vary simultaneously. Thus in a

dynamo, the voltage increases with the speed of rotation, and a

characteristic curve may be based on the relations between the speed of

rotation and voltage developed. The current produced by a dynamo varies

with the electro-motive force, and a curve can express the relations

between the electro-motive force and the current produced.

A characteristic curve is usually laid out by rectangular co-ordinates

(see Co-ordinates). Two lines are drawn at right angles to each other,

one vertical, and the other horizontal. One set of data are marked off

on the horizontal line, say one ampere, two amperes, and so on, in the

case of a dynamo's characteristic curve.

For each amperage of current there is a corresponding voltage in the

circuit. Therefore on each ampere mark a vertical is erected, and on

that the voltage corresponding to such amperage is laid off. This gives

a series of points, and these points may be connected by a curve. Such

curve will be a characteristic curve.

The more usual way of laying out a curve is to work directly upon the

two axes. On one is laid off the series of values of one set of data; on

the other the corresponding series of values of the other dependent

data. Vertical lines or ordinates, q. v., are erected on the horizontal

line or axis of abscissas at the points laid off; horizontal lines or

abscissas, q. v., are drawn from the points laid off on the vertical

line or axis of ordinates. The characteristic curve is determined by the

intersections of each corresponding pair of abscissa and ordinate.

169  STANDARD ELECTRICAL DICTIONARY.

Variations exist in characteristic curve methods. Thus to get the

characteristic of a commutator, radial lines may be drawn from a circle

representing its perimeter. Such lines may be of length proportional to

the voltage developed on the commutator at the points whence the lines

start. A cut giving an example of such a curve is given in Fig. 125.

(See Curve of Distribution of Potential in Armature.)

There is nothing absolute in the use of ordinates or abscissas. They may

be interchanged. Ordinarily voltages are laid off as ordinates, but the

practise may be reversed. The same liberty holds good for all

characteristic curves. Custom, however, should be followed.

Synonym--Characteristic.

Fig. 120. CHARACTERISTIC CURVE OF A DYNAMO

WITH HORSE POWER CURVES.

Curve, Characteristic, of Converter.

The characteristic curve of the secondary circuit of an alternating

current converter. It gives by the usual methods (see Curve,

Characteristic,) the relations between the electro-motive force and the

current in the secondary circuit at a fixed resistance. If connected in

parallel a constant electro-motive force is maintained, and the curve is

virtually a straight line. If connected in series an elliptical curve is

produced.

170   STANDARD ELECTRICAL DICTIONARY.

Curve, Charging.

In secondary battery manipulation, a curve indicating the increase of

voltage as the charging is prolonged. The rise in voltage with the

duration of the charging current is not uniform. In one case, shown in

the cut, there was a brief rapid rise of about 0.1 volt; then a long

slow rise for 0.15 volt; then a more rapid rise for nearly 0.40 volt,

and then the curve became a horizontal line indicating a cessation of

increase of voltage. The charging rate should be constant.

The horizontal line is laid off in hours, the vertical in volts, so that

the time is represented by abscissas and the voltage by ordinates of the

curve.

Fig. 121. CHARGING CURVE OF A SECONDARY BATTERY.

Curve, Discharging.

A characteristic curve of a storage battery, indicating the fall in

voltage with hours of discharge. The volts may be laid off on the axis

of ordinates, and the hours of discharging on the axis of abscissas. To

give it meaning the rate of discharge must be constant.

Curve, Electro-motive Force.

A characteristic curve of a dynamo. It expresses the relation between

its entire electromotive force, as calculated by Ohm's Law, and the

current intensities corresponding thereto. To obtain the data the dynamo

is driven with different resistances in the external circuit and the

current is measured for each resistance. This gives the amperes. The

total resistance of the circuit, including that of the dynamo, is known.

By Ohm's Law the electro-motive force in volts is obtained for each case

by multiplying the total resistance of the circuit in ohms by the

amperes of current forced through such resistance. Taking the voltages

thus calculated for ordinates and the corresponding amperages for

abscissas the curve is plotted. An example is shown in the cut.

171  STANDARD ELECTRICAL DICTIONARY.

Curve, External Characteristic.

A characteristic curve of a dynamo, corresponding to the electro-motive

force curve, except that the ordinates represent the voltages of the

external circuit, the voltages as taken directly from the terminals of

the machine, instead of the total electro-motive force of the circuit.

The dynamo is run at constant speed. The resistance of the external

circuit is varied. The voltages at the terminals of the machine and the

amperages of current corresponding thereto are determined. Using the

voltages thus determined as ordinates and the corresponding amperages as

abscissas the external characteristic curve is plotted.

This curve can be mechanically produced. A pencil may be moved against a

constant force by two electro-magnets pulling at right angles to each

other. One must be excited by the main current of the machine, the other

by a shunt current from the terminals of the machine. The point of the

pencil will describe the curve.

Fig. 122. CHARACTERISTIC CURVE OF A DYNAMO.

Curve, Horse Power.

Curves indicating electric horse power. They are laid out with

co-ordinates, volts being laid off on the axis of ordinates, and amperes

on the axis of abscissas generally. The curves are drawn through points

where the product of amperes by volts equals 746. On the same diagram 1,

2, 3 .... and any other horse powers can be plotted if within the

limits. See Fig. 120.

Curve, Isochasmen.

A line drawn on the map of the earth's surface indicating the locus of

equal frequency of auroras.

172   STANDARD ELECTRICAL DICTIONARY.

Curve, Life.

A characteristic curve showing the relations between the durability and

conditions affecting the same in any appliance. It is used most for

incandescent lamps. The hours of burning before failure give ordinates,

and the rates of burning, expressed indirectly in volts or in

candle-power, give abscissas. For each voltage or for each candle-power

an average duration is deducible from experience, so that two dependent

sets of data are obtained for the construction of the curve.

Curve, Load.

A characteristic curve of a dynamo, expressing the relation between its

voltage and the amount of excitation under a definite condition of

ampere load, at a constant speed. The ordinates represent voltage, the

abscissas ampere turns in the field, and the curves may be constructed

for a flow of 0, 50, 100, or .. , or any other number of amperes.

Fig. 123. LOAD CURVES.

Curve, Magnetization.

A characteristic curve of an electromagnet, indicating the relation of

magnetization to exciting current. Laying off on the axis of ordinates

the quantities of magnetism evoked, and the corresponding strengths of

the exciting current on the axis of abscissas, the curve can be plotted.

It first rises rapidly, indicating a rapid increase of magnetization,

but grows nearly horizontal as the iron becomes more saturated. The

effect due to the coils alone, or the effect produced in the absence of

iron is a straight line, because air does not change in permeability.

Curve of Distribution of Potential in Armature.

A characteristic curve indicating the distribution of potential

difference between adjoining sections of the commutator of an armature

in different positions all around it. The potential differences are

taken by a volt-meter or potential galvanometer, connection with the

armature being made by two small metal brushes, held at a distance apart

equal to the distance from centre to centre of two adjoining commutator

bars. The curve is laid out as if by polar co-ordinates extending around

the cross-section of the commutator, with the distances from the

commutator surface to the curve proportional to the potential

differences as determined by shifting the pair of brushes all around the

commutator.

The above is S. P. Thompson's method. Another method of W. M. Mordey

involves the use of a pilot brush. (See Brush, Pilot.) Otherwise the

method is in general terms identical with the above.

173  STANDARD ELECTRICAL DICTIONARY.

Fig. 124. MAGNETIZATION CURVE.

Fig. 125. ARMATURE: CURVE.

Fig. 126. DEVELOPMENT OF ARMATURE CURVE.

Curve of Dynamo.

The characteristic curve of a dynamo. (See Curve, Characteristic.)

Curve of Sines.

An undulating curve representing wave motion. It is produced by

compounding a simple harmonic motion, or a two and fro motion like that

of an infinitely long pendulum with a rectilinear motion. Along a

horizontal line points may be laid off to represent equal periods of

time. Then on each point a perpendicular must be erected. The length of

each must be equal to the length of path traversed by the point up to

the expiration of each one of the given intervals of time. The abscissas

are proportional to the times and the ordinates to the sines of angles

proportional to the times. Thus if a circle be drawn upon the line and

divided into thirty-two parts of equal angular value, the sines of these

angles may be taken as the ordinates and the absolute distance or length

of arc of the angle will give the abscissas.

Synonyms--Sine Curve--Sinusoidal Curve--Harmonic Curve.

Fig. 127. CURVE OF SINES.

174   STANDARD ELECTRICAL DICTIONARY.

Curve of Saturation of the Magnetic Circuit.

A characteristic curve whose ordinates may represent the number of

magnetic lines of force induced in a magnetic circuit, and whose

abscissas may represent the ampere turns of excitation or other

representative of the inducing force.

Curve of Torque.

A characteristic curve showing the relations between torque, q. v., and

current in a dynamo or motor.

Curve, Permeability Temperature.

A characteristic curve expressing the changes in permeability of a

paramagnetic substance as the temperature changes. The degrees of

temperature may be abscissas, and the permeabilities corresponding

thereto ordinates of the curve.

Cut In. v.

To connect any electric appliance, mechanism or conductor, into a

circuit.

Cut Out. v.

The reverse of to cut in; to remove from a circuit any conducting

device, and sometimes so arranged as to leave the circuit completed in

some other way.

Cut Out.

An appliance for removing any apparatus from an electric circuit, so

that no more current shall pass through such apparatus, and sometimes

providing means for closing the circuit so as to leave it complete after

the removal of the apparatus.

175    STANDARD ELECTRICAL DICTIONARY.

Cut Out, Automatic.

(a) A mechanism for automatically shunting an arc or other lamp when it

ceases to work properly. It is generally worked by an electro-magnet of

high resistance placed in parallel with the arc. If the arc grows too

long the magnet attracts its armature, thereby completing a shunt of

approximately the resistance of the arc, and which replaces it until the

carbons approach again to within a proper distance. Sometimes a strip or

wire of fusible metal is arranged in shunt with the arc. When the arc

lengthens the current through the wire increases, melts it and a spring

is released which acts to complete or close a shunt circuit of

approximately arc-resistance.

(b) See Safety Device--Safety Fuse.

(c) See below.

Cut-out, Magnetic.

A magnetic cut-out is essentially a coil of wire with attracted core or

armature. When the coil is not excited the core, by pressing down a

strip of metal or by some analogous arrangement, completes the circuit.

When the current exceeds a certain strength the core rises as it is

attracted and the circuit is opened.

Cut-out, Safety.

A block of porcelain or other base carrying a safety fuse, which melts

and breaks the circuit before the wire connected to it is dangerously

heated.

Synonyms--Fuse Block--Safety Catch--Safety Fuse.

Cut Out, Wedge.

A cut out operated by a wedge. The line terminals consist of a spring

bearing against a plate, the circuit being completed through their point

of contact. A plug or wedge composed of two metallic faces insulated

from each other is adapted to wedge the contact open. Terminals of a

loop circuit are connected to the faces of the wedge. Thus on sliding it

into place, the loop circuit is brought into series in the main circuit.

Synonym--Plug Cut Out--Spring Jack.

Cutting of Lines of Force.

A field of force is pictured as made up of lines of force; a conductor

swept through the field is pictured as cutting these lines. By so doing

it produces potential difference or electro-motive force in itself with

a current, if the conductor is part of a closed circuit.

Cycle of Alternation.

A full period of alternation of an alternating current. It begins

properly at the zero line, goes to a maximum value in one sense and

returns to zero, goes to maximum in the other sense and returns to zero.

Cystoscopy.

Examination of the human bladder by the introduction of a special

incandescent electric lamp. The method is due to Hitze.

176   STANDARD ELECTRICAL DICTIONARY.

Damper.

(a) A copper frame on which the wire in a galvanometer is sometimes

coiled, which acts to damp the oscillations of the needle.

(b) A tube of brass or copper placed between the primary and secondary

coils of an induction coil. It cuts off induction and diminishes the

current and potential of the secondary circuit. On pulling it out, the

latter increases. It is used on medical coils to adjust their strength

of action.

Damping.

Preventing the indicator of an instrument from oscillating in virtue of

its own inertia or elasticity. In a galvanometer it is defined as

resistance to quick vibrations of the needle, in consequence of which it

is rapidly brought to rest when deflected (Ayrton). In dead-beat

galvanometers (see Galvanometer, Dead-Beat,) damping is desirable in

order to bring the needle to rest quickly; in ballistic galvanometers

(see Galvanometer, Ballistic,) damping is avoided in order to maintain

the principle of the instrument. Damping may be mechanical, the

frictional resistance of air to an air-vane, or of a liquid to an

immersed diaphragm or loosely fitting piston, being employed. A

dash-pot, q. v., is an example of the latter. It may be

electro-magnetic. A mass of metal near a swinging magnetic needle tends

by induced currents to arrest the oscillations thereof, and is used for

this purpose in dead-beat galvanometers. This is termed, sometimes,

magnetic friction. The essence of damping is to develop resistance to

movement in some ratio proportional to velocity, so that no resistance

is offered to the indicator slowly taking its true position. (See

Galvanometer, Dead-Beat.)

Dash-Pot.

A cylinder and piston, the latter loosely fitting or perforated, or some

equivalent means being provided to permit movement. The cylinder may

contain a liquid such as glycerine, or air only. Thus the piston is

perfectly free to move, but any oscillations are damped (see Damping).

In some arc lamps the carbon holder is connected to a dash-pot to check

too sudden movements of the carbon. The attachment may be either to the

piston or to the cylinder. In the Brush lamp the top of the carbon

holder forms a cylinder containing glycerine, and in it a loosely

fitting piston works. This acts as a dash-pot.

Dead Beat. adj.

Reaching its reading quickly; applied to instruments having a moving

indicator, which normally would oscillate back and forth a number of

times before reaching its reading were it not prevented by damping. (See

Galvanometer, Aperiodic--Damping.)

Dead Earth.

A fault in a telegraph line which consists in the wire being thoroughly

grounded or connected to the earth.

177  STANDARD ELECTRICAL DICTIONARY.

Dead Point of an Alternator.

A two-phase alternator of the ordinary type connected as a motor to

another alternator cannot start itself, as it has dead points where the

relations and polarity of field and armature are such that there is no

torque or turning power.

Dead-Turns.

In the winding of an armature, a given percentage of the turns, it may

be 80 per cent., more or less, is assumed to be active; the other 20 per

cent. or thereabouts, is called dead-turns. This portion represents the

wire on such portions of the armature as comes virtually outside of the

magnetic field. They are termed dead, as not concurring to the

production of electro-motive force.

Dead Wire.

(a) The percentage or portion of wire on a dynamo or motor armature that

does not concur in the production of electromotive force. The

dead-turns, q. v., of a drum armature or the inside wire in a Gramme

ring armature are dead wire.

(b) A disused and abandoned electric conductor, such as a telegraph

wire.

(c) A wire in use, but through which, at the time of speaking, no

current is passing.

Death, Electrical.

Death resulting from electricity discharged through the animal system.

The exact conditions requisite for fatal results have not been

determined. High electro-motive force is absolutely essential; a

changing current, pulsatory or alternating, is most fatal, possibly

because of the high electro-motive force of a portion of each period.

Amperage probably has something to do with it, although the total

quantity in coulombs may be very small. As applied to the execution of

criminals, the victim is seated in a chair and strapped thereto. One

electrode with wet padded surface is placed against his head or some

adjacent part. Another electrode is placed against some of the lower

parts, and a current from an alternating dynamo passed for 15 seconds or

more. The potential difference of the electrodes is given at 1,500 to

2,000 volts, but of course the maximum may be two or three times the

measured amount, owing to the character of the current.

Decalescence.

The converse of recalescence, q. v. When a mass of steel is being heated

as it reaches the temperature of recalescence it suddenly absorbs a

large amount of heat, apparently growing cooler.

Deci.

Prefix originally used in the metric system to signify one-tenth of, now

extended to general scientific units. Thus decimeter means one-tenth of

a meter; decigram, one-tenth of a gram.

Declination, Angle of.

The angle intercepted between the true meridian and the axis of a

magnetic needle at any place. The angle is measured to east or west,

starting from the true meridian as zero.

178   STANDARD ELECTRICAL DICTIONARY.

Declination of the Magnetic Needle.

The deviation of the magnetic needle from the plane of the earth's

meridian. It is also called the variation of the compass. (See Magnetic

Elements.)

Decomposition.

The reduction of a compound substance into its constituents, as in

chemical analysis. The constituents may themselves be compounds or

proximate constituents, or may be elemental or ultimate constituents.

Decomposition, Electrolytic.

The decomposition or separation of a compound liquid into its

constituents by electrolysis. The liquid must be an electrolyte, q. v.,

and the decomposition proceeds subject to the laws of electrolysis, q.

v. See also Electrolytic Analysis.

Decrement.

When a suspension needle which has been disturbed is oscillating the

swings gradually decrease in amplitude if there is any damping, as there

always is. The decrement is the ratio of the amplitude of one

oscillation to the succeeding one. This ratio is the same for any

successive swings.

De-energize.

To cut off its supply of electric energy from an electric motor, or any

device absorbing and worked by electric energy.

Deflagration.

The explosive or violent volatilizing and dissipating of a substance by

heat, violent oxidation and similar means. It may be applied among other

things to the destroying of a conductor by an intense current, or the

volatilization of any material by the electric arc.

Deflecting Field.

The field produced in a galvanometer by the current which is being

tested, and which field deflects the needle, such deflection being the

measure of the current strength.

Deflection.

In magnetism the movement out of the plane of the magnetic meridian of a

magnetic needle, due to disturbance by or attraction towards a mass of

iron or another magnet.

Deflection Method.

The method of electrical measurements in which the deflection of the

index of the measuring instrument is used as the measure of the current

or other element under examination. It is the opposite of and is to be

distinguished from the zero or null method, q. v. In the latter

conditions are established which make the index point to zero and from

the conditions necessary for this the measurement is deduced. The

Wheatstone Bridge, q. v., illustrates a zero method, the sine or the

tangent compass, illustrates a deflection method. The use of deflection

methods involves calibration, q. v., and the commercial measuring

instruments, such as ammeters and volt meters, which are frequently

calibrated galvanometers, are also examples of deflection instruments.

179  STANDARD ELECTRICAL DICTIONARY.

Degeneration, Reaction of.

The diminished sensibility to electro-therapeutic treatment exhibited by

the human system with continuance of the treatment in question. The

general lines of variation are stated in works on the subject.

Deka.

Prefix originally used in the metric system to signify multiplying by

ten, as dekameter, ten meters, dekagram, ten grams; now extended to many

scientific terms.

De la Rive's Floating Battery.

A small galvanic couple, immersed in a little floating cell and

connected through a coil of wire immediately above them. When the

exciting battery solution is placed in the cell the whole, as it floats

in a larger vessel, turns until the coil lies at right angles to the

magnetic needle. Sometimes the two plates are thrust through a cork and

floated thus in a vessel of dilute sulphuric acid.

A magnet acts to attract or repel the coil in obedience to Ampére's

Theory, (See Magnetism, Ampere's Theory of.)

Delaurier's Solution.

A solution for batteries of the Bunsen and Grenet type. It is of the

following composition:

Water,                2,000 parts;

potassium bichromate,   184 parts;

sulphuric acid,         428 parts.

Demagnetization.

Removal of magnetism from a paramagnetic substance. It is principally

used for watches which have become magnetized by exposure to the

magnetic field surrounding dynamos or motors.

The general principles of most methods are to rotate the object, as a

watch, in a strong field, and while it is rotating to gradually remove

it from the field, or to gradually reduce the intensity of the field

itself to zero. A conical coil of wire within which the field is

produced in which the watch is placed is sometimes used, the idea being

that the field within such a coil is strongest at its base. Such a coil

supplied by an alternating current is found effectual (J. J. Wright).

If a magnetized watch is made to turn rapidly at the end of a twisted

string and is gradually brought near to and withdrawn from the poles of

a powerful dynamo it may be considerably improved.

A hollow coil of wire connected with a pole changer and dip-battery has

been used. The battery creates a strong field within the coil. The watch

is placed there and the pole changer is worked so as to reverse the

polarity of the field very frequently. By the same action of the pole

changer the plates of the battery are gradually withdrawn from the

solution so as to gradually reduce the magnetic field to zero while

constantly reversing its polarity. (G. M. Hopkins.)

Steel may be demagnetized by jarring when held out of the magnetic

meridian, or by heating to redness.

180   STANDARD ELECTRICAL DICTIONARY.

Density, Electric Superficial.

The relative quantity of electricity residing as an electric charge upon

a unit area of surface. It may be positive or negative.

Synonyms--Density of Charge--Surface Density.

Dental Mallet, Electric.

A dentist's instrument for hammering the fillings as inserted into

teeth. It is a little hammer held in a suitable handle, and which is

made to strike a rapid succession of blows by electro-magnetic motor

mechanism.

Depolarization.

(a) The removal of permanent magnetism. (See Demagnetization.)

(b) The prevention of the polarization of a galvanic cell. It is

effected in the Grove battery by the reduction of nitric acid; in the

Bunsen, by the reduction of chromic acid; in the Smee battery,

mechanically, by the platinum coated or rather platinized negative

plate. Other examples will be found under the description of various

cells and batteries. A fluid which depolarizes is termed a depolarizer

or depolarizing fluid or solution. (See Electropoion Fluid.)

Deposit, Electrolytic.

The metal or other substance precipitated by the action of a battery or

other current generator.

Derivation, Point of.

A point where a circuit branches or divides into two or more leads. The

separate branches then receive derived or partial currents.

Desk Push.

A press or push button, with small flush rim, for setting into the

woodwork of a desk.

Detector.

A portable galvanometer, often of simple construction, used for rough or

approximate work.

Detector, Lineman's.

A portable galvanometer with a high and a low resistance actuating coil,

constructed for the use of linemen and telegraph constructors when in

the field, and actually putting up, repairing or testing lines.

Deviation, Quadrantal.

Deviation of the compass in iron or steel ships due to the magnetization

of horizontal beams by the earth's induction. The effect of this

deviation disappears when the ship is in the plane of the electric

meridian, or at right angles thereto; its name is taken from the fact

that a swing of the ship through a quadrant brings the needle from zero

deviation to a maximum and back to zero.

181  STANDARD ELECTRICAL DICTIONARY.

Deviation, Semicircular.

Deviation of the compass in iron or steel ships due to vertical

induction. (See Induction, Vertical.) The effect of this induction

disappears when the ship is in the electric meridian. Its name is

derived from the fact that a swing of the ship through half the circle

brings the needle from zero deviation to a maximum and back to zero.

Dextrotorsal. adj.

Wound in the direction or sense of a right-handed screw; the reverse of

sinistrotorsal, q. v.

Fig. 128. DEXTROTORSAL HELIX.

Diacritical. adj.

(a) The number of ampere turns, q. v., required to bring an iron core to

one half its magnetic saturation, q. v., is termed the diacritical

number.

(b) The diacritical point of magnetic saturation is proposed by Sylvanus

P. Thompson as a term for the coefficient of magnetic saturation which

gives a magnet core one-half its maximum magnetization.

Diagnosis, Electro.

A medical diagnosis of a patient's condition based on the action of

different parts of the body under electric excitement.

Diamagnetic. adj.

Possessing a negative coefficient of magnetic susceptibility; having

permeability inferior to that of air. Such substances placed between the

poles of a magnet are repelled; if in the form of bars, they tend to

turn so as to have their long axis at right angles to the line joining

the poles. The reason is that the lines of force always seek the easiest

path, and these bodies having higher reluctance than air, impede the

lines of force, and hence are as far as possible pushed out of the way.

The above is the simplest explanation of a not well understood set of

phenomena. According to Tyndall, "the diamagnetic force is a polar

force, the polarity of diamagnetic bodies being opposed to that of

paramagnetic ones under the same conditions of excitement." Bismuth is

the most strongly diamagnetic body known; phosphorus, antimony, zinc,

and many others are diamagnetic. (See Paramagnetic.)

182   STANDARD ELECTRICAL DICTIONARY.

Diagometer.

An apparatus for use in chemical analysis for testing the purity of

substances by the time required for a charged surface to be discharged

through them to earth. It is the invention of Rousseau.

An electrometer is charged with a dry pile. One of its terminals is

connected with one surface of the solution or substance to be tested,

and the other with the other surface. The time of discharge gives the

index of the purity of the substance.

Diamagnetic Polarity.

Treating diamagnetism as due to a polar force, the polarity of a

diamagnetic body is the reverse of the polarity of iron or other

paramagnetic bodies. A bar-shaped diamagnetic body in a field of force

tends to place itself at right angles to the lines of force.

Diamagnetism.

(a) The science or study of diamagnetic substances and phenomena.

(b) The magnetic property of a diamagnetic substance.

Diameter of Commutation.

The points on the commutator of a closed circuit ring--or

drum--armature, which the brushes touch, and whence they take the

current, mark the extremities of the diameter of commutation. Were it

not for the lag this would be the diameter at right angles to the line

connecting the centers of the opposite faces of the field. It is always

a little to one side of this position, being displaced in the direction

of rotation. In open circuit armatures the brushes are placed on the

diameter at right angles to this one, and sometimes the term diameter of

commutation is applied to it. All that has been said is on the

supposition that the armature divisions correspond not only in

connection but in position with those of the armature coils. Of course,

the commutator could be twisted so as to bring the diameter of

commutation into any position desired.

Diapason, Electric.

A tuning-fork or diapason kept in vibration by electricity. In general

principle the ends of the fork act as armatures for an electro-magnet,

and in their motion by a mercury cup or other form of contact they make

and break the circuit as they vibrate. Thus the magnet alternately

attracts and releases the leg, in exact harmony with its natural period

of vibration.

Diaphragm.

(a) In telephones and microphones a disc of iron thrown into motion by

sound waves or by electric impulses, according to whether it acts as the

diaphragm of a transmitter or receiver. It is generally a plate of

japanned iron such as used in making ferrotype photographs. (See

Telephone and Microphone.)

(b) A porous diaphragm is often used in electric decomposition cells and

in batteries. The porous cup represents the latter use.

[Transcriber's note: Japanned--covered with heavy black lacquer, like

enamel paint.]

183  STANDARD ELECTRICAL DICTIONARY.

Dielectric.

A non-conductor; a substance, the different parts of which may, after an

electric disturbance, remain, without any process of readjustment, and

for an indefinite period of time, at potentials differing to any extent

(Daniell). There is no perfect dielectric. The term dielectric is

generally only used when an insulator acts to permit induction to take

place through it, like the glass of a Leyden jar.

Dielectric Constant.

The number or coefficient expressing the relative dielectric capacity of

a medium or substance. (See Capacity, Specific Inductive.)

Dielectric, Energy of.

In a condenser, the conducting coatings are merely to conduct the

current all over the surface they cover; the keeping the electricities

separated is the work of the dielectric, and represents potential energy

which appears in the discharge. The amount of energy is proportional to

the charge, and to the potential difference. As any electrified body

implies an opposite electrification somewhere, and a separating

dielectric, the existence of a condenser is always implied.

[Transcriber's note: The energy stored in a capacitor (condenser) is

(Q*Q)/2C = (Q*V)/2 = (C*V*V)/2

The energy is proportional to the voltage SQUARED or the charge SQUARED.]

Dielectric Polarization.

A term due to Faraday. It expresses what he conceived to be the

condition of a dielectric when its opposite faces are oppositely

electrified. The molecules are supposed to be arranged by the

electrification in a series of polar chains, possibly being originally

in themselves seats of opposite polarities, or having such imparted to

them by the electricities. The action is analogous to that of a magnet

pole on a mass of soft iron, or on a pile of iron filings.

Dielectric Strain.

The strain a solid dielectric is subjected to, when its opposite

surfaces are electrified. A Leyden jar dilates under the strain, and

when discharged gives a dull sound. The original condition is not

immediately recovered. Jarring, shaking, etc., assist the recovery from

strain. The cause of the strain is termed Electric Stress. (See Stress,

Electric.) This is identical with the phenomenon of residual charge.

(See Charge, Residual.) Each loss of charge is accompanied with a

proportional return of the dielectric towards its normal condition.

Dielectric Resistance.

The mechanical resistance a body offers to perforation or destruction by

the electric discharge.

Dielectric Strength.

The resistance to the disruptive discharge and depending on its

mechanical resistance largely or entirely. It is expressible in volts

per centimeter thickness. Dry air requires 40,000 volts per centimeter

for a discharge.

184   STANDARD ELECTRICAL DICTIONARY.

Differential Winding Working.

A method of working an electro-magnet intermittently, so as to avoid

sparking. The magnet is wound with two coils. One is connected straight

into the circuit, the other is connected in parallel therewith with a

switch inserted. The coils are so connected that when the switch is

closed the two are in opposition, the current going through them in

opposite senses. Thus one overcomes the effect of the other and the

magnet core shows no magnetism, provided the two coils are of equal

resistance and equal number of convolutions or turns.

Fig. 129. DIFFERENTIAL WINDING WORKING

OF ELECTRO-MAGNETIC APPARATUS.

Diffusion.

A term properly applied to the varying current density found in

conductors of unequal cross sectional area. In electro-therapeutics it

is applied to the distribution of current as it passes through the human

body. Its density per cross-sectional area varies with the area and

with the other factors.

Diffusion Creep.

When electrodes of an active circuit are immersed in a solution of an

electrolyte, a current passes electrolytically if there is a sufficient

potential difference. The current passes through all parts of the

solution, spreading out of the direct prism connecting or defined by the

electrodes. To this portion of the current the above term is applied. If

the electrodes are small enough in proportion to the distance between

them the current transmission or creep outside of the line becomes the

principal conveyor of the current so that the resistance remains the

same for all distances.

Dimensions and Theory of Dimensions.

The expression of the unitary value of a physical quantity in one or

more of the units of length (L), time (T) and mass (M) is termed the

dimensions of such quantity. Thus the dimension or dimensions of a

distance is simply L; of an angle, expressible by dividing the arc by

the radius is L/L; of a velocity, expressible by distance divided by

time--L/T; of acceleration, which is velocity acquired in a unit of

time, and is therefore expressible by velocity divided by time--L/T/T or

L/T2; of momentum, which is the product of mass into velocity--M*L/T; of

kinetic energy taken as the product of mass into the square of

velocity--M*(L2/T2); of potential energy taken as the product of mass

into acceleration into space-M*(L/T2)*L reducing to M*(L2/T2). The

theory is based on three fundamental units and embraces all electric

quantities. The simple units generally taken are the gram, centimeter

and second and the dimensions of the fundamental compound units are

expressed in terms of these three, forming the centimeter-gram-second or

C. G. S. system of units. Unless otherwise expressed or implied the

letters L, M and T, may be taken to indicate centimeter, gram and second

respectively. It is obvious that very complicated expressions of

dimensions may be built up, and that a mathematical expression of

unnamed quantities may be arrived at. Dimensions in their application by

these symbols are subject to the laws of algebra. They were invented by

Fourier and were brought into prominence by J. Clerk Maxwell. Another

excellent definition reads as follows: "By the dimensions of a physical

quantity we mean the quantities and powers of quantities, involved in

the measurement of it." (W. T. A. Emtage.)

185  STANDARD ELECTRICAL DICTIONARY.

Dimmer.

An adjustable choking coil used for regulating the intensity of electric

incandescent lights. Some operate by the introduction and withdrawal of

an iron core as described for the choking coil (see Coil, Choking),

others by a damper of copper, often a copper ring surrounding the coil

and which by moving on or off the coil changes the potential of the

secondary circuit.

Dip of Magnetic Needle.

The inclination of the magnetic needle. (See Elements, Magnetic.)

Dipping.

(a) Acid or other cleaning processes applied by dipping metals in

cleaning or pickling solutions before plating in the electroplater's

bath.

(b) Plating by dipping applies to electroplating without a battery by

simple immersion. Copper is deposited on iron from a solution of copper

sulphate in this way.

Synonym--Simple Immersion.

Dipping Needle.

A magnet mounted in horizontal bearings at its centre of gravity. Placed

in the magnetic meridian it takes the direction of the magnetic lines of

force of the earth at that point. It is acted on by the vertical

component of the earth's magnetism, as it has no freedom of horizontal

movement. (See Magnetic Elements, and Compass, Inclination.)

Directing Magnet.

In a reflecting galvanometer the magnet used for controlling the

magnetic needle by establishing a field. It is mounted on the spindle of

the instrument above the coil and needle.

Synonym--Controlling Magnet.

186   STANDARD ELECTRICAL DICTIONARY.

Direction.

(a) The direction of an electric current is assumed to be from a

positively charged electrode or terminal to a negatively charged one in

the outer circuit. (See Current.)

(b) The direction of magnetic and electro-magnetic lines of force is

assumed to be from north to south pole of a magnet in the outer circuit.

It is sometimes called the positive direction. Their general course is

shown in the cuts diagrammatically. The circles indicate a compass used

in tracing their course. The magnetic needle tends to place itself in

the direction of or tangential to the lines of force passing nearest it.

(c) The direction of electrostatic lines of force is assumed to be out

of a positively charged and to a negatively charged surface.

Fig. 130. DIRECTION OF LINES OF FORCE OF A PERMANENT MAGNET.

Fig. 131, DIRECTION OF LINES OF FORCE OF AN ELECTRO-MAGNET.

187   STANDARD ELECTRICAL DICTIONARY.

Directive Power.

In magnetism the power of maintaining itself in the plane of the

magnetic meridian, possessed by the magnetic needle.

Discharge, Brush.

The static discharge of electricity into or through the air may be of

the brush or spark form. The brush indicates the escape of electricity

in continuous flow; the spark indicates discontinuity. The conditions

necessary to the production of one or the other refer to the nature of

the conductor, and of other conductors in its vicinity and to the

electro-motive force or potential difference; small alterations may

transform one into the other. The brush resembles a luminous core whose

apex touches the conductor. It is accompanied by a slight hissing noise.

Its luminosity is very feeble. The negative conductor gives a smaller

brush than that of the positive conductor and discharges it more

readily. When electricity issues from a conductor, remote from an

oppositely excited one, it gives an absolutely silent discharge, showing

at the point of escape a pale blue luminosity called electric glow, or

if it escapes from points it shows a star-like centre of light. It can

be seen in the dark by placing a point on the excited conductor of a

static-electric machine.

Synonyms--Silent Discharge--Glow Discharge.

Discharge, Conductive.

A discharge of a static charge by conduction through a conductor.

Discharge, Convective.

The discharge of static electricity from an excited conductor through

air or rarefied gas; it is also called the quiet or silent discharge.

The luminous effect in air or gas at atmospheric pressures takes the

form of a little brush from a small positive electrode; the negative

shows a star. The phenomena of Gassiot's cascade, the philosopher's egg

and Geissler tubes, all of which may be referred to, are instances of

convective discharge.

Discharge, Dead Beat.

A discharge that is not oscillatory in character.

Discharge, Disruptive.

A discharge of a static charge through a dielectric. It involves

mechanical perforation of the dielectric, and hence the mere mechanical

strength of the latter has much to do with preventing it. A disruptive

discharge is often oscillatory in character; this is always the case

with the discharge of a Leyden jar.

188   STANDARD ELECTRICAL DICTIONARY.

Discharge, Duration of.

The problem of determining this factor has been attacked by various

observers. Wheatstone with his revolving mirror found it to be 1/24000

second. Fedderson, by interposing resistance, prolonged it to 14/10000

and again to 138/10000 second. Lucas & Cazin made it from 26 to 47

millionths of a second. All these experiments were performed with Leyden

jars.

Discharge, Impulsive.

A disruptive discharge produced between conductors by suddenly produced

potential differences. The self-induction of the conductor plays an

especially important part in discharges thus produced.

Discharge, Lateral.

(a) A lightning discharge, which sometimes takes place between a

lightning rod and the building on which it is.

(b) In the discharge of a Leyden jar or condenser the discharge which

takes the alternative path, q. v.

Discharge, Oscillatory.

The sudden or disruptive discharge of a static condenser, such as a

Leyden jar, or of many other charged conductors, is oscillatory in

character. The direction of the currents rapidly changes, so that the

discharge is really an alternating current of excessively short total

duration. The discharge sends electro-magnetic waves through the ether,

which are exactly analogous to those of light but of too long period to

affect the eye.

Synonym--Surging Discharge.

[Transcriber's note: Marconi's transmission across the English channel

occurs in 1897, five years after the publication of this book.]

Fig. 132. DISCHARGER.

Discharger.

An apparatus for discharging Leyden jars. It consists of a conductor

terminating in balls, and either jointed like a tongs or bent with a

spring-action, so that the balls can be set at distances adapted to

different sized jars. It has an insulating handle or a pair of such. In

use one ball is brought near to the coating and the other to the spindle

ball of the jar. When nearly or quite in contact the jar discharges.

Synonyms--Discharging Rod--Discharging Tongs.

189  STANDARD ELECTRICAL DICTIONARY.

Discharger, Universal.

An apparatus for exposing substances to the static discharge spark. It

consists of a base with three insulating posts. The central post carries

an ivory table to support the object. The two side posts carry

conducting rods, terminating in metal balls, and mounted with universal

joints. A violent shock can be given to any object placed on the table.

Synonym--Henley's Universal Discharger.

Discharge, Silent.

This term is sometimes applied to the glow or brush discharge and

sometimes to the condition of electric effluvium. (See Discharge,

Brush--Effluvium, Electric.)

Discharge, Spark.

The discontinuous discharge of high tension electricity through a

dielectric or into the air produces electric sparks. These are quite

strongly luminous, of branching sinuous shape, and in long sparks the

luminosity varies in different parts of the same spark. A sharp noise

accompanies each spark. High density of charge is requisite for the

formation of long sparks.

Disconnection.

The separation of two parts of, or opening a circuit, as by turning a

switch, unscrewing a binding screw, or the like. The term is sometimes

used to indicate a class of faults in telegraph circuits. Disconnections

may be total, partial or intermittent, and due to many causes, such as

open or partially replaced switches, oxidized or dirty contact points,

or loose joints.

Displacement, Electric.

A conception of the action of charging a dielectric. The charge is all

on the surface. This fact being granted, the theory of displacement

holds that charging a body is the displacing of electricity, forcing it

from the interior on to the surface, or vice versa, producing a positive

or negative charge by displacement of electricity. While displacement is

taking place in a dielectric there is assumed to be a movement or

current of electricity called a displacement current.

Disruptive Tension.

When the surface of a body is electrified, it tends to expand, all

portions of the surface repelling each other. The film of air

surrounding such a body is electrified too, and is subjected to a

disruptive tension, varying in intensity with the square of the density.

Dissimulated Electricity.

The electricity of a bound charge. (See Charge, Bound.)

Dissociation.

The separation of a chemical compound into its elements by a

sufficiently high degree of heat. All compounds are susceptible of

dissociation, so that it follows that combustion is impossible at high

temperatures.

190   STANDARD ELECTRICAL DICTIONARY.

Distance, Critical, of Alternative Path.

The length of air gap in an alternative path whose resistance joined to

the impedance of the rest of the conductors of the path just balances

the impedance of the other path.

Distance, Sparking.

The distance between electrodes, which a spark from a given Leyden jar

or other source will pass across.

Synonym--Explosive Distance.

Distillation.

The evaporation of a liquid by heat, and sometimes in a vacuum, followed

by condensation of the vapors, which distil or drop from the end of the

condenser. It is claimed that the process is accelerated by the liquid

being electrified.

Distributing Box.

In an electric conduit system, a small iron box provided for giving

access to the cable for the purpose of making house and minor

connections.

Synonym--Hand Hole.

Distributing Switches.

Switch systems for enabling different dynamos to supply different lines

of a system as required. Spring jacks, q. v., are used for the lines,

and plug switches for the dynamo leads. Thus, dynamos can be thrown in

or out as desired, without putting out the lights.

Distribution of Electric Energy, Systems of.

The systems of electric current distribution from central stations or

from private generating plants, mechanical or battery, the latter

primary or secondary. They include in general the alternating current

system and direct current systems. Again, these may be subdivided into

series and multiple arc, multiple-series and series-multiple

distribution, and the three, four, or five wire system may be applied to

multiple arc or multiple series systems. (See Alternating

Current--Current System--Multiple Arc--Multiple Series--Series

Multiple--Three Wire System.)

Door Opener, Electric.

An apparatus for opening a door by pushing back the latch. A spring then

draws the door open, and it is closed against the force of the spring by

the person entering. Electro-magnetic mechanism actuates the latch, and

is operated by a switch or press-button. Thus a person on the upper

floor can open the hall door without descending.

Dosage, Galvanic.

In electro-therapeutics the amount of electric current or discharge, and

duration of treatment given to patients.

Double Carbon Arc Lamp.

An arc lamp designed to burn all night, usually constructed with two

parallel sets of carbons, one set replacing the other automatically, the

current being switched from the burnt out pair to the other by the

action of the mechanism of the lamp.

191  STANDARD ELECTRICAL DICTIONARY.

Double Fluid Theory.

A theory of electricity. Electricity is conveniently treated as a fluid

or fluids. According to the double fluid hypothesis negative electricity

is due to a preponderance of negative fluid and vice versa. Like fluid

repels like, and unlike attracts unlike; either fluid is attracted by

matter; the presence in a body of one or the other induces

electrification; united in equal proportions they neutralize each other,

and friction, chemical decomposition and other causes effect their

separation. The hypothesis, while convenient, is overshadowed by the

certainty that electricity is not really a fluid at all. (See Single

Fluid Theory--Fluid, Electric.)

Synonym--Symmer's Theory.

[Transcriber's note: Current is the motion of negative electrons in a

conductor or plasma. Unequal distribution of electrons is static

electricity. The relatively immobile nuclei of atoms are positive when

one or more of its electrons is absent and accounts for part of the

current in electrolysis and plasmas.]

Double Fluid Voltaic Cell.

A cell in which two fluids are used, one generally as depolarizer

surrounding the negative plate, the other as excitant surrounding the

positive plate. A porous diaphragm or difference in specific gravities

is used to keep the solutions separate and yet permit the essential

electrolytic diffusion. Grove's Cell, Bunsen's Cell, and Daniell's Cell,

all of which may be referred to, are of this type, as are many others.

Double Wedge.

A plug for use with a spring-jack. It has connection strips at its end

and another pair a little distance back therefrom, so that it can make

two loop connections at once.

Synonym--Double Plug.

Doubler.

A continuously acting electrophorous, q.v.; an early predecessor of the

modern electric machines. It is now no longer used.

D. P.

Abbreviation for Potential Difference.

Drag.

The pull exercised by a magnetic field upon a conductor moving through

it or upon the motion of an armature in it.

Dreh-strom. (German)

Rotatory currents; a system of currents alternating in periodic

succession of phases and producing a rotatory field. (See Field,

Rotatory--Multiphase Currents.)

Drill Electric.

A drill for metals or rock worked by an electro-magnetic motor. For

metals a rotary motion, for rocks a reciprocating or percussion action

is imparted. It is used by shipbuilders for drilling holes in plates

which are in place in ships, as its flexible conductors enable it to be

placed anywhere. For rock-drilling a solenoid type of construction is

adopted, producing rapid percussion.

192   STANDARD ELECTRICAL DICTIONARY.

Drip Loop.

A looping downward of wires entering a building, so that rain water, as

it runs along the wire, will drip from the lowest part of the loop

instead of following the wire into or against the side of the building.

Driving Horns.

Projections on the periphery of an armature of a dynamo for holding the

winding in place and preventing its displacement. Various arrangements

have been adopted. They are sometimes wedges or pins and are sometimes

driven into spaces left in the drum core. The toothed disc armature

cores make up an armature in which the ridges formed by the teeth form

practically driving horns.

Dronier's Salt.

A substance for solution for use in bichromate batteries. It is a

mixture of one-third potassium bichromate and two-thirds potassium

bisulphate. It is dissolved in water to make the exciting fluid.

Drop, Automatic.

A switch or circuit breaker, operating to close a circuit by dropping

under the influence of gravity. It is held up by a latch, the circuit

remaining open, until the latch is released by a current passing through

an electro-magnet. This attracting an armature lets the drop fall. As it

falls it closes a local or second circuit, and thus may keep a bell

ringing until it is replaced by hand. It is used in burglar alarms, its

function being to keep a bell ringing even though the windows or door by

which entrance was made is reclosed.

193   STANDARD ELECTRICAL DICTIONARY.

Fig. 133. THE MAGIC DRUM.

Drum, Electric.

A drum with a mechanism within for striking the head with a hammer or

some equivalent method so as to be used as a piece of magical apparatus.

In the one shown in the cut a sort of telephone action is used to

produce the sound, the electro-magnet D and armature being quite

screened from observation through the hole. (See Fig. 133) A ring, C,

shown in Fig. 133, with two terminals, the latter shown by the unshaded

portions a a, and a suspending hook E, also with two terminals, and two

suspending conductors A, B, carry the current to the magnet. A sudden

opening or closing of the circuit produces a sound.

Dub's Laws.

1. The magnetism excited at any transverse section of a magnet is

proportional to the square root of the distance between the given

section and the end.

2. The free magnetism at any given transverse section of a magnet is

proportional to the difference between the square root of half the

length of the magnet and the square root of the distance between the

given section and the nearest end.

Duct.

The tube or compartment in an electric subway for the reception of a

cable. (See Conduit, Electric Subway.)

Dyad.

A chemical term; an element which in combination replaces two monovalent

elements; one which has two bonds or is bivalent.

Dyeing, Electric.

The producing mordanting or other dyeing effects on goods in dyeing by

the passage of an electric current.

Dynamic Electricity.

Electricity of relatively low potential and large quantity; current

electricity as distinguished from static electricity; electricity in

motion.

194   STANDARD ELECTRICAL DICTIONARY.

Dynamo, Alternating Current.

A dynamo-electric machine for producing an alternating current; an

alternator. They are classified by S. P. Thompson into three classes--I.

Those with stationary field-magnet and rotating armature. II. Those with

rotating field magnet and stationary armature. III. Those with both

field magnet part and armature part stationary, the amount of magnetic

induction from the latter through the former being caused to vary or

alternate in direction by the revolution of appropriate pieces of iron,

called inductors. Another division rests on whether they give one simple

alternating current, a two phase current, or whether they give multi

phase currents. (See Current, Alternating--Currents, Multiphase.)

A great many kinds of alternators have been constructed. Only an outline

of the general theory can be given here. They are generally multipolar,

with north and south poles alternating around the field. The armature

coils, equal in number in simple current machines, to the poles, are

wound in opposite senses, so that the current shall be in one direction,

though in opposite senses, in all of them at anyone time. As the

armature rotates the coils are all approaching their poles at one time

and a current in one sense is induced in every second coil, and one in

the other sense in the other coils. They are all in continuous circuit

with two open terminals, each connected to its own insulated connecting

ring on the shaft. As the coils pass the poles and begin to recede from

them the direction changes, and the current goes in the other direction

until the next poles are reached and passed. Thus there are as many

changes of direction of current per rotation as there are coils in the

armature or poles in the field.

Fig. 134. ALTERNATING CURRENT DYNAMO WITH

SEPARATE EXCITER MOUNTED ON MAIN SHAFT.

195  STANDARD ELECTRICAL DICTIONARY.

The field-magnets whose windings may be in series are often excited by a

separate direct current generation. Some are self-exciting, one or more

of the armature coils being separated from the rest, and connected to a

special commutator, which rectifies its current.

By properly spacing the coils with respect to the poles of the field,

and connecting each set of coils by itself to separate connecting rings,

several currents can be taken from the same machine, which currents

shall have a constant difference in phase. It would seem at first sight

that the same result could be attained by using as many separate

alternators as there were currents to be produced. But it would be

almost impossible to preserve the exact relation of currents and current

phase where each was produced by its own machine. The currents would

overrun each other or would lag behind. In a single machine with

separate sets of coils the relation is fixed and invariable.

Fig. I35. DIAGRAM OF ARRANGEMENT OF ARMATURE COILS AND

COLLECTING RINGS IN AN ALTERNATING CURRENT DYNAMO.

Dynamo, Alternating Current, Regulation of.

Transformers, converters, or induction coils are used to regulate

alternating current dynamos, somewhat as compound winding is applied in

the case of direct-current dynamos. The arrangement consists in

connecting the primary of an induction coil or transformer into the

external circuit with its secondary connected to the field circuit. Thus

the transformer conveys current to the field picked up from the main

circuit, and represents to some extent the shunt of a direct-current

machine.

Dynamo, Commercial Efficiency of.

The coefficient, q. v., obtained by dividing the mechanically useful or

available work of a dynamo by the mechanical energy absorbed by it. This

only includes the energy available in the outer circuit, for doing

useful work.

196   STANDARD ELECTRICAL DICTIONARY.

Fig. 136. COMPOUND WOUND DYNAMO.

Dynamo. Compound.

A compound wound dynamo; one which has two coils on its field magnet;

one winding is in series with the external circuit and armature; the

other winding is in parallel with the armature winding, or else with the

armature winding and field winding, both in series. (See Winding, Long

Shunt--Winding, Short Shunt.)

Such a dynamo is, to a certain extent, self-regulating, the two coils

counteracting each other, and bringing about a more regular action for

varying currents than that of the ordinary shunt or series dynamo.

The extent of the regulation of such a machine depends on the

proportions given its different parts. However good the self-regulating

may be in a compound wound machine, it can only be perfect at one

particular speed.

To illustrate the principle on which the approximate regulation is

obtained the characteristic curve diagram may be consulted.

Fig. 137. CURVES OF SERIES AND SHUNT WINDINGS SUPERIMPOSED.

One curve is the curve of a series winding, the other that of a shunt

winding, and shows the variation of voltage in each with resistance in

the external or working circuit. The variation is opposite in each case.

It is evident that the two windings could be so proportioned on a

compound machine that the resultant of the two curves would be a

straight line. This regulation would then be perfect and automatic, but

only for the one speed.

197  STANDARD ELECTRICAL DICTIONARY.

Dynamo, Direct Current.

A dynamo giving a current of unvarying direction, as distinguished from

an alternator or alternating current dynamo.

Dynamo, Disc.

A dynamo with a disc armature, such as Pacinotti's disc, q. v. (See also

Disc, Armature.) The field magnets are disposed so that the disc rotates

close to their poles, and the poles face or are opposite to the side or

sides of the disc. The active leads of wire are those situated on the

face or faces of the disc.

Fig. 138. POLECHKO'S DISC DYNAMO.

Dynamo-electric Machine.

A machine driven by power, generally steam power, and converting the

mechanical energy expended on driving it into electrical energy of the

current form. The parts of the ordinary dynamo may be summarized as

follows: First, A circuit as complete as possible of iron. Such circuit

is composed partly of the cores of an electro-magnet or of several

electro-magnets, and partly of the cylindrical or ring-shaped core of an

armature which fits as closely as practicable between the magnet ends or

poles which are shaped so as to partly embrace it. Second, of coils of

insulated wire wound upon the field-magnet cores. When these coils are

excited the field-magnets develop polarity and the circuit just spoken

of becomes a magnetic circuit, interrupted only by the air gaps between

the poles and armatures. Thirdly, of coils of insulated wire upon the

armature core. These coils when rotated in the magnetic field cut

magnetic lines of force and develop electro-motive force.

198   STANDARD ELECTRICAL DICTIONARY.

Fourthly, of collecting mechanism, the commutator in direct current

dynamos, attached to the armature shaft and rotating with it. This

consists of insulated rings, or segments of rings to which the wire

coils of the armature are connected, and on which two springs of copper

or plates of carbon or some other conductor presses. The electro-motive

force developed by the cutting of lines of force, by the wires of the

armature, shows itself as potential difference between the two springs.

If the ends of a conductor are attached, one to each of these brushes,

the potential difference will establish a current through the wire. By

using properly divided and connected segments on the commutator the

potential difference and consequent direction of the current may be kept

always in the same sense or direction. It is now clear that the external

wire may be connected with the windings of the field-magnet. In such

case the excitement of the field-magnets is derived from the armature

and the machine is self-excited and entirely self-contained.

The above is a general description of a dynamo. Sometimes the coils of

the field-magnets are not connected with the armature, but derive their

current from an outside source. Such are termed separately excited

dynamos.

Some general features of dynamo generators may be seen in the

definitions under this head and elsewhere. The general conception is to

cut lines of force with a conductor and thus generate electromotive

force, or in some way to change the number of lines of force within a

loop or circuit with the same effect.

Dynamo, Electroplating.

A dynamo designed for low potential and high current intensity. They are

wound for low resistance, frequently several wires being used in

parallel, or ribbon, bar or rectangular conductors being employed. They

are of the direct current type. They should be shunt wound or they are

liable to reverse. They are sometimes provided with resistance in the

shunt, which is changed as desired to alter the electro-motive force.

Dynamo, Equalizing.

A combination for three and five-wire systems. A number of armatures or

of windings on the same shaft are connected across the leads. If the

potential drops at any pair of mains, the armature will begin to be

driven by the other mains, acting to an extent as an element of a motor,

and will raise the potential in the first pair.

Dynamo, Far Leading.

A motor dynamo, used to compensate the drop of potential in long mains.

Into the mains at a distant point a series motor is connected, driving a

dynamo placed in shunt across the mains. The dynamo thus driven raises

the potential difference between the two mains.

199  STANDARD ELECTRICAL DICTIONARY.

Dynamograph.

A printing telegraph in which the message is printed at both

transmitting and receiving ends.

Dynamo, Inductor.

A generator in which the armature or current-generating windings are all

comprised upon the poles of the field magnets. Masses of iron, which

should be laminated and are the inductors, are carried past the field

magnet poles concentrating in their passage the lines of force, thus

inducing currents in the coils. In one construction shown in the cut the

field magnets a, a .. are U shaped and are arranged in a circle, their

poles pointing inwards. A single exciting coil c, c ... is wound around

the circle in the bend of the V-shaped segments. The poles carry the

armature coils e, e ... The laminated inductors i, i ... are mounted on

a shaft S, by spiders h, to be rotated inside the circle of magnets,

thus generating an alternating current.

Synonym--Inductor Generator.

Fig. 139. INDUCTOR DYNAMO.

Dynamo, Interior Pole.

A dynamo with a ring armature, with field magnet pole pieces which

extend within the ring.

200   STANDARD ELECTRICAL DICTIONARY.

Dynamo, Iron Clad.

A dynamo in which the iron of the field magnet is of such shape as to

enclose the field magnet coils as well as the armature.

Dynamometer.

A device or apparatus for measuring force applied, or rate of

expenditure of energy by, or work done in a given time by a machine. A

common spring balance can be used as a force dynamometer, viz: to

determine how hard a man is pulling and the like. The steam engine

indicator represents an energy-dynamometer of the graphic type, the

instrument marking an area whence, with the aid of the fixed factors of

the engine, the work done may be determined. Prony's Brake, q. v., is a

type of the friction dynamometer, also of the energy type. In the latter

type during the experiment the whole power must be turned on or be

expended on the dynamometer.

Dynamo, Motor.

A motor dynamo is a machine for (a) converting a continuous current at

any voltage to a continuous current of different strength at a different

voltage or for (b) transforming a continuous current into an alternating

one, and vice versa.

For the first type see Transformer, Continuous Current; for the second

type see Transformer, Alternating Current.

Dynamo, Multipolar.

A dynamo having a number of field magnet poles, not merely a single

north and a single south pole. The field magnet is sometimes of a

generally circular shape with the poles arranged radially within it, the

armature revolving between the ends.

Dynamo, Non-polar.

A name given by Prof. George Forbes to a dynamo invented by him. In it a

cylinder of iron rotates within a perfectly self-contained iron-clad

field magnet. The current is taken off by brushes bearing near the

periphery, at two extremities of a diameter. A machine with a disc 18

inches in diameter was said to give 3,117 amperes, with 5.8 volts E. M.

F. running at 1,500 revolutions per second. The E. M. F. of such

machines varies with the square of the diameter of the disc or cylinder.

Dynamo, Open Coil.

A dynamo the windings of whose armatures may be grouped in coils, which

are not connected in series, but which have independent terminals. These

terminals are separate divisions of the commutator and so spaced that

the collecting brushes touch each pair belonging to the same coil

simultaneously. As the brushes come in contact with the sections forming

the terminals they take current from the coil in question. This coil is

next succeeded by another one, and so on according to the number of

coils employed.

Dynamo, Ring.

A dynamo the base of whose field magnets is a ring in general shape, or

perhaps an octagon, and with poles projecting inwardly therefrom.

201   STANDARD ELECTRICAL DICTIONARY.

Dynamo, Coupling of.

Dynamos can be coupled exactly like batteries and with about the same

general results. An instance of series coupling would be given by the

dynamos in the three wire system when no current is passing through the

neutral wire, and when the lamps on each side of it are lighted in equal

number.

Dynamo, Self-exciting.

A dynamo which excites its own field. The majority of dynamos are of

this construction. Others, especially alternating current machines, are

separately excited, the field magnets being supplied with current from a

separate dynamo or current generator.

Dynamo, Separate Circuit.

A dynamo in which the field magnet coils are entirely disconnected from

the main circuit, and in which current for the field is supplied by

special coils carried for the purpose by the same armature, or by a

special one, in either case a special commutator being provided to

collect the current.

Dynamo, Separately Excited.

A dynamo whose field magnets are excited by a separate current

generator, such as a dynamo or even a battery. Alternating current

dynamos are often of this construction. Direct current dynamos are not

generally so. The term is the opposite of self-exciting.

Fig. 140. SERIES DYNAMO.

Dynamo, Series.

A dynamo whose armature, field winding, and external circuit are all in

series.

In such a dynamo short circuiting or lowering the resistance of the

external circuit strengthens the field, increases the electro-motive

force and current strength and may injure the winding by heating the

wire, and melting the insulation.

202   STANDARD ELECTRICAL DICTIONARY.

Dynamo, Shunt.

A dynamo whose field is wound in shunt with the external circuit. Two

leads are taken from the brushes; one goes around the field magnets to

excite them; the other is the external circuit.

In such a dynamo the lowering of resistance on the outer circuit takes

current from the field and lowers the electro-motive force of the

machine. Short circuiting has no heating effect.

Fig. 141.   SHUNT DYNAMO.

Dynamo, Single Coil.

A dynamo whose field magnet is excited by a single coil. Several such

have been constructed, with different shapes of field magnet cores, in

order to obtain a proper distribution of poles.

Dynamo, Tuning Fork.

A dynamo in which the inductive or armature coils were carried at the

ends of the prongs of a gigantic tuning fork, and were there maintained

in vibration opposite the field magnets. It was invented by T. A.

Edison, but never was used.

Dynamo, Uni-polar.

A dynamo in which the rotation of a conductor effects a continuous

increase in the number of lines cut, by the device of arranging one part

of the conductor to slide on or around the magnet. (S. P. Thomson.)

Faraday's disc is the earliest machine of this type.

203  STANDARD ELECTRICAL DICTIONARY.

Dyne.

The C. G. S. or fundamental unit of force. It is the force which can

impart an acceleration of one centimeter per second to a mass of one

gram in one second. It is equal to about 1/981 the weight of a gram,

this weight varying with the latitude.

Earth.

(a) The earth is arbitrarily taken as of zero electrostatic potential.

Surfaces in such condition that their potential is unchanged when

connected to the earth are said to be of zero potential. All other

surfaces are discharged when connected to the earth, whose potential,

for the purposes of man at least, never changes.

(b) As a magnetic field of force the intensity of the earth's field is

about one-half a line of force per square centimeter.

(c) The accidental grounding of a telegraph line is termed an earth, as

a dead, total, partial, or intermittent earth, describing the extent and

character of the trouble.

[Transcriber's note: Fallen power lines can produce voltage gradients on

the earth's surface that make walking in the area dangerous, as in

hundreds of volts per foot. Lightning may be associated with substantial

changes in the static ground potential.]

Earth, Dead.

A fault, when a telegraph or other conductor is fully connected to earth

or grounded at some intermediate point.

Synonyms--Solid Earth--Total Earth.

Earth, Partial.

A fault, when a telegraph or other conductor is imperfectly connected to

earth or grounded at some intermediate point.

Earth Plate.

A plate buried in the earth to receive the ends of telegraph lines or

other circuits to give a ground, q. v. A copper plate is often used. A

connection to a water or gas main gives an excellent ground, far better

than any plate. When the plate oxidizes it is apt to introduce

resistance.

Earth Return.

The grounding of a wire of a circuit at both ends gives the circuit an

earth return.

Earth, Swinging.

A fault, when a telegraph or other conductor makes intermittent

connection with the earth. It is generally attributable to wind action

swinging the wire, whence the name.

Ebonite.

Hard vulcanized India rubber, black in color. Specific resistance in

ohms per cubic centimeter at 46º C. (115º F.): 34E15 (Ayrton); specific

inductive capacity, (air = 1): 2.56 (Wüllner); 2.76 (Schiller); 3.15

(Boltzmann). It is used in electrical apparatus for supporting members

such as pillars, and is an excellent material for frictional generation

of potential. Its black color gives it its name, and is sometimes made a

point of distinction from Vulcanite, q. v.

204   STANDARD ELECTRICAL DICTIONARY.

Economic Coefficient.

The coefficient of electric efficiency. (See Efficiency, Electric.)

Edison Effect.

A continuous discharge resulting in a true current which takes place

between a terminal of an incandescent lamp filament and a plate placed

near it. The lamp must be run at a definitely high voltage to obtain it.

Ediswan.

An abbreviation for Edison-Swan; the trade name of the incandescent lamp

used in Great Britain, and of other incandescent system apparatus.

Fig. 142. GYMNOTUS ELECTRICUS.

Eel, Electric (Gymnotus Electricus).

An eel capable of effecting the discharge of very high potential

electricity, giving painful or dangerous shocks. Its habitat is the

fresh water, in South America. Faraday investigated it and estimated its

shock as equal to that from fifteen Leyden jars, each of 1.66 square

feet of coating. (See Animal Electricity and Ray, Electric.)

Effect, Counter-inductive.

A counter-electro-motive force due to induction, and opposing a current.

Efficiency.

The relation of work done to energy absorbed. A theoretically perfect

machine would have the maximum efficiency in which the two qualities

named would be equal to each other. Expressed by a coefficient, q. v.,

the efficiency in such case would be equal to 1. If a machine produced

but half the work represented by the energy it absorbed, the rest

disappearing in wasteful expenditure, in heating the bearings, in

overcoming the resistance of the air and in other ways, its efficiency

would be expressed by the coefficient 1/2 or .5, or if one hundred was

the basis, by fifty per centum. There are a number of kinds of

efficiencies of an electric generator which are given below.

Efficiency, Commercial.

Practical efficiency of a machine, obtained by dividing the available

output of work or energy of a machine by the energy absorbed by the same

machine. Thus in a dynamo part of the energy is usefully expended in

exciting the field magnet, but this energy is not available for use in

the outer circuit, is not a part of the output, and is not part of the

dividend.

If M represents the energy absorbed, and W the useful or available

energy, the coefficient of commercial efficiency is equal to W/M. M is

made up of available, unavailable and wasted (by Foucault currents,

etc.,) energy. Calling available energy W, unavailable but utilized

energy w, and wasted energy m, the expression for the coefficient of

commercial efficiency becomes

W / ( W + w + m )

when M = W + w + m

Synonym--Net efficiency.

205   STANDARD ELECTRICAL DICTIONARY.

Efficiency, Electrical.

In a dynamo or generator the relation of total electric energy produced,

both wasted and useful or available to the useful or available

electrical energy. If we call W the useful electric and w the wasted

electric energy, the coefficient of electrical efficiency is equal to

W / ( W + w )

Synonyms--Intrinsic Efficiency--Economic Coefficient--Coefficient of

Electrical Efficiency.

Efficiency of Conversion.

In a dynamo or generator the relation of energy absorbed to total

electric energy produced. Part of the electric energy is expended in

producing the field and in other ways. Thus a generator with high

efficiency of conversion may be a very poor one, owing to the

unavailable electric energy which it produces. The coefficient of

Efficiency of Conversion is obtained by dividing the total electric

energy produced by the energy absorbed in working the dynamo. If M

represents the energy absorbed, or work done in driving the dynamo or

generator, W the useful electric, and w the wasted electrical energy,

then the coefficient of efficiency of conversion is equal to

(W + w ) / M

In the quantity M are included besides available (W) and unavailable (w)

electric energy, the totally wasted energy due to Foucault currents,

etc., calling the latter m, the above formula may be given

( W+ w ) / (W + w + m )

This coefficient may refer to the action of a converter, q. v., in the

alternating system. Synonym--Gross Efficiency.

Efficiency of Secondary Battery, Quantity.

The coefficient obtained by dividing the ampere-hours obtainable from a

secondary battery by the ampere hours required to charge it.

Efficiency of Secondary Battery, Real.

The coefficient obtained by dividing the energy obtainable from a

secondary battery by the energy absorbed in charging it. The energy is

conveniently taken in watt-hours and includes the consideration of the

spurious voltage. (See Battery, Secondary.)

206   STANDARD ELECTRICAL DICTIONARY.

Efflorescence.

The appearance of a dry salt upon the walls of a vessel containing a

solution above the normal water-line from evaporation of a liquid. It

appears in battery jars and in battery carbons, in the latter

interfering with the electrical connections, and oxidizing or rusting

them. (See Creeping.)

Effluvium, Electric.

When a gas is made to occupy the position of dielectric between two

oppositely electrified surfaces a peculiar strain or condition of the

dielectric is produced, which promotes chemical change. The condition is

termed electrical effluvium or the silent discharge. By an apparatus

specially constructed to utilize the condition large amounts of ozone

are produced.

Synonym--Silent Discharge.

Elastic Curve.

A crude expression for a curve without projections or sudden

sinuosities; such a curve as can be obtained by bending an elastic strip

of wood.

Electrepeter.

An obsolete name for a key, switch or pole changer of any kind.

Elasticity, Electric.

The phenomenon of the dielectric is described under this term. When a

potential difference is established between two parts of the dielectric,

a flow of electricity displacement current starts through the

dielectric, which current is due to the electric stress, but is

instantly arrested by what has been termed the electric elasticity of

the dielectric. This is expressed by

( electric stress ) / ( electric strain )

and in any substance is inversely proportional to the specific inductive

capacity.

Electricity.

It is impossible in the existing state of human knowledge to give a

satisfactory definition of electricity. The views of various authorities

are given here to afford a basis for arriving at the general consensus

of electricians.

We have as yet no conception of electricity apart from the electrified

body; we have no experience of its independent existence. (J. E. H.

Gordon.)

What is Electricity? We do not know, and for practical purposes it is

not necessary that we should know. (Sydney F. Walker.)

Electricity … is one of those hidden and mysterious powers of nature

which has thus become known to us through the medium of effects.

(Weale's Dictionary of Terms.)

This word Electricity is used to express more particularly the cause,

which even today remains unknown, of the phenomena that we are about to

explain. (Amédée Guillemin.)

207  STANDARD ELECTRICAL DICTIONARY.

Electricity is a powerful physical agent which manifests itself mainly

by attractions and repulsions, but also by luminous and heating effects,

by violent commotions, by chemical decompositions, and many other

phenomena. Unlike gravity, it is not inherent in bodies, but it is

evoked in them by a variety of causes … (Ganot's Physics.)

Electricity and magnetism are not forms of energy; neither are they

forms of matter. They may, perhaps, be provisionally defined as

properties or conditions of matter; but whether this matter be the

ordinary matter, or whether it be, on the other hand, that

all-pervading ether by which ordinary matter is surrounded, is a question

which has been under discussion, and which now may be fairly held to be

settled in favor of the latter view. (Daniell's Physics.)

The name used in connection with an extensive and important class of

phenomena, and usually denoting the unknown cause of the phenomena or

the science that treats of them. (Imperial Dictionary.)

Electricity. . . is the imponderable physical agent, cause, force or the

molecular movement, by which, under certain conditions, certain

phenomena, chiefly those of attraction and repulsion, . . . are

produced. (John Angell.)

It has been suggested that if anything can rightly be called

"electricity," this must be the ether itself; and that all electrical

and magnetic phenomena are simply due to changes, strains and motions in

the ether. Perhaps negative electrification. . .means an excess of

ether, and positive electrification a defect of ether, as compared with

the normal density. (W. Larden.)

Electricity is the name given to the supposed agent producing the

described condition (i. e. electrification) of bodies. (Fleeming

Jenkin.)

There are certain bodies which, when warm and dry, acquire by friction,

the property of attracting feathers, filaments of silk or indeed any

light body towards them. This property is called Electricity, and bodies

which possess it are said to be electrified. (Linnaeus Cumming.)

What electricity is it is impossible to say, but for the present it is

convenient to look upon it as a kind of invisible something which

pervades all bodies. (W. Perren Maycock.)

What is electricity? No one knows. It seems to be one manifestation of

the energy which fills the universe and which appears in a variety of

other forms, such as heat, light, magnetism, chemical affinity,

mechanical motion, etc. (Park Benjamin.)

208   STANDARD ELECTRICAL DICTIONARY.

The theory of electricity adopted throughout these lessons is, that

electricity, whatever its true nature, is one, not two; that this

Electricity, whatever it may prove to be, is not matter, and is not

energy; that it resembles both matter and energy in one respect,

however, in that it can neither be created nor destroyed. (Sylvanus P.

Thomson.)

In Physics a name denoting the cause of an important class of phenomena

of attraction and repulsion, chemical decomposition, etc., or,

collectively, these phenomena themselves. (Century Dictionary.)

A power in nature, often styled the electric fluid, exhibiting itself,

when in disturbed equilibrium or in activity, by a circuit movement, the

fact of direction in which involves polarity, or opposition of

properties in opposite directions; also, by attraction for many

substances, by a law involving attraction between substances of unlike

polarity, and repulsion between those of like; by exhibiting accumulated

polar tension when the circuit is broken; and by producing heat, light,

concussion, and often chemical changes when the circuit passes between

the poles, or through any imperfectly conducting substance or space. It

is evolved in any disturbance of molecular equilibrium, whether from a

chemical, physical, or mechanical cause. (Webster's Dictionary.)

In point of fact electricity is not a fluid at all, and only in a few of

its attributes is it at all comparable to a fluid. Let us rather

consider electricity to be a condition into which material substances

are thrown. . .(Slingo & Brooker.)

[Transcriber's note: 2008 Dictionary: Phenomena arising from the

behavior of electrons and protons caused by the attraction of particles

with opposite charges and the repulsion of particles with the same

charge.]

Electricity, Cal.

The electricity produced in the secondary of a transformer by changes of

temperature in the core. This is in addition to the regularly induced

current.

Synonym--Acheson Effect.

Electrics.

Substances developing electrification by rubbing or friction; as

Gilbert, the originator of the term, applied it, it would indicate

dielectrics. He did not know that, if insulated, any substance was one

of his "electrics." A piece of copper held by a glass handle becomes

electrified by friction.

Electrification.

The receiving or imparting an electric charge to a surface; a term

usually applied to electrostatic phenomena.

Electrization.

A term in electro-therapeutics; the subjection of the human system to

electric treatment for curative, tonic or diagnostic purposes.

Electro-biology.

The science of electricity in its relation to the living organism,

whether as electricity is developed by the organism, or as it affects

the same when applied from an external source.

209  STANDARD ELECTRICAL DICTIONARY.

Electro-capillarity.

The relations between surface tension, the potential difference and the

electrostatic capacity of fluids in contact. Although nominally in

contact such surfaces are separated by about one-twenty-millionth of a

centimeter (1/50000000 inch) ; thus a globule of mercury and water in

which it is immersed constitute an electrostatic accumulator of definite

electrostatic capacity. Again the mercury and water being in electric

connection differ in potential by contact (see Contact Theory). A

definite surface tension is also established. Any change in one of these

factors changes the other also. A current passed through the contact

surfaces will change the surface tension and hence the shape of the

mercury globule. Shaking the globule will change its shape and capacity

and produce a current. Heating will do the same. (See Electrometer,

Capillary; and Telephone, Capillary.) Mercury and water are named as

liquids in which the phenomena are most conveniently observed. They are

observable in other parallel cases.

Electro-chemical Equivalent.

The quantity of an element or compound liberated from or brought into

combination, electrolytically, by one coulomb of electricity. The

electro-chemical equivalent of hydrogen is found by experiment to be

.0000105 gram. That of any other substance is found by multiplying this

weight by its chemical equivalent referred to hydrogen, which is its

atomic or molecular weight divided by its valency. Thus the atomic

weight of oxygen is 16, its valency is 2, its equivalent is 16/2 = 8;

its electro-chemical equivalent is equal to .0000105 X 8 = .000840 gram.

Electro-chemical Series.

An arrangement of the elements in the order of their relative electrical

affinities so that each element is electro-negative to all the elements

following it, and electro-positive to the elements preceding it. The

usual series begins with oxygen as the most electro-negative and ends

with potassium as the most electro-positive element. There is, of

course, no reason why other series of compound radicals, such as

sulphion (SO4), etc., should not also be constructed. For each liquid

acting on substances a separate series of the substances acted on may be

constructed. Thus for dilute sulphuric acid the series beginning with

the negatively charged or most attacked one is zinc, amalgamated or

pure, cadmium, iron, tin, lead, aluminum, nickel, antimony, bismuth,

copper, silver, platinum. In other liquids the series is altogether

different.

Electro--chemistry.

The branch of electricity or of chemistry treating of the relations

between electric and chemical force in different compounds and

reactions. (See Electrolysis--Electrochemical series--Electro-chemical

Equivalent .)

210   STANDARD ELECTRICAL DICTIONARY.

Electro-culture.

The application of electricity to the cultivation of plants. In one

system wires are stretched or carried across the bed under the surface,

and some are connected to one pole and others to the other pole of a

galvanic battery of two or more elements. In some experiments improved

results have thus been obtained.

Another branch refers to the action of the electric arc light on

vegetation. This has an effect on vegetation varying in results.

Electrode.

(a) The terminal of an open electric circuit.

(b) The terminals of the metallic or solid conductors of an electric

circuit, immersed in an electrolytic solution.

(c) The terminals between which a voltaic arc is formed, always in

practice made of carbon, are termed electrodes.

(d) In electro-therapeutics many different electrodes are used whose

names are generally descriptive of their shape, character, or uses to

which they are to be applied. Such are aural electrodes for the ears,

and many others.

(e) The plates of a voltaic battery.

Electrode, Indifferent.

A term in electro-therapeutics. An electrode to which no therapeutic

action is attributed but which merely provides a second contact with the

body to complete the circuit through the same. The other electrode is

termed the therapeutic electrode.

Electrodes, Erb's Standards of.

Proposed standard sizes for medical electrodes as follows:

Name.          Diameter.

Fine     Electrode,   1/2  centimeter   .2      inch

Small       "         2       "         .8        "

Medium      "       7.5       "        3.0        "

Large       "       6X2       "        2.4 X .8   "

Very large  "      16x8       "        6.4 x 3.2  "

Electrodes, Non-polarizable.

In electro-therapeutics electrodes whose contact surface is virtually

porous clay saturated with zinc chloride solution. The series terminate

in amalgamated zinc ends, enclosed each in a glass tube, and closed with

clay. Contact of metal with the tissues is thus avoided.

Electrode, Therapeutic.

A term in electro-therapeutics. An electrode applied to the body for the

purpose of inducing therapeutic action, or for giving the basis for an

electric diagnosis of the case. The other electrode is applied to

complete the circuit only; it is termed the indifferent electrode.

Electro-diagnosis.

The study of the condition of a patient by the reactions which occur at

the terminals or kathode and anode of an electric circuit applied to the

person. The reactions are divided into kathodic and anodic reactions.

211   STANDARD ELECTRICAL DICTIONARY.

Electro-dynamic. adj.

The opposite of electrostatic; a qualification of phenomena due to

current electricity.

Synonym--Electro-kinetic.

Electro-dynamic Attraction and Repulsion.

The mutual attraction and repulsion exercised by currents of electricity

upon each other. The theory of the cause is based upon stress of the

luminiferous ether and upon the reaction of lines of force upon each

other. For a resumé of the theory see Induction, Electro-magnetic.

Electro-dynamics.

The laws of electricity in a state of motion; the inter-reaction of

electric currents. It is distinguished from electro-magnetic induction

as the latter refers to the production of currents by induction. The

general laws of electro-dynamics are stated under Induction,

Electro-magnetic, q. v.

Synonym--Electro-kinetics.

Fig. 143. DIAGRAM OF CONNECTIONS OF

SIEMENS' ELECTRO-DYNAMOMETER.

212   STANDARD ELECTRICAL DICTIONARY.

Electro-dynamometer, Siemens'.

An apparatus for measuring currents by the reaction between two coils,

one fixed and one movable, through which the current to be measured

passes. It is one of the oldest commercial ammeters or current

measurers. It comprises a fixed coil of a number of convolutions and a

movable coil often of only one convolution surrounding the other. The

movable coil is suspended by a filament or thread from a spiral spring.

The spring is the controlling factor. Connection is established through

mercury cups so as to bring the two coils in series. In use the spring

and filament are adjusted by turning a milled head to which they are

connected until the coils are at right angles. Then the current is

turned on and deflects the movable coil. The milled head is turned until

the deflection is overcome. The angle through which the head is turned

is proportional to the square of the current. The movable coil must in

its position at right angles to the fixed one lie at right angles to the

magnetic meridian.

Thus in the diagram, Fig. 143 A B C D is the fixed coil; E F G H is the

movable coil; S is the spiral spring attached at K to the movable coil.

The arrows show the course of the current as it goes through the coils.

Electrolier.

A fixture for supporting electric lamps; the analogue in electric

lighting of the gasolier or gas chandelier. Often both are combined, the

same fixture being piped and carrying gas burners, as well as being

wired and carrying electric lamps.

Electrolysis.

The separation of a chemical compound into its constituent parts or

elements by the action of the electric current. The compound may be

decomposed into its elements, as water into hydrogen and oxygen, or into

constituent radicals, as sodium sulphate into sodium and sulphion, which

by secondary reactions at once give sodium hydrate and sulphuric acid.

The decomposition proceeds subject to the laws of electrolysis. (See

Electrolysis, Laws of.) For decomposition to be produced there is for

each compound a minimum electro-motive force or potential difference

required. The current passes through the electrolyte or substance

undergoing decomposition entirely by Electrolytic Conduction, q. v. in

accordance with Grothüss' Hypothesis, q. v. The electrolyte therefore

must be susceptible of diffusion and must be a fluid.

The general theory holds that under the influence of a potential

difference between electrodes immersed in an electrolyte, the molecules

touching the electrodes are polarized, in the opposite sense for each

electrode. If the potential difference is sufficient the molecules will

give up one of their binary constituents to the electrode, and the other

constituent will decompose the adjoining molecule, and that one being

separated into the same two constituents will decompose its neighbor,

and so on through the mass until the other electrode is reached. This

one separates definitely the second binary constituent from the

molecules touching it.

213   STANDARD ELECTRICAL DICTIONARY.

Thus there is an exact balance preserved. Just as many molecules are

decomposed at one electrode as at the other, and the exact chain of

decomposition runs through the mass. Each compound electrolyzed develops

a binary or two-fold composition, and gives up one constituent to one

electrode and the other to the other.

Fig. 144. ACTION OF MOLECULES IN A SOLUTION

BEFORE AND DURING ELECTROLYSIS.

The cut shows the assumed polarization of an electrolyte. The upper row

shows the molecules in irregular order before any potential difference

has been produced, in other words, before the circuit is closed. The

next row shows the first effects of closing the circuit, and also

indicates the polarization of the mass, when the potential difference is

insufficient for decomposition. The third row indicates the

decomposition of a chain of molecules, one constituent separating at

each pole.

214   STANDARD ELECTRICAL DICTIONARY.

Electrolysis, Laws of.

The following are the principal laws, originally discovered by

Faraday, and sometimes called Faraday's Laws of Electrolysis:

1. Electrolysis cannot take place unless the electrolyte is a conductor.

Conductor here means an electrolytic conductor, one that conducts by its

own molecules traveling, and being decomposed. (See Grothüss'

Hypothesis.)

II. The energy of the electrolytic action of the current is the same

wherever exercised in different parts of the circuit.

III. The same quantity of electricity--that is the same current for the

same period----- decomposes chemically equivalent quantities of the

bodies it decomposes, or the weights of elements separated in

electrolytes by the same quantity of electricity (in coulombs or some

equivalent unit) are to each other as their chemical equivalent.

IV. The quantity of a body decomposed in a given time is proportional to

the strength of the current.

To these may be added the following:

V. A definite and fixed electro-motive force is required for the

decomposition of each compound, greater for some and less for others.

Without sufficient electro-motive force expended on the molecule no

decomposition will take place. (See Current, Convective.)

Electrolyte.

A body susceptible of decomposition by the electric current, and capable

of electrolytic conduction. It must be a fluid body and therefore

capable of diffusion, and composite in composition. An elemental body

cannot be an electrolyte.

Electrolytic Analysis.

Chemical analysis by electrolysis. The quantitative separation of a

number of metals can be very effectively executed. Thus, suppose that a

solution of copper sulphate was to be analyzed. A measured portion of

the solution would be introduced into a weighed platinum vessel. The

vessel would be connected to the zinc plate terminal of a battery. From

the other terminal of the battery a wire would be brought and would

terminate in a plate of platinum. This would be immersed in the solution

in the vessel. As the current would pass the copper sulphate would be

decomposed and eventually all the copper would be deposited in a firm

coating on the platinum. The next operations would be to wash the metal

with distilled water, and eventually with alcohol, to dry and to weigh

the dish with the adherent copper. On subtracting the weight of the dish

alone from the weight of the dish and copper, the weight of the metallic

copper in the solution would be obtained.

In similar ways many other determinations are effected. The processes of

analysis include solution of the ores or other substances to be analyzed

and their conversion into proper form for electrolysis. Copper as just

described can be precipitated from the solution of its sulphate. For

iron and many other metals solutions of their double alkaline oxalates

are especially available forms for analysis.

The entire subject has been worked out in considerable detail by

Classen, to whose works reference should be made for details of

processes.

Electrolytic Convection.

It is sometimes observed that a single cell of Daniell battery, for

instance, or other source of electric current establishing too low a

potential difference for the decomposition of water seems to produce a

feeble but continuous decomposition. This is very unsatisfactorily

accounted for by the hydrogen as liberated combining with dissolved

oxygen. (Ganot.) The whole matter is obscure. (See Current, Convection.)

215  STANDARD ELECTRICAL DICTIONARY.

Electrolytic Conduction.

Conduction by the travel of atoms or radicals from molecule to molecule

of a substance with eventual setting free at the electrodes of the atoms

or radicals as elementary molecules or constituent radicals. A substance

to be capable of acting as an electrolytic conductor must be capable of

diffusion, and must also have electrolytic conductivity. Such a body is

called an electrolyte. (See Grothüss' Hypothesis--Electrolysis--

Electrolysis, Laws of--Electro-chemical Equivalent.)

Electro-magnet.

A mass, in practice always of iron, around which an electric circuit is

carried, insulated from the iron. When a current is passed through the

circuit the iron presents the characteristics of a magnet. (See

Magnetism, Ampére's Theory of--Solenoid--Lines of Force.) In general

terms the action of a circular current is to establish lines of force

that run through the axis of the circuit approximately parallel thereto,

and curving out of and over the circuit, return into themselves outside

of the circuit. If a mass of iron is inserted in the axis or elsewhere

near such current, it multiplies within itself the lines of force, q. v.

(See also Magnetic Permeability--Permeance--Magnetic Induction,

Coefficient of Magnetic Susceptibility--Magnetization, Coefficient of

Induced.) These lines of force make it a magnet. On their direction,

which again depends on the direction of the magnetizing current, depends

the polarity of the iron. The strength of an electro-magnet, below

saturation of the core (see Magnetic Saturation), is proportional nearly

to the ampere-turns, q. v. More turns for the same current or more

current for the same turns increase its strength.

In the cut is shown the general relation of current, coils, core and

line of force. Assume that the magnet is looked at endwise, the observer

facing one of the poles; then if the current goes around the core in the

direction opposite to that of the hands of a clock, such pole will be

the north pole. If the current is in the direction of the hands of a

clock the pole facing the observer will be the south pole. The whole

relation is exactly that of the theoretical Ampérian currents, already

explained. The direction and course of the lines of force created are

shown in the cut.

The shapes of electro-magnets vary greatly. The cuts show several forms

of electro- magnets. A more usual form is the horseshoe or double limb

magnet, consisting generally of two straight cores, wound with wire and

connected and held parallel to each other by a bar across one end, which

bar is called the yoke.

In winding such a magnet the wire coils must conform, as regards

direction of the current in them to the rule for polarity already cited.

If both poles are north or both are south poles, then the magnet cannot

be termed a horseshoe magnet, but is merely an anomalous magnet. In the

field magnets of dynamos the most varied types of electro-magnets have

been used. Consequent poles are often produced in them by the direction

of the windings and connections.

To obtain the most powerful magnet the iron core should be as short and

thick as possible in order to diminish the reluctance of the magnetic

circuit. To obtain a greater range of action a long thin shape is

better, although it involves waste of energy in its excitation.

216   STANDARD ELECTRICAL DICTIONARY.

Fig. 145 DIAGRAM OF AN ELECTRO-MAGNET SHOWING RELATION OF

CURRENT AND WINDING TO ITS POLARITY AND LINES OF FORCE.

Fig. 146. ANNULAR ELECTRO-MAGNET

Electro-magnet, Annular.

An electro-magnet consisting of a cylinder with a circular groove cut in

its face, in which groove a coil of insulated wire is placed. On the

passage of a current the iron becomes polarized and attracts an armature

towards or against its grooved face. The cut shows the construction of

an experimental one. It is in practice applied to brakes and clutches.

In the cut of the electro-magnetic brake (see Brake, Electro-magnetic),

C is the annular magnet receiving its current through the brushes, and

pressed when braking action is required against the face of the moving

wheel. The same arrangement, it can be seen, may apply to a clutch.

217  STANDARD ELECTRICAL DICTIONARY.

Fig. 147. BAR ELECTRO-MAGNET.

Electro-magnet, Bar.

A straight bar of iron surrounded with a magnetizing coil of wire. Bar

electromagnets are not much used, the horseshoe type being by far the

more usual.

Electro-magnet, Club-foot.

An electro-magnet, one of whose legs only is wound with wire, the other

being bare.

Fig. 148. CLUB-FOOT ELECTRO-MAGNETS WITH HINGED ARMATURES.

Electro-magnet, Hinged.

An electro-magnet whose limbs are hinged at the yoke. On excitation by a

current the poles tend to approach each other.

Fig. 149. ELECTRO-MAGNET, HINGED

Electro-magnetic Attraction and Repulsion.

The attraction and repulsion due to electromagnetic lines of force,

which lines always tend to take as short a course as possible and also

seek the medium of the highest permeance. This causes them to

concentrate in iron and steel or other paramagnetic substance and to

draw them towards a magnet by shortening the lines of force connecting

the two. It is exactly the same attraction as that of the permanent

magnet for its armature, Ampére's theory bringing the latter under the

same title. In the case of two magnets like poles repel and unlike

attract. In the case of simple currents, those in the same direction

attract and those in opposite directions repel each other. This refers

to constant current reactions. Thus the attraction of unlike poles of

two magnets is, by the Ampérian theory, the attraction of two sets of

currents of similar direction, as is evident from the diagram. The

repulsion of like poles is the repulsion of unlike currents and the same

applies to solenoids, q. v. (See Magnetism and do. Ampére's Theory

of--Induction, Electro-dynamic--Electro-magnetic Induction.)

218   STANDARD ELECTRICAL DICTIONARY.

Electro-magnetic Control.

Control of a magnet, iron armature, or magnetic needle in a

galvanometer, ammeter, voltmeter or similar instrument by an

electro-magnetic field, the restitutive force being derived from an

electro-magnet. The restitutive force is the force tending to bring the

index to zero.

Electro-magnetic Field of Force.

A field of electro-magnetic lines of force, q. v., established through

the agency of an electric current. A wire carrying a current is

surrounded by circular concentric lines of force which have the axis of

the wire as the locus of their centres. Electro-magnets produce lines of

force identical with those produced by permanent magnets. (See Field of

Force--Magnetic Field of Force--Controlling Field--Deflecting Field.)

Electro-magnetic Induction.

When two currents of unlike direction are brought towards each other,

against their natural repulsive tendency work is done, and the

consequent energy takes the form of a temporary increase in both

currents. When withdrawn, in compliance with the natural tendency of

repulsion, the currents are diminished in intensity, because energy is

not expended on the withdrawal, but the withdrawal is at the expense of

the energy of the system. The variations thus temporarily produced in

the currents are examples of electro-magnetic induction. The currents

have only the duration in each case of the motion of the circuits. One

circuit is considered as carrying the inducer current and is termed the

primary circuit and its current the primary current, the others are

termed the secondary circuit and current respectively. We may assume a

secondary circuit in which there is no current. It is probable that

there is always an infinitely small current at least, in every closed

circuit. Then an approach of the circuits will induce in the secondary

an instantaneous current in the reverse direction. On separating the two

circuits a temporary current in the same direction is produced in the

secondary.

219  STANDARD ELECTRICAL DICTIONARY.

A current is surrounded by lines of force. The approach of two circuits,

one active, involves a change in the lines of force about the secondary

circuit. Lines of force and current are so intimately connected that a

change in one compels a change in the other. Therefore the induced

current in the secondary may be attributed to the change in the field of

force in which it lies, a field maintained by the primary circuit and

current. Any change in a field of force induces a current or change of

current in any closed circuit in such field, lasting as long as the

change is taking place. The new current will be of such direction as to

oppose the change. (See Lenz's Law.)

The action as referred to lines of force may be figured as the cutting

of such lines by the secondary circuit, and such cutting may be brought

about by moving the secondary in the field. (See Lines of Force--Field

of Force.) The cutting of 1E8 lines of force per second by a closed

circuit induces an electro-motive force of one volt. (See Induction,

Mutual, Coefficient of.)

Electro-magnet, Iron Clad.

A magnet whose coil and core are encased in a iron jacket, generally

connected to one end of the core. This gives at one end two poles, one

tubular, the other solid, and concentric with each other. It is

sometimes called a tubular magnet.

Electro-magnet, One Coil.

An electro-magnet excited by one coil. In some dynamos the field magnets

are of this construction, a single coil, situated about midway between

the poles, producing the excitation.

Electro-magnetic Leakage.

The leakage of lines of force in an electro-magnet; the same as magnetic

leakage. (See Magnetic Leakage.)

Electro-magnetic Lines of Force.

The lines of force produced in an electro-magnetic field. They are

identical with Magnetic Lines of Force, q. v. (See also Field of

Force-Line of Force.)

Electro-magnetic Stress.

The stress in an electro-magnetic field of force, showing itself in the

polarization of light passing through a transparent medium in such a

field. (See Magnetic Rotary Polarization.)

Electro-magnetic Theory of Light.

This theory is due to J. Clark Maxwell, and the recent Hertz experiments

have gone far to prove it. It holds that the phenomena of light are due

to ether waves, identical in general factors with those produced by

electro-magnetic induction of alternating currents acting on the ether.

In a non-conductor any disturbance sets an ether wave in motion owing to

its restitutive force; electricity does not travel through such a

medium, but can create ether waves in it. Therefore a non-conductor of

electricity is permeable to waves of ether or should transmit light, or

should be transparent. A conductor on the other hand transmits

electrical disturbances because it has no restitutive force and cannot

support an ether wave. Hence a conductor should not transmit light, or

should be opaque. With few exceptions dielectrics or non-conductors are

transparent, and conductors are opaque.

220   STANDARD ELECTRICAL DICTIONARY.

Again, the relation between the electrostatic and electro-magnet units

of quantity is expressed by 1 : 30,000,000,000; the latter figure in

centimeters gives approximately the velocity of light. The

electro-magnetic unit depending on electricity in motion should have

this precise relation if an electro-magnetic disturbance was propagated

with the velocity of light. If an electrically charged body were whirled

around a magnetic needle with the velocity of light, it should act in

the same way as a current circulating around it. This effect to some

extent has been shown experimentally by Rowland.

A consequence of these conclusions is (Maxwell) that the specific

inductive capacity of a non-conductor or dielectric should be equal to

the square of its index of refraction for waves of infinite length. This

is true for some substances--sulphur, turpentine, petroleum and benzole.

In others the specific inductive capacity is too high, e. g., vegetable

and animal oils, glass, Iceland spar, fluor spar, and quartz.

Electro-magnetic Unit of Energy.

A rate of transference of energy equal to ten meg-ergs per second.

Electro-magnetism.

The branch of electrical science treating of the magnetic relations of a

field of force produced by a current, of the reactions of

electro-magnetic lines of force, of the electromagnetic field of force,

of the susceptibility, permeability, and reluctance of diamagnetic and

paramagnetic substances, and of electro-magnets in general.

Electro-magnet, Long Range.

An electro-magnet so constructed with extended pole pieces or otherwise,

as to attract its armature with reasonably constant force over a

considerable distance. The coil and plunger, q. v., mechanisms

illustrate one method of getting an extended range of action. When a

true electro-magnet is used, one with an iron core, only a very limited

range is attainable at the best. (See Electro-magnet, Stopped Coil--do.

Plunger.)

Electro-magnet, Plunger.

An electro-magnet with hollow coils, into which the armature enters as a

plunger. To make it a true electro-magnet it must have either a yoke,

incomplete core, or some polarized mass of iron.

Electro-magnet, Polarized.

An electro-magnet consisting of a polarized or permanently magnetized

core wound with magnetizing coils, or with such coils on soft iron cores

mounted on its ends. The coils may be wound and connected so as to

cooperate with or work against the permanent magnet on which it is

mounted. In Hughes' magnet shown in the cut it is mounted in opposition,

so that an exceedingly feeble current will act to displace the armature,

a, which is pulled away from the magnet by a spring, s.

221   STANDARD ELECTRICAL DICTIONARY.

Fig. 150 HUGHES' POLARIZED ELECTRO-MAGNET

Electro-magnets, Interlocking.

Electro-magnets so arranged that their armatures interlock. Thus two

magnets, A A and B B, may be placed with their armatures, M and N, at

right angles and both normally pulled away from the poles. When the

armature M is attracted a catch on its end is retained by a hole in the

end of the other armature N, and when the latter armature N is attracted

by its magnet the armature M is released. In the mechanism shown in the

cut the movements of the wheel R are controlled. Normally it is held

motionless by the catch upon the bottom of the armature M, coming

against the tooth projecting from its periphery. A momentary current

through the coils of the magnet A A releases it, by attracting M, which

is caught and retained by N, and leaves it free to rotate. A momentary

current through the coils of the magnet B B again releases M, which

drops down and engages the tooth upon R and arrests its motion.

Fig. 151. INTERLOCKING ELECTRO-MAGNETS.

222   STANDARD ELECTRICAL DICTIONARY.

Electro-magnet, Stopped Coil.

An electro-magnet consisting of a tubular coil, in which a short fixed

core is contained, stopping up the aperture to a certain distance, while

the armature is a plunger entering the aperture. This gives a longer

range of action than usual.

Electro-magnet, Surgical.

An electro-magnet, generally of straight or bar form, fitted with

different shaped pole pieces, used for the extraction of fragments of

iron or steel from the eyes. Some very curious cases of successful

operations on the eyes of workmen, into whose eyes fragments of steel or

iron had penetrated, are on record.

Electro-medical Baths.

A bath for the person provided with connections and electrodes for

causing a current of electricity of any desired type to pass through the

body of the bather. Like all electro-therapeutical treatment, it should

be administered under the direction of a physician only.

Electro-metallurgy.

(a) In the reduction of ores the electric current has been proposed but

never extensively used, except in the reduction of aluminum and its

alloys. (See Reduction of Ores, Electric.)

(b) Electro-plating and deposition of metal from solutions is another

branch. (See Electroplating and Electrotyping.)

(c) The concentration of iron ores by magnetic attraction may come under

this head. (See Magnetic Concentration of Ores.)

Electrometer.

An instrument for use in the measurement of potential difference, by the

attraction or repulsion of statically charged bodies. They are

distinguished from galvanometers as the latter are really current

measurers, even if wound for use as voltmeters, depending for their

action upon the action of the current circulating in their coils.

Electrometer, Absolute.

An electrometer designed to give directly the value of a charge in

absolute units. In one form a plate, a b, of conducting surface is

supported or poised horizontally below a second larger plate C, also of

conducting surface. The poised plate is surrounded by a detached guard

ring--an annular or perforated plate, r g r' g'--exactly level and even

with it as regards the upper surface. The inner plate is carried by a

delicate balance. In use it is connected to one of the conductors and

the lower plate to earth or to the other. The attraction between them is

determined by weighing. By calculation the results can be made absolute,

as they depend on actual size of the plates and their distance, outside

of the potential difference of which of course nothing can be said. If S

is the area of the disc, d the distance of the plates, V-V1 the

difference of their potential, which is to be measured, and F the force

required to balance their attraction, we have:

F = ( ( V - V1 )^2 * S )  / ( 8 * PI * d^2 )

223  STANDARD ELECTRICAL DICTIONARY.

If  V = 0 this reduces to

F =  ( V^2 * S ) / ( 8 * PI * d^2 )  (2)

or

V =  d * SquareRoot( (8 * PI * F ) / S )   (3)

As F is expressed as a weight, and S and a as measures of area and

length, this gives a means of directly obtaining potential values in

absolute measure. (See Idiostatic Method--Heterostatic Method.)

Synonyms--Attracted Disc Electrometer--Weight Electrometer.

Fig. 152. SECTION OF BASE OF PORTABLE ELECTROMETER.

In some forms the movable disc is above the other, and supported at the

end of a balance beam. In others a spring support, arranged so as to

enable the attraction to be determined in weight units, is adopted. The

cuts, Figs. 152 and 154, show one of the latter type, the portable

electrometer. The disc portion is contained within a cylindrical vessel.

Fig. 153. DIAGRAM ILLUSTRATING

THEORY OF ABSOLUTE ELECTROMETER.

Referring to Fig. 152  g is the stationary disc, charged through the

wire connection r; f is the movable disc, carried by a balance beam

poised at i on a horizontal and transverse stretched platinum wire,

acting as a torsional spring. The position of the end k of the balance

beam shows when the disc f is in the plane of the guard ring h h. The

end k is forked horizontally and a horizontal sighting wire or hair is

fastened across the opening of the fork. When the hair is midway between

two dots on a vertical scale the lever is in the sighted position, as it

is called, and the disc is in the plane of the guard ring.

224   STANDARD ELECTRICAL DICTIONARY.

Fig. 154. PORTABLE ELECTROMETER.

The general construction is seen in Fig. 154. There the fixed disc D is

carried by insulating stem g1. The charging electrode is supported by an

insulating stem g2, and without contact with the box passes out of its

cover through a guard tube E, with cover, sometimes called umbrella, V.

The umbrella is to protect the apparatus from air currents. At m is the

sighting lens. H is a lead box packed with pumice stone, moistened with

oil of vitriol or concentrated sulphuric acid, to preserve the

atmosphere dry. Before use the acid is boiled with some ammonium

sulphate to expel any corrosive nitrogen oxides, which might corrode the

brass.

In use the upper disc is charged by its insulated electrode within the

tube E; the movable disc is charged if desired directly through the case

of the instrument. The upper disc is screwed up or down by the

micrometer head M, until the sighted position is reached. The readings

of the micrometer on the top of the case give the data for calculation.

225   STANDARD ELECTRICAL DICTIONARY.

Fig. 155. LIPPMAN'S CAPILLARY ELECTROMETER.

Electrometer, Capillary.

An electrometer for measuring potential difference by capillary action,

which latter is affected by electrostatic excitement. A tube A contains

mercury; its end drawn out to a fine aperture dips into a vessel B which

contains dilute sulphuric acid with mercury under it, as shown. Wires

running from the binding-posts a and b connect one with the mercury in

A, the other with that in B. The upper end of the tube A connects with a

thick rubber mercury reservoir T, and manometer H. The surface tension

of the mercury-acid film at the lower end of the tube A keeps all in

equilibrium. If now a potential difference is established between a and

b, as by connecting a battery thereto, the surface tension is increased

and the mercury rises in the tube B. By screwing down the compressing

clamp E, the mercury is brought back to its original position. The

microscope M is used to determine this position with accuracy. The

change in reading of the manometer gives the relation of change of

surface tension and therefore of potential. Each electrometer needs

special graduation or calibration, but is exceedingly sensitive and

accurate. It cannot be used for greater potential differences than .6

volt, but can measure .0006 volt. Its electrostatic capacity is so small

that it can indicate rapid changes. Another form indicates potential

difference by the movement of a drop of sulphuric acid in a horizontal

glass tube, otherwise filled with mercury, and whose ends lead into two

mercury cups or reservoirs. The pair of electrodes to be tested are

connected to the mercury vessels. The drop moves towards the negative

pole, and its movement for small potential differences (less than one

volt) is proportional to the electro-motive force or potential

difference.

226   STANDARD ELECTRICAL DICTIONARY.

Electrometer Gauge.

An absolute electrometer (see Electrometer, Absolute) forming an

attachment to a Thomson quadrant electrometer. It is used to test the

potential of the flat needle connected with the inner surface of the

Leyden jar condenser of the apparatus. This it does by measuring the

attraction between itself and an attracting disc, the latter connected

by a conductor with the interior of the jar.

Electrometer, Lane's.

A Leyden jar with mounted discharger, so that when charged to a certain

point it discharges itself. It is connected with one coating of any jar

whose charge is to be measured, which jar is then charged by the other

coating. As the jar under trial becomes charged to a certain point the

electrometer jar discharges itself, and the number of discharges is the

measure of the charge of the other jar. It is really a unit jar, q. v.

Fig. 156. THOMSON'S QUADRANT ELECTROMETER.

Fig. 157. HENLEY'S QUADRANT ELECTROSCOPE.

227  STANDARD ELECTRICAL DICTIONARY.

Electrometer, Quadrant.

(a) Sir William Thomson's electrometer, a simple form of which is shown

in the cut, consists of four quadrants of metal placed horizontally;

above these a broad flat aluminum needle hangs by a very fine wire,

acting as torsional suspension. The quadrants are insulated from each

other, but the opposite ones connect with each other by wires. The

apparatus is adjusted so that, when the quadrants are in an unexcited

condition the needle is at rest over one of the diametrical divisions

between quadrants. The needle by its suspension wire is in communication

with the interior of a Leyden jar which is charged. The whole is covered

with a glass shade, and the air within is kept dry by a dish of

concentrated sulphuric acid so that the jar retains its charge for a

long time and keeps the needle at approximately a constant potential. If

now two pairs of quadrants are excited with opposite electricities, as

when connected with the opposite poles of an insulated galvanic cell,

the needle is repelled by one pair and attracted by the other, and

therefore rotates through an arc of greater or less extent. A small

concave mirror is attached above the needle and its image is reflected

on a graduated screen. This makes the smallest movement visible.

Sometimes the quadrants are double, forming almost a complete box,

within which the needle moves.

(b) Henley's quadrant electrometer is for use on the prime conductor of

an electric machine, for roughly indicating the relative potential

thereof. It consists of a wooden standard attached perpendicularly to

the conductor. Near one end is attached a semi-circular or quadrant arc

of a circle graduated into degrees or angular divisions. An index,

consisting of a straw with a pith-bell attached to its end hangs from

the center of curvature of the arc. When the prime conductor is charged

the index moves up over the scale and its extent of motion indicates the

potential relatively.

When the "quadrant electrometer" is spoken of it may always be assumed

that Sir William Thomson's instrument is alluded to. Henley's instrument

is properly termed a quadrant electroscope. (See Electroscope.)

Electro-motive Force.

The cause which produces currents of electricity. In general it can be

expressed in difference of potentials, although the term electro-motive

force should be restricted to potential difference causing a current. It

is often a sustained charging of the generator terminals whence the

current is taken. Its dimensions are

(work done/the quantity of electricity involved),

or ( M * (L^2) /(T^2 ) ) / ((M^.5) * (L^.5)) = ( (M^.5) * (L^1.5) ) /(T^2)

The practical unit of electro-motive force is the volt, q. v. It is

often expressed in abbreviated form, as E. M. D. P., or simply as D. P.,

i. e., potential difference.

Electro-motive force and potential difference are in many cases

virtually identical, and distinctions drawn between them vary with

different authors. If we consider a closed electric circuit carrying a

current, a definite electro-motive force determined by Ohm's law from

the resistance and current obtains in it. But if we attempt to define

potential difference as proper to the circuit we may quite fail.

Potential difference in a circuit is the difference in potential between

defined points of such circuit. But no points in a closed circuit can be

found which differ in potential by an amount equal to the entire

electro-motive force of the circuit. Potential difference is properly

the measure of electro-motive force expended on the portion of a circuit

between any given points. Electro-motive force of an entire circuit, as

it is measured, as it were, between two consecutive points but around

the long portion of the circuit, is not conceivable as merely potential

difference. Taking the circle divided in to degrees as an analogy, the

electro-motive force of the entire circuit might be expressed as 360º,

which are the degrees intervening between two consecutive points,

measured the long way around the circle. But the potential difference

between the same two points would be only 1º, for it would be measured

by the nearest path.

[Transcriber's notes: If 360º is the "long" way, 0º is the "short". A

formal restatement of the above definition of EMF: "If a charge Q passes

through a device and gains energy U, the net EMF for that device is the

energy gained per unit charge, or U/Q. The unit of EMF is a volt, or

newton-meter per coulomb."]

228   STANDARD ELECTRICAL DICTIONARY.

Electro-motive Force, Counter.

A current going through a circuit often has not only true or ohmic

resistance to overcome, but meets an opposing E. M. F. This is termed

counter-electro-motive force. It is often treated in calculations as

resistance, and is termed spurious resistance. It may be a part of the

impedance of a circuit.

In a primary battery hydrogen accumulating on the negative plate

develops counter E. M. F. In the voltaic arc the differential heating of

the two carbons does the same. The storage battery is changed by a

current passing in the opposite direction to its own natural current;

the polarity of such a battery is counter E. M. F.

Electro-motive Force, Unit.

Unit electro-motive force is that which is created in a conductor moving

through a magnetic field at such a rate as to cut one unit line of force

per second. It is that which must be maintained in a circuit of unit

resistance to maintain a current of unit quantity therein. It is that

which must be maintained between the ends of a conductor in order that

unit current may do unit work in a second.

Electro-motive Intensity.

The force acting upon a unit charge of electricity. The mean force is

equal to the difference of potential between two points within the field

situated one centimeter apart, such distance being measured along the

lines of force. The term is due to J. Clerk Maxwell.

Electro-motive Series.

Arrangement of the metals and carbon in series with the most

electro-positive at one end, and electronegative at the other end. The

following are examples for different exciting liquids:

Dilute Sulphuric   Dilute Hydrochloric   Caustic   Potassium

Acid               Acid.                 Potash.   Sulphide.

Zinc               Zinc                  Zinc      Zinc

Cadmium            Cadmium               Tin       Copper

Tin                Tin                   Cadmium   Cadmium

Lead               Lead                  Antimony  Tin

Iron               Iron                  Lead      Silver

Nickel             Copper                Bismuth   Antimony

Bismuth            Bismuth               Iron      Lead

Antimony           Nickel                Copper    Bismuth

Copper             Silver                Nickel    Nickel

Silver             Antimony              Silver    Iron

Gold

Platinum

Carbon

In each series the upper metal is the positive, dissolved or attacked

element.

229  STANDARD ELECTRICAL DICTIONARY.

Electro-motograph.

An invention of Thomas A. Edison. A cylinder of chalk, moistened with

solution of caustic soda, is mounted so as to be rotated by a handle. A

diaphragm has an arm connected to its center. This arm is pressed

against the surface of the cylinder by a spring. When the cylinder is

rotated, a constant tension is exerted on the diaphragm. If a current is

passed through the junction of arm and cylinder the electrolytic action

alters the friction so as to change the stress upon the diaphragm.

If the current producing this effect is of the type produced by the

human voice through a microphone the successive variations in strain

upon the diaphragm will cause it to emit articulate sounds. These are

produced directly by the movement of the cylinder, the electrolytic

action being rather the regulating portion of the operation. Hence very

loud sounds can be produced by it. This has given it the name of the

loud- speaking telephone.

The same principle may be applied in other ways. But the practical

application of the motograph is in the telephone described.

Fig. 158. ELECTRO-MOTOGRAPH TELEPHONE

Electro-motor.

This term is sometimes applied to a current generator, such as a voltaic

battery.

Electro-muscular Excitation.

A term in medical electricity indicating the excitation of muscle as the

effect of electric currents of any kind.

Electro-negative. adj.

Appertaining to negative electrification; thus of the elements oxygen is

the most electro-negative, because if separated by electrolytic action

from any combination, it will be charged with negative electricity.

230   STANDARD ELECTRICAL DICTIONARY.

Electro-optics.

The branch of natural science treating of the relations between light

and electricity. Both are supposed to be phenomena of or due to the

luminiferous ether. To it may be referred the following:

(a) Electro-magnetic Stress and Magnetic Rotary Polarization;

(b) Dielectric Strain; all of which may be referred to in this book;

(c) Change in the resistance of a conductor by changes in light to which

it is exposed (see Selenium);

(d) The relation of the index of refraction of a dielectric to the

dielectric constant (see Electro-magnetic Theory of Light);

(e) The identity (approximate) of the velocity of light in centimeters

and the relative values of the electrostatic and electro-magnet units

of intensity, the latter being 30,000,000,000 times greater than the

former, while the velocity of light is 30,000,000,000 centimeters per

second.

Electrophoric Action.

The action of an electrophorous; utilized in influence machines. (See

Electrophorous.)

Fig. 159. ELECTROPHOROUS.

Electrophorous.

An apparatus for the production of electric charges of high potential by

electrostatic induction, q. v. It consists of a disc of insulating

material B, such as resin or gutta percha, which is held in a shallow

metal-lined box or form. The disc may be half an inch thick and a foot

or more in diameter, or may be much smaller and thinner. A metal disc A,

smaller in diameter is provided with an insulating handle which may be

of glass, or simply silk suspension strings. To use it the disc B is

excited by friction with a cat-skin or other suitable substance. The

metallic disc is then placed on the cake of resin exactly in its centre,

so that the latter disc or cake projects on all sides. Owing to

roughness there is little real electric contact between the metal and

dielectric. On touching the metal disc a quantity of negative

electricity escapes to the earth. On raising it from the cake it comes

off excited positively, and gives a spark and is discharged. It can be

replaced, touched, removed and another spark can be taken from it, and

so on as long as the cake stays charged.

The successive discharges represent electrical energy expended. This is

derived from the muscular energy expended by the operator in separating

the two discs when oppositely excited. As generally used it is therefore

an apparatus for converting muscular or mechanical energy into electric

energy.

231   STANDARD ELECTRICAL DICTIONARY.

Electro-physiology.

The science of the electric phenomena of the animal system. It may also

be extended to include plants. The great discovery of Galvani with the

frog's body fell into this branch of science. The electric fishes,

gymnotus, etc., present intense phenomena in the same.

Electroplating.

The deposition by electrolysis of a coating of metal upon a conducting

surface. The simplest system makes the object to be plated the negative

electrode or plate in a galvanic couple. Thus a spoon or other object

may be connected by a wire to a plate of zinc. A porous cup is placed

inside a battery jar. The spoon is placed in the porous cup and the zinc

outside it. A solution of copper sulphate is placed in the porous cup,

and water with a little sodium or zinc sulphate dissolved in it,

outside. A current starts through the couple, and copper is deposited on

the spoon.

A less primitive way is to use a separate battery as the source of

current; to connect to the positive plate by a wire the object to be

plated, and a plate of copper, silver, nickel or other metal to the

other pole of the battery. On immersing both object and plate (anode) in

a bath of proper solution the object will become plated.

In general the anode is of the same material as the metal to be

deposited, and dissolving keeps up the strength of the bath. There are a

great many points of technicality involved which cannot be given here.

The surface of the immersed object must be conductive. If not a fine

wire network stretched over it will gradually fill up in the bath and

give a matrix. More generally the surface is made conductive by being

brushed over with plumbago. This may be followed by a dusting of iron

dust, followed by immersion in solution ot copper sulphate. This has the

effect of depositing metallic copper over the surface as a starter for

the final coat.

Attention must be paid to the perfect cleanliness of the objects, to the

condition of the bath, purity of anodes and current density.

Voltaic batteries are largely used for the current as well as special

low resistance dynamos. Thermo-electric batteries are also used to some

extent but not generally.

Electro-pneumatic Signals.

Signals, such as railroad signals or semaphores, moved by compressed

air, which is controlled by valves operated by electricity. The House

telegraph, which was worked by air controlled by electricity, might come

under this term, but it is always understood as applied to railroad

signals, or their equivalent.

232   STANDARD ELECTRICAL DICTIONARY.

Electropoion Fluid.

An acid depolarizing solution for use in zinc-carbon couples, such as

the Grenet battery. The following are formulae for its preparation:

(a) Dissolve one pound of potassium bichromate in ten pounds of water,

to which two and one-half pounds of concentrated sulphuric acid have

been gradually added. The better way is to use powdered potassium

bichromate, add it to the water first, and then gradually add the

sulphuric acid with constant stirring.

(b) To three pints of water add five fluid ounces of concentrated

sulphuric acid; add six ounces pulverized potassium bichromate.

(c) Mix one gallon concentrated sulphuric acid and three gallons of

water. In a separate vessel dissolve six pounds potassium bichromate in

two gallons of boiling water. Mix the two.

The last is the best formula. Always use electropoion fluid cold. (See

Trouvé's Solution--Poggendorff's Solution--Kakogey's Solution--

Tissandrier's Solution--Chutaux's Solution.)

Electro-positive. adj.

Appertaining to positive electrification; thus potassium is the most

electro-positive of the elements. (See Electro-negative.)

Electro-puncture.

The introduction into the system of a platinum point or needle,

insulated with vulcanite, except near its point, and connected as the

anode of a galvanic battery. The kathode is a metal one, covered with a

wet sponge and applied on the surface near the place of puncture. It is

used for treatment of aneurisms or diseased growths, and also for

removal of hair by electrolysis. (See Hair, Removal of by Electrolysis.)

Synonym--Galvano-puncture.

Electro-receptive. adj.

A term applied to any device or apparatus designed to receive and absorb

electric energy. A motor is an example of an electro-receptive

mechanism.

Electroscope.

An apparatus for indicating the presence of an electric charge, and also

for determining the sign, or whether the charge is positive or negative.

The simplest form consists of a thread doubled at its centre and hung

therefrom. On being charged, or on being connected to a charged body the

threads diverge. A pair of pith balls may be suspended in a similar way,

or a couple of strips of gold leaf within a flask (the gold leaf

electroscope). To use an electroscope to determine the sign of the

charge it is first slightly charged. The body to be tested is then

applied to the point of suspension, or other charging point. If at once

further repelled the charge of the body is of the same sign as the

slight charge first imparted to the electroscope leaves; the leaves as

they become more excited will at once diverge more. If of different sign

they will at first approach as their charge is neutralized and will

afterwards diverge.

The gold-leaf electroscope is generally enclosed in a glass bell jar or

flask. Sometimes a pair of posts rise, one on each side, to supply

points of induction from the earth to intensify the action. (See

Electrometer, Quadrant--Electroscope, Gold leaf, and others.)

233  STANDARD ELECTRICAL DICTIONARY.

Electroscope, Bennett's.

A gold-leaf electroscope, the suspended leaves of which are contained in

a glass shade or vessel of dry air. On the inside of the glass shade are

two strips of gold leaf, which rise from the lower edge a short

distance, being pasted to the glass, and connected to the ground. These

act by induction to increase the sensitiveness of the instruments.

Electroscope, Bohenberger's.

A condensing electroscope (see Electroscope, Condensing) with a single

strip of gold leaf suspended within the glass bell. This is at an equal

distance from the opposite poles of two dry piles (see Zamboni's Dry

Pile) standing on end, one on each side of it. As soon as the leaf is

excited it moves toward one and away from the other pile, and the sign

of its electrification is shown by the direction of its motion.

Electroscope, Condensing.

A gold leaf electroscope, the glass bell of which is surmounted by an

electrophorous or static condenser, to the lower plate of which the

leaves of gold are suspended or connected.

In use the object to be tested is touched to the lower plate, and the

upper plate at the same time is touched by the finger. The plates are

now separated. This reduces the capacity of the lower plate greatly and

its charge acquires sufficient potential to affect the leaves, although

the simple touching may not have affected them at all.

Electroscope, Gold Leaf.

An electroscope consisting of two leaves of gold leaf hung in contact

with each other from the end of a conductor. When excited they diverge.

The leaves are enclosed in a glass vessel.

Fig. 160. GOLD LEAF ELECTROSCOPE.

234   STANDARD ELECTRICAL DICTIONARY.

Electroscope, Pith Ball.

Two pith balls suspended at opposite ends of a silk thread doubled in

the middle. When charged with like electricity they repel each other.

The extent of their repulsion indicates the potential of their charge.

Electrostatic Attraction and Repulsion.

The attraction and repulsion of electrostatically charged bodies for

each other, shown when charged with electricity. If charged with

electricity of the same sign they repel each other. If with opposite

they attract each other. The classic attraction and subsequent repulsion

of bits of straw and chaff by the excited piece of amber is a case of

electrostatic attraction and repulsion. (See Electricity,

Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction and

Repulsion.)

Electrostatic Induction, Coefficient of.

The coefficient expressing the ratio of the charge or change of charge

developed in one body to the potential of the inducing body.

Electrostatic Lines of Force.

Lines of force assumed to exist in an electrostatic field of force, and

to constitute the same. In general they correspond in action and

attributes with elcctro-magnetic lines of force. They involve in almost

all cases either a continuous circuit, or a termination at both ends in

oppositely charged surfaces.

Fig. 161. ELECTROSTATIC LINES OF FORCE

BETWEEN NEAR SURFACES.

Fig. 162. ELECTROSTATIC LINKS OF FORCE

BETWEEN DISTANT SURFACES.

235   STANDARD ELECTRICAL DICTIONARY.

The cut, Fig. 161, shows the general course taken by lines of force

between two excited surfaces when near together. Here most of them are

straight lines reaching straight across from surface to surface, while a

few of them arch across from near the edges, tending to spread. If the

bodies are drawn apart the spreading tendency increases and the

condition of things shown in the next cut, Fig. 162, obtains. There is

an axial line whose prolongations may be supposed to extend

indefinitely, as occupying a position of unstable equilibrium. Here the

existence of a straight and unterminated line of force may be assumed.

A direction is predicated to lines of force corresponding with the

direction of an electric current. They are assumed to start from a

positively charged and to go towards a negatively charged surface. A

positively charged body placed in an electrostatic field of force will

be repelled from the region of positive into or towards the region of

negative potential following the direction of the lines of force, not

moving transversely to them, and having no transverse component in its

motion.

[Transcriber's note: More precisely, "A positively charged body placed

in an electrostatic field of force will be repelled from the region of

positive into or towards the region of negative potential ACCELERATING

in the direction of the lines of force, not ACCELERATING transversely to

them, and having no transverse component in its ACCELERATION."

Previously acquired momentum can produce a transverse component of

VELOCITY.]

Electrostatics.

The division of electric science treating of the phenomena of electric

charge, or of electricity in repose, as contrasted with electro-dynamics

or electricity in motion or in current form. Charges of like sign repel,

and of unlike sign attract each other. The general inductive action is

explained by the use of the electrostatic field of force and

electrostatic lines of force, q. v. The force of attraction and

repulsion of small bodies or virtual points, which are near enough to

each other, vary as the square of the distance nearly, and with the

product of the quantities of the charges of the two bodies.

Electrostatic Refraction.

Dr. Kerr found that certain dielectrics exposed to electric strain by

being placed between two oppositely excited poles of a Holtz machine or

other source of very high tension possess double refracting powers, in

other words can rotate a beam of polarized light, or can develop two

complimentary beams from common light. Bisulphide of carbon shows the

phenomenon well, acting as glass would if the glass were stretched in

the direction of the electrostatic lines of force. To try it with glass,

holes are drilled in a plate and wires from an influence machine are

inserted therein. The discharge being maintained through the glass it

polarizes light.

Synonym--Kerr Effect.

Electrostatic Series.

A table of substances arranged in the order in which they are

electrostatically charged by contact, generally by rubbing against each

other. The following series is due to Faraday. The first members become

positively excited when rubbed with any of the following members, and

vice versa. The first elements correspond to the carbon plate in a

galvanic battery, the succeeding elements to the zinc plate.

Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--Flint

Glass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--the

Metals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are some

irregularities. A feather lightly drawn over canvas is negatively

electrified; if drawn through folds pressed against it it is positively

excited. Many other exceptions exist, so that the table is of little

value.

236   STANDARD ELECTRICAL DICTIONARY.

Electrostatic Stress.

The stress produced upon a transparent medium in an electrostatic field

of force by which it acquires double refracting or polarizing properties

as regards the action of such medium upon light. (See Electrostatic

Refraction.)

Electro-therapeutics or Therapy.

The science treating of the effects of electricity upon the animal

system in the treatment and diagnosis of disease.

Electrotonus.

An altered condition of functional activity occurring in a nerve

subjected to the passage of an electric current. If the activity is

decreased, which occurs near the anode, the state is one of

anelectrotonus, if the activity is increased which occurs near the

kathode the condition is one of kathelectrotonus.

Electrotype.

The reproduction of a form of type or of an engraving or of the like by

electroplating, for printing purposes. The form of type is pressed upon

a surface of wax contained in a shallow box. The wax is mixed with

plumbago, and if necessary some more is dusted and brushed over its

surface and some iron dust is sprinkled over it also. A matrix or

impression of the type is thus obtained, on which copper is deposited by

electroplating, q. v.

Element, Chemical.

The original forms of matter that cannot be separated into constituents

by any known process. They are about seventy in number. Some of the

rarer ones are being added to or cancelled with the progress of chemical

discovery. For their electric relations see Electro-chemical

Equivalents--Electro-chemical Series.

The elements in entering into combination satisfy chemical affinity and

liberate energy, which may take the form of electric energy as in the

galvanic battery, or of heat energy, as in the combustion of carbon or

magnesium. Therefore an uncombined element is the seat of potential

energy. (See Energy, Potential.) In combining the elements always

combine in definite proportions. A series of numbers, one being proper

to each element which denote the smallest common multipliers of these

proportions, are called equivalents. Taking the theory of valency into

consideration the product of the equivalents by the valencies gives the

atomic weights.

237   STANDARD ELECTRICAL DICTIONARY.

Element, Mathematical.

A very small part of anything, corresponding in a general way to a

differential, as the element of a current.

Element of a Battery Cell.

The plates in a galvanic couple are termed elements, as the carbon and

zinc plates in a Bunsen cell. The plate unattacked by the solution, as

the carbon plate in the above battery, is termed the negative plate or

element; the one attacked, as the zinc plate, is termed the positive

plate or element.

Synonym--Voltaic Element.

Elements, Electrical Classification of.

This may refer to Electro-chemical Series, Electrostatic Series, or

Thermo-electric Series, all of which may be referred to.

Element, Thermo-electric.

One of the metals or other conductors making a thermo-electric couple,

the heating of whose junction produces electro-motive force and a

current, if on closed circuit. The elements of a couple are respectively

positive and negative, and most conductors can be arranged in a series

according to their relative polarity. (See Thermo-electric Series.)

Elongation.

The throw of the magnetic needle. (See Throw.)

Synonym--Throw.

Embosser, Telegraph.

A telegraphic receiver giving raised characters on a piece of paper. It

generally refers to an apparatus of the old Morse receiver type, one

using a dry point stylus, which pressing the paper into a groove in the

roller above the paper, gave raised characters in dots and lines.

Fig. 163. MORSE RECEIVER.

238   STANDARD ELECTRICAL DICTIONARY.

E. M. D. P.

Abbreviation for "electro-motive difference of potential" or for

electro-motive force producing a current as distinguished from mere

inert potential difference.

E. M. F.

Abbreviation for "electro-motive force."

Fig. 164. END-ON METHOD.

End-on Method.

A method of determining the magnetic moment of a magnet. The magnet

under examination, N S, is placed at right angles to the magnetic

meridian, M O R, and pointing directly at or "end on" to the centre of a

compass needle, n s. From the deflection a of the latter the moment is

calculated.

Endosmose, Electric.

The inflowing current of electric osmose. (See Osmose, Electric.)

End Play.

The power to move horizontally in its bearings sometimes given to

armature shafts. This secures a more even wearing of the commutator

faces. End play is not permissible in disc armatures, as the attraction

of the field upon the face of the armature core would displace it

endwise. For such armatures thrust-bearings preventing end play have to

be provided.

Energy.

The capacity for doing work. It is measured by work units which involve

the exercise of force along a path of some length. A foot-pound,

centimeter-gram, and centimeter-dyne are units of energy and work.

The absolute unit of energy is the erg, a force of one dyne exercised

over one centimeter of space. (See Dyne.)

The dimensions of energy are

force (M * L / T^2) * space (L) = M * (L^2 / T^2).

Energy may be chemical (atomic or molecular), mechanical,

electrical, thermal, physical, potential, kinetic, or actual, and other

divisions could be formulated.

239   STANDARD ELECTRICAL DICTIONARY.

Energy, Atomic.

The potential energy due to atomic relations set free by atomic change;

a form of chemical energy, because chemistry refers to molecular as well

as to atomic changes. When atomic energy loses the potential form it

immediately manifests itself in some other form, such as heat or

electric energy. It may be considered as always being potential energy.

(See Energy, Chemical.)

[Transcriber's note: This item refers to chemical energy, that is

manifest in work done by electric forces during re-arrangement of

electrons. Atomic energy now refers to re-arrangement of  nucleons

(protons and neutrons) and the resulting conversion of mass into

energy.]

Energy, Chemical.

A form of potential energy (see Energy, Potential) possessed by elements

in virtue of their power of combining with liberation of energy, as in

the combination of carbon with oxygen in a furnace; or by compounds in

virtue of their power of entering into other combinations more

satisfying to the affinities of their respective elements or to their

own molecular affinity. Thus in a galvanic couple water is decomposed

with absorption of energy, but its oxygen combines with zinc with

evolution of greater amount of energy, so that in a voltaic couple the

net result is the setting free of chemical energy, which is at once

converted into electrical energy in current form, if the battery is on a

closed circuit.

Energy, Conservation of.

A doctrine accepted as true that the sum of energy in the universe is

fixed and invariable. This precludes the possibility of perpetual

motion. Energy may be unavailable to man, and in the universe the

available energy is continually decreasing, but the total energy is the

same and never changes.

[Transcriber's note: If mass is counted a energy (E=m*(c^2)) then energy

is strictly conserved.]

Energy, Degradation of.

The reduction of energy to forms in which it cannot be utilized by man.

It involves the reduction of potential energy to kinetic energy, and the

reduction of kinetic energy of different degrees to energy of the same

degree. Thus when the whole universe shall have attained the same

temperature its energy will have become degraded or non-available. At

present in the sun we have a source of kinetic energy of high degree, in

coal a source of potential energy. The burning of all the coal will be

an example of the reduction of potential to kinetic energy, and the

cooling of the sun will illustrate the lowering in degree of kinetic

energy. (See Energy, Conservation of--Energy, Potential--Energy,

Kinetic.)

Energy, Electric.

The capacity for doing work possessed by electricity

under proper conditions. Electric energy may be either kinetic or

potential. As ordinary mechanical energy is a product of force and

space, so electric energy is a product of potential difference and

quantity. Thus a given number of coulombs of electricity in falling a

given number of volts develop electric energy. The dimensions are found

therefore by multiplying electric current intensity quantity

((M^.5) * (L^.5)),

by electric potential

((M^.5)*(L^1.5) / (T^2)),

giving (M * (L^2)/(T^2)),

the dimensions of energy in general as it should be.

The absolute unit of electric energy in electro-magnetic measure is

(1E-7) volt coulombs.

240   STANDARD ELECTRICAL DICTIONARY.

The practical unit is the volt-coulomb. As the volt is equal to 1E8

absolute units of potential and the coulomb to 0.1 absolute units of

quantity, the volt-coulomb is equal to 1E7 absolute units of energy.

The volt-coulomb is very seldom used, and the unit of Electric Activity

or Power (see Power, Electric), the volt-ampere, is universally used.

This unit is sometimes called the Watt, q. v., and it indicates the rate

of expenditure or of production of electric energy.

The storing up in a static accumulator or condenser of a given charge of

electricity, available for use with a given change of potential

represents potential electric energy.

The passing of a given quantity through a conductor with a given fall of

potential represents kinetic electric energy.

In a secondary battery there is no storage of energy, but the charging

current simply accumulates potential chemical energy in the battery,

which chemical energy is converted into electric energy in the discharge

or delivery of the battery.

It is customary to discuss Ohm's law in this connection; it is properly

treated under Electric Power, to which the reader is referred. (See

Power, Electric.)

[Transcriber's note: A volt-ampere or watt is a unit of power. A

volt-coulomb-second or watt-second is a unit of energy. Power multiplied by

time yields energy.]

Energy, Electric Transmission of.

If an electric current passes through a conductor all its energy is

expended in the full circuit. Part of the circuit may be an electrical

generator that supplies energy as fast as expended. Part of the circuit

may be a motor which absorbs part of the energy, the rest being expended

in forcing a current through the connecting wires and through the

generator. The electric energy in the generator and connecting wires is

uselessly expended by conversion into heat. That in the motor in great

part is utilized by conversion into mechanical energy which can do

useful work. This represents the transmission of energy. Every electric

current system represents this operation, but the term is usually

restricted to the transmission of comparatively large quantities of

energy.

A typical installation might be represented thus. At a waterfall a

turbine water wheel is established which drives a dynamo. From the

dynamo wires are carried to a distant factory, where a motor or several

motors are established, which receive current from the dynamo and drive

the machinery. The same current, if there is enough energy, may be used

for running lamps or electroplating. As electric energy (see Energy,

Electric,) is measured by the product of potential difference by

quantity, a very small wire will suffice for the transmission of a small

current at a high potential, giving a comparatively large quantity of

energy. It is calculated that the energy of Niagara Falls could be

transmitted through a circuit of iron telegraph wire a distance of over

1,000 miles, but a potential difference of 135,000,000 volts would be

required, something quite impossible to obtain or manage.

[Transcriber's note: Contemporary long distance power transmission lines

use 115,000 to 1,200,000 volts. At higher voltages corona discharges

(arcing) create unacceptable losses.]

241  STANDARD ELECTRICAL DICTIONARY.

Energy, Kinetic.

Energy due to matter being actually in motion. It is sometimes called

actual energy. The energy varies directly with the mass and with the

square of the velocity. It is represented in formula by .5 *M * (v^2).

Synonyms--Actual Energy--Energy of Motion--Dynamic Energy.

Energy, Mechanical.

The energy due to mechanical change or motion, virtually the same as

molar energy. (See Energy, Molar.)

Energy, Molar.

The energy of masses of matter due to movements of or positions of

matter in masses; such as the kinetic energy of a pound or of a ton in

motion, or the potential energy of a pound at an elevation of one

hundred feet.

Energy, Molecular.

The potential energy due to the relations of molecules and set free by

their change in the way of combination. It is potential for the same

reason that applies to atomic and chemical energy, of which latter it is

often a form, although it is often physical energy. The potential energy

stored up in vaporization is physical and molecular energy; the

potential energy stored up in uncombined potassium oxide and water, or

calcium oxide (quicklime) and water is molecular, and when either two

substances are brought together kinetic, thermal or heat energy is set

free, as in slaking lime for mortar.

Energy of an Electrified Body.

An electrified body implies the other two elements of a condenser. It is

the seat of energy set free when discharged. (See Dielectric, Energy

of.) The two oppositely charged bodies tend to approach. This tendency,

together with the distances separating them, represents a potential

energy.

Energy of Stress.

Potential energy due to stress, as the stretching of a spring. This is

hardly a form of potential energy. A stressed spring is merely in a

position to do work at the expense of its own thermal or kinetic energy

because it is cooled in doing work. If it possessed true potential

energy of stress it would not be so cooled.

Energy of Position.

Potential energy due to position, as the potential energy of a pound

weight raised ten feet (ten foot lbs.). (See Energy, Potential.)

Energy, Physical.

The potential energy stored up in physical position or set free in

physical change. Thus a vapor or gas absorbs energy in its vaporization,

which is potential energy, and appears as heat energy when the vapor

liquefies.

242   STANDARD ELECTRICAL DICTIONARY.

Energy, Potential, or Static Energy.

The capacity for doing work in a system due to advantage of position or

other cause, such as the stress of a spring. A pound weight supported

ten feet above a plane has ten foot lbs. of potential energy of position

referred to that plane. A given weight of an elementary substance

represents potential chemical energy, which will be liberated as actual

energy in its combination with some other element for which it has an

affinity. Thus a ton of coal represents a quantity of potential chemical

energy which appears in the kinetic form of thermal energy when the coal

is burning in a furnace. A charged Leyden jar represents a source of

potential electric energy, which becomes kinetic heat energy as the same

is discharged.

Energy, Thermal.

A form of kinetic molecular energy due to the molecular motion of bodies

caused by heat.

Entropy.

Non-available energy. As energy may in some way or other be generally

reduced to heat, it will be found that the equalizing of temperature,

actual and potential, in a system, while it leaves the total energy

unchanged, makes it all unavailable, because all work represents a fall

in degree of energy or a fall in temperature. But in a system such as

described no such fall could occur, therefore no work could be done. The

universe is obviously tending in that direction. On the earth the

exhaustion of coal is in the direction of degradation of its high

potential energy, so that the entropy of the universe tends to zero.

(See Energy, Degradation of.)

[Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLE

ENERGY tends to zero.]

Entropy, Electric.

Clerk Maxwell thought it possible to recognize in the Peltier effect, q.

v., a change in entropy, a gain or loss according to whether the

thermo-electric junction was heated or cooled. This is termed Electric

Entropy. (See Energy, Degradation of.)

243  STANDARD ELECTRICAL DICTIONARY.

Fig. 165. EPINUS' CONDENSER,

Epinus' Condenser.

Two circular brass plates, A and B, are mounted on insulating supports,

and arranged to be moved towards or away from each other as desired.

Between them is a plate of glass, C, or other dielectric. Pith balls may

be suspended back of each brass plate as shown. The apparatus is charged

by connecting one plate to an electric machine and the other to the

earth. The capacity of the plate connected to the machine is increased

by bringing near to it the grounded plate, by virtue of the principle of

bound charges. This apparatus is used to illustrate the principles of

the electric condenser. It was invented after the Leyden jar was

invented.

Fig. 166. EPINUS' CONDENSER.

E. P. S.

Initials of Electrical Power Storage; applied to a type of secondary

battery made by a company bearing that title.

Fig. 167. CAM EQUALIZER.

244   STANDARD ELECTRICAL DICTIONARY.

Equalizer.

In electro-magnetic mechanism an arrangement for converting the pull of

the electro-magnet varying in intensity greatly over its range of

action, into a pull of sensibly equal strength throughout. The use of a

rocking lever acting as a cam, with leverage varying as the armature

approaches or recedes from the magnet core is one method of effecting

the result. Such is shown in the cut. E is an electro-magnet, with

armature a. A and B are the equalizer cams. The pull on the short end of

the cam B is sensibly equal for its whole length.

Many other methods have been devised, involving different shapes of pole

pieces, armatures or mechanical devices other than the one just shown.

Equipotential. adj.

Equal in potential; generally applied to surfaces. Thus every magnetic

field is assumed to be made up of lines of force and intersecting those

lines, surfaces, plane, or more or less curved in contour, can be

determined, over all parts of each one of which the magnetic intensity

will be identical. Each surface is the locus of equal intensity. The

same type of surface can be constructed for any field of force, such as

an electrostatic field, and is termed an equipotential surface.

Equipotential Surface, Electrostatic.

A surface in an electrostatic field of force, which is the locus of all

points of a given potential in such field; a surface cutting all the

lines of force at a point of identical potential. Lines of force are cut

perpendicularly by an equipotential surface, or are normal thereto.

Equipotential Surface, Magnetic and Electro-magnetic.

A surface bearing the same relation to a magnetic or electro-magnetic

field of force that an electrostatic equipotential surface (see

Equipotential Surface, Electrostatic,) does to an electrostatic field of

force.

Equivalent, Chemical.

The quotient obtained by dividing the atomic weight of an element by its

valency.

Equivalents, Electro-chemical.

The weight of any substance set free by one coulomb of electricity. The

following give some equivalents expressed in milligrams:

Hydrogen            .0105    Mercury (mercurous)   2.10

Gold                .6877    Iron (ferric)          .1964

Silver             1.134     Iron (ferrous)         .294

Copper (cupric)     .3307    Nickel                 .3098

Mercury (mercuric) 1.05      Zinc                   .3413

Lead               1.0868    Chlorine               .3728

Oxygen              .89

245   STANDARD ELECTRICAL DICTIONARY.

Equivalent, Electro-mechanical.

The work or energy equivalent to unit quantities of electric energy, q.

v.; or equivalent to a unit current in a conductor whose ends differ one

unit of potential. The unit of electric energy taken is the watt-second

or volt-coulomb. One volt-coulomb is equal to

Ergs                  1E7   [10000000]

Foot Pound           .737337

Gram-degree C.       .24068

Horse Power Second   .0013406

Pound-degree F.      .000955

One horse power is equal to 745.943 volt coulombs per second.

Equivalent, Electro-thermal.

The heat produced by a unit current passing through a conductor with

unit difference of potential at its ends; the heat equivalent of a

volt-coulomb or watt-second. It is equal to

Gram-degree C.   .24068

Pound-degree F.  .000955

Equivalent, Thermo-chemical.

The calories evolved by the combination of one gram of any substance

with its equivalent of another substance being determined, the product

obtained by multiplying this number by the equivalent (atomic or

molecular weight / valency) of the first element or substance is the

thermo-chemical equivalent. If expressed in kilogram calories, the

product of the thermo-chemical equivalent by 0.43 gives the voltage

required to effect such decomposition.

The following are thermo-chemical equivalents of a few combinations:

Water                34.5

Zinc oxide           43.2

Iron protoxide       34.5

Iron Sesquioxide     31.9 X 3

Copper oxide         19.2

Equivolt.

"The mechanical energy of one volt electro-motive force exerted under

unit conditions through one equivalent of chemical action in grains."

(J. T. Sprague.) This unit is not in general use as the unit of electric

energy, the volt-coulomb and (for rate of electric energy) the

volt-ampere being always used.

Erg.

The absolute or fundamental C. G. S. unit of work or energy. The work

done or energy expended in moving a body through one centimeter against

a resistance of one dyne.

Erg-ten.

Ten millions of ergs, or ten meg-ergs.

Escape.

A term applied to leakage of current.

Etching, Electric.

A process of producing an etched plate. The plate is coated with wax,

and the design traced through as in common etching. It is then placed in

a bath and is connected to the positive terminal from a generator, whose

negative is immersed in the same bath, so that the metal is dissolved by

electrolytic action. By attaching to the other terminal and using a

plating bath, a rough relief plate may be secured, by deposition in the

lines of metal by electroplating.

Synonym--Electric Engraving.

246   STANDARD ELECTRICAL DICTIONARY.

Ether.

The ether is a hypothetical thing that was invented to explain the

phenomena of light. Light is theoretically due to transverse vibrations

of the ether. Since the days of Young the conception of the ether has

extended, and now light, "radiant heat," and electricity are all treated

as phenomena of the ether. Electrical attraction and repulsion are

explained by considering them due to local stresses in the ether;

magnetic phenomena as due to local whirlpools therein. The ether was

originally called the luminiferous ether, but the adjective should now

be dropped. Its density is put at 936E-21 that of water, or equal to

that of the atmosphere at 210 miles above the earth's surface. Its

rigidity is about 1E-9 that of steel (see Ten, Powers of); as a whole it

is comparable to an all-pervading jelly, with almost perfect elasticity.

The most complete vacuum is filled with ether.

All this is a hypothesis, for the ether has never been proved to exist.

Whether gravitation will ever be explained by It remains to be seen.

[Transcriber's note: The Michelson-Morley experiment in 1887 (five years

before this book) cast serious doubt on the ether. In 1905 Einstein

explained electromagnetic phenomenon with photons. In 1963 Edward M.

Purcell used special relativity to derive the existence of magnetism and

radiation.]

Eudiometer.

A graduated glass tube for measuring the volumes of gases. In its

simplest form it is simply a cylindrical tube, with a scale etched or

engraved upon it, closed at one end and open at the other. The gas to be

measured is collected in it over a liquid, generally water, dilute

sulphuric acid in the gas voltameter, or mercury. Many different shapes

have been given them by Hoffmann, Ure, Bunsen and others.

Evaporation, Electric.

The superficial sublimation or evaporation of a substance under the

influence of negative electricity. It is one of the effects investigated

by Crookes in his experiments with high vacua. He found that when a

metal, even so infusible as platinum, was exposed to negative

electrification in one of his high vacuum tubes, that it was volatilized

perceptibly. A cadmium electrode heated and electrified negatively was

found to give a strong coating of metal on the walls of the tube. Even

in the open air the evaporation of water was found to be accelerated by

negative electrification.

Exchange, Telephone.

The office to which telephone wires lead in a general telephone system.

In the office by a multiple switch board, or other means, the different

telephones are interconnected by the office attendants, so that any

customers who desire it may be put into communication with each other.

The exchange is often termed the Central Office, although it may be only

a branch office.

Excitability, Faradic.

The action produced in nerve or muscle of the animal system by an

alternating or intermitting high potential discharge from an induction

coil.

247   STANDARD ELECTRICAL DICTIONARY.

Excitability, Galvanic.

The same as Faradic excitability, except that it refers to the effects

of the current from a galvanic battery.

Excitability of Animal System, Electric.

The susceptibility of a nerve or muscle to electric current shown by the

effect produced by its application.

Exciter.

A generator used for exciting the field magnet of a dynamo. In

alternating current dynamos, e. g., of the Westinghouse type, a special

dynamo is used simply to excite the field magnet. In central station

distribution the same is often done for direct current dynamos.

Exosmose, Electric.

The outflowing current of electric osmose. (See Osmose, Electric.)

Expansion, Coefficient of.

The number expressing the proportional increase in size, either length,

area or volume, of a substance under the influence generally of heat.

There are three sets of coefficients, (1) of linear expansion, (2) of

superficial expansion, (3) of cubic expansion or expansion of volume.

The first and third are the only ones much used. They vary for different

substances, and for the same substance at different temperatures. They

are usually expressed as decimals indicating the mixed number referred

to the length or volume of the body at the freezing point as unity.

Expansion, Electric.

(a) The increase in volume of a condenser, when charged

electrostatically. A Leyden jar expands when charged, and contracts when

discharged.

(b) The increase in length of a bar of iron when magnetized.

This is more properly called magnetic expansion or magnetic elongation.

Exploder.

(a) A small magneto-generator for producing a current for heating the

wire in an electric fuse of the Abel type (see Fuse, Electric), and

thereby determining an explosion.

(b) The term may also be applied to a small frictional or influence

machine for producing a spark for exploding a spark fuse.

Explorer.

A coil, similar to a magnetizing coil (see Coil, Magnetizing), used for

investigating the electro-magnetic circuit and for similar purposes. If

placed around an electro-magnet and connected with a galvanometer, it

will produce a deflection, owing to a momentary induced current, upon

any change in the magnet, such as removing or replacing the armature. It

is useful in determining the leakage of lines of force and for general

investigations of that nature. It is often called an exploring coil.

Hughes' Induction Balance (see Induction Balance, Hughes') is sometimes

called a Magnetic Explorer. The exploring coil may be put in circuit

with a galvanometer for quantitative measurements or with a telephone

for qualitative ones.

248   STANDARD ELECTRICAL DICTIONARY.

Extension Bell Call.

A system of relay connection, q. v., by which a bell is made to continue

ringing after the current has ceased coming over the main line. It is

designed to prolong the alarm given by a magneto call bell, q. v., which

latter only rings as long as the magneto handle is turned. A vibrating

electric bell (see Bell, Electric,) is connected in circuit with a local

battery and a switch normally open, but so constructed as to close the

circuit when a current is passed and continue to do so indefinitely. The

distant circuit is connected to this switch. When the magneto is worked

it acts upon the switch, closes the local battery circuit and leaves it

closed, while the bell goes on ringing until the battery is exhausted or

the switch is opened by hand.

Eye, Electro-magnetic.

An apparatus used in exploring a field of electro-magnetic radiations.

It is a piece of copper wire 2 millimeters (.08 inch) in diameter, bent

into an almost complete circle 70 millimeters (.28 inch) in diameter,

with terminals separated by an air gap. This is moved about in the

region under examination, and by the production of a spark indicates the

locality of the loops or venters in systems of stationary waves.

248   STANDARD ELECTRICAL DICTIONARY.

F.

Abbreviation for Fahrenheit, as 10º F., meaning 10º Fahrenheit. (See

Fahrenheit Scale.)

Fahrenheit Scale.

A thermometer scale in use in the United States and England. On this

scale the temperature of melting ice is 32°; that of condensing steam is

212°; the degrees are all of equal length. Its use is indicated by the

letter F., as 180° F. To convert its readings into centigrade, subtract

32 and multiply by 5/9. (b) To convert centigrade into F. multiply by

9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82.2° C. Again

180° C. = (180 * 9/5) + 32 = 324° F.

[Transcribers note: 180° C. = (180 * 9/5) + 32 = 356° F. ]

The additions and subtractions must be algebraic in all cases. Thus when

the degrees are minus or below zero the rules for conversion might be

put thus: To convert degrees F. below zero into centigrade to the number

of degrees F. add 32, multiply by 5/9 and place a minus sign (-) before

it. (b) To convert degrees centigrade below zero into Fahrenheit,

multiply the number of degrees by 9/5, subtract from 32 if smaller; if

greater than 32 subtract 32 therefrom, and prefix a minus sign, thus:

-10° C. = 32 - (10 * 9/5) = 14°. Again, -30°C. = (30 * 9/5) - 32 = 22 =

-22° F.

249  STANDARD ELECTRICAL DICTIONARY.

Farad.

The practical unit of electric capacity; the capacity of a conductor

which can retain one coulomb of electricity at a potential of one volt.

The quantity of electricity charged upon a conducting surface raises its

potential; therefore a conductor of one farad capacity can hold two

coulombs at two volts potential, and three coulombs at three volts, and

so on. The electric capacity of a conductor, therefore, is relative

compared to others as regards its charge, for the latter may be as great

as compatible with absence of sparking and disruptive discharge. In

other words, a one farad or two farad conductor may hold a great many

coulombs. Charging a conductor with electricity is comparable to pumping

air into a receiver. Such a vessel may hold one cubic foot of air at

atmospheric pressure and two at two atmospheres, and yet be of one cubic

foot capacity however much air is pumped into it.

The farad is equal to one fundamental electrostatic unit of capacity

multiplied by 9E11 and to one electro-magnetic unit multiplied by 1E-9.

The farad although one of the practical units is far too large, so the

micro-farad is used in its place. The capacity of a sphere the size of

the earth is only .000636 of a farad.

[Transcriber's note: Contemporary calculations give about .000720

farad.]

Faraday, Effect.

The effect of rotation of its plane produced upon a polarized beam of

light by passage through a magnetic field. (See Magnetic Rotary

Polarization.)

Faraday's Cube.

To determine the surface action of a charge, Faraday constructed a room,

twelve feet cube, insulated, and lined with tinfoil. This room he

charged to a high potential, but within it he could detect no excitement

whatever. The reason was because the electricity induced in the bodies

within the room was exactly equal to the charge of the room-surface, and

was bound exactly by it. The room is termed Faraday's cube.

Faraday's Dark Space.

A non-luminous space between the negative and positive glows, produced

in an incompletely exhausted tube through which a static discharge, as

from an induction coil, is produced. It is perceptible in a rarefaction

of 6 millimeters (.24 inch) and upwards. If the exhaustion is very high

a dark space appears between the negative electrode and its discharge.

This is known as Crookes' dark space.

Faraday's Disc.

A disc of any metal, mounted so as to be susceptible of rotation in a

magnetic field of force, with its axis parallel to the general direction

of the lines of force. A spring bears against its periphery and another

spring against its axle. When rotated, if the springs are connected by a

conductor, a current is established through the circuit including the

disc and conductor. The radius of the disc between the spring contacts

represents a conductor cutting lines of force and generating a potential

difference, producing a current. If a current is sent through the

motionless wheel from centre to periphery it rotates, illustrating the

doctrine of reversibility. As a motor it is called Barlow's or

Sturgeon's Wheel. If the disc without connections is rapidly rotated it

produces Foucault currents, q. v., within its mass, which resist its

rotation and heat the disc.

250   STANDARD ELECTRICAL DICTIONARY.

Fig. 168. "FARADAY'S NET."

Faraday's Net.

An apparatus for showing that the electric charge resides on the

surface. It consists of a net, conical in shape and rather deep, to

whose apex two threads, one on each side, are attached. Its mouth is

fastened to a vertical ring and the whole is mounted on an insulating

support.

It is pulled out to its full extent and is electrified. No charge can be

detected inside it. By pulling one of the threads it is turned with the

other side out. Now all the charge is found on the outside just as

before, except that it is of course on the former inside surface of the

bag. The interior shows no charge.

Faraday's Transformer.

The first transformer. It was made by Michael Faraday. It was a ring of

soft iron 7/8 inch thick, and 6 inches in external diameter. It was

wound with bare wire, calico being used to prevent contact of the wire

with the ring and of the layers of wire with each other, while twine was

wound between the convolutions to prevent the wires from touching.

Seventy-two feet of copper wire, 1/20 inch diameter, were wound in three

superimposed coils, covering about one-half of the ring. On the other

half sixty feet of copper wire were wound in two superimposed coils.

Faraday connected his coils in different ways and used a galvanometer to

measure the current produced by making and breaking one of the circuits

used as a primary.

The coil is of historic interest.

Faraday's Voltameter.

A voltameter, in which the coulombs of current are measured by the

volume of the gas evolved from acidulated water. (See Voltameter, Gas.)

Faradic. adj.

Referring to induced currents, produced from induction coils. As Faraday

was the original investigator of the phenomena of electro-magnetic

induction, the secondary or induced electro-magnetic currents and their

phenomena and apparatus are often qualified by the adjective Faradic,

especially in electro-therapeutics. A series of alternating

electrostatic discharges, as from an influence machine (Holtz), are

sometimes called Franklinic currents. They are virtually Faradic, except

as regards their production.

251   STANDARD ELECTRICAL DICTIONARY.

Faradic Brush.

A brush for application of electricity to the person. It is connected as

one of the electrodes of an induction coil or magneto generator. For

bristles wire of nickel plated copper is generally employed.

Faradization.

In medical electricity the analogue of galvanization; the effects due to

secondary or induced currents; galvanization referring to currents from

a galvanic battery; also the process of application of such currents.

Faults.

Sources of loss of current or of increased resistance or other troubles

in electric circuits.

Feeder.

A lead in an electric central station distribution system, which lead

runs from the station to some point in the district to supply current.

It is not used for any side connections, but runs direct to the point

where current is required, thus "feeding" the district directly. In the

two wire system a feeder may be positive or negative; in the three wire

system there is also a neutral feeder. Often the term feeder includes

the group of two or of three parallel lines.

Feeder Equalizer.

An adjustable resistance connected in circuit with a feeder at the

central station. The object of the feeder being to maintain a definite

potential difference at its termination, the resistance has to be varied

according to the current it is called on to carry.

Feeder, Main or Standard.

The main feeder of a district. The standard regulation of pressure

(potential difference between leads) in the district is often determined

by the pressure at the end of the feeder.

Feeder, Negative.

The lead or wire in a set of feeders, which is connected to the negative

terminal of the generator.

Feeder, Neutral.

In the three wire system the neutral wire in a set of feeders. It is

often made of less diameter than the positive and negative leads.

Feeder, Positive.

The lead or wire in a set of feeders, which wire is connected to the

positive terminal of the generator.

Ferranti Effect.

An effect as yet not definitely explained, observed in the mains of the

Deptford, Eng., alternating current plant. It is observed that the

potential difference between the members of a pair of mains rises or

increases with the distance the place of trial is from the station.

[Transcriber's note: This effect is due to the voltage drop across the

line inductance (due to charging current) being in phase with the

sending end voltages. Both capacitance and inductance are responsible

for producing this phenomenon.  The effect is more pronounced in

underground cables and with very light loads.]

252  STANDARD ELECTRICAL DICTIONARY.

Ferro-magnetic. adj.

Paramagnetic; possessing the magnetic polarity of iron.

Fibre and Spring Suspension.

A suspension of the galvanometer needle used in marine galvanometers.

The needle is supported at its centre of gravity by a vertically

stretched fibre attached at both its ends, but with a spring

intercalated between the needle and one section of the fibre.

Fibre Suspension.

Suspension, as of a galvanometer needle, by a vertical or hanging fibre

of silk or cocoon fibre, or a quartz fibre. (See Quartz.)

This suspension, while the most delicate and reliable known, is very

subject to disturbance and exacts accurate levelling of the instrument.

Fibre suspension is always characterized by a restitutive force. Pivot

suspension, q. v., on the other hand, has no such force.

Field, Air.

A field the lines of force of which pass through air; the position of a

field comprised within a volume of air.

Field, Alternating.

Polarity or direction being attributed to lines of force, if such

polarity is rapidly reversed, an alternating field results. Such field

may be of any kind, electro-magnetic or electrostatic. In one instance

the latter is of interest. It is supposed to be produced by high

frequency discharges of the secondary of an induction coil, existing in

the vicinity of the discharging terminals.

Field Density.

Field density or density of field is expressed in lines of force per

unit area of cross-section perpendicular to the lines of force.

Field, Distortion of.

The lines of force reaching from pole to pole of an excited field magnet

of a dynamo are normally symmetrical with respect to some axis and often

with respect to several. They go across from pole to pole, sometimes

bent out of their course by the armature core, but still symmetrical.

The presence of a mass of iron in the space between the pole pieces

concentrates the lines of force, but does not destroy the symmetry of

the field.

When the armature of the dynamo is rotated the field becomes distorted,

and the lines of force are bent out of their natural shape. The new

directions of the lines of force are a resultant of the lines of force

of the armature proper and of the field magnet. For when the dynamo is

started the armature itself becomes a magnet, and plays its part in

forming the field. Owing to the lead of the brushes the polarity of the

armature is not symmetrical with that of the field magnets. Hence the

compound field shows distortion. In the cut is shown diagrammatically

the distortion of field in a dynamo with a ring armature. The arrow

denotes the direction of rotation, and n n * * * and s s * * * indicate

points of north and south polarity respectively.

253  STANDARD ELECTRICAL DICTIONARY.

The distorted lines must be regarded as resultants of the two induced

polarities of the armature, one polarity due to the induction of the

field, the other to the induction from its own windings. The positions

of the brushes have much to do with determining the amount and degree of

distortion. In the case of the ring armature it will be seen that some

of the lines of force within the armature persist in their polarity and

direction, almost as induced by the armature windings alone, and leak

across without contributing their quota to the field. Two such lines are

shown in dotted lines.

In motors there is a similar but a reversed distortion.

Fig. 169. DISTORTION OF FIELD IN A

RING ARMATURE OF AN ACTIVE DYNAMO.

Fig. 170. DISTORTION OF FIELD IN A

RING ARMATURE OF AN ACTIVE MOTOR.

254   STANDARD ELECTRICAL DICTIONARY.

Field, Drag of.

When a conductor is moved through a field so that a current is generated

in it, the field due to that current blends with the other field and

with its lines of force, distorting the field, thereby producing a drag

upon its own motion, because lines of force always tend to straighten

themselves, and the straightening would represent cessation of motion in

the conductor. This tendency to straightening therefore resists the

motion of the conductor and acts a drag upon it.

Field of Force.

The space in the neighborhood of an attracting or repelling mass or

system. Of electric fields of force there are two kinds, the

Electrostatic and the Magnetic Fields of Force, both of which may be

referred to. A field of force may be laid out as a collection of

elements termed Lines of Force, and this nomenclature is universally

adopted in electricity. The system of lines may be so constructed that

(a) the work done in passing from one equipotential surface to the next

is always the same; or (b) the lines of force are so laid out and

distributed that at a place in which unit force is exercised there is a

single line of force passing through the corresponding equipotential

surface in each unit of area of that surface. The latter is the

universal method in describing electric fields. It secures the following

advantages:--First: The potential at any point in the field of space

surrounding the attracting or repelling mass or masses is found by

determining on which imaginary equipotential surface that point lies.

Second: If unit length of a line of force cross n equipotential

surfaces, the mean force along that line along the course of that part

of it is equal to n units; for the difference of potential of the two

ends of that part of the line of force = n; it is also equal to F s (F

= force), because it represents numerically a certain amount of work;

but s = I, whence n = F. Third: The force at any part of the field

corresponds to the extent to which the lines of force are crowded

together; and thence it may be determined by the number of lines of

force which pass through a unit of area of the corresponding

equipotential surface, that area being so chosen as to comprise the

point in question. (Daniell.)

Field of Force, Electrostatic.

The field established by the attracting, repelling and stressing

influence of an electrostatically charged body. It is often termed an

Electrostatic Field. (See Field of Force.)

255   STANDARD ELECTRICAL DICTIONARY.

Field of Force of a Current.

A current establishes a field of force around itself, whose lines of

force form circles with their centres on the axis of the current. The

cut, Fig. 172, shows the relation of lines of force to current.

Fig. 171. EXPERIMENT SHOWING LINES OF FORCE

SURROUNDING AN ACTIVE CONDUCTOR.

Fig. 172. DIAGRAM OF FIELD OF FORCE

SURROUNDING AN ACTIVE CONDUCTOR.

Fig. 173. LINK OF FORCE INDUCED BY A

CURRENT SHOWING THE MAGNETIC WHIRLS.

The existence of the field is easily shown by passing a conductor

vertically through a horizontal card. On causing a current to go through

the wire the field is formed, and iron filings dropped upon the card,

tend, when the latter is gently tapped, to take the form of circles. The

experiment gives a version of the well-known magnetic figures, q. v. See

Fig. 171.

The cut shows by the arrows the relation of directions of current to the

direction of the lines of force, both being assumptions, and merely

indicating certain fixed relations, corresponding exactly to the

relations expressed by the directions of electro-magnetic or magnetic

lines of force

256   STANDARD ELECTRICAL DICTIONARY.

Field, Pulsatory.

A field produced by pulsatory currents. By induction such field can

produce an alternating current.

Field, Rotating.

In a dynamo the field magnets are sometimes rotated instead of the

armature, the latter being stationary. In Mordey's alternator the

armature, nearly cylindrical, surrounds the field, and the latter

rotates within it, the arrangement being nearly the exact reverse of the

ordinary one. This produces a rotating field.

Field, Rotatory.

A magnetic field whose virtual poles keep rotating around its centre of

figure. If two alternating currents differing one quarter period in

phase are carried around four magnetizing coils placed and connected in

sets of two on the same diameter and at right angles to each other, the

polarity of the system will be a resultant of the combination of their

polarity, and the resultant poles will travel round and round in a

circle. In such a field, owing to eddy currents, masses of metal,

journaled like an armature, will rotate, with the speed of rotation of

the field.

Field, Stray.

The portion of a field of force outside of the regular circuit;

especially applied to the magnetic field of force of dynamos expressing

the portion which contributes nothing to the current generation.

Synonym--Waste Field.

Field, Uniform.

A field of force of uniform density. (See Field Density.)

Figure of Merit.

In the case of a galvanometer, a coefficient expressing its delicacy. It

is the reciprocal of the current required to deflect the needle through

one degree. By using the reciprocal the smaller the current required the

larger is the figure of merit. The same term may be applied to other

instruments.

It is often defined as the resistance of a circuit through which one

Daniell's element will produce a deflection of one degree on the scale

of the instrument. The circuit includes a Daniell's cell of resistance

r, a rheostat R, galvanometer G and shunt S. Assume that with the shunt

in parallel a deflection of a divisions is obtained. The resistance of

the shunted galvanometer is (GS/G+S ; the multiplying power m of the

shunt is S+G/S; the formula or figure of merit is m d (r+R +G S/G+S).

The figure of merit is larger as the instrument is more sensitive.

Synonym--Formula of Merit.

257  STANDARD ELECTRICAL DICTIONARY.

Filament.

A thin long piece of a solid substance. In general it is so thin as to

act almost like a thread, to be capable of standing considerable

flexure. The distinction between filament and rod has been of much

importance in some patent cases concerning incandescent lamps. As used

by electricians the term generally applies to the carbon filament of

incandescent lamps. This as now made has not necessarily any fibres, but

is entitled to the name of filament, partly by convention, partly by its

relative thinness and want of stiffness. (See Incandescent

Lamps--Magnetic Filament.)

Fire Alarm, Electric, Automatic.

A system of telegraph circuits, at intervals supplied with thermostats

or other apparatus affected by a change of temperature, which on being

heated closes the circuit and causes a bell to ring. (See Thermostat.)

Fire Alarm Telegraph System.

A system of telegraphic lines for communicating the approximate location

of a fire to a central station and thence to the separate fire-engine

houses in a city or district. It includes alarm boxes, distributed at

frequent intervals, locked, with the place where the key is kept

designated, or in some systems left unlocked. On opening the door of the

box and pulling the handle or otherwise operating the alarm, a

designated signal is sent to the central station. From this it is

telegraphed by apparatus worked by the central station operator to the

engine houses. The engines respond according to the discipline of the

service.

Fire Cleansing.

Freeing the surface of an article to be plated from grease by heating.

Fire Extinguisher, Electric, Automatic.

A modification of the electric fire alarm (see Fire Alarm, Electric,

Automatic), in which the thermostats completing the circuits turn on

water which, escaping through the building, is supposed to reach and

extinguish a fire.

Flashing in a Dynamo or Magneto-electric Generator.

Bad adjustment of the brushes at the commutator, or other fault of

construction causes the production of voltaic arcs at the commutator of

a generator, to which the term flashing is applied.

Flashing of Incandescent Lamp Carbons.

A process of treatment for the filaments of incandescent lamps. The

chamber before sealing up is filled with a hydro-carbon vapor or gas,

such as the vapor of a very light naphtha (rhigolene). A current is then

passed through the filament heating it to redness. The more attenuated

parts or those of highest resistance are heated the highest, and

decompose most rapidly the hydro-carbon vapor, graphitic carbon being

deposited upon these parts, while hydrogen is set free. This goes on

until the filament is of uniform resistance throughout. It gives also a

way of making the resistance of the filament equal to any desired number

of ohms, provided it is originally of high enough resistance. The

process increases the conductivity of the filament.

After flashing the chambers are pumped out and sealed up.

258   STANDARD ELECTRICAL DICTIONARY.

Flashing Over.

A phenomenon observed in high potential dynamos. On a sudden alteration

of the resistance of the circuit a long blue spark will be drawn out

around the surface of the commutator from brush to brush. The spark is

somewhat of the nature of an arc, and may seriously injure commutators

whose sections are only separated by mica, or other thin insulation. In

the case of commutators whose sections are separated by air spaces it is

not so injurious.

Flats.

In a commutator of a dynamo, the burning or wearing away of a commutator

segment to a lower level than the rest. Sometimes two adjacent bars will

be thus affected, causing a flat place on the commutator. It is not

always easy to account for the formation of flats. They may have their

origin in periodic vibrations due to bad mounting, or to sparking at the

particular point.

Floor Push.

A press or push button constructed to be set into the floor to be

operated by pressing with the foot. It is used to ring an alarm bell,

sound a buzzer or for similar service.

Fluid, Depolarizing.

A fluid used in voltaic batteries to dispose of the hydrogen, which goes

to the negative plate. This it does by oxidizing it. Chromic acid,

nitric acid, and chloric acids are among the constituents of liquid

depolarizers. (See Electropoion Fluid.)

Fluid, Electric.

The electric current and charge have sometimes been attributed to a

fluid. The theory, which never was much more than hypothetical, survives

to some extent in the single and double fluid theory. (See Single Fluid

Theory-Double Fluid Theory.)

Fluorescence.

The property of converting ether waves of one length, sometimes of

invisible length, into waves of another length (visible). AEsculin,

quinine salts, uranium glass and other substances exhibit this

phenomenon. The phenomenon is utilized in the production of Geissler

tubes.

Flush Boxes.

A heavy iron box covered with a heavy hand plate and laid flush (whence

the name), or even with the surface of a roadway. Into it conductors of

an underground system lead, and it is used to make connections therewith

and for examining the leakage of the conductors and for similar

purposes. It is a "man-hole" (q. v.) in miniature.

Fluviograph.

An electric registering tide gauge or water level gauge.

259  STANDARD ELECTRICAL DICTIONARY.

Fly or Flyer, Electric.

A little wheel, ordinarily poised on a point, like a compass needle. It

carries several tangentially directed points, all pointing in the same

sense. When connected with a source of electricity of high potential it

revolves by reaction. The tension of its charge is highest at the

points, the air there is highly electrified and repelled, the reaction

pushing the wheel around like a Barker's mill or Hero's steam engine.

Sometimes the flyer is mounted with its axis horizontal and across the

rails on a railroad along which it travels.

Synonym--Reaction Wheel.

Foci Magnetic.

The two points on the earth's surface where the magnetic intensity is

greatest. They nearly coincide in position with the magnetic poles.

Fog, Electric.

Fogs occurring when the atmosphere is at unusually high potential and

accompanied by frequent change of such polarity.

Following Horns.

In dynamo-electric machines the projecting ends of the pole pieces

towards which the outer uncovered perimeter of the armature turns in its

regular operations. The leading horns are those away from which the

armature rotates. In considering rotation the exposed portion of the

superficies of the armature is considered. The definition would have to

be reversed if the part facing the pole pieces were considered.

Synonym--Trailing Horns.

Foot-candle.

A unit of illuminating power; the light given by one standard candle at

a distance of one foot. The ordinary units of illuminating power are

entirely relative; this is definite. It is due to Carl Herring.

Foot-pound.

A practical unit of work or energy. The quantity of work required to

raise a pound one foot, or one hundred pounds one-hundredth of a foot,

and so on; or the potential energy represented by a weight at an

elevation under these conditions.

Foot-step.

In a dynamo with armature at the lower end of its field magnets, the

plate generally of zinc, interposed between it and the iron base plate

to prevent the leakage of lines of force outside of the circuit. Any

diamagnetic material which is mechanically suitable may be used.

Force.

Force may be variously defined.

(a) Any cause of change of the condition of matter with respect to

motion or rest.

(b) A measurable action upon a body under which the state of rest of

that body, or its state of uniform motion in a straight line, suffers

change.

(c) It may be defined by its measurement as the rate of change of

momentum, or

(d) as the rate at which work is done per unit of space traversed.

Force is measured by the acceleration or change of motion it can impart

to a body of unit mass in a unit of time, or, calling

force, F,

mass, m

acceleration per second a

we have F = m a.

The dimensions of force are

mass (M) * acceleration (L/(T^2)) = (M*L)/(T^2).

260   STANDARD ELECTRICAL DICTIONARY.

Force de Cheval. Horse power (French).

It is the French or metric horse power.

It is equal to:

542.496    Foot lbs. per second.

.9864   English Horse Power.

75.0      Kilogram-meters per second.

Force, Electro-magnetic.

The mechanical force of attraction or repulsion acting on the

electro-magnetic unit of quantity. Its intensity varies with the square

of the distance. It may also be defined as electric force in the

electro-magnetic system.

Its dimensions are equal to

mechanical force ((M*L)/(T^2)) divided by quantity ((M^.5)*(L^.5))

= ((M^.5)*(L^.5))/(T^2).

Force, Electrostatic.

The force by which electric matter or electrified surfaces attract or

repel each other. It is also termed electric force (not good) and

electro-motive intensity. It is the mechanical force acting upon a unit

quantity of electricity. Its intensity varies with the square of the

distance.

Its dimensions are therefore equal to

(quantity * unity / (square of distance) Q. * 1 / (L^2)

= ((M^.5) * (L^1.5) )/ T*1 / (L^2)

= ((M^.5) * (L^.5)) / T

These dimensions are also those of potential difference.

[Transcriber's Note: The image of the preceding paragraph is included

for "clarity".]

The objection to the term electric force is that it may be applied also

to electro-magnetic force, and hence be a source of confusion.

Forces, Parallelogram of.

The usual method of composing forces or resolving a force. The sides of

a parallelogram of forces represent component forces and the diagonal

represents the resultant. See Component--Resultant--Forces, Composition

of--Forces, Resolution of.

Forces, Composition of.

When several forces act in a different direction upon a point they may

be drawn or graphically represented as arrows or lines emanating from

the point in the proper direction and of lengths proportional to the

force they exercise. Any two can be treated as contiguous sides of a

parallelogram and the parallelogram can be completed. Then its diagonal,

called the resultant, will represent the combined action of the two

forces, both as regards direction and intensity. This is the composition

of two forces.

If more than two forces act upon the given point the resultant can be

composed with any of the others and a new force developed. The new

resultant can be combined with another force, and the process kept up,

eliminating the components one by one until a final resultant of all is

obtained. This will give the exact direction and intensity of the

forces, however many or varied.

261   STANDARD ELECTRICAL DICTIONARY.

Forces, Resolution of.

The developing from a single force treated as a resultant, two other

forces in any desired direction. The reverse of composition of forces.

(See Forces, Composition of--Forces, Parallelogram

of--Components--Resultant.)

Force, Tubes of.

Aggregations of lines of force, either electrostatic or magnetic. They

generally have a truncated, conical or pyramidal shape and are not

hollow. Every cross-section contains the same number of lines. The name

it will seem is not very expressive.

Force, Unit of.

The fundamental or C. G. S. unit or force is the dyne, q. v.

The British unit of force is the poundal (the force which will produce

an acceleration of one foot per second in a mass of one pound). It is

equal to about 10/322 pound. A force cannot be expressed accurately in

weight units, because weight varies with the latitude.

Forming.

The process of producing secondary battery plates from lead plates by

alternately passing a charging current through the cell and then

allowing it to discharge itself and repeating the operation. (See

Battery, Secondary, Planté's.)

Foundation Ring.

In a dynamo armature the ring-shaped core on which Gramme ring armatures

and other ring armatures are wound.

Fourth State of Matter.

Gas so rarefied that its molecules do not collide, or rarely do so;

radiant matter, q. v.

[Transcriber's note: This term now refers to plasma, an ionized gas,

which contains free electrons. The ions and electrons move somewhat

independently making plasma electrically conductive. It responds

strongly to electromagnetic fields.]

Frame.

In a dynamo the bed-piece is sometimes called the frame.

Franklin's Experiment.

Franklin proved the identity of lightning and electricity by flying a

kite in a thunder storm. The kite was of silk so as to endure the

wetting. When the string became wet sparks could be taken from a key

attached to its end. The main string was of hemp; at the lower end was a

length of silk to insulate it. The key was attached near the end of and

to the hemp string.

Franklin's Plate.

A simple form of condenser. It consists of a plate of glass coated on

each side with tinfoil with a margin of about an inch of clear glass.

One coating may be grounded as indicated in the cut, and the plate

charged like a Leyden jar. Or one side may be connected with one

terminal, and the other with the other terminal of an influence machine

and the pane will be thus charged.

Synonym--Fulminating Pane.

262   STANDARD ELECTRICAL DICTIONARY.

Fig. 174. FRANKLIN'S PLATE.

Franklin's Theory.

The single fluid theory, q. v., of electricity.

Frequency.

The number of double reversals or complete alternations per second in an

alternating current.

Synonym--Periodicity.

Frictional Electricity.

Electricity produced by friction of dissimilar substances. (See

Electrostatic Series.) The contact theory holds that friction plays only

a secondary rôle in this process; that it increases the thoroughness of

contact, and tends to dry the rubbing surfaces, but that the charges

induced are due to contact of dissimilar substances, not to friction of

one against the other.

Frictional Heating.

The heating of a conductor by the passage of a current; the Joule

effect, q. v.

Fringe.

The outlying edge of a magnetic field.

Frog, Galvani's Experiment With.

A classic experiment in electricity, leading to the discovery of current

or dynamic electricity. If a pair of legs of a recently killed frog are

prepared with the lumbar nerves exposed near the base of the spinal

column, and if a metallic conductor, one half-length zinc and the other

half-length copper, is held, one end between the lumbar nerves and the

spine, and the other end against one of the muscles of the thigh or

lower legs, the moment contact occurs and the circuit is completed

through the animal substance the muscles contract and the leg is

violently drawn upwards. Galvani, in 1786, first performed, by accident,

this famous experiment, it is said, with a scalpel with which he was

dissecting the animal. He gave his attention to the nerves and muscles.

Volta, more happily, gave his attention to the metals and invented the

voltaic battery, described by him in a letter to Sir Joseph Banks, dated

1800.

Frog, Rheoscopic.

If the nerve or living muscle of a frog is suddenly dropped upon another

living muscle so as to come in contact with its longitudinal and

transverse sections, the first muscle will contract on account of the

stimulation of its nerve due to the passage of a current derived from

the second muscle (Ganot). The experiment goes under the above title.

263   STANDARD ELECTRICAL DICTIONARY.

Frying.

A term applied to a noise sometimes produced in a voltaic arc due to too

close approach of the carbons to each other. It has been suggested that

it may be due to volatilization of the carbon. (Elihu Thomson.)

Fulgurite.

An irregular and tubular mass of vitrified quartz, believed to be formed

by melting under the lightning stroke.

Fig. 175. CRUCIBLE, ELECTRIC.

Furnace, Electric.

A furnace in which the heat is produced by the electric current. It has

hitherto been practically used only in the extraction of aluminum and

silicium  from their ores. The general principle involves the formation

of an arc between carbon electrodes. The substances to be treated are

exposed to the heat thus produced. Sometimes the substances in the arc

form imperfect conductors, and incandescence takes a part in the action.

Sometimes the substances are merely dropped through the arc.

[Transcriber's note: Silicium is silicon.]

Fuse Board.

A tablet on which a number of safety fuses are mounted. Slate is

excellent material for the tablet, as it is incombustible, and is easily

drilled and worked.

Fuse Box.

A box containing a safety fuse. Porcelain is an excellent material for

its base. No combustible material should enter into its composition.

Fuse, Cockburn.

A safety fuse or cut off which consists of a wire of pure tin running

from terminal to terminal, to whose centre a leaden ball is secured by

being cast into position. The connection with the terminals is made by

rings at the ends of the wire through which the terminal screws are

passed and screwed home. When the tin softens under too heavy a current

the weight of the shot pulls it apart.

Fig. 176 COCKBURN SAFETY FUSE.

264  STANDARD ELECTRICAL DICTIONARY.

Fig. 177. ELECTRIC FUSE.

Fuse, Electric.

A fuse for igniting an explosive by electricity. There are two kinds. In

one a thin wire unites the ends of the two conducting wires as they

enter the case of the fuse. The larger wires are secured to the case, so

that no strain comes on the fine wire. On passing a current of

sufficient strength the small wire is heated. In use the fuse is bedded

in powder, which again may be surrounded by fulminating powder, all

contained in a copper or other metallic case. Such a detonator is used

for exploding guncotton and other high explosives.

The other kind of fuse is similar, but has no thin connecting wire. The

ends of the conductors are brought nearer together without touching. In

use a static discharge is produced across from end to end of the

conductors, igniting a proper explosive placed there as in the other

case.

The first kind of fuse is generally operated by a battery or small

mechanical generator--the latter by a spark coil, frictional or

influence machine or by a Leyden jar.

264  STANDARD ELECTRICAL DICTIONARY.

Galvanic. adj.

Voltaic; relating to current electricity or the electrolytic and

electro-chemical relations of metals. (For titles in general under this

head see Voltaic--or the main title.)

Galvanic Element.

A galvanic couple with exciting fluid and adjuncts; a galvanic cell. The

word element is sometimes applied to the electrodes of a cell, as the

carbon element or zinc element.

265  STANDARD ELECTRICAL DICTIONARY.

Galvanic Polarization.

The polarization of a voltaic couple. (See Polarization.)

Galvanism.

The science of voltaic or current electricity.

Galvanization.

(a) Electroplating or depositing a metal over the surface of another by

electrolysis.

(b) In medical electricity the effects produced on any part of the

system by the current of voltaic battery. Various descriptive

qualifications are prefixed, such as "general" galvanization, indicating

its application as applied to the whole body, "local" for the reverse

case, and so on.

Galvanization, Labile.

Application of the galvanic current in electro-therapeutics where one

sponge electrode is employed which is rubbed or moved over the body, the

other being in constant contact with the body.

Galvanized Iron.

Iron coated with zinc by cleaning and immersion in melted zinc. The iron

is prevented from rusting by galvanic action. It forms the negative

element in a couple of which the zinc is the positive element. From this

electric protective action the name is derived.

Galvano-cautery, Chemical.

Electro-therapeutic treatment with sharp electrodes, one of which is

inserted in the tissue and a current passed by completing the circuit

through the tissue so as to electrolyze or decompose the fluids of the

tissue. It is applied in the removal of hair or extirpation of the

follicle. The process is not one of heating, and is improperly named

cautery.

Galvano-faradization.

In medical electricity the application of the voltaic and induced or

secondary current simultaneously to any part of the system.

Galvanometer.

An instrument for measuring current strength and sometimes for measuring

inferentially potential difference, depending on the action of a

magnetic field established by the current, such action being exerted on

a magnetic needle or its equivalent.

A current passing through a conductor establishes circular lines of

force. A magnetic needle placed in their field is acted on and tends to

place itself parallel with the lines, in accordance with the principles

of current induction. (See Induction, Electro-magnetic.) A common

compass held near a conductor through which a current is passing tends

to place itself at right angles to such conductor. For a maximum effect

the conductor or the part nearest the needle should lie in the magnetic

meridian. If at right angles thereto its action will only strengthen the

directive force of the earth's induction or magnetic field, as the

needle naturally points north and south. Such combination is virtually a

galvanometer.

266   STANDARD ELECTRICAL DICTIONARY.

A typical galvanometer comprises a flat coil of wire placed horizontally

within which a magnetic needle is delicately poised, so as to be free to

rotate with the least possible friction. The needle may be supported on

a sharp point like a compass needle, or may be suspended by a long fine

filament. It should be covered by a glass plate and box, or by a glass

shade. Finally a graduated disc may be arranged to show the amount of

deflection of the needle.

In use the apparatus is turned about until the needle, as acted on by

the earth's magnetic field, lies parallel to the direction of the coils

of wire. On passing a current through the coil the needle is deflected,

more or less, according to its strength.

By using exceedingly fine wire, long enough to give high resistance, the

instrument can be used for very high potentials, or is in condition for

use in determining voltage. By using a coil of large wire and low

resistance it can be employed in determining amperage. In either case

the deflection is produced by the current.

The needle is often placed above or below the coil so as only to receive

a portion of its effect, enough for all practical purposes in the

commoner class of instruments.

The galvanometer was invented by Schweigger a short time after Oersted's

discovery, q. v.

Galvanometer, Absolute.

A galvanometer giving absolute readings; properly one whose law of

calibration can be deduced from its construction. Thus the diameter of

the coil, and the constants and position of a magnetic needle suspended

in its field being known, the current intensity required to deflect the

needle a given number of degrees could be calculated.

Galvanometer, Aperiodic.

A galvanometer whose needle is damped (see Damping) as, for instance, by

the proximity of a plate of metal, by an air vane or otherwise, so that

it reaches its reading with hardly any oscillation. A very light needle

and a strong magnetic field also conduce to vibrations of short period

dying out very quickly. Such galvanometers are termed "dead-beat." No

instrument is absolutely dead-beat, only relatively so.

267  STANDARD ELECTRICAL DICTIONARY.

Fig. 178. ASTATIC GALVANOMETER.

Galvanometer, Astatic.

A galvanometer with a pair of magnetic needles connected astatically, or

parallel with their poles in opposition. (See Astatic Needle.) Each

needle has its own coil, the coils being wound in opposite directions so

as to unite in producing deflections in the same sense. As there should

be some directive tendency this is obtained by one of the magnets being

slightly stronger than the other or by the proximity of a fixed and

adjustable controlling magnet, placed nearer one needle than the other.

For small deflections the currents producing them are proportional to

their extent.

Galvanometer, Ballistic.

A galvanometer whose deflected element has considerable moment of

inertia; the exact opposite of an aperiodic or dead beat galvanometer.

(See Galvanometer, Aperiodic.) All damping by air vanes or otherwise

must be carefully done away with.

Fig. 179. SIEMENS & HALSKE'S GALVANOMETER.

Siemens & Halske's galvanometer is of the reflecting or mirror type (see

Galvanometer, Reflecting) with suspended, bell-shaped magnet, in place

of the ordinary magnetic needle, or astatic combination of the lightest

possible weight in the regular instrument. A copper ball drilled out to

admit the magnet is used as damper in the ordinary use of the

instrument. To convert it into a ballistic galvanometer the copper ball

is removed. The heavy suspended magnet then by its inertia introduces

the desired element into the instrument.

268   STANDARD ELECTRICAL DICTIONARY.

Referring to the cut, Fig. 179, M is the suspended magnet, with north

and south poles n and s; S is the reflecting mirror; r is the tube

containing the suspending thread; R is the damper removed for ballistic

work.

The ballistic galvanometer is used to measure quantities of electricity

in an instantaneous discharge, which discharge should be completed

before the heavy needle begins to move. The extreme elongation or throw

of the needle is observed, and depends (1) on the number of coulombs (K)

that pass during the discharge; (2) on the moment of inertia of the

needle and attached parts; (3) on the moment of the controlling forces,

i. e., the forces tending to pull the needle back to zero; (4) on the

moment of the damping forces; (5) on the moment of the deflecting forces

due to a given constant current. The formula is thus expressed:

K = (P / PI ) * A * sin( kº / 2 ) / tan( aº )

in which K = coulombs discharged; P = periodic time of vibration of

needle; A = amperes producing a steady deflection equal to  aº  ; kº =

first angular deflection of needle. For accuracy kº and aº should both

be small and the damping so slight as to be negligible. Otherwise a

correction for the latter must be applied. For approximate work for kº

and aº the deflections read on the scale may be used with the following

formula:

K = (P / PI ) * ( A / 2 ) * ( kº / aº )

Galvanometer Constant.

Assume a galvanometer with a very short needle and so placed with

respect to its coils that the magnetic field produced by a current

circulating in them is sensibly uniform in the neighborhood of the

needle, with its lines of force at right angles thereto. The field is

proportional to the current i, so that it may be denoted by G i. Then G

is the galvanometer constant. If now the angle of deflection of the

needle is ? against the earth's field H, M being the magnetic moment of

the needle we have G i M cos ? = H M sin ? or i = (H/G)* tan ?. H/G is

the reduction factor; variable as H varies for different places.

For a tangent galvanometer the constant G is equal to  2*PI*(n/a), in

which n denotes the number of turns of wire, and a denotes the radius of

the circle.

Galvanometer, Differential.

A galvanometer in which the needle is acted on by two coils wound in

opposition, each of equal deflecting action and of equal resistance. If

a current is divided between two branches or parallel conductors, each

including one of the coils, when the needle points to zero the

resistances of the two branches will bc equal. In the cut, C C'

represent the coils, and A and B the two leads into which the circuit, P

Q, is divided.

269  STANDARD ELECTRICAL DICTIONARY.

Fig. 180. THEORY OF DIFFERENTIAL GALVANOMETER.

Fig. 181. DIFFERENTIAL GALVANOMETER.

Galvanometer, Direct Reading.

A calibrated galvanometer, whose scale is graduated by volts or amperes,

instead of degrees.

Galvanometer, Marine. (Sir William Thomson's.)

A galvanometer of the reflecting type, for use on shipboard. A fibre

suspension is adopted for the needle. The fibre is attached to a fixed

support at one end and to a spring at the other, and the needle is

suspended by its centre of gravity. This secures it to a considerable

extent from disturbance due to the rolling of the ship. A thick iron box

encloses the needle, etc., to cut off any magnetic action from the ship.

(See Galvanometer, Reflecting.)

Galvanometer, Potential.

A galvanometer wound with fine German silver wire to secure high

resistance used for determination of potential difference.

Galvanometer, Proportional.

A galvanometer so constructed that the deflections of its index are

proportional to the current passing. It is made by causing the

deflecting force to increase as the needle is deflected, more and more,

or by causing the restitutive force to diminish under like conditions,

or by both. The condition is obtained in some cases by the shape and

position of the deflecting coils.

Galvanometer, Quantity.

A galvanometer for determining quantities of electricity, by the

deflections produced by discharging the quantities through their coils.

It is a ballistic galvanometer with very little or no damping.

270   STANDARD ELECTRICAL DICTIONARY.

Fig. 182. PRINCIPLE OF REFLECTING GALVANOMETER.

Fig. 183. REFLECTING GALVANOMETER.

Galvanometer, Reflecting.

A galvanometer the deflections of whose needle are read by an image

projected by light reflected from a mirror attached to the needle or to

a vertical wire carrying the needle. A lamp is placed in front of the

instrument facing the mirror. The light of the lamp is reflected by the

mirror upon a horizontal scale above the lamp. An image of a slit or of

a wire may be caused thus to fall upon the scale, the mirror being

slightly convex, or a lens being used to produce the projection.

271  STANDARD ELECTRICAL DICTIONARY.

If the mirror swings through a horizontal arc, the reflected image will

move, in virtue of a simple geometrical principle, through an arc of

twice as many degrees. The scale can be placed far from the mirror, so

that the ray of light will represent a weightless index of very great

length, and minute deflections of the needle will be shown distinctly

upon the scale.

In the cut, Fig. 182, the ray of light from the lamp passes through the

aperture, m m, and is made parallel by the lens, L. At s is the mirror

attached to the needle and moving with it. A scale placed at t receives

the reflection from the mirror. The cut, Fig. 183, shows one form of the

instrument set up for use.

Synonym--Mirror Galvanometer.

Galvanometer Shunt.

To prevent too much current passing through a galvanometer (for fear of

injury to its insulation) a shunt is sometimes placed in parallel with

it. The total current will be distributed between galvanometer and shunt

in the inverse ratio of their respective resistances. (See Multiplying

Power of a Shunt.)

272   STANDARD ELECTRICAL DICTIONARY.

Fig. 184. SINE GALVANOMETER.

Galvanometer, Sine.

A galvanometer whose measurements depend upon the sine of the angle of

deflection produced when the coil and needle lie in the same vertical

plane.

The needle, which may be a long one, is surrounded by a coil, which can

be rotated about a vertical axis passing through the point of suspension

of the needle. Starting with the needle at rest in the plane of the

coil, a current is passed through the coil deflecting the needle, the

coil is swung around deflecting the needle still more, until the needle

lies in the plane of the coil; the intensity of the current will then be

in proportion to the sine of the angle through which the coil and needle

move.

In the galvanometer M is a circle carrying the coil, N is a scale over

which the needles, m and n, move, the former being a magnetic needle,

the latter an index at right angles and attached thereto; a and b are

wires carrying the current to be measured. The circles, M and N, are

carried by a base, O, around which they rotate. H is a fixed horizontal

graduated circle. In use the circle, M, is placed in the magnetic

meridian, the current is passed through the coil, M; the needle is

deflected; M is turned until its plane coincides with the direction of

the needle, m. The current strength is proportional to the sine of the

angle of deflection. This angle is measured by the vernier, C, on the

circle, H. The knob, A, is used to turn the circle, M.

273  STANDARD ELECTRICAL DICTIONARY.

Fig. 185. TANGENT GALVANOMETER.

Galvanometer, Tangent.

A galvanometer in which the tangents of the angles of deflection are

proportional to the currents producing such deflections.

For this law to apply the instrument in general must fulfill the

following conditions:

(1) The needle must be controlled by a uniform magnetic field such as

that of the earth;

(2) the diameter of the coil must be large compared to the length of the

needle;

(3) the centre of suspension of the needle must be at the centre of the

coil;

(4) the magnetic axis of the needle must lie in the plane of the coil

when no current is passing.

If a single current strength is to be measured the best results will be

attained when the deflection is 45°; in comparing two currents the best

results will be attained when the deflections as nearly as possible are

at equal distances on both sides of 45°.

The needle should not exceed in length one-tenth the diameter of the

coil.

For very small deflections any galvanometer follows the law of

tangential deflection.

As for very small deflections the tangents are practically equal to the

arcs subtended, for such deflections the currents are proportional to

the deflections they produce.

The sensibility is directly proportional to the number of convolutions

of wire and inversely proportional to their diameter.

The tangent law is most accurately fulfilled when the depth of the coil

in the radial direction is to the breadth in the axial direction as

squareRoot(3):squareRoot(2), or about as 11:9.

Galvanometer, Torsion.

A galvanometer whose needle is suspended by a long filament or by a

thread and spiral spring against whose force of torsion the movements of

the needle are produced. The current strength is determined by bringing

the needle back to its position of rest by turning a hand-button or

other arrangement. The angle through which this is turned gives the

angle of torsion. From this the current strength is calculated on the

general basis that it is proportional to the angle of torsion.

Fig. 186. TORSION GALVANOMETER.

274   STANDARD ELECTRICAL DICTIONARY.

Galvanometer, Vertical.

A galvanometer whose needle is mounted on a horizontal axis and is

deflected in a vertical plane. One of the poles is weighted to keep it

normally vertical, representing the control. It is not used for accurate

work.

Synonym--Upright Galvanometer.

Fig. 187. VERTICAL GALVANOMETER.

Galvanometer, Volt- and Ampere-meter.

A galvanometer of Sir William Thomson's invention embodying the tangent

principle, and having its sensibility adjustable by moving the magnetic

needle horizontally along a scale (the "meter") towards or away from the

coil. A curved magnet is used to adjust the control. The leads are

twisted to prevent induction.

The instrument is made with a high resistance coil for voltage

determinations, and with a low resistance coil for amperage

determinations.

At one end of a long base board a vertical coil with its plane at right

angles to the axis of the board is mounted. A scale (the "meter" of the

name) runs down the centre of the board. A groove also runs down the

centre. The magnetic needle is contained in a quadrant-shaped

glass-covered box which slides up and down the groove. A number of short

parallel needles mounted together, with an aluminum pointer are used.

Fig. 188. SIR WILLIAM THOMSON'S

AMPERE-METER GALVANOMETER.

275   STANDARD ELECTRICAL DICTIONARY.

In the cut P is the base board, M is a glass covered case containing the

magnetic needle, and sliding along the base board, being guided by the

central groove, C, is the coil. Between the coil and the needle is the

arched or bent controlling magnet. The long twisted connecting wires are

seen on the right hand.

Galvano-plastics.

The deposition of metals by electrolysis, a disused term replaced

by electro-deposition, electroplating, and electro-metallurgy.

Galvano-puncture.

An operation in medical electricity. (See Electro-puncture.)

Galvanoscope.

An instrument, generally of the galvanometer type, used for ascertaining

whether a current is flowing or not. Any galvanoscope, when calibrated,

if susceptible thereof, becomes a galvanometer.

Gas, Electrolytic.

Gas produced by the decomposition, generally of water, by electrolysis.

It may be hydrogen or oxygen, or a mixture of the two, according to how

it is collected. (See Gases, Mixed.)

Gases, Mixed.

The mixture of approximately one volume of oxygen and two volumes of

hydrogen collected in the eudiometer of a gas voltameter or other

electrolytic apparatus.

Gassing.

The evolution of gas from the plates of a storage battery in the

charging process, due to too high voltage in the circuit of the charging

dynamo.

Gastroscope.

An apparatus for illuminating by an incandescent lamp the interior of

the stomach, and with prisms to refract the rays of light so that the

part can be seen. The stomach is inflated with air, if desirable, to

give a better view. An incandescent platinum spiral in a water jacket

has been employed for the illumination.

Gassiot's Cascade.

A goblet lined for half its interior surface with tinfoil. It is placed

in the receiver of an air pump from the top of whose bell a conductor

descends into it, not touching the foil. On producing a good

rarefaction, and discharging high tension electricity from between the

conductor just mentioned and the metal of the machine, a luminous effect

is produced, as if the electricity, pale blue in color, was overflowing

the goblet.

Gauss.

A name suggested for unit intensity of magnetic field. Sylvanus P.

Thomson proposed for its value the intensity of a field of 1E8 C. G. S.

electro-magnetic units. J. A. Fleming proposed the strength of field

which would develop one volt potential difference in a wire 1E6

centimeters long, moving through such field with a velocity of one

centimeter per second. This is one hundred times greater than Thomson's

standard. Sir William Thomson suggested the intensity of field produced

by a current of one ampere at a distance of one centimeter

The gauss is not used to any extent; practical calculations are based on

electro-magnetic lines of force.

276   STANDARD ELECTRICAL DICTIONARY.

Gauss' Principle.

An electric circuit acts upon a magnetic pole in such a way as to make

the number of lines of force that pass through the circuit a maximum.

Fig. 189. GAUSS' TANGENT POSITION.

Gauss, Tangent Positions of.

The "end on" and "broadside" methods of determining magnetization

involve positions which have been thus termed. (See Broadside Method and

End on Method.)

Gear, Magnetic Friction.

Friction gear in which the component wheels are pressed against each

other by electromagnetic action. In the cut, repeated from Adherence,

Electro-magnetic, the magnetizing coil makes the wheels, which are of

iron, press strongly together.

Fig. 190. MAGNETIC FRICTION GEAR.

277   STANDARD ELECTRICAL DICTIONARY.

Geissler Tubes.

Sealed tubes of glass containing highly rarefied gases, and provided

with platinum electrodes extending through the glass tightly sealed as

they pass through it, and often extending a short distance beyond its

interior surface.

On passing through them the static discharge luminous effects are

produced varying with the degree of exhaustion, the contents (gas), the

glass itself, or solutions surrounding it. The two latter conditions

involve fluorescence phenomena often of a very beautiful description.

The pressure of the gas is less than one-half of a millimeter of

mercury. If a complete vacuum is produced the discharge will not pass.

If too high rarefaction is produced radiant matter phenomena (see

Radiant State) occur.

Geissler tubes have been used for lighting purposes as in mines, or for

illuminating the interior cavities of the body in surgical or medical

operations.

Generating Plate.

The positive plate in a voltaic couple, or the plate which is dissolved;

generally a plate of zinc.

Synonyms--Positive Plate--Positive Element.

Generator, Current.

Any apparatus for maintaining an electric current. It may be as regards

the form of energy it converts into electrical energy, mechanical, as a

magneto or dynamo electric machine or generator; thermal, as a

thermo-electric battery; or chemical, as a voltaic battery; all of which

may be consulted.

Generator, Secondary.

A secondary or storage battery. (See Battery, Secondary.)

German Silver.

An alloy of copper, 2 parts, nickel, 1 part, and zinc, 1 part. Owing to

its high resistance and moderate cost and small variation in resistance

with change of temperature, it is much used for resistances. From Dr.

Mathiessen's experiment the following constants are deduced in legal

ohms:

Relative Resistance (Silver = 1),      13.92

Specific Resistance at 0° C. (32F.),   20.93 microhms.

Resistance of a wire,

(a) 1 foot long, weighing 1 grain,      2.622   ohms.

1 foot long, 1/1000 inch thick,       125.91     "

1 meter long, weighing 1 gram,          1.830    "

1 meter long, 1 millimeter thick,       0.2666   "

Resistance of a 1 inch cube at 0°C. (32° F.),   8.240 microhms.

Approximate percentage increase of resistance per 1° C. (1.8° F.) at

about 20° C. (68° F.), 0.044 per cent.

Gilding, Electro-.

The deposition of gold by an electric current, or electrolytically in

the electroplating bath.

Gilding Metal.

A special kind of brass, with a high percentage of copper, used to make

objects which are to be gilded by electrolysis.

278   STANDARD ELECTRICAL DICTIONARY.

Gimbals.

A suspension used for ships' compasses and sometimes for other

apparatus. It consists of a ring held by two journals, so as to bc free

to swing in one plane. The compass is swung upon this ring, being placed

concentrically therewith. Its journals are at right angles to those of

the ring. This gives a universal joint by which the compass, weighted

below its line of support, is always kept horizontal.

Fig. 191. COMPASS SUSPENDED IN GIMBALS.

Glass.

A fused mixture of silicates of various oxides. It is of extremely

varied composition and its electric constants vary greatly. Many

determinations of its specific resistance have been made. For flint

glass at 100° C. (212° F.) about (2.06E14) ohms --at 60° C (140° F.)

(1.020E15) (Thomas Gray) is given, while another observer (Beetz) gives

for glass at ordinary temperatures an immeasurably high resistance. It

is therefore a non-conductor of very high order if dry. As a dielectric

the specific inductive capacity of different samples of flint glass is

given as 6.57--6.85--7.4--10.1 (Hopkinson), thus exceeding all other

ordinary dielectrics. The densest glass, other things being equal, has

the highest specific inductive capacity.

Gold.

A metal, one of the elements; symbol Au. c .; atomic weight, 196.8;

equivalent, 65.6; valency, 3; specific gravity 19.5.

It is a conductor of electricity.

Annealed.   Hard drawn.

Relative Resistance (Annealed Silver = 1),   1.369       1.393

Specific Resistance,                         2.058       2.094

Resistance of a wire at 0° C. (32°F.)

(a) 1 foot long, weighing 1 grain,          57.85     58.84   ohms

(b) 1 foot long, 1/1000 inch thick,         12.38     12.60    "

(c) 1 meter long, weighing 1 gram,            .4035     .4104  "

(d) 1 meter long, 1 millimeter thick,         .02620    .02668 "

Resistance of a 1 inch cube at 0° C.(32° F.)  .8102     .8247

Approximate increase in resistance per 0° C., (1.8° F)

at about 20° C. (68° F.), 0.365 per cent.

Electro-chemical equivalent (Hydrogen = .0105), .6888

279   STANDARD ELECTRICAL DICTIONARY.

Gold Bath.

A solution of gold used for depositing the metal in the electroplating

process.

A great number of formulae have been devised, of which a few

representative ones are given here.

COLD BATHS.            HOT BATHS.

Water,               10,000  10,000  10,000  10,000   5,000  3,000

Potassium Cyanide,      200      --     200      10      --     50

Gold,                   100      15     100      10      10     10

Potassium Ferrocyanide,  --     200      --      --     150     --

Potassium Carbonate,     --     150      --      --      50     --

Ammonium Chloride,       --      30      --      --      20     --

Aqua Ammoniae,           --      --     500      --      --     --

Sodium Phosphate,        --      --      --     600      --     --

Sodium Bisulphite,       --      --      --     100      --     --

(Roseleur.)

In the baths the gold is added in the form of neutral chloride, Auric

chloride (Au Cl6).

Gold Stripping Bath.

A bath for removing gold from plated articles without dissolving the

base in order to save the precious metal. A bath of 10 parts of

potassium cyanide and 100 parts of water may be used, the articles to be

stripped being immersed therein as the anode of an active circuit. If

the gilding is on a silver or copper basis, or on an alloy of these

metals the same solution attacks the base and dissolves it, which is

objectionable. For silver articles it is enough to heat to cherry red

and throw into dilute sulphuric acid. The gold scales off in metallic

spangles. For copper articles, a mixture of 10 volumes concentrated

sulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acid

may be used by immersion only, or with a battery. The sulphuric acid in

such large excess is supposed to protect the copper. For copper articles

concentrated sulphuric acid alone with the battery may be used. This

does not sensibly attack the copper if it is not allowed to become

diluted. Even the dampness of the air may act to dilute it.

Graduator.

Apparatus for enabling the same line to be used for telegraph signals

and telephoning.

One type consists in coils with iron cores or simply electromagnets.

These act to retard the current in reaching its full power and also

prolong it. This gives a graduated effect to the signals, so that the

telephone diaphragm is not audibly affected by the impulses.

The telephoning current is so slight and so rapid in its characteristic

changes that it is without effect upon the ordinary telegraph.

280   STANDARD ELECTRICAL DICTIONARY.

Gram.

The unit of weight in the metric system; accepted as the unit of

mass in the absolute of C. G. S. system of units. It is the

one-thousandth part of mass of a standard weight preserved under proper

conditions in Paris, and supposed to be the mass of a cubic decimeter of

distilled water at the temperature of the maximum density of water. The

standard is the kilogram; the temperature is 3.9º C. (39º F.). The

standard kilogram is found to be not exactly the weight of a cubic

decimeter of water, the latter weighing 1.000013 kilogram.

If therefore the defined gram on the water basis is taken as the unit it

varies very slightly from the accepted gram.

1 gram is equal to 15.43234874 grains. (Prof. W. H. Miller.)

Gram-atom.

The number of grams of an element equal numerically to the atomic

weight, as 16 grams of oxygen, 1 gram of hydrogen, 35.5 grams of

chlorine; all which might be expressed as gram-atoms of oxygen, hydrogen

and chlorine respectively.

The gram-atom approximately expresses the number of gram-calories

required to heat one gram of the substance 1º C. (1.8º F.). This is in

virtue of Dulong and Petit's discovery that the atomic weight of an

element multiplied by its specific heat gives approximately a constant

for all elements.

[Transcriber's note: A gram-atom is the mass, in grams, of one mole of

atoms in a monatomic element. A mole consists of Avogadro's number of

atoms, approximately 6.02214E23.]

Gram-molecule.

The number of grams of a substance equal numerically to its molecular

weight.

Graphite.

Carbon; one of three allotropic modifications of this element. It occurs

in nature as a mineral.

It is used as a lubricant for machinery; for commutator brushes; for

making surfaces to be plated conductive, and for mixing with manganese

binoxide in Leclanché cells.

Gravitation.

A natural force which causes all masses of matter to attract each other.

Its cause is unknown; it is often supposed to be due to the luminiferous

ether.

[Transcriber's note: Einstein's explanation of gravity, General

Relativity and the curvature of space-time, came 23 years later, 1915.]

281  STANDARD ELECTRICAL DICTIONARY.

Gravity, Acceleration of.

The velocity imparted to a body in one second by the action of

gravitation at any standard point upon the earth's surface in a vacuum.

This will vary at different places, owing principally to the variation

in centrifugal force due to the earth's rotation. For standard valuation

it must be reduced to sea level. The following are examples of its

variation:

Equator,          978.1028       centimeters per second

Paris,            980.94                   "

Greenwich         981.I7                   "

Edinburgh,        981.54                   "

Pole (N. or S.),  983.1084 (theoretical)   "

As round numbers for approximate calculations 981 centimeters or 32.2

feet may be employed.

[Transcriber's note: The acceleration of gravity at the equator is also

reduced by the increased distance from the center of the earth

(equatorial bulge). Increased altitude reduces gravity. Reduced air

density at altitude reduces buoyancy and increases apparent weight.

Local variations of rock density affects gravity.]

Gravity, Control.

Control by weight. In some ammeters and voltmeters gravity is the

controlling force.

Grid.

A lead plate perforated or ridged for use in a storage battery as the

supporter of the active materials and in part as contributing thereto

from its own substance.

Ground.

The contact of a conductor of an electric circuit with the earth,

permitting the escape of current if another ground exists.

Ground-wire.

A metaphorical term applied to the earth when used as a return circuit.

Fig. 192. GROVE'S GAS BATTERY.

Grove's Gas Battery.

A voltaic battery depending for its action on the oxidation of hydrogen

instead of the oxidation of zinc. Its action is more particularly

described under Battery, Gas. In the cut B, B1 * * * are the terminals

of the positive or hydrogen electrodes, marked H, and A, Al * * * are

the terminals of the negative or oxygen electrodes marked O, while M, M1

* * * is dilute sulphuric acid.

282   STANDARD ELECTRICAL DICTIONARY.

Guard Ring.

An annular horizontal surface surrounding the balanced disc in the

absolute electrometer. (See Electrometer, Absolute.)

Guard Tube.

A metal tube surrounding a dry pile used with a quadrant electrometer,

or other electrometers of that type. It prevents the capacity of the

lower brass end of the pile (which brass end closes the glass tube

containing the discs) from momentary change by approach of some

conductor connected to the earth. There are other guard tubes also.

Gun, Electro-magnetic.

An electro-magnet with tubular core. If, when it is excited a piece of

an iron rod is pushed into the central aperture of the core and is

released, the magnetic circle will try to complete itself by pushing the

rod out so that it can thus be discharged, as if from a popgun.

Synonym--Electric Popgun.

Fig. 193. "ELECTRIC POPGUN."

Gutta Percha.

The hardened milky juice of a tree, the Isonandra gutta, growing in

Malacca and other parts of the Eastern Archipelago. It is much used as

an insulator or constituent of insulators.

Resistance after several minutes electrification per 1 centimeter cube

at 54º C. (75º F.),  4.50E14 ohms.

The specific resistance varies--from 2.5E13 to 5.0E14 ohms. A usual

specification is 2.0E14 ohms. The influence of temperature on its

resistance is given in Clark & Bright's empirical formula, R = R0 at, in

which R is the resistance at temperature tº C--Ro the resistance at 0º C

(32º F), a is the coefficient .8944.

The resistance increases with the time of passage of the current, the

variation being less the higher the temperature.

283   STANDARD ELECTRICAL DICTIONARY.

Time of            Relative Resistance     Relative Resistance

Electrification.   at 0º C (32º F.)        at 24º C (75º F.)

1 minute        100                     5.51

2   "           127.9                   6.

5   "           163.1                   6.66

10   "           190.9                   6.94

20   "           230.8                   7.38

30   "           250.6                   7.44

60   "           290.4                   7.6

90   "           318.3                   7.66

In cable testing one minute is generally taken as the time of

electrification.

Pressure increases the resistance by the formula Rp=R (1+ .00327 P) in

which Rp is the resistance at pressure p--R resistance at atmospheric

pressure--p pressure in atmospheres. Thus in the ocean at a depth of

4,000 meters (2.4855 miles), the resistance is more than doubled. The

longer the pressure is applied, the greater is the resistance.

The specific inductive capacity of gutta percha is 4.2.

Good gutta percha should not break when struck with a hammer, should

recover its shape slowly, and it should support much more than 300 times

its own weight.

Gyrostatic Action of Armatures.

Owing to gyrostatic action a rotating armature resists any change of

direction of its axis. On ships and in railway motors which have to turn

curves this action occurs. A 148 lb. armature running at 1,300

revolutions per minute may press with 30 lbs. on each journal as the

ship rolls through an angle of 20° in 16 seconds.

283   STANDARD ELECTRICAL DICTIONARY.

H.

(a) The symbol for the horizontal component of the earth's

magnetization.

(b) The symbol for the intensity of a magnetizing force or field. The

symbol H, as it is generally used, may mean either the number of dynes

which act upon a unit pole, or the number of lines of force per

centimeter.

(c) The symbol for the unit of self-induction.

Hair, Removal of, by Electrolysis.

A method of depilation by destruction of individual hair follicles by

electrolysis.

A fine platinum electrode is thrust into a hair follicle. It is the

negative electrode. The positive electrode is in contact with the body

of the person under treatment; it is often a sponge electrode simply

held in his hand. A current of two to four milliamperes from an E. M. F.

of 15 to 20 volts, is passed. This destroys the follicle, the hair is

removed and never grows again. A gradual increase of current is advised

for the face. As only one hair is removed at once, but a small number

are taken out at a sitting.

284  STANDARD ELECTRICAL DICTIONARY.

Haldat's Figures.

With a pole of a strong bar magnet, used like a pencil, imaginary

figures are drawn upon a hard steel plate, such as a saw-blade. The

pattern is gone over several times. By dusting iron filings on a sheet

of paper laid over the steel plate, while horizontal, very complicated

magnetic figures are produced.

Hall's Experiment.

A cross of thin metal, such as gold leaf, is secured upon a pane of

glass. To two opposite arms a battery is connected in circuit with them.

To the other two arms a galvanometer is connected in circuit. If the

cross is put into a field of force whose lines are perpendicular

thereto, the galvanometer will disclose a constant current. The current

is pushed, as it were, into the galvanometer circuit. Other metals have

been used with similar results. They must be thin or the experiment

fails. If the arm receiving the battery current is horizontal, and if it

flows from left to right, and if the lines of force go from downward

through the cross, the current in the galvanometer circuit will flow

from the observer through the other arms of the cross, if the cross is

of gold, silver, platinum or tin, and the reverse if of iron. The

experiment has indicated a possible way of reaching the velocity of

electricity in absolute measure.

Hall Effect.

The effect observed in Hall's experiment, q. v.

Hall Effect, Real.

A transverse electro-motive force in a conductor through which a current

is passing produced by a magnetic field.

Hall Effect, Spurious.

A spurious electro-motive force produced in a conductor, through which a

current is passing by changes in conductivity of the conductor brought

about by a magnetic field.

Hanger Board.

A board containing two terminals, a suspending hook, and a switch, so

that an arc lamp can be introduced into a circuit thereby, or can be

removed as desired.

Harmonic Receiver.

A receiver containing a vibrating reed, acted on by an electro-magnet.

Such a reed answers only to impulses tuned to its own pitch. If such are

received from the magnet it will vibrate. Impulses not in tune with it

will not affect it. (See Telegraph, Harmonic.)

Head Bath, Electric.

A fanciful name for an electro-medical treatment of the head. The

patient is insulated by an insulating stool or otherwise. His person is

connected with one terminal of an influence machine. An insulated

metallic circle, with points of metal projecting inward or downward, is

placed about the head. The circle is connected with the other pole of

the machine. On working it a silent or brush discharge with air

convection streams occurs between the patient's head and the circle of

points.

285   STANDARD ELECTRICAL DICTIONARY.

Head-light, Electric.

An electric head-light for locomotives has been experimented with. It

includes the parabolic reflection of the regular light with an arc-lamp

in place of the oil lamp. An incandescent lamp may be used in the same

place, but has no great advantage over oil as regards illuminating

power.

Heat.

A form of kinetic energy, due to a confused oscillatory movement of the

molecules of a body. Heat is not motion, as a heated body does not

change its place; it is not momentum, but it is the energy of motion. If

the quantity of molecular motion is doubled the momentum of the

molecules is also doubled, but the molecular mechanical energy or heat

is quadrupled.

As a form of energy it is measured by thermal units. The calorie is the

most important, and unfortunately the same term applies to two units,

the gram-degree C. and the kilogram-degree C. (See Calorie.) Calories

are determined by a calorimeter, q. v.

Independent of quantity of heat a body may be hotter or colder.

Thermometers are used to determine its temperature.

Heat is transmitted by conduction, a body conducting it slowly for some

distance through its own substance. Bodies vary greatly in their

conductivity for heat. It is also transmitted by convection of gases or

liquids, when the heated molecules traveling through the mass impart

their heat to other parts. Finally it is transmitted by ether waves with

probably the speed of light. This mode of transmission and the phenomena

of it were attributed to radiant heat. As a scientific term this is now

dropped by many scientists. This practice very properly restricts the

term "heat" to kinetic molecular motion.

The mechanical equivalent of heat is the number of units of work which

the energy of one unit quantity of heat represents. (See Equivalents,

Mechanical and Physical.)

Heat, Atomic.

The product of the specific heat of an element by its atomic weight. The

product is approximately the same for all the elements, and varies as

determined between 5.39 and 6.87. The variations are by some attributed

principally to imperfection of the work in determining them. The atomic

heat represents the number of gram calories required to raise the

temperature of a gram atom (a number of grams equal numerically to the

atomic weight) one degree centigrade.

286   STANDARD ELECTRICAL DICTIONARY.

Heat, Electric.

This term has been given to the heat produced by the passage of a

current of electricity through a conductor. It is really electrically

produced heat, the above term being a misnomer.

The rise of temperature produced in a cylindrical conductor by a current

depends upon the diameter of the conductor and on the current. The

length of the wire has only the indirect connection that the current

will depend upon the resistance and consequently upon its length.

The quantity of heat produced in a conductor by a current is in

gram-degree C. units equal to the product of the current, by the

electro-motive force or potential difference maintained between the ends

of the wire, by .24.

The cube of the diameter of a wire for a given rise of temperature

produced in such conductor by a current is equal approximately to the

product of the square of the current, by the specific resistance (q. v.)

of the material of the conductor, by .000391, the whole divided by the

desired temperature in centigrade units.

Heat, Electrical Convection of.

A term applied to the phenomena included under the Thomson effect, q.

v., the unequal or differential heating effect produced by a current of

electricity in conductors whose different parts are maintained at

different temperatures.

Heater, Electric.

An apparatus for converting electrical energy into thermal energy.

An incandescent lamp represents the principle, and in the Edison meter

has been used as such to maintain the temperature of the solutions.

Heaters for warming water and other purposes have been constructed,

utilizing conductors heated by the passage of the current as a source of

heat. (See also Heating Magnet.)

Heating Error.

In voltmeters the error due to alteration of resistance of the coil by

heating. If too strong a current is sent through the instrument, the

coils become heated and their resistance increased. They then do not

pass as much current as they should for the potential difference to

which they may be exposed. Their readings then will be too low. One way

of avoiding the trouble is to have a key in circuit, and to pass only an

instantaneous or very brief current through the instrument and thus get

the reading before the coils have time to heat.

The heating error does not exist for ammeters, as they are constructed

to receive the entire current, and any heating "error" within their

range is allowed for in the dividing of the scale.

Heating Magnet.

An electro-magnet designed to be heated by Foucault currents induced in

its core by varying currents in the windings. It has been proposed as a

source of artificial heat, a species of electric heating apparatus for

warming water, or other purposes.

287   STANDARD ELECTRICAL DICTIONARY.

Heat, Irreversible.

The heat produced by an electric current in a conductor of identical

qualities and temperature throughout. Such heat is the same whatever the

direction of the current. The heating effect is irreversible because of

the absence of the Thomson effect, q. v.) or Peltier effect, q. v.

Heat, Mechanical Equivalent of.

The mechanical energy corresponding to a given quantity of heat energy.

Mechanical energy is generally represented by some unit of weight and

height, such as the foot-pound; and heat energy is represented by a

given weight of water heated a given amount, such as a pound-degree

centigrade. Joule's equivalent is usually accepted; it states that

772.55 foot pounds of mechanical energy are equivalent to 1 pound-degree

F. (one pound avds. of water raised in temperature one degree

Fahrenheit). Other equivalencies have also been deduced.

Heat, Molecular.

The product of a specific heat of the compound by its molecular weight.

It is approximately equal to the sum of the atomic heats of its

constituent elements.

The molecular heat represents the number of gram calories required to

raise the temperature of a gram-molecule (a number of grams equal

numerically to the molecular weight) one degree centigrade.

The molecular heat is approximately equal for all substances.

Heat, Specific.

The capacity of a body for heat; a coefficient representing the relative

quantity of heat required to raise the temperature of an identical

weight of a given body a defined and identical amount.

The standard of comparison is water; its specific heat is taken as

unity. The specific heats by weight of other substances are less than

unity. The specific heat varies with the temperature. Thus the specific

heat of water is more strictly 1+.00015 tº C.

Specific heat is greater when a substance is in the liquid than when it

is in the solid state. Thus the specific heat of ice is 0.489; less

than half that of water. It differs with the allotropic modifications of

bodies; the specific heat of graphite is .202; of diamond, .147.

The product of the specific heat by the atomic weight of elements gives

a figure approximately the same. A similar law applies in the case of

molecules. (See Heat, Atomic-Heat, Molecular.)

The true specific heat of a substance should be separated from the heat

expended in expanding a body against molecular and atomic forces, and

against the atmospheric pressure. So far this separation has not been

possible to introduce in any calculations.

288   STANDARD ELECTRICAL DICTIONARY.

Heat, Specific, of Electricity.

A proposed term to account for the heat absorbed or given out in

unhomogeneous conductors, by the Thomson effect, or Peltier effect (see

Effect, Thomson--Effect, Peltier.) If a current of electricity be

assumed to exist, then under the action of these effects it may be

regarded as absorbing or giving out so many coulombs of heat, and thus

establishing a basis for specific heat.

Heat Units.

The British unit of heat is the pound degree F--the quantity of heat

required to raise the temperature of a pound of water from 32° to 33° F.

The C. G. S. unit is the gram-degree C.; another metric unit is the

kilogram-degree C. The latter is the calorie; the former is sometimes

called the small calorie or the joule; the latter is sometimes called

the large calorie. The term joule is also applied to a quantity of heat

equivalent to the energy of a watt-second or volt-coulomb. This is equal

to .24l gram degree calorie.

Hecto.

A prefix to terms of measurement--meaning one hundred times, as

hectometer, one hundred meters.

Heliograph.

An apparatus for reflecting flashes of light to a distant observer. By

using the Morse telegraph code messages may thus be transmitted long

distances. When possible the sun's light is used.

Helix.

A coil of wire; properly a coil wound so as to follow the outlines of a

screw without overlaying itself.

Fig. 194. LEFT-HANDED HELIX.

Fig. 195. RIGHT-HANDED HELIX.

Henry.

The practical unit of electro-magnetic or magnetic inductance. It is

equal to 1E9 C. G. S., or absolute units of inductance. As the

dimensions of inductance are a length the henry is equal to 1E9

centimeters, or approximately to one quadrant of the earth measured on

the meridian.

Synonyms--Secohm--Quadrant--Quad.

289   STANDARD ELECTRICAL DICTIONARY.

Hermetically Sealed.

Closed absolutely tight. Glass vessels, such as the bulbs of

incandescent lamps, are hermetically sealed often by melting the glass

together over any opening into their interior.

Heterostatic Method.

A method of using the absolute or attracted disc electrometer. (See

Electrometer Absolute.) The formula for its idiostatic use, q. v.,

involves the determination of d, the distance between the suspended and

fixed discs. As this is difficult to determine the suspended disc and

guard ring may be kept at one potential and the lower fixed disc is then

connected successively with the two points whose potential difference is

to be determined. Their difference is determined by the difference

between d and d', the two distances between the discs. This difference

is the distance through which the micrometer screw is moved. The

heterostatic formula is:

V' - V = (d' - d)* squareRoot( 8*PI*F / S )

in which V and V' are potentials of the two points; d' and d the two

distances between the discs necessary for equilibrium; S the area of the

disc and F the force of attraction in dynes. (See Idiostatic Method.)

High Bars of Commutator.

Commutator bars, which in the natural wear of the commutator, project

beyond the others. The surface then requires turning down, as it should

be quite cylindrical.

High Frequency.

A term used as a noun or as an adjective to indicate in an alternating

current, the production of a very great number of alternations per unit

of time--usually expressed as alternations per second.

Hissing.

A term applied to a noise sometimes produced by a voltaic arc; probably

due to the same cause as frying, q. v.

Hittorf's Solution.

A solution used as a resistance. It is a solution of cadmium iodide in

amylic alcohol. Ten per cent. of the salt is used. It is contained in a

tube with metallic cadmium electrodes. (See Resistance, Hittorf' s.)

Fig. 196. HITTORF'S RESISTANCE TUBE.

290   STANDARD ELECTRICAL DICTIONARY.

Holders.

(a) The adjustable clamps for holding the armature brushes of dynamos

and motors.

(b) The clamps for holding the carbons of arc lamps.

(c) The clamps for holding safety fuses, q. v.

(d) Holders for Jablochkoff candles and other electric candles. (See

Candle Holders.)

(e) A box or block of porcelain for holding safety fuses.

Hood.

A tin hood placed over an arc-lamp. Such hoods are often truncated cones

in shape, with the small end upwards. They reflect a certain amount of

light besides protecting the lamp to some extent from rain.

Horns.

The extensions of the pole pieces of a dynamo or motor. (See Following

Horns-Leading Horns.)

Synonym--Pole Tips.

Horse Power.

A unit of rate of work or activity. There are two horse powers.

The British horse power is equal to 33,000 pounds raised one foot per

minute, or 550 foot pounds per second, or 1.0138 metric horse power.

The metric horse power (French) is equal to 75 kilogram-meters, or 542

foot pounds per second, or .986356 British horse power.

H. P. is the abbreviation for horse power. (See Horse Power, Electric.)

Horse Power, Actual.

The rate of activity of a machine, as actually developed in condition

for use. It is less than the indicated or total horse power, because

diminished by the hurtful resistances of friction, and other sources of

waste. It is the horse power that can be used in practise, and which in

the case of a motor can be taken from the fly-wheel.

Horse Power, Electric.

The equivalent of a mechanical horse power in electric units, generally

in volt-amperes or watts; 745.943 watts are equivalent to the activity

of one British horse power; 735.75 are equivalent to one metric horse

power. The number 746 is usually taken in practical calculations to give

the equivalency.

[Transcriber's note: Contemporary values are: Mechanical (British)

horsepower = 745.6999 Watts; Metric horsepower = 735.49875 Watts]

Horse Power, Indicated.

The horse power of an engine as indicated by its steam pressure, length

of stroke, and piston area, and vacuum, without making any deduction for

friction or hurtful resistances. The steam pressure is in accurate work

deduced from indicator diagrams.

Horse Power, Hour.

A horse power exerted for one hour, or the equivalent thereof. As the

horse power is a unit of activity, the horse power hour is a unit of

work or of energy. It is equal to 1,980,000 foot pounds.

H. P.

Abbreviation for "horse power."

291   STANDARD ELECTRICAL DICTIONARY.

Hughes' Electro-magnet.

A horseshoe electro-magnet with polarized core. It is made by mounting

two bobbins of insulated wire on the ends of a permanent horseshoe

magnet. It was devised for use in Hughes' printing telegraph, where very

quick action is required. The contact lasts only .053 second, 185

letters being transmitted per minute.

Fig. 197 HUGHES' ELECTRO-MAGNET.

Fig. 198. HUGHES' INDUCTION BALANCE.

Hughes' Induction Balance.

An apparatus for determining the presence of a concealed mass of metal.

The apparatus is variously connected. The cut shows a representative

form; a and a' are two primary coils, each consisting of 100 meters (328

feet) of No. 32 silk covered copper wire (0.009 inch diameter) wound on

a boxwood spool ten inches in depth; b and b' are secondary coils. All

coils are supposed to be alike. The primary coils are joined in series

with a battery of three or four Daniell cells. A microphone m is

included in the same circuit. The secondary coils are joined in series

with a telephone and in opposition with each other. The clock is used to

produce a sound affecting the microphone. If all is exactly balanced

there will be no sound produced in the telephone. This balance is

brought about by slightly varying the distance of one of the secondaries

from the primary, until there is no sound in the telephone. If now a

piece of metal is placed within either of the coils, it disturbs the

balance and the telephone sounds.

292   STANDARD ELECTRICAL DICTIONARY.

To measure the forces acting a sonometer or audiometer is used. This is

shown in the upper part of the cut. Two fixed coils, c and e are mounted

at the ends of a graduated bar. A movable coil d is connected in the

telephone circuit; c and e by a switch can be connected with the battery

and microphone circuit, leaving out the induction balance coils. The

ends of the coils c and e, facing each other are of the same polarity.

If these coils, c and e, were equal in all respects, no sound would be

produced when d was midway between them. But they are so wound that the

zero position for d is very near one of them, c.

Assume that a balance has been obtained in the induction balance with

the coil d at zero. No sound is heard whether the switch is moved to

throw the current into one or the other circuit. A piece of metal placed

in one of the balance coils will cause the production of a sound. The

current is turned into the sonometer and d is moved until the same

sound, as tested by rapid movements of the switch, is heard in both

circuits. The displacement of d gives the value of the sound.

A milligram of copper is enough to produce a loud sound. Two coins can

be balanced against each other, and by rubbing one of them, or by

breathing on one of them, the balance will be disturbed and a sound will

be produced.

Prof. Hughes has also dispensed with the audiometer. He has used a strip

of zinc tapering from a width of 4 mm. (.16 inch) at one end to a sharp

edge or point at the other. The piece to be tested being in place in one

coil, the strip is moved across the face of the other until a balance is

obtained.

As possible uses the detection of counterfeit coins, the testing of

metals for similarity of composition and the location of bullets in the

body have been suggested. Care has to be taken that no masses of metal

interfere. Thus in tests of the person of a wounded man, the presence of

an iron truss, or of metallic bed springs may invalidate all

conclusions.

The same principle is carried out in an apparatus in which the parts are

arranged like the members of a Wheatstone bridge. One pair of coils is

used, which react on each other as primary and secondary coils. One of

the coils is in series with a telephone in the member of the bridge

corresponding to that containing the galvanometer of the Wheatstone

bridge. The latter is more properly termed an induction bridge.

Synonyms--Inductance Bridge--Inductance Balance--Induction Bridge.

293   STANDARD ELECTRICAL DICTIONARY.

Hydro-electric. adj.

(a) A current produced by a voltaic couple or the couple itself is

sometimes thus characterized or designated as a "hydro-electric current"

or a "hydro-electric couple." It distinguishes them from

thermo-electric.

(b) Armstrong's steam boiler electric machine (see Hydroelectric

Machine) is also termed a hydro-electric machine.

Hydro-electric Machine.

An apparatus for generating high potential difference by the escape of

steam through proper nozzles.

It consists of a boiler mounted on four glass legs or otherwise

insulated. An escape pipe terminates in a series of outlets so shaped as

to impede the escape of the steam by forcing it out of the direct

course. These jets are lined with hard wood. They are enclosed in or led

through a box which is filled with cold water.

Fig. 199. ARMSTRONG'S HYDRO-ELECTRIC MACHINE.

This is to partly condense the steam so as to get it into the vesicular

state, which is found essential to its action. Dry steam produces no

excitation. If the boiler is fired and the steam is permitted to escape

under the above conditions the vesicles presumably, or the "steam" is

found to be electrified. A collecting comb held against the jet becomes

charged and charges any connected surface.

294   STANDARD ELECTRICAL DICTIONARY.

The boiler in the above case is negatively and the escaping "steam" is

positively charged. By changing the material of the linings of the jets,

or by adding turpentine the sign of the electricity is reversed. If the

water contains acid or salts no electricity is produced. The regular

hydro-electric machine is due to Sir William Armstrong.

Faraday obtained similar results with moist air currents.

Hydrogen.

An element existing under all except the most extreme artificial

conditions of pressure and cold as a gas. It is the lightest of known

substances. Atomic weight, 1; molecular weight, 2; equivalent, 1;

valency, 1; specific gravity, .0691-.0695. (Dumas & Boussingault.)

It is a dielectric of about the same resistance as air. Its specific

inductive capacity at atmospheric pressure is:

.9997 (Baltzman)   .9998 (Ayrton)

Electro-chemical equivalent, .0105 milligram.

The above is usually taken as correct. Other values are as follows:

.010521 (Kohllrausch)   .010415 (Mascart)

The electro-chemical equivalent of any element is obtained by

multiplying its equivalent by the electro-chemical equivalent of

hydrogen. The value .0105 has been used throughout this book.

Hygrometer.

An instrument for determining the moisture in the air. One form consists

of a pair of thermometers, one of which has its bulb wrapped in cloth

which is kept moist during the observation. The evaporation is more or

less rapid according to the dryness or moisture of the air, and as the

temperature varies with this evaporation the relative readings of the

two thermometers give the basis for calculating the hygrometric state of

the air. Another form determines the temperature at which dew is

deposited on a silver surface, whence the calculations are made.

Hysteresis, Magnetic.

A phenomenon of magnetization of iron. It may be attributed to a sort of

internal or molecular friction, causing energy to be absorbed when iron

is magnetized. Whenever therefore the polarity or direction of

magnetization of a mass of iron is rapidly changed a considerable

expenditure of energy is required. It is attributed to the work done in

bringing the molecules into the position of polarity.

295   STANDARD ELECTRICAL DICTIONARY.

The electric energy lost by hysteresis may be reduced by vibrations or

jarring imparted to the iron, thus virtually substituting mechanical for

electrical work.

On account of hysteresis the induced magnetization of a piece of iron or

steel for fields of low intensity will depend on the manner in which the

material has been already magnetized. Let the intensity of field

increase, the magnetization increasing also; then lower the intensity;

the substance tends to and does retain some of its magnetism. Then on

again strengthening the field it will have something to build on, so

that when it attains its former intensity the magnetization will exceed

its former value. For a moderate value of intensity of field the

magnetization can have many values within certain limits.

Synonym--Hysteresis--Hysteresis, Static--Magnetic Friction.

Hysteresis, Viscous.

The gradual increase or creeping up of magnetization when a magnetic

force is applied with absolute steadiness to a piece of iron. It may

last for half an hour or more and amount to several per cent. of the

total magnetization. It is a true magnetic lag.

295   STANDARD ELECTRICAL DICTIONARY.

I.

A symbol sometimes used to indicate current intensity. Thus Ohm's law is

often expressed I = E/R, meaning current intensity is equal to

electro-motive force divided by resistance. C is the more general symbol

for current intensity.

Ideoelectrics or Idioelectrics.

Bodies which become electric by friction. This was the old definition,

the term originating with Gilbert. It was based on a misconception, as

insulation is all that is requisite for frictional electrification,

metals being thus electrified if held by insulating handles. The term is

virtually obsolete; as far as it means anything it means insulating

substances such as scaling wax, sulphur, or glass.

Idle Coils.

Coils in a dynamo, in which coils no electro-motive force is being

generated. This may occur when, as a coil breaks connection with the

commutator brush, it enters a region void of lines of magnetic force, or

where the lines are tangential to the circle of the armature.

Idiostatic Method.

A method of using the absolute or attracted disc electrometer. (See

Electrometer, Absolute.) The suspended disc and guard ring are kept at

the same potential, which is that of one of the points whose potential

difference is to be determined; the lower fixed disc is connected to the

other of the points whose potential difference is to be determined. Then

we have the formula

V = d * SquareRoot( 8 * PI * F ) / S

in which d is the distance between the discs, V is the difference of

potential of the two points, F the force of attraction between the discs

in dynes, and S the area of the suspended disc. (See Heterostatic

Method.)

296   STANDARD ELECTRICAL DICTIONARY.

Idle Poles.

Poles of wire sealed into Crookes' tubes, not used for the discharge

connections, but for experimental connections to test the effect of

different excitation on the discharge.

Idle Wire.

In a dynamo the wire which plays no part in generating electro-motive

force. In a Gramme ring the wire on the inside of the ring is idle wire.

Igniter.

In arc lamps with fixed parallel carbons of the Jablochkoff type (see

Candle, Jablochkoff) a strip of carbon connects the ends of the carbons

in the unused candle. This is necessary to start the current. Such strip

is called an igniter. It burns away in a very short time when an arc

forms producing the light, and lasts, if all goes well, until the candle

burns down to its end. Without the igniter the current would not start

and no arc would form.

I. H. P.

Symbol for indicated horse-power.

Illuminating Power.

The relative light given by any source compared with a standard light,

and stated in terms of the same, as a burner giving an illuminating

power of sixteen candles. For standards see Candle, Carcel--Methven

Standard--Pentane Standard.

Illuminating Power, Spherical.

The illuminating power of a lamp or source of light may vary in

different directions, as in the case of a gas burner or incandescent

lamp. The average illuminating power determined by photometric test or

by calculation in all directions from the source of light is called the

spherical illuminating power, or if stated in candles is called the

spherical candle power.

Illumination, Unit of.

An absolute standard of light received by a surface. Preece proposed as

such the light received from a standard candle (see Candle, Standard) at

a distance of 12.7 inches. The object of selecting this distance was to

make it equal to the Carcel Standard (see Carcel), which is the light

given by a Carcel lamp at a distance of one meter.

From one-tenth to one-fiftieth this degree of illumination was found in

gas-lighted streets by Preece, depending on the proximity of the gas

lamps.

Image, Electric.

An electrified point or system of points on one side of a surface which

would produce on the other side of that surface the same electrical

action which the actual electrification of that surface really does

produce. (Maxwell.)

The method of investigating the distribution of electricity by electric

images is due to Sir William Thomson. The conception is purely a

theoretical one, and is of mathematical value and interest.

297   STANDARD ELECTRICAL DICTIONARY.

Impedance.

The ratio of any impressed electro-motive force to the current which it

produces in a conductor. For steady currents it is only the resistance.

For variable currents it may include besides resistance inductance and

permittance. It is the sum of all factors opposing a current, both ohmic

and spurious resistances. It is often determined and expressed as ohms.

Synonym--Apparent Resistance--Virtual Resistance.

Impedance, Oscillatory.

The counter-electro-motive force offered to an oscillatory discharge, as

that of a Leyden jar. It varies with the frequency of the discharge

current.

Synonym--Impulsive Impedance.

Impressed Electro-motive Force.

The electro-motive force expending itself in producing current induction

in a neighboring circuit.

Impulse.

(a) An electro-magnetic impulse is the impulse produced upon the

luminiferous ether by an oscillatory discharge or other varying type of

current; the impulse is supposed to be identical, except as regards

wave-length, with a light wave.

(b) An electro-motive impulse is the electro-motive force which rises so

high as to produce an impulsive or oscillatory discharge, such as that

of a Leyden jar.

Incandescence, Electric.

The heating or a conductor to red, or, more etymologically, to white

heat by the passage of an electric current. The practical conditions are

a high intensity of current and a low degree of conductance of the

conductor relatively speaking.

Inclination Map.

A map showing the locus of equal inclination or dips of the magnetic

needle. The map shows a series of lines, each one of which follows the

places at which the dip of the magnetic needle is identical. The map

changes from year to year. (See Magnetic Elements.)

Independence of Currents in Parallel Circuits.

If a number of parallel circuits of comparatively high resistance are

supplied by a single generator of comparatively low resistance, the

current passed through each one will be almost the same whether a single

one or all are connected. Under the conditions named the currents are

practically independent of each other.

[Transcriber's note: The current in each parallel branch depends on the

resistance/impedance of that branch. Only if they all have the same

impedance will the current be the same.]

Indicating Bell.

An electric bell arranged to drop a shutter or disclose in some other

way a designating number or character when rung.

298   STANDARD ELECTRICAL DICTIONARY.

Indicator.

(a) An apparatus for indicating the condition of a distant element, such

as the water level in a reservoir, the temperature of a drying room or

cold storage room or any other datum. They are of the most varied

constructions.

(b) The receiving instrument in a telegraph system is sometimes thus

termed.

Indicator, Circuit.

A galvanometer used to show when a circuit is active, and to give an

approximate measurement of its strength. It is a less accurate and

delicate form of instrument than the laboratory appliance.

Inductance.

The property of a circuit in virtue of which it exercises induction and

develops lines of force. It is defined variously. As clear and

satisfactory a definition as any is the following, due to Sumpner and

Fleming: Inductance is the ratio between the total induction through a

circuit to the current producing it. "Thus taking a simple helix of five

turns carrying a current of two units, and assuming that 1,000 lines of

force passed through the central turn, of which owing to leakage only

900 thread the next adjacent on each side, and again only 800 through

the end turns, there would be 800 + 900 + 1000 + 900 + 800, or 4,400

linkages of lines with the wire, and this being with 2 units of current,

there would be 2,200 linkages with unit current, and consequently the

self-inductance of the helix would be 2,200 centimetres." (Kennelly.)

Inductance, as regards its dimensions is usually reduced to a length,

hence the last word of the preceding quotation.

The practical unit of inductance is termed the henry, from Prof. Joseph

Henry; the secohm, or the quad or quadrant. The latter alludes to the

quadrant of the earth, the value in length of the unit in question.

[Transcriber's note: (L (di/dt) = V). A current changing at the rate of

one ampere per second through a one henry inductance produces one volt.

A sinusoidal current produces a voltage 90 degrees ahead of the current,

a cosine (the derivative of sine is cosine). One volt across one henry

causes the current to increase at one ampere per second.]

Induction, Coefficient of Self.

The coefficient of self-induction of a circuit is the quantity of

induction passing through it per unit current in it. If a given circuit

is carrying a varying current it is producing a varying quantity of

magnetic induction through itself. The quantity of induction through the

circuit due to its current is generally proportional to its current. The

quantity for unit current is the coefficient of self-induction.

(Emtage.)

Induction, Cross.

The induction of magnetic lines of force in a dynamo armature core by

the current passing around such armature. These lines in a symmetrical

two pole machine are at right angles to the lines of force which would

normally extend across the space between the two magnet poles. The joint

magnetizing effect of the field and of the cross induction produces a

distorted field between the poles .

Synonym--Cross-magnetizing Effect.

299   STANDARD ELECTRICAL DICTIONARY.

Induction, Electro-magnetic.

The inter-reaction of electromagnetic lines of force with the production

of currents thereby.

A current passing through a conductor establishes around it a field of

force representing a series of circular lines of force concentric with

the axis of the conductor and perpendicular thereto. These lines of

force have attributed to them, as a representative of their polarity,

direction. This is of course purely conventional. If one is supposed to

be looking at the end of a section of conductor, assuming a current be

passing through it towards the observer, the lines of force will have a

direction opposite to the motion of the hands of a watch. The idea of

direction may be referred to a magnet. In it the lines of force are

assumed to go from the north pole through the air or other surrounding

dielectric to the south pole.

Two parallel wires having currents passing through them in the same

direction will attract each other. This is because the oppositely

directed segments of lines of force between the conductors destroy each

other, and the resultant of the two circles is an approximation to an

ellipse. As lines of force tend to be as short as possible the

conductors tend to approach each other to make the ellipse become of as

small area as possible, in other words to become a circle.

If on the other hand the currents in the conductors are in opposite

directions the segments of the lines of force between them will have

similar directions, will, as it were, crowd the intervening ether and

the wires will be repelled.

Fig. 200. ATTRACTION OF CONDUCTORS CARRYING SIMILAR CURRENTS.

By Ampére's theory of magnetism, (see Magnetism, Ampére's Theory of,) a

magnet is assumed to be encircled by currents moving in the direction

opposite to that of the hands of a watch as the observer faces the north

pole. A magnet near a wire tends to place the Ampérian currents parallel

to the wire, and so that the portion of the Ampérian currents nearest

thereto will correspond in direction with the current in the wire.

300   STANDARD ELECTRICAL DICTIONARY.

This is the principle of the galvanometer. A number of methods of

memoria technica have been proposed to remember it by.

Thus if we imagine a person swimming with the current and always facing

the axis of the conductor, a magnetic needle held where the person is

supposed to be will have its north pole deflected to the right hand of

the person.

Fig. 201. REPULSION OF CONDUCTORS

CARRYING OPPOSITE CURRENTS.

Again if we think of a corkscrew, which as it is turned screws itself

along with the current, the motion of the handle shows the direction of

the lines of force and the direction in which the north pole of a needle

is deflected. This much is perhaps more properly electro-dynamics, but

is necessary as a basis for the expression of induction.

If a current is varied in intensity in one conductor it will induce a

temporary current in another conductor, part of which is parallel to the

inducing current and which conductor is closed so as to form a circuit.

If the inducing current is decreased the induced current in the near and

parallel portion of the other circuit will be of identical direction; if

increased the induced current will be of opposite direction.

This is easiest figured by thinking of the lines of force surrounding

the inducing conductor. If the current is decreased these can be

imagined as receiving a twist or turn contrary to their normal

direction, as thereby establishing a turn or twist in the ether

surrounding the other wire corresponding in direction with the direction

of the original lines of force, or what is the same thing, opposite in

direction to the original twist. But we may assume that the

establishment of such a disturbance causes a current, which must be

governed in direction with the requirements of the new lines of force.

The same reasoning applies to the opposite case.

301    STANDARD ELECTRICAL DICTIONARY.

The general statement of a variable current acting on a neighboring

circuit also applies to the approach or recession of an unvarying

current, and to the cutting of lines of force by a conductor at right

angles thereto. For it is evident that the case of a varying current is

the case of a varying number of lines of force cutting or being cut by

the neighboring conductor. As lines of force always imply a current,

they always imply a direction of such current. The cutting of any lines

of force by a closed conductor always implies a change of position with

reference to all portions of such conductor and to the current and

consequently an induced current or currents in one or the other

direction in the moving conductor.

As the inducing of a current represents energy abstracted from that of

the inducing circuit, the direction of the induced current is determined

by (Lenz's Law) the rule that the new current will increase already

existing resistances or develop new ones to the disturbance of the

inducing field.

In saying that a conductor cutting lines of force at right angles to

itself has a current induced in it, it must be understood that if not at

right angles the right angle component of the direction of the wire acts

in generating the current. The case resolves itself into the number of

lines of force cut at any angle by the moving wire.

The lines of force may be produced by a magnet, permanent or electro.

This introduces no new element. The magnet may be referred, as regards

direction of its lines of force, to its encircling currents, actual or

Ampérian, and the application of the laws just cited will cover all

cases.

Induction, Coefficient of Mutual.

The coefficient of mutual induction of two circuits is the quantity of

magnetic induction passing through either of them per unit current in

the other. (Emtage.) It is also defined as the work which must be done

on either circuit, against the action of unit current in each, to take

it away from its given position to an infinite distance from the other;

and also as the work which would be done by either circuit on the other

in consequence of unit current in each, as the other moves from an

infinite distance to its given position with respect to the other

conductor. It depends on the form, size, and relative position of the

two circuits; and on the magnetic susceptibilities of neighboring

substances.

The ether surrounding two circuits of intensity i' and i" must possess

energy, expressible (Maxwell) as 1/2 L i2 + M i i + 1/2 N i12. It can be

shown that M i i1 in any given position of the two circuits is

numerically equal (1) to the mutual potential energy of the two circuits

(2) to the number of lines of induction, which being due to A, pass from

A through B, or equally being due to B, pass from B through A, and M is

styled the coefficient of mutual induction. (Daniell.)

302   STANDARD ELECTRICAL DICTIONARY.

Induction, Electrostatic.

An electrostatic charge has always an opposite and bound charge. This

may be so distributed as not to be distinguishable, in which case the

charge is termed, incorrectly but conventionally, a free charge. But

when a charge is produced an opposite and equal one always is formed,

which is the bound charge. The region between the two charges and

permeated by their lines of force, often curving out so as to embrace a

volume of cross-sectional area larger than the mean facing area of the

excited surfaces, is an electrostatic field of force. The establishing

of an electrostatic field, and the production of a bound charge are

electrostatic induction.

An insulated conductor brought into such a field suffers a

redistribution of its electricity, or undergoes electrostatic induction.

The parts nearest respectively, the two loci of the original and the

bound charges, are excited oppositely to such charges. The conductor

presents two new bound charges, one referred to the original charge, the

other to the first bound charge.

Induction, Horizontal.

In an iron or steel ship the induction exercised upon the compass needle

by the horizontal members of the structure, such as deck-beams, when

they are polarized by the earth's magnetic induction. This induction

disappears four times in swinging a ship through a circle; deviation due

to it is termed quadrantal deviation. (See Deviation, Quadrantal.)

Induction, Lateral.

A term formerly used to express the phenomenon of the alternative

discharge of a Leyden jar or other oscillatory discharge of electricity.

(See Discharge, Alternative.)

Induction, Magnetic.

The magnetization of iron or other paramagnetic substance by a magnetic

field.

On account of its permeability or multiplying power for lines of force,

a paramagnetic body always concentrates lines of force in itself if

placed in a magnetic field, and hence becomes for the time being a

magnet, or is said to be polarized.

As the tendency of lines of force is to follow the most permeable path,

a paramagnetic bar places itself lengthwise or parallel with the

prevailing direction of the lines of force so as to carry them as far on

their way as possible. Every other position of the bar is one of

unstable equilibrium or of no equilibrium. The end of the bar where the

lines of force enter (see Lines of Force) is a south pole and is

attracted towards the north pole of the magnet.

The production of magnetic poles under these conditions in the bar is

shown by throwing iron filings upon it. They adhere to both ends but not

to the middle.

Induction, Mutual, Electro-magnetic.

The induction due to two electric currents reacting on each other.

303  STANDARD ELECTRICAL DICTIONARY.

Induction, Mutual, Electrostatic.

A charged body always induces a charge upon any other body near it; and

the same charge in the second body will induce the other charge in the

first body if the latter is unexcited. In other words the second body's

induction from the first is the measure of the charge the second would

require to induce in the first its own (the second's) induced charge.

This is the law of mutual electrostatic induction.

Induction, Open Circuit.

Inductive effects produced in open circuits. By oscillatory discharges a

discharge can be produced across a break in a circuit otherwise

complete. The requirements for its production involve a correspondence

or relation of its dimensions to the inducing discharge. The whole is

analogous to the phenomena of sound resonators and sympathetic

vibrations. Synonym--Oscillatory induction.

Induction, Self-.

(a) A phenomenon of electric currents analogous to the inertia of

matter. Just as water which fills a pipe would resist a sudden change in

its rate of motion, whether to start from rest, to cease or decrease its

motion, so an electric current requires an appreciable time to start and

stop. It is produced most strongly in a coiled conductor, especially if

a core of iron is contained within it.

As in the case of two parallel wires, one bearing currents which vary,

momentary currents are induced in the other wire, so in a single

conductor a species of inertia is found which retards and prolongs the

current. If a single conductor is twisted into a helix or corresponding

shape, its separate turns react one on the other in accordance with the

general principles of electromagnetic induction. (See Induction,

Electro-magnetic.) Thus when a current is suddenly formed the coils

acting upon each other retard for an instant its passage, producing the

effect of a reverse induced current or extra current opposing the

principal current. Of course no extra current is perceptible, but only

the diminution. When the current is passing regularly and the current is

broken, the corresponding action prolongs the current or rather

intensifies it for an instant, producing the true extra current. This is

current self-induction.

[Transcriber's note: See inductance.]

Synonyms--Electric Inertia--Electro-dynamic Capacity.

(b) A permanent magnet is said to tend to repel its own magnetism, and

thus to weaken itself; the tendency is due to magnetic self-induction.

Induction Sheath.

In the brush dynamo a thin sheet of copper surrounding the magnet cores

with edges soldered together. The winding is outside of it. Its object

is to absorb extra currents set up by variations in magnetic intensity

in the cores. These currents otherwise would circulate in the cores.

304   STANDARD ELECTRICAL DICTIONARY.

Induction, Unit of Self-.

The unit of self-induction is the same as that of induction in general.

It is the henry, q. v.

Induction, Unipolar.

Induction produced in a conductor which continuously cuts the lines of

force issuing from one pole of a magnet. As the lines of force are

always cut in the same sense a continuous and constant direction current

is produced.

Induction, Vertical.

In an iron or steel ship the induction or attraction exercised in the

compass by vertical elements of the structure. Such vertical masses of

iron in the northern hemisphere would have their upper ends polarized as

south poles, and would affect the magnet as soon as the vessel swung out

of the magnetic meridian. Thus this induction disappears twice in

swinging a ship through a complete circle; deviation due to it is termed

semi-circular deviation. (See Deviation, Semi-circular.)

Fig. 202. INDUCTOR DYNAMO.

Inductophone.

A method of train telegraphy. The train carries a circuit including a

coil, and messages are picked up by it from coils along the line into

which an alternating current is passed. A telephone is used as a

receiver in place of a sounder or relay. The invention, never

practically used, is due to Willoughby Smith.

305    STANDARD ELECTRICAL DICTIONARY.

Inductor.

(a) In a current generator a mass of iron, generally laminated, which is

moved past a magnet pole to increase the number of lines of force

issuing therefrom. It is used in inductor dynamos. (See Dynamo

Inductor.) In the cut Fig. 202, of an inductor dynamo i, i, are the

laminated inductors.

(b) In influence machines the paper or tinfoil armatures on which the

electrification is induced.

Inertia.

A force in virtue of which every body persists in its state of motion or

rest except so far as it is acted on by some force.

Inertia, Electro-magnetic.

This term is sometimes applied to the phenomena of self-induction, or

rather to the cause of these phenomena.

Infinity Plug.

A plug in a resistance box, which on being pulled out of its seat opens

the circuit or makes it of infinite resistance. The plug seats itself

between two brass plates which are not connected with each other in any

way. The other plates are connected by resistance coils of varying

resistance.

Influence, Electric.

Electric induction, which may be either electrostatic, current, or

electro-magnetic.

Insolation, Electric.

Exposure to powerful arc-light produces effects resembling those of

sun-stroke. The above term or the term "electric sun-stroke" has been

applied to them.

[Transcriber's note: Operators of arc welders are prone to skin cancer

from ultra violet rays if not properly protected.]

Installation.

The entire apparatus, buildings and appurtenances of a technical or

manufacturing establishment. An electric light installation, for

instance, would include the generating plant, any special buildings, the

mains and lamps.

Insulating Stool.

A support for a person, used in experiments with static generators. It

has ordinarily a wooden top and glass legs. It separates one standing on

it from the earth and enables his surface to receive an electrostatic

charge. This tends to make his hair stand on end, and anyone on the

floor who touches him will receive a shock.

Insulating Tape.

Prepared tape used in covering the ends of wire where stripped for

making joints. After the stripped ends of two pieces are twisted

together, and if necessary soldered and carefully cleaned of soldering

fluid, they may be insulated by being wound with insulating tape.

The tape is variously prepared. It may be common cotton or other tape

saturated with any insulating compound, or may be a strip of gutta

percha or of some flexible cement-like composition.

306   STANDARD ELECTRICAL DICTIONARY.

Insulating Varnish.

Varnish used to coat the surface of glass electrical apparatus, to

prevent the deposition of hygrometric moisture, and also in the

construction of magnetizing and induction coils and the like. Shellac

dissolved in alcohol is much used. Gum copal dissolved in ether is

another. A solution of sealing wax in alcohol is also used. If applied

in quantities these may need baking to bring about the last drying. (See

Shellac Varnish.)

Insulator.

(a) Any insulating substance.

(b) A telegraph or line insulator for telegraph wires. (See Insulator,

Line or Telegraph.)

Synonyms--Dielectric--Non-conductor.

Insulator Cap.

A covering or hood, generally of iron, placed over an insulator to

protect it from injury by fracture with stones or missiles.

Insulator, Fluid.

(a) For very high potentials, as in induction coils or alternating

circuits, fluid insulators, such as petroleum or resin oil, have been

used. Their principal merit is that if a discharge does take place

through them the opening at once closes, so that they are self-healing.

(b) Also a form of telegraph or line insulator in which the lower rim is

turned up and inwards, so as to form an annular cup which is filled with

oil.

Insulator, Line or Telegraph.

A support often in the shape of a collar or cap, for a telegraph or

other wire, made of insulating material. Glass is generally used in the

United States, porcelain is adopted for special cases; pottery or stone

ware insulators have been used a great deal in other countries.

Sometimes the insulator is an iron hook set into a glass screw, which is

inserted into a hole in a telegraph bracket. Sometimes a hook is caused

to depend from the interior of an inverted cup and the space between the

shank of the hook and cup is filled with paraffine run in while melted.

Insulators are tested by measuring their resistance while immersed in a

vessel of water.

Intensity. Strength.

The intensity of a current or its amperage or strength; the intensity or

strength of a magnetic field or its magnetic density; the intensity or

strength of a light are examples of its use. In the case of dynamic

electricity it must be distinguished from tension. The latter

corresponds to potential difference or voltage and is not an attribute

of current; intensity has no reference to potential and is a

characteristic of current.

Intensity of a Magnetic Field.

The intensity of a magnetic field at any point is measured by the force

with which it acts on a unit magnet pole placed at that point. Hence

unit intensity of field is that intensity of field which acts on a unit

pole with a force of one dyne. (S. P. Thomson.) (See Magnetic Lines of

Force.)

307   STANDARD ELECTRICAL DICTIONARY.

Intercrossing.

Crossing a pair of conductors of a metallic circuit from side to side to

avoid induction from outside sources.

Intermittent.

Acting at intervals, as an intermittent contact, earth, or grounding of

a telegraph wire.

Interpolar Conductor.

A conductor connecting the two poles of a battery or current generator;

the external circuit in a galvanic circuit.

Interpolation.

A process used in getting a closer approximation to the truth from two

varying observations, as of a galvanometer. The process varies for

different cases, but amounts to determining an average or deducing a

proportional reading from the discrepant observed ones.

Interrupter.

A circuit breaker. It may be operated by hand or be automatic. (See

Circuit Breaker--Circuit Breaker, Automatic--and others.)

Interrupter, Electro-magnetic, for a Tuning Fork.

An apparatus for interrupting a current which passes through an

electromagnet near and facing one of the limbs of a tuning fork. The

circuit is made and broken by the vibrations of another tuning fork

through which the current passes. The second one is thus made to

vibrate, although it may be very far off and may not be in exact unison

with the first. The first tuning fork has a contact point on one of its

limbs, to close the circuit; it may be one which dips into a mercury

cup.

Intrapolar Region.

A term in medical electricity, denoting the part of a nerve through

which a current is passing.

Ions.

The products of decomposition produced in any given electrolysis are

termed ions, the one which appears at the anode or negative electrode is

the anion. The electrode connected to the carbon or copper plate of a

wet battery is an anode. Thus in the electrolysis of water oxygen is the

anion and hydrogen is termed the kation. In this case both anion and

kation are elements. In the decomposition of copper sulphate the anion

is properly speaking sulphion (S O4), a radical, and the kation is

copper, an element. Electro-negative elements or radicals are anions,

such as oxygen, sulphion, etc., while electro-positive ones are kations,

such as potassium. Again one substance may be an anion referred to one

below it and a kation referred to one above it, in the electro-chemical

series, q. v. Anion means the ion which goes to the anode or positive

electrode; kation, the ion which goes to the kathode or negative

electrode.

[Transcriber's note: An ion is an atom or molecule that has lost or

gained one or more valence electrons, giving it a positive or negative

electrical charge. A negatively charged ion, with more electrons than

protons in its nuclei, is an anion. A positively charged ion, with fewer

electrons than protons, is a cation. The electron was discovered five

years after this publication.]

308   STANDARD ELECTRICAL DICTIONARY.

Iron.

A metal; one of the elements; symbol, Fe; atomic weight, 56;

equivalent, 28 and 14, ; valency, 4 and 2.

It is a conductor of electricity. The following data are at

0° C. 32° F., with annealed metal.

Specific Resistance,   9.716 microhms.

Relative Resistance.   6.460

Resistance of a wire,

(a) 1 foot long weighing 1 grain,      1.085   ohms.

(b) 1 foot long 1/1000 inch thick,    58.45     "

(c) 1 meter long weighing 1 gram,       .7570   "

(d) 1 meter long, 1 millimeter thick,   .1237   "

Percentage increase in resistance per degree C. (1.8° F.)

at about 20° C. (68°F.), about 0.5 per cent.

Resistance of a 1 inch cube,   3.825 microhms.

Electro-chemical equivalent (Hydrogen = .0105), .147 and .294

Iron, Electrolytic.

Iron deposited by electrolytic action. Various baths are employed for

its formation. (See Steeling.) It has very low coercive power, only

seven to ten times that of nickel.

Ironwork Fault of a Dynamo.

A short circuiting of a dynamo by, or any connection of its coils with,

the iron magnet cores or other iron parts.

Isochronism.

Equality of periodic time; as of the times of successive beats of a

tuning fork, or of the times of oscillations of a pendulum.

Isoclinic Lines.

The lines denoting the locus of sets of equal dips or inclinations of

the magnetic needle upon the earth's surface, the magnetic parallels, q.

v. These lines are very irregular. (See Magnetic Elements.)

Isoclinic Map.

A map showing the position of isoclinic lines.

Isodynamic Lines.

Lines marking the locus of places of equal magnetic intensity on the

earth's surface. (See Magnetic Elements, Poles of Intensity.)

Isodynamic Map.

A map showing the position of isodynamic lines. (See Poles of

Intensity.)

Isogonic Lines.

Lines on a map marking the locus of or connecting those points where the

declination or variation of the magnetic needle is the same. (See

Magnetic Elements--Declination of Magnetic Needle.)

Synonyms--Isogonal Lines--Halleyan Lines.

309  STANDARD ELECTRICAL DICTIONARY.

Isogonic Map.

A map showing the isogonic lines. On such a map each line is

characterized and marked with the degrees and direction of variation of

the compass upon itself.

Synonym--Declination Map.

[Transcriber's note: The file Earth_Declination_1590_1990.gif provided

by the U.S. Geological Survey (http://www.usgs.gov) is an animation of

the declination of the entire earth.]

Isolated Plant, Distribution or Supply.

The system of supplying electric energy by independent generating

systems, dynamo or battery, for each house, factory or other place, as

contra-distinguished from Central Station Distribution or Supply.

Isotropic.

(Greek, equal in manner.)

Having equal properties in all directions; the reverse of anisotropic,

q. v. Thus a homogeneous mass of copper or silver has the same specific

resistance in all directions and is an isotropic conductor. Glass has

the same specific inductive capacity in all directions and is an

isotropic medium or dielectric. The same applies to magnetism. Iron is

an isotropic paramagnetic substance. (See Anisotropic.) The term applies

to other branches of physics also.

I. W. G.

Contraction for Indian Wire Gauge--the gauge adopted in British India.

309  STANDARD ELECTRICAL DICTIONARY.

J.

Symbol for the unit joule, the unit of electric energy.

Jacobi's Law.

A law of electric motors. It states that the maximum work of a motor is

performed when the counter-electromotive force is equal to one-half the

electro-motive force expended on the motor.

Jewelry.

Small incandescent lamps are sometimes mounted as articles of jewelry in

scarf-pins or in the hair. They may be supplied with current from

storage or from portable batteries carried on the person.

Joint, American Twist.

A joint for connecting telegraph wires, especially aerial lines. Its

construction is shown in the cut. The end of each wire is closely wound

around the straight portion of the other wire for a few turns.

Fig. 203. AMERICAN TWIST JOINT.

310   STANDARD ELECTRICAL DICTIONARY.

Joint, Britannia.

A joint for uniting the ends of telegraph and electric wires. The ends

of the wires are scraped clean and laid alongside each other for two

inches, the extreme ends being bent up at about right angles to the

wire. A thin wire is wound four or five times around one of the wires,

back of the joint, the winding is then continued over the lapped

portion, and a few more turns are taken around the other single wire.

The whole is then soldered.

Fig. 204. BRITANNIA JOINT.

Joint, Butt.

A joint in belting or in wire in which the ends to be joined are cut off

square across, placed in contact and secured. It ensures even running

when used in belting. Any irregularity in thickness of a belt affects

the speed of the driven pulley. As dynamos are generally driven by

belts, and it is important to drive them at an even speed to prevent

variations in the electro-motive force, butt joints should be used on

belting for them, unless a very perfect lap joint is made, which does

not affect either the thickness or the stiffness of the belt.

When a butt joint is used in wire a sleeve may be used to receive the

abutting ends, which may be secured therein by soldering. This species

of joint has been used on lightning rods and may more properly be termed

a sleeve joint.

Joint, Lap.

(a) In belting a joint in which the ends are overlapped, and riveted or

otherwise secured in place. If made without reducing the thickness of

the ends it is a bad joint for electrical work, as it prevents even

running of machinery to which it is applied. Hence dynamo belts should

be joined by butt joints, or if by lap joints the ends should be shaved

off so that when joined and riveted, there will be no variation in the

thickness of the belt.

(b) In wire lap joints are made by overlapping the ends of the wire and

soldering or otherwise securing. The Britannia joint (see Joint,

Britannia,) may be considered a lap-joint.

Joint, Marriage.

A joint for stranded conductors used for Galende's cables. It is made

somewhat like a sailor's long splice. Each one of the strands is wound

separately into the place whence the opposite strand is unwound and the

ends are cut off so as to abutt. In this way all are smoothly laid in

place and soldering is next applied.

Fig. 205. MARRIAGE JOINT.

311   STANDARD ELECTRICAL DICTIONARY.

Joint, Sleeve.

A joint in electric conductors, in which the ends of the wires are

inserted into and secured in a metallic sleeve or tube, whose internal

diameter is just sufficient to admit them.

Joint, Splayed.

The method of joining the ends of stranded conductors. The insulating

covering is removed, the wires are opened out, and the center wire,

heart or core of the cable is cut off short. The two ends are brought

together, the opened out wires are interlaced or crotched like the

fingers of the two hands, and the ends are wound around the body of the

cable in opposite directions. The joint is trimmed and well soldered.

Tinned wire with rosin flux for the soldering is to be recommended.

Insulating material is finally applied by hand, with heat if necessary.

Joints in Belts.

Belt-joints for electric plants where the belts drive dynamos should be

made with special care. The least inequality affects the electro-motive

force. Butt joints are, generally speaking, the best, where the ends of

the belt are placed in contact and laced. Lap-joints are made by

overlapping the belt, and unless the belt is carefully tapered so as to

preserve uniform strength, the speed of the dynamo will vary and also

the electromotive force.

Joulad.

A name proposed to be substituted for "joule," q. v. It has not been

adopted.

Joule.

This term has been applied to several units.

(a) The practical C. G. S. unit of electric energy and work--the

volt-coulomb. It is equal to 1E7 ergs--0.73734 foot pound.--.00134 horse

power seconds. A volt-ampere represents one joule per second.

(b) It has also been used as the name of the gram-degree C. thermal

unit--the small calorie.

Synonym--Joulad.

Joule Effect.

The heating effect of a current passing through a conductor. It varies

with the product of the resistance by the square of the current, or with

(C^2)*R.

Joule's Equivalent.

The mechanical equivalent of heat, which if stated in foot-pounds per

pound-degree F. units, is 772 (772.55). (See Equivalents.)

Junction Box.

In underground distribution systems, an iron casing or box in which the

feeders and mains are joined, and where other junctions are made.

Synonym--Fishing Box.

311   STANDARD ELECTRICAL DICTIONARY.

K.

The symbol for electrostatic capacity.

Kaolin.

A product of decomposition of feldspar, consisting approximately of

silica, 45, alumina, 40, water, 15. It was used in electric candles of

the Jablochkoff type as a constituent of the insulating layer or

colombin. Later it was abandoned for another substance, as it was found

that it melted and acted as a conductor.

312   STANDARD ELECTRICAL DICTIONARY.

Kapp Line of Force.

A line of force proposed by Kapp. It is equal to 6,000 C. G. S. lines of

force, and the unit of area is the square inch. Unfortunately it has

been adopted by many manufacturers, but its use should be discouraged,

as it is a departure from the uniform system of units.

One Kapp line per square inch = 930 C. G. S. lines per square

centimeter.

Kathelectrotonus.

A term used in medical electricity or electro-therapeutics to indicate

the increased functional activity induced in a nerve by the proximity of

the kathode of an active circuit which is completed through the nerve.

The converse of anelectrotonus.

Kathode.

The terminal of an electric circuit whence an electrolyzing current

passes from a solution. It is the terminal connected to the zinc plate

of a primary battery.

Kathodic Closure Contraction.

A term in electro-therapeutics; the contractions near where the kathode

of an active circuit is applied to the body, which are observed at the

instant when the circuit is closed.

Kathodic Duration Contraction.

A term in electro-therapeutics; the contraction near where the kathode

of an active circuit is applied to the body for a period of time.

K. C. C.

Abbreviation for Kathodic Closure Contraction, q. v.

K. D. C.

Abbreviation for Kathodic Duration Contraction, q. v.

Keeper.

A bar of soft iron used to connect the opposite poles of a horseshoe

magnet or the opposite poles of two bar magnets placed side by side. It

is designed to prevent loss of magnetism. The armature of a horseshoe

magnet is generally used as its keeper. For bar magnets a keeper is used

for each end, the magnets being laid side by side, with their poles in

opposite direction but not touching, and a keeper laid across at each

end connecting the opposite poles.

Kerr Effect.

The effect of an electrostatic field upon polarized light traversing a

dielectric contained within the field. (See Electrostatic Refraction.)

Kerr's Experiment.

Polarized light reflected from the polished face of a magnet pole has

its plane of polarization rotated; when it is reflected from the north

pole the rotation is from left to right.

313    STANDARD ELECTRICAL DICTIONARY.

Key.

A switch adapted for making and breaking contact easily when worked by

hand, as a Morse telegraph key.

Key Board.

A board or tablet on which keys or switches are mounted.

Key-board.

(a) A switch board, q. v.

(b) A set of lettered keys similar to those of a typewriter employed in

some telegraph instruments. As each key is depressed it produces the

contact or break requisite for the sending of the signal corresponding

to the letter marked upon the key. The signal in printing telegraphs, on

which such key-boards are used, is the reprinting of the letter at the

distant end of the line.

Key, Bridge.

A key for use with a Wheatstone Bridge, q.v. It is desirable to first

send a current through the four arms of the bridge in using it for

testing resistances and then through the galvanometer, because it takes

a definite time for the current to reach its full strength. This is

especially the case if the element being measured has high static

capacity, as a long ocean cable. If the galvanometer connections were

completed simultaneously with the bridge connections a momentary swing

would be produced even if the arms bore the proper relation to each

other. This would cause delay in the testing. A bridge key avoids this

by first connecting the battery circuit through the arms of the bridge,

and then as it is still further depressed the galvanometer circuit is

completed.

314   STANDARD ELECTRICAL DICTIONARY.

Fig. 206. CHARGE AND DISCHARGE KEY

Key, Charge and Discharge.

A key for use in observing the discharge of a condenser immediately

after removing the battery. In one typical form it has two contacts, one

below and one above, and being a spring in itself is pressed up against

the upper one. Connections are so made that when in its upper position

it brings the two coatings of the condenser in circuit with the

galvanometer. When depressed it does the same for a battery. In use it

is depressed and suddenly released when the galvanometer receives the

full charge, before there has been time for leakage. This is one method

of connection illustrating its principle.

In the cut L is the spring-key proper. S2, is the upper contact screw

against which the spring normally presses. In this position the

galvanometer G is in circuit with the opposite coatings of the condenser

C. On depressing the contact S2, is broken and S1, is made. This brings

the battery B in circuit with the condenser coatings. On releasing the

key it springs up and the galvanometer receives the effect of the charge

of the condenser as derived from the battery.

Key, Double Contact.

A key arranged to close two distinct circuits, holding the first closed

until the second is completed. It is used for Wheatstone bridge work.

Key, Double Tapper.

A telegraph key giving contacts alternately for currents in opposite

directions, used in needle telegraphy.

Key, Increment.

A key for use in duplex and quadruplex telegraphy. Its action is to

increase the line current, not merely to suddenly turn current into it.

315   STANDARD ELECTRICAL DICTIONARY.

Fig. 207. KEMPE'S DISCHARGE KEY.

Key, Kempe's Discharge.

A key giving a charging, discharging and insulating connection, for

static condenser work. Referring to the cut l is a lever or spring with

upper discharging contact s, and lower charging contact s'. In use it is

pressed down by the insulating handle or finger piece C, until caught by

the hook attached to the key I. This hook is lower down than that on the

key D, and holds it in contact with the charging contact piece S'. On

pressing the key I, marked or designated "Insulate," it springs up,

breaks contact at S', and catching against the hook on D, which key is

designated "Discharge," remains insulated from both contacts; next on

pressing D it is released and springs up and closes the discharge

contact S. It is a form of charge and discharge key. (See Key, Charge

and Discharge.)

Key, Magneto-electric.

A telegraph key whose movements operate what is virtually a small

magneto-generator, so as to produce currents of alternating direction,

one impulse for each motion of the key. It is employed for telegraphing

without a line battery, a polarized relay being used. In one very simple

form a key is mounted on a base with a permanent magnet and connected to

the armature, so that when the key is pressed downwards it draws the

armature away from the poles of the magnet. If the magnet or its

armature is wound with insulated wire this action of the key will cause

instantaneous currents to go through a circuit connected to the magnet

or armature coils.

Fig. 208. SIEMENS' MAGNETO-ELECTRIC KEY.

In Siemens & Halske's key an H armature E is pivoted between the poles N

S, of a powerful compound horseshoe magnet, G G. It is wound with fine

wire and a key handle H is provided for working it. In its normal

position the handle is drawn upward, and the end S S of the armature

core is in contact with the south pole S of the permanent magnet, and

the end D D with the north pole. This establishes the polarity of the

armature. On depressing the key the contacts are broken and in their

place the end D D comes in contact with the south pole and the end S S

with the north pole. This suddenly reverses the polarity of the armature

and sends a momentary current through the armature coil which is in

circuit with the line. The cut only shows the principle of the key,

whose construction is quite complicated.

316   STANDARD ELECTRICAL DICTIONARY.

Key, Make and Break.

An ordinary electric key, usually making a contact when depressed, and

rising by spring action when released, and in its rise breaking the

contact.

Fig. 209. PLUG KEY

Key, Plug.

An appliance for closing a circuit. Two brass blocks are connected to

the terminals, but are disconnected from each other. A brass plug

slightly coned or with its end split so as to give it spring action is

thrust between the blocks to complete the circuit. It is used in

Resistance coils and elsewhere. (See Coil, Resistance.) Grooves are

formed in the blocks to receive the plug.

Key, Reversing.

(a) A double key, arranged so that by depressing one key a current flows

in one direction, and by depressing the other a current flows in the

opposite direction. It is used in connection with a galvanometer in

experimental, testing or measuring operations.

(b) A key effecting the same result used in quadruplex telegraphy.

Key, Sliding-Contact.

A name given to the key used for making instantaneous contacts with the

metre wire of a metre bridge, q. v. The name is not strictly correct,

because it is important that there should be no sliding contact made, as

it would wear out the wire and make it of uneven resistance.

It is a key which slides along over the wire and which, when depressed,

presses a platinum tipped knife edge upon the wire. On being released

from pressure the key handle springs up and takes the knife edge off the

wire. This removal is essential to avoid wearing the wire, whose

resistance per unit of length must be absolutely uniform.

Key, Telegraph.

The key used in telegraphy for sending currents as desired over the

line. It consists of a pivoted lever with finger piece, which lever when

depressed makes contact between a contact point on its end and a

stationary contact point on the base. This closes the circuit through

the line. When released it springs up and opens the line circuit.

Kilo.

A prefix to the names of units; it indicates one thousand times, as

kilogram, one thousand grams. A few such units are given below.

Kilodyne.

A compound unit; one thousand dynes. (See Dyne.)

Kilogram.

A compound unit; one thousand grams; 2.2046 pounds avds.

317  STANDARD ELECTRICAL DICTIONARY.

Kilojoule.

A compound unit; one thousand joules, q. v.

Kilometer.

A compound unit; one thousand meters; 3280.899 feet; 0.621382 statute

miles. (See Meter.)

Kilowatt.

A compound unit; one thousand watts, q. v.

Kine.

An absolute or C. G. S. unit of velocity or rate of motion; one

centimeter per second; proposed by the British Association.

Kirchoff's Laws.

These relate to divided circuits.

I. When a steady current branches, the quantity of electricity arriving

by the single wire is equal to the quantity leaving the junction by the

branches. The algebraical sum of the intensities of the currents passing

towards (or passing from) the junction is equal to zero; Summation(C) =

0 (Daniell.) In the last sentence currents flowing towards the point are

considered of one sign and those flowing away from it of the other.

II. In a metallic circuit comprising within it a source of permanent

difference of potential, E, the products of the intensity of the current

within each part of the circuit into the corresponding resistance are,

if the elements of current be all taken in cyclical order together,

equal to E; Summation(C * r) =E. In a metallic circuit in which there is

no source of permanent difference of potential E = 0, and Summation(C *

r)  = 0.

This law applies to each several mesh of a wire network as well as to a

single metallic loop, and it holds good even when an extraneous current

is passed through the loop. (Daniell.)

In this statement of the two laws E stands for electro-motive force, C

for current intensity; and r for resistance of a single member of the

circuit.

[Transcriber's note: These laws may be restated as: At any point in an

steady-state electrical circuit, the directed sum of currents flowing

towards that point is zero. The directed sum of the electrical potential

differences around any closed circuit is zero.]

Knife-edge Suspension.

The suspension of an object on a sharp edge of steel or agate. The knife

edge should abut against a plane. The knife edge is generally carried by

the poised object. Its edge then faces downward and on the support one

or more plane or approximately plane surfaces are provided on which it

rests. In the ordinary balance this suspension can be seen. It is

sometimes used in the dipping needle.

It is applied in cases where vertical oscillations are to be provided

for.

Knot.

The geographical mile; a term derived from the knots on the log line,

used by navigators. It is equal to 6,087 feet.

Synonyms--Nautical Mile--Geographical Mile.

[Transcriber's note: A knot is a velocity, 1 nautical mile per hour, not

a distance. The contemporary definition is: 1 international knot = 1

nautical mile per hour = 1.852 kilometres per hour = 1.1507794 miles per

hour = 0.51444444 meters per second = 6076.1152 feet per hour.]

318   STANDARD ELECTRICAL DICTIONARY.

Kohlrausch's Law.

A law of the rate of travel of the elements and radicals in solutions

under the effects of electrolysis. It states that each element under the

effects of electrolysis has a rate of travel for a given liquid, which

is independent of the element with which it was combined. The rates of

travel are stated for different elements in centimeters per hour for a

potential difference of one or more volts per centimeter of path.

[Friedrich Wilhelm Georg Kohlrausch (1840-1910)]

Kookogey's Solution.

An acid exciting and depolarizing solution for a zinc-carbon couple,

such as a Bunsen battery. Its formula is: Potassium bichromate, 227

parts; water, boiling, 1,134 parts; while boiling add very carefully and

slowly 1,558 parts concentrated sulphuric acid. All parts are by weight.

Use cold.

Krizik's Cores.

Cores of iron for use with magnetizing coils, q. v. They are so shaped,

the metal increasing in quantity per unit of length, as the centre is

approached, that the pull of the excited coil upon them will as far as

possible be equal in all positions. A uniform cylinder is attracted with

varying force according to its position; the Krizik bars or cores are

attracted approximately uniformly through a considerable range.

318   STANDARD ELECTRICAL DICTIONARY.

L.

Symbol for length and also for the unit of inductance or coefficient of

induction, because the dimensions of inductance are length.

Lag, Angle of.

(a) The angle of displacement of the magnetic axis of an armature of a

dynamo, due to its magnetic lag. The axis of magnetism is displaced in

the direction of rotation. (See Magnetic Lag.)

(b) The angle expressing the lag of alternating current and

electro-motive force phases.

Laminated. adj.

Made up of thin plates, as a laminated armature core or converter core.

Lamination.

The building up of an armature core or other thing out of plates. The

cores of dynamo armatures or of alternating current converters are often

laminated. Thus a drum armature core may consist of a quantity of thin

iron discs, strung upon a rod and rigidly secured, either with or

without paper insulation between the discs. If no paper is used the film

of oxide on the iron is relied on for insulation. The object of

lamination is to break up the electrical continuity of the core, so as

to avoid Foucault currents. (See Currents, Foucault.) The laminations

should be at right angles to the direction of the Foucault currents

which would be produced, or in most cases should be at right angles to

the active parts of the wire windings.

319   STANDARD ELECTRICAL DICTIONARY.

Lamination of Armature Conductors.

These are sometimes laminated to prevent the formation of eddy currents.

The lamination should be radial, and the strips composing it should be

insulated from each other by superficial oxidation, oiling or

enamelling, and should be united only at their ends.

Fig. 210. PILSEN ARC LAMP.

Lamp, Arc.

A lamp in which the light is produced by a voltaic arc. Carbon

electrodes are almost universally employed. Special mechanism, operating

partly by spring or gravity and partly by electricity, is employed to

regulate the distance apart of the carbons, to let them touch when no

current passes, and to separate them when current is first turned on.

The most varied constructions have been employed, examples of which will

be found in their places. Lamps may in general be divided into classes

as follows, according to their regulating mechanism and other features:

(a) Single light regulators or monophotes. Lamps through whose

regulating mechanism the whole current passes. These are only adapted to

work singly; if several are placed in series on the same circuit, the

action of one regulator interferes with that of the next one.

(b) Multiple light regulators or polyphotes. In these the regulating

mechanism and the carbons with their arc are in parallel; the regulating

device may be a single magnet or solenoid constituting a derived or

shunt-circuit lamp, or it may include two magnets working differentially

against or in opposition to each other constituting a differential lamp.

320   STANDARD ELECTRICAL DICTIONARY.

(c) Lamps with fixed parallel carbons termed candles (q. v., of various

types).

(d) Lamps without regulating mechanism. These include lamps with

converging carbons, whose object was to dispense with the regulating

mechanism, but which in some cases have about as much regulating

mechanism as any of the ordinary arc lamps.

Lamp, Contact.

A lamp depending for its action on loose contact between two carbon

electrodes. At the contact a species of incandescence with incipient

arcs is produced. One of the electrodes is usually flat or nearly so,

and the other one of pencil shape rests upon it.

Lamp, Differential Arc.

An arc lamp, the regulation of the distance between whose carbons

depends on the differential action of two separate electrical coils. The

diagram illustrates the principle. The two carbons are seen in black;

the upper one is movable, The current arrives at A. It divides, and the

greater part goes through the low resistance coil M to a contact roller

r, and thence by the frame to the upper carbon, and through the arc and

lower carbon to B, where it leaves the lamp. A smaller portion of the

current goes through the coil M1 of higher resistance and leaves the

lamp also at B. A double conical iron core is seen, to which the upper

carbon holder is attached. This is attracted in opposite directions by

the two coils. If the arc grows too long its resistance increases and

the coil M1 receiving more current draws it down and thus shortens the

arc. If the arc grows too short, its resistance falls, and the coil M

receives more current and draws the core upwards, thus lengthening the

arc. This differential action of the two cores gives the lamp its name.

R is a pulley over which a cord passes, one end attached to the core and

the other to a counterpoise weight, W.

Fig. 211. DIAGRAM OF THE PILSEN DIFFERENTIAL ARC LAMP.

321   STANDARD ELECTRICAL DICTIONARY.

Lamp, Holophote.

A lamp designed for use alone upon its own circuit. These have the

regulating mechanism in series with the carbon and arc, so that the

whole current goes through both. (See Lamp, Arc.)

Synonym--Monophote Lamp.

Lamp-hour.

A unit of commercial supply of electric energy; the volt-coulombs

required to maintain an electric lamp for one hour. A sixteen-candle

power incandescent lamp is practically the lamp alluded to, and requires

about half an ampere current at 110 volts, making a lamp-hour equal to

about 198,000 volt-coulombs.

[Transcriber's note: 0.55 KW hours.]

Lamp, Incandescent.

An electric lamp in which the light is produced by heating to whiteness

a refractory conductor by the passage of a current of electricity. It is

distinguished from an arc lamp (which etymologically is also an

incandescent lamp) by the absence of any break in the continuity of its

refractory conductor. Many different forms and methods of construction

have been tried, but now all have settled into approximately the same

type.

The incandescent lamp consists of a small glass bulb, called the

lamp-chamber, which is exhausted of air and hermetically sealed. It

contains a filament of carbon, bent into a loop of more or less simple

shape. This shape prevents any tensile strain upon the loop and also

approximates to the outline of a regular flame.

Fig. 212. INCANDESCENT ELECTRIC LAMP.

322   STANDARD ELECTRICAL DICTIONARY.

The loop is attached at its ends to two short pieces of platinum wire,

which pass through the glass of the bulb and around which the glass is

fused. As platinum has almost exactly the same coefficient of

heat-expansion as glass, the wires do not cause the glass to crack.

The process of manufacture includes the preparation of the filament.

This is made from paper, silk, bamboo fibre, tamidine, q. v., or other

material. After shaping into the form of the filament the material is

carbonized at a high heat, while embedded in charcoal, or otherwise

protected from the air. The flashing process (see Flashing of

incandescent Lamp Carbons) may also be applied. The attachment to the

platinum wires is effected by a minute clamp or by electric soldering.

The loop is inserted and secured within the open globe, which the glass

blower nearly closes, leaving one opening for exhaustion.

The air is pumped out, perhaps first by a piston pump, but always at the

end by a mercurial air pump. (See Pump, Geissler--and others.) As the

exhaustion becomes high a current is passed through the carbons heating

them eventually to white heat so as to expel occluded gas. The occluded

gases are exhausted by the pump and the lamp is sealed by melting the

glass with a blowpipe or blast-lamp flame. For the exhaustion several

lamps are usually fastened together by branching glass tubes, and are

sealed off one by one.

The incandescent lamps require about 3.5 watts to the candle power, or

give about 12 sixteen-candle lamps to the horse power expended on them.

Generally incandescent lamps are run in parallel or on multiple arc

circuits. All that is necessary in such distribution systems is to

maintain a proper potential difference between the two leads across

which the lamps are connected. In the manufacture of lamps they are

brought to an even resistance and the proper voltage at which they

should be run is often marked upon them. This may be fifty volts and

upward. One hundred and ten volts is a very usual figure. As current one

ampere for a fifty-volt, or about one-half an ampere for a one hundred

and ten volt lamp is employed.

Lamp, Incandescent, Three Filament.

A three filament lamp is used for three phase currents. It has three

filaments whose inner ends are connected, and each of which has one

leading-in wire. The three wires are connected to the three wires of the

circuit. Each filament receives a current varying in intensity, so that

there is always one filament passing a current equal to the sum of the

currents in the other two filaments.

Lamp, Lighthouse.

A special type of arc light. It is adapted for use in a lighthouse

dioptric lantern, and hence its arc has to be maintained in the same

position, in the focus of the lenses. The lamps are so constructed as to

feed both carbons instead of only one, thereby securing the above

object.

323   STANDARD ELECTRICAL DICTIONARY.

Lamp, Pilot.

A lamp connected to a dynamo, and used by its degree of illumination to

show when the dynamo on starting becomes excited, or builds itself up.

Lamp, Polyphote.

An arc lamp adapted to be used, a number in series, upon the same

circuit. The electric regulating mechanism is placed in shunt or in

parallel with the carbons and arc. (See Lamp, Arc.)

Lamps, Bank of.

A number of lamps mounted on a board or other base, and connected to

serve as voltage indicator or to show the existence of grounds, or for

other purposes.

Lamp, Semi-incandescent.

A lamp partaking of the characteristics of both arc and incandescence; a

lamp in which the imperfect contact of two carbon electrodes produces a

part of or all of the resistance to the current which causes

incandescence.

The usual type of these lamps includes a thin carbon rod which rests

against a block of carbon. The species of arc formed at the junction of

the two heats the carbons. Sometimes the upper carbon or at least its

end is heated also by true incandescence, the current being conveyed

near to its end before entering it.

Semi-incandescent lamps are not used to any extent now.

Lamp Socket.

A receptacle for an incandescent lamp; the lamp being inserted the

necessary connections with the two leads are automatically made in most

sockets. The lamps may be screwed or simply thrust into the socket and

different ones are constructed for different types of lamps. A key for

turning the current on and off is often a part of the socket.

Latent Electricity.

The bound charge of static electricity. (See Charge, Bound.)

Law of Intermediate Metals.

A law of thermo-electricity. The electro-motive force between any two

metals is equal to the sum of electro-motive forces between each of the

two metals and any intermediate metal in the thermo-electric series, or

the electro-motive force between any two metals is equal to the sum of

the electromotive forces between all the intermediate ones and the

original two metals; it is the analogue of Volta's Law, q. v.

Law of Inverse Squares.

When force is exercised through space from a point, its intensity varies

inversely with the square of the distance. Thus the intensity of light

radiated by a luminous point at twice a given distance therefrom is of

one-fourth the intensity it had at the distance in question.

Gravitation, electric and magnetic attraction and repulsion and other

radiant forces are subject to the same law.

324   STANDARD ELECTRICAL DICTIONARY.

Law of Successive Temperatures.

A law of thermo-electricity. The electro-motive force due to a given

difference of temperature between the opposite junctions of the metals

is equal to the sum of the electro-motive forces produced by fractional

differences of temperature, whose sum is equal to the given difference

and whose sum exactly fills the given range of temperature.

Law, Right-handed Screw.

This rather crude name is given by Emtage to a law expressing the

relation of direction of current in a circuit to the positive direction

of the axis of a magnet acted on by such current. It is thus expressed:

A right-handed screw placed along the axis of the magnet and turned in

the direction of the current will move in the positive direction, i. e.,

towards the north pole of the axis of the magnet.

Lead.

A metal; one of the elements; symbol Pb. Atomic weight, 207;

equivalent, 103-1/2; valency, 2.

Lead may also be a tetrad, when its equivalent is 51.75.

The following data are at 0º C. (32º F.) with compressed metal:

Relative Resistance, (Silver = l)     13.05

Specific Resistance,                  19.63   microhms.

Resistance of a wire,

(a) 1 ft. long, weighing 1 grain,       3.200   ohms.

(b) 1 meter long, weighing 1 gram,      2.232  "

(c) 1 meter long, 1 millimeter thick,    .2498  "

Resistance of 1 inch cube,              7.728   microhms.

Electro-Chemical Equivalent (Hydrogen = .0105)   1.086   mgs.

Leading Horns.

The tips of pole pieces in a dynamo, which extend in the direction of

movement of the armature.

Leading-in Wires.

The platinum wires passing through the glass of an incandescent

lamp-chamber, to effect the connection of the carbon filament with the

wires of the circuit.

Lead of Brushes, Negative.

In a motor the brushes are set backwards from their normal position, or

in a position towards the direction of armature rotation or given a

negative lead instead of a positive one, such as is given to dynamo

brushes.

Leak.

A loss or escape of electricity by accidental connection either with the

ground or with some conductor. There are various kinds of leak to which

descriptive terms are applied.

Leakage.

The loss of current from conductors; due to grounding at least at two

places, or to very slight grounding at a great many places, or all along

a line owing to poor insulation. In aerial or pole telegraph lines in

wet weather there is often a very large leakage down the wet poles from

the wire. (See Surface Leakage--Magnetic Leakage.)

325   STANDARD ELECTRICAL DICTIONARY.

Leakage Conductor.

A conductor placed on telegraph poles to conduct directly to earth any

leakage from a wire and thus prevent any but a very small portion

finding its way into the other wires on the same pole. It presents a

choice of evils, as it increases the electrostatic capacity of the line,

and thus does harm as well as good. It consists simply of a wire

grounded and secured to the pole.

Leg of Circuit.

One lead or side of a complete metallic circuit.

Lenz's Law.

A law expressing the relations of direction of an inducing current or

field of force to the current induced by any disturbance in the

relations between such field and any closed conductor within its

influence. It may be variously expressed.

(a) If the relative position of two conductors, A and B, be changed, of

which A is traversed by a current, a current is induced in B in such a

direction that, by its electro-dynamic action on the current in A, it

would have imparted to the conductors a motion of the contrary kind to

that by which the inducing action was produced. (Ganot.)

(b) The new (induced) current will increase the already existing

resistances, or develop new resistance to that disturbance of the field

which is the cause of induction. (Daniell.)

(c) When a conductor is moving in a magnetic field a current is induced

in the conductor in such a direction as by its mechanical action to

oppose the motion. (Emtage.)

(d) The induced currents are such as to develop resistance to the change

brought about.

Letter Boxes, Electric.

Letter boxes with electrical connections to a bell or indicator of some

sort, which is caused to act by putting a letter into the box.

Leyden Jar.

A form of static condenser.

In its usual form it consists of a glass jar. Tinfoil is pasted around

the lower portions of its exterior and interior surfaces, covering from

one-quarter to three-quarters of the walls in ordinary examples. The

rest of the glass is preferably shellacked or painted over with

insulating varnish, q. v. The mouth is closed with a wooden or cork

stopper and through its centre a brass rod passes which by a short chain

or wire is in connection with the interior coating of the jar. The top

of the rod carries a brass knob or ball.

If such a jar is held by the tinfoil-covered surface in one hand and its

knob is held against the excited prime conductor of a static machine its

interior becomes charged; an equivalent quantity of the same electricity

is repelled through the person of the experimenter to the earth and when

removed from the conductor it will be found to hold a bound charge. If

the outer coating and knob are both touched or nearly touched by a

conductor a disruptive discharge through it takes place.

326   STANDARD ELECTRICAL DICTIONARY.

Fig. 213. LEYDEN JAR WITH DISCHARGER.

If one or more persons act as discharging conductors they will receive a

shock. This is done by their joining hands, a person at one end touching

the outer coating and another person at the other end touching the knob.

From an influence machine a charge can be taken by connecting the

coating to one electrode and the knob to the other.

Fig. 214. SULPHURIC ACID LEYDEN JAR.

327   STANDARD ELECTRICAL DICTIONARY.

Leyden Jar, Sir William Thomson's.

An especially efficient form of Leyden jar. It consists of a jar with

outer tinfoil coating only. For the interior coating is substituted a

quantity of concentrated sulphuric acid. The central rod is of lead with

a foot, which is immersed in the acid and from which the rod rises. A

wooden cover partly closes the jar, as the central tube through which

the rod passes is so large as not to allow the wood to touch it. Thus

any leakage from inner to outer coating has to pass over the inside and

outside glass surfaces. In the common form of jar the wooden cover may

short circuit the uncoated portion of the inner glass surface. In the

cut a simplified form of Thomson's Leyden jar is shown, adapted for

scientific work.

Lichtenberg's Figures.

If the knob of a Leyden jar or other exited electrode is rubbed over the

surface of ebonite, shellac, resin or other non-conducting surface it

leaves it electrified in the path of the knob. If fine powder such as

flowers of sulphur or lycopodium is dusted over the surface and the

excess is blown away, the powder will adhere where the surface was

electrified, forming what are called Lichtenberg's Figures, Lycopodium

and sulphur show both positive and negative figures, that is to say,

figures produced by a positively or negatively charged conductor. Red

lead adheres only to negative figures. If both positive and negative

figures are made and the surface is sprinkled with both red lead and

flowers of sulphur each picks out its own figure, the sulphur going

principally to the positive one.

The red lead takes the form of small circular heaps, the sulphur

arranges itself in tufts with numerous diverging branches. This

indicates the difference in the two electricities. The figures have been

described as "a very sensitive electrosope for investigating the

distribution of electricity on an insulating surface." (Ganot.)

Life of Incandescent Lamps.

The period of time a lamp remains in action before the carbon filament

is destroyed. The cause of a lamp failing may be the volatilization of

the carbon of the filament, causing it to become thin and to break; or

the chamber may leak. The life of the lamp varies; 600 hours is a fair

estimate. Sometimes they last several times this period.

The higher the intensity at which they are used the shorter is their

life. From their prime cost and the cost of current the most economical

way to run them can be approximately calculated.

[Transcriber's note: Contemporary incandecent buls are rated for 1000

hours; flourescent bulbs up to 24000 hours; LED lamps up to 100000 hours.]

Lightning.

The electrostatic discharge to the earth or among themselves of clouds

floating in the atmosphere. The discharge is accompanied by a spark or

other luminous effect, which may be very bright and the effects, thermal

and mechanical, are often of enormous intensity.

The lightning flash is white near the earth, but in the upper regions

where the air is rarefied it is of a blue tint, like the spark of the

electric machine. The flashes are often over a mile in length, and

sometimes are four or five miles long. They have sometimes a curious

sinuous and often a branching shape, which has been determined by

photography only recently. To the eye the shape seems zigzag.

328   STANDARD ELECTRICAL DICTIONARY.

In the case of a mile-long flash it has been estimated that 3,516,480 De

la Rue cells, q. v., would be required for the development of the

potential, giving the flash over three and one-half millions of volts.

But as it is uncertain how far the discharge is helped on its course by

the rain drops this estimate may be too high.

There are two general types of flash. The so-called zigzag flash

resembles the spark of an electric machine, and is undoubtedly due to

the disruptive discharge from cloud to earth. Sheet lightning has no

shape, simply is a sudden glow, and from examination of the spectrum

appears to be brush discharges (see Discharge, Brush) between clouds.

Heat lightning is attributed to flashes below the horizon whose light

only is seen by us. Globe or ball lightning takes the form of globes of

fire, sometimes visible for ten seconds, descending from the clouds. On

reaching the earth they sometimes rebound, and sometimes explode with a

loud detonation. No adequate explanation has been found for them.

The flash does not exceed one-millionth of a second in duration; its

absolute light is believed to be comparable to that of the sun, but its

brief duration makes its total light far less than that of the sun for

any period of time.

If the disruptive discharge passes through a living animal it is often

fatal. As it reaches the earth it often has power enough to fuse sand,

producing fulgurites, q. v. (See also Back Shock or Stroke of

Lightning.)

Volcanic lightning, which accompanies the eruptions of volcanoes, is

attributed to friction of the volcanic dust and to vapor condensation.

[Transcriber's note: The origin of lightning is still (2008) not fully

understood, but is thought to relate to charge separation in the

vertical motion of water droplets and ice crystals in cloud updrafts. A

lightning bolt carries a current of 40,000 to 120,000 amperes, and

transfers a charge of about five coulombs. Nearby air is heated to about

10,000 °C (18,000 °F), almost twice the temperature of the Sun’s

surface.]

Lightning Arrester.

An apparatus for use with electric lines to carry off to earth any

lightning discharge such lines may pick up. Such discharge would imperil

life as well as property in telegraph offices and the like.

Arresters are generally constructed on the following lines. The line

wires have connected to them a plate with teeth; a second similar plate

is placed near this with its teeth opposite to those of the first plate

and nearly touching it. The second plate is connected by a low

resistance conductor to ground. Any lightning discharge is apt to jump

across the interval, of a small fraction of an inch, between the

oppositely placed points and go to earth.

Another type consists of two plates, placed face to face, and pressing

between them a piece of paper or mica. The lightning is supposed to

perforate this and go to earth. One plate is connected to the line, the

other one is grounded.

The lightning arrester is placed near the end of the line before it

reaches any instrument. (See Alternative Paths.)

329   STANDARD ELECTRICAL DICTIONARY.

Fig. 215. COMB OR TOOTHED LIGHTNING ARRESTER.

Fig. 216. FILM OR PLATE LIGHTNING ARRESTER.

Lightning Arrester, Counter-electro-motive Force.

An invention of Prof. Elihu Thompson. A lightning arrester in which the

lightning discharge sets up a counter-electro-motive force opposed to

its own. This it does by an induction coil. If a discharge to earth

takes place it selects the primary of the coil as it has low

self-induction. In its discharge it induces in the secondary a reverse

electro-motive force which protects the line.

Lightning Arrester Plates.

The toothed plates nearly in contact, tooth for tooth, or the flat

plates of a film lightning arrester, which constitute a lightning

arrester. Some advocate restricting the term to the plate connected to

the line.

Lightning Arrester, Vacuum.

A glass tube, almost completely exhausted, into which the line wire is

fused, while a wire leading to an earth connection has its end fused in

also.

A high tension discharge, such as that of lightning, goes to earth

across the partial vacuum in preference to going through the line, which

by its capacity and self-induction opposes the passage through it of a

lightning discharge.

It is especially adapted for underground and submarine lines.

330   STANDARD ELECTRICAL DICTIONARY.

Lightning, Ascending.

Lightning is sometimes observed which seems to ascend. It is thought

that this may be due to positive electrification of the earth and

negative electrification of the clouds.

Lightning, Globe or Globular.

A very unusual form of lightning discharge, in which the flashes appear

as globes or balls of light. They are sometimes visible for ten seconds,

moving so slowly that the eye can follow them. They often rebound on

striking the ground, and sometimes explode with a noise like a cannon.

They have never been satisfactorily explained. Sometimes the phenomenon

is probably subjective and due to persistence of vision.

Lightning Jar.

A Leyden jar whose coatings are of metallic filings dusted on to the

surface while shellacked, and before the varnish has had time to dry. In

its discharge a scintillation of sparks appears all over the surface.

Line of Contact.

The line joining the points of contact of the commutator brushes in a

dynamo or motor.

Synonym--Diameter of Commutation.

Lines of Force.

Imaginary lines denoting the direction of repulsion or attraction in a

field of force, q. v. They may also be so distributed as to indicate the

relative intensity of all different parts of the field. They are normal

to equipotential surfaces. (See Electro-magnetic Lines of

Force--Electrostatic Lines of Force--Magnetic Lines of Force.)

Lines of Induction.

Imaginary lines within a body marking the direction taken within it by

magnetic induction. These are not necessarily parallel to lines of

force, but may, in bodies of uniform agglomeration, or in crystalline

bodies, take various directions.

Synonym--Lines of Magnetic Induction.

Lines of Slope.

Lines in a field of force which mark the directions in which the

intensity of force in the field most rapidly falls away.

Links, Fuse.

Links made of more or less easily fusible metal, for use as safety

fuses.

Listening Cam.

In a telephone exchange a cam or species of switch used to connect the

operator's telephone with a subscriber's line.

331  STANDARD ELECTRICAL DICTIONARY.

Lithanode.

A block of compressed lead binoxide, with platinum connecting foils for

use as an electrode in a storage battery. It has considerable capacity,

over 5 ampere-hours per pound of plates, but has not met with any

extended adoption.

Load.

In a dynamo the amperes of current delivered by it under any given

conditions.

Local Action.

(a) In its most usual sense the electric currents within a battery, due

to impurities in the zinc, which currents may circulate in exceedingly

minute circuits, and which waste zinc and chemicals and contribute

nothing to the regular current of the battery. Amalgamated or chemically

pure zinc develops no local action.

(b) The term is sometimes applied to currents set up within the armature

core or pole pieces of a dynamo. (See Currents, Foucault.)

Local Battery.

A battery supplying a local circuit (q. v.); in telegraphy, where it is

principally used, the battery is thrown in and out of action by a relay,

and its current does the work of actuating the sounder and any other

local or station instruments. (See Relay.)

Local Circuit.

A short circuit on which are placed local apparatus or instruments. Such

circuit is of low resistance and its current is supplied by a local

battery, q. v. Its action is determined by the current from the main

line throwing its battery in and out of circuit by a relay, q. v., or

some equivalent.

Local Currents.

Currents within the metal parts of a dynamo. (See Currents, Foucault.)

In a galvanic battery. where there is local action, q. v., there are

also local currents, though they are not often referred to.

Localization.

Determining the position of anything, such as a break in a cable, or a

grounding in a telegraph line. In ocean cables two typical cases are the

localization of a break in the conductor and of a defect in the

insulation admitting water. The first is done by determining the static

capacity of the portion of the line which includes the unbroken portion

of the conductor; the other by determining the resistance of the line on

a grounded circuit.

Locus.

A place. The word is used to designate the locality or position of, or

series of positions of definite conditions and the like. Thus an

isogonic line is the locus of equal declinations of the magnetic needle;

it is a line passing through all places on the earth's surface where the

condition of a given declination is found to exist.

332   STANDARD ELECTRICAL DICTIONARY.

Lodestone.

Magnetic magnetite; magnetite is an ore of iron, Fe3 04 which is

attracted by the magnet. Some samples possess polarity and attract iron.

The latter are lodestones.

Synonym--Hercules Stone

Logarithm.

The exponent of the power to which it is necessary to raise a fixed

number to produce a given number. The fixed number is the base of the

system. There are two systems; one, called the ordinary system, has 10

for its base, the other, called the Naperian system, has 2.71828 for its

base. The latter are also termed hyperbolic logarithms, and are only

used in special calculations.

Log, Electric.

An apparatus for measuring the speed of a ship. A rotating helical vane

of known pitch is dragged behind the vessel. As the helix rotates its

movements may actuate electric machinery for registering its rotations.

The number of these in a given time, multiplied by the pitch of the

vane, gives the distance traversed in such time.

Loop.

A portion of a circuit introduced in series into another circuit. The

latter circuit is opened by a spring-jack, q. v. or other device, and

the loop inserted. By loops any number of connections can be inserted

into a circuit in series therewith, and in series or in parallel with

one another.

Loop Break.

A double bracket or similar arrangement for holding on insulators the

ends of a conductor which is cut between them, and to which are

connected the ends of a loop. The space between the insulators may be

about a foot.

Luces.

This may be used as the plural of lux, q. v. It is the Latin plural.

Luminous Jar.

A Leyden jar whose coatings are of lozenge-shaped pieces of tinfoil

between which are very short intervals. When discharged, sparks appear

all over the surface where the lozenges nearly join.

Lux.

A standard of illumination, q. v., as distinguished from illuminating

power.

It is the light given by one candle at a distance of 12.7 inches--by a

carcel, q. v., at a distance of one meter---or by 10,000 candles at

105.8 feet.

It was proposed by W. H. Preece. All the above valuations are identical.

332   STANDARD ELECTRICAL DICTIONARY.

M.

(a) Symbol of gaseous pressure equal to one-millionth of an atmosphere.

(b) The Greek m, µ, is used as the symbol of magnetic permeability.

333   STANDARD ELECTRICAL DICTIONARY.

Machine, Cylinder Electric.

A frictional electric machine whose rotating glass is in the shape of a

cylinder instead of a disc as in the more recent machines.

Fig. 217. PLATE FRICTIONAL ELECTRIC MACHINE.

Machine, Frictional Electric.

An apparatus for development of high tension electricity by contact

action, brought about by friction.

It consists of a plate or cylinder of glass mounted on insulating

standards and provided with a handle for turning it. One or more

cushions of leather are held on an insulated support, so as to rub

against the plate or cylinder as it is turned. A metal comb or combs are

held on another insulating support so as to be nearly in contact with

the surface of the glass plate at a point as far removed as possible

from the rubbers. The combs are attached to a brass ball or round-ended

cylinder, which is termed the prime conductor.

In use either the prime conductor or cushions are connected by a chain

or otherwise with the earth. Assume it to be the cushions. As the

machine is worked by turning the plate, the glass and cushion being in

contact develop opposite electricities. The glass is charged with

positive electricity, and as it turns carries it off and as it reaches

the prime conductor by induction and conduction robs it of its negative

electricity. Meanwhile the cushions negatively excited deliver their

charge to the earth. The action thus goes on, the prime conductor being

charged with positive electricity.

334   STANDARD ELECTRICAL DICTIONARY.

If the prime conductor is connected to the earth and the cushions are

left insulated, negative electricity can be collected from the cushions.

In some machines both prime conductor and cushions are kept insulated

and without ground contact. Electrodes connecting with each are brought

with their ends close enough to maintain a sparking discharge.

Machine Influence.

A static electric machine working by induction to build up charges of

opposite nature on two separate prime conductors. In general they are

based on the principle of the electrophorous. Work is done by the

operator turning the handle. This rotates a disc and draws excited parts

of it away from their bound charges. This represents a resistance to

mechanical motion. The work absorbed in overcoming this mechanical

resistance appears as electric energy. There are various types of

influence machines, the Holtz, Toeppler-Holtz and Wimshurst being the

most used. The electrophorous, q. v., is a type of influence machine.

Machine, Holtz Influence.

A static electric machine. It includes two plates, one of which is

rapidly rotated in front of the other. Two armatures of paper are

secured to the back of the stationary plate at opposite ends of a

diameter. To start it one of these is charged with electricity. This

charge by induction acts through the two thicknesses of glass upon a

metal bar carrying combs, which lies in front of the further side of the

movable plate. The points opposite the armature repel electrified air,

which strikes the movable disc and charges it. A second rod with comb at

the opposite end of the same diameter acts in the reverse way. Thus

opposite sections of the disc are oppositely charged and the combs with

them. By induction these portions of the disc react upon the two

armatures. The opposite electricities escape from the armatures by paper

tongues which are attached thereto and press against the back of the

movable plate. As the plate rotates the opposite electricities on its

face neutralize the electricity repelled from the combs. The charges on

the back strengthen the charges of the armatures and brass combs. Thus

the machine builds up, and eventually a discharge of sparks takes place

from the poles of the brass combs.

335   STANDARD ELECTRICAL DICTIONARY.

Machine, Toeppler-Holtz.

A modification of the Holtz machine. The priming charge of the armatures

is produced by friction of metallic brushes against metallic buttons on

the face of the rotating plate. (See Machine, Holtz.)

Machine, Wimshurst.

A form of static influence machine. It consists of two plates of glass,

on which radial sectors of tinfoil are pasted. Both plates are rotated

in opposite directions. The sectors of the two plates react one upon the

other, and electric charges of opposite sign accumulate on the opposite

sides of the plates and are collected therefrom by collecting combs.

Mack.

A name, derived from Maxwell, and suggested for the unit of inductance.

It is due to Oliver Heaviside, but has never been adopted. (See Henry.)

Magne-Crystallic Action.

The action of a supposed force of the same name, proposed by Faraday. It

relates to the different action of a magnetic field upon crystalline

bodies, according to the position of their axes of crystallization. A

needle of tourmaline, normally paramagnetic, if poised with its axis

horizontal, is diamagnetic. Bismuth illustrates the same phenomenon. The

subject is obscure. Faraday thought that he saw in it the action of a

specific force.

Magnet.

A body which tends when suspended by its centre of gravity to lay itself

in a definite direction, and to place a definite line within it, its

magnetic axis, q. v., in a definite direction, which, roughly speaking,

lies north and south. The same bodies have the power of attracting iron

(Daniell), also nickel and cobalt.

Magnets are substances which possess the power of attracting iron.

(Ganot.)

[Transcriber's note: Edward Purcell and others have explained magnetic

and electromagnetic phenomenon as relativistic effects related to

electrostatic attraction. Magnetism is caused by Lorentz contraction of

space along the direction of a current. Electromagnetic waves are caused

by charge acceleration and the resulting disturbance of the

electrostatic field. (Electricity and Magnetism: Berkeley Physics

Course Volume 2, 1960)]

Magnet, Anomalous.

A magnet possessing more than the normal number (two) of poles. If two

straight magnets are placed end to end with their south poles in

juxtaposition the compound bar will seem to possess three poles, one at

each end and one in the middle. The apparent pole in the middle is

really made up of two consequent poles, q. v. It sometimes happens that

when a single long thin bar is magnetized consequent poles are produced,

although such magnet is in one piece. This may be accidental, as in such

case it is quite hard to avoid anomalous poles, or, as in the field

magnets of some forms of dynamos, anomalous poles may be purposely

produced.

Magnet, Artificial.

A magnet formed artificially by any method of magnetization (see

Magnetism) applicable to permanent magnets, electro-magnets and

solenoids. It expresses the distinction from the natural magnets or

lodestone, q. v. It is made of steel in practice magnetized by some of

the methods described under Magnetization.

336   STANDARD ELECTRICAL DICTIONARY.

Magnet, Axial.

A straight-solenoid with axial core.

Magnet, Bar.

A bar magnet is one in the shape of a bar, i. c., straight with parallel

sides and considerably longer than wide or deep.

Magnet, Bell-shaped.

A form of permanent magnet used in some galvanometers. In shape it is a

thick-sided cylindrical box with two slots cut out of opposite sides, so

as to make it represent a horseshoe magnet. Its shape enables it to be

surrounded closely by a mass of copper, for damping its motion, to

render the instrument dead-beat. Such a magnet is used in Siemens &

Halske's galvanometer.

Magnet Coil.

A coil to be thrust over an iron core, to make an electro-magnet. They

are often wound upon paper or wooden bobbins or spools, so as to be

removable from the core if desired.

Magnet, Compensating.

(a) A magnet fastened near a compass on an iron or steel ship to

compensate the action of the metal of the ship upon the magnetic needle.

The ship itself always has some polarity and this is neutralized by one

or more compensating magnets.

(b) See below.

Magnet, Controlling.

A magnet attached to a galvanometer by which the directive tendency of

its magnetic needle is adjusted. In the reflecting galvanometer it often

is a slightly curved magnet carried by a vertical brass spindle rising

from the center of the instrument, and which magnet may be slid up and

down on the spindle to regulate or adjust its action.

Synonym--Compensating Magnet.

Magnet, Compound.

A permanent magnet, built up of a number of magnets. Small bars can be

more strongly magnetized than large. Hence a compound magnet may be made

more powerful than a simple one.

Magnet Core.

The iron bar or other mass of iron around which insulated wire is wound

for the production of an electro-magnet. The shapes vary greatly,

especially for field magnets of dynamos and motors. For these they are

usually made of cast iron, although wrought iron is preferable from the

point of view of permeability.

Magnet, Damping.

A damping magnet is one used for bringing an oscillating body to rest.

The body may be a metallic disc or needle, and the action of the magnet

depends on its lines of force which it establishes, so that the body has

to cut them, and hence has its motion resisted.

337   STANDARD ELECTRICAL DICTIONARY.

Magnet, Deflection of.

The change of position of a magnet from the plane of the earth's

meridian in which it normally is at rest into another position at some

angle thereto, by the effect of an artificial magnetic field, as the

deflection of a galvanometer needle.

Magnet, Electro-.

A magnet consisting of a bar of iron, bundle of iron wires, iron tube or

some equivalent, around which a coil of insulated wire is wound. Such

combination becomes polarized when a current is passed through it and is

an active magnet. On the cessation of the current its magnetism in part

or almost completely disappears. (See Electro-magnet.)

Magnet, Equator of.

In a magnet the locus of points of no attractive power and of no

polarity. In a symmetrical, evenly polarized magnet it is the imaginary

line girdling the centre. The terms Neutral Point or Neutral Line have

displaced it.

Synonyms--Neutral Line--Neutral Point.

Magnet, Field.

A magnet, generally an electro-magnet, used to produce the field in a

dynamo or motor.

Magnet, Haarlem.

Celebrated magnets made in Haarlem, Holland. Logeman, Van Wetteren,

Funckler and Van der Willigen were the makers who gave the celebrity to

the magnets. They were generally horseshoe magnets, and would carry

about twenty times their own weight.

Magnet, Horseshoe.

A magnet of U shape--properly one with the poles brought a little closer

together than the rest of the limbs. For direct lifting and attractive

effects it is the most generally adopted type. Its advantage as regards

lifting effect is due to small reluctance, q. v., offered by a complete

iron circuit, such as the armature and magnet together produce. As the

term is now used it is applied to any U shaped magnet.

Fig. 218. JOULE'S ELECTRO-MAGNET.

Magnet, Joule's Electro.

An electro-magnet of the shape of a cylinder with a longitudinal segment

cut-off. It is wound with wire as shown. The segment cut-off is a piece

of the same shape as the armature. It is of high power.

338   STANDARD ELECTRICAL DICTIONARY.

Magnetic Adherence.

The tendency of a mass of iron to adhere to the poles of a magnet. It is

best figured as due to the virtual shortening of lines of force, as the

more permeable iron gives a better path for them than the air can

afford, and consequently a virtually shorter one.

Magnetic Attraction and Repulsion.

The attraction of a magnet for iron, steel, nickel and cobalt and of

unlike poles of magnets for each other. It is identical with

electro-magnetic attraction, q.v. (Also see Electro-magnetism.)

Magnetic Attraction and Repulsion, Coulomb's Law of.

Magnetic attraction and repulsion are inversely as the square of the

distance. (Ganot.)

While theoretically true in the case of isolated poles, in practise it

does not generally apply on account of the large diameter and relative

shortness of magnets.

Magnetic Axis.

The line connecting the poles of a magnet. It does not generally

coincide exactly with any symmetrical axis of figure. In such cases an

error is introduced into the indications of the needle which must be

determined and allowed for in compasses. To determine it with a magnetic

needle the suspension cup is made removable, so that the needle can be

reversed. Readings are taken with one side of the needle and then with

the other side of the needle up, and the average corresponds with the

position of the magnetic axis in both positions of the needle.

Magnetic Azimuth.

The angle, measured on a horizontal circle, between the magnetic

meridian and a great circle of the earth passing through the observer

and any observed body. It is the astronomical azimuth of a body referred

to the magnetic meridian and therefore subject to the variation of the

compass. The angle is the magnetic azimuth of the observed body.

Magnetic Battery.

A name for a compound permanent magnet; one made up by bolting or

clamping together, or to single soft iron pole pieces, a number of

single permanent magnets. There are a number of forms of compound

magnets. In making them care has to be taken to have them of even

strength. It is also well to have them slightly separated. The object of

both these precautions is to prevent a stronger element or magnet from

depolarizing its neighbor.

Synonym--Compound Magnet.

Magnetic Bridge.

An apparatus for testing the relative permeability of iron. It consists

of a rectangular system of iron cores. Three of the sides are wound with

wire as shown. The other side is built up of double bars, and from the

centre two curved arms rise, as shown in the cut. The arms do not touch.

Between them a short magnet is suspended by a filament, which also

carries a mirror and an index.

339   STANDARD ELECTRICAL DICTIONARY.

Fig. 219. MAGNETIC BRIDGE.

A lamp and scale are provided as in the reflecting galvanometer. When

adjusted the magnetic needle hangs as shown in the cut, Fig. 219,

without any tendency to turn towards either curved pole piece. If all

iron parts are symmetrical and of similar metal, a current through the

coils will make no difference. It will work in magnetic opposition upon

the two arms, or, in other words, will maintain both arms at identical

potential.

Fig. 220. POLE PIECES, MAGNETIC NEEDLE

AND MIRROR OF MAGNETIC BRIDGE.

If there is the least difference in permeability, length or thickness

between any of the iron bars the magnetic potential of the two curved

arms will differ, and the magnetic needle will turn one way or the

other. In practical use different samples of iron are substituted for

the unwound members of the fourth side of the parallelogram, and the

needle by its motions indicates the permeability.

In the cut, Fig. 220, D D are the ends of the curved pole pieces; A the

wire carrying the mirror B and magnetic needle N, and E is the index

which shows the larger deflections.

340   STANDARD ELECTRICAL DICTIONARY.

Magnetic Circuit.

A magnetic field of force is characterized by the presence of lines of

force, which, while approximately parallel, curve around and tend to

form closed curves. The polarity of a field of force is referred to an

imaginary direction of the lines of force from the north pole through

space to the south pole, and in the part of the field corresponding to

the body of the magnet, from the south to the north pole. The cut

indicates these features. Hence the magnetic field of force is termed

the magnetic circuit, and to it are attributed a species of resistance

termed reluctance, q. v., and the producing cause of the field or lines

of force is termed sometimes magneto-motive force, q. v.) corresponding

to the electro-motive force. The modern treatment of the magnetic

circuit is similar to the application of Ohm's law and the laws of

resistance and conductivity to the electric circuit.

Magnetic Circuit, Double.

A magnetic circuit which virtually represents two horseshoe magnets

placed with their like poles in contact. It is used for field magnets,

the armatures occupying a place between the consequent poles.

Fig. 221. ONE-HALF PORTION OF A DOUBLE MAGNETIC CIRCUIT.

Magnetic Concentration of Ores.

The concentration of ores or the freeing them from their gangue by

magnetic attraction. It is only applicable to those cases in which

either the ore itself or the gangue is attracted by the magnet. Its

principal application is to the concentration of magnetic iron sands.

(See Magnetic Concentration.)

Magnetic Concentrator.

An apparatus similar to a magnetic separator, q. v., but used to

concentrate magnetic iron sands. By the action of electro-magnets the

magnetic iron sand (magnetite) is separated from the sand with which it

is mixed.

Magnetic Conductivity and Conductance.

The first notion of permeance and of the magnetic circuit included the

idea of magnetic conductivity, which conducted lines of force urged by

magneto-motive force through a magnetic circuit. The terms are displaced

by permeability and permeance.

341   STANDARD ELECTRICAL DICTIONARY.

Magnetic Continuity.

The completeness of a magnetic circuit, as when the armature of a

horseshoe magnet is in contact with both poles. It is an attribute of a

paramagnetic substance only and is identical for permanent magnets or

for electro-magnets. An air space intervening between armature and

magnet poles, or a space filled with any diamagnetic substance prevents

continuity, although the lines of force to some extent still find their

way around. The leakage is increased by discontinuity.

Magnetic Control.

Control of a magnetic needle, magnet, iron index or armature, in a

galvanometer, ammeter or voltmeter by a magnetic field; the restitutive

force being derived from a permanent magnet.

Magnetic Couple.

The couple of magnetic force which tends to bring the magnetic needle

into the plane of the magnetic meridian. One force is represented by the

imaginary pull upon the north pole, and the other by the opposite pull

upon the south pole of the needle. The moment of the couple varies from

a maximum when the needle is at right angles to the plane of the

magnetic meridian to zero when it is in such plane.

Magnetic Creeping.

Viscous hysteresis; the slow increase of magnetism in a paramagnetic

body when exposed to induction.

Fig. 222. MAGNETIC CURVES OR FIGURES.

Magnetic Curves.

The pictorial representation of magnetic lines of force. It is generally

produced by scattering filings on a sheet of paper or pane of glass held

over a magnet. The filings arrange themselves in characteristic curves.

Tapping the paper or pane of glass facilitates the arrangement, or

jarring the filings off a smaller magnet, so that they fall polarized

upon the paper, is thought by some to improve the effect. The group of

curves forms what are termed magnetic figures, q. v.

342   STANDARD ELECTRICAL DICTIONARY.

Magnetic Declination.

The angular deviation of the magnetic needle, causing it to rest at an

angle with the true meridian; the variation of the compass. (See

Magnetic Elements.)

Magnetic Density.

The intensity of magnetization expressed in lines of force per stated

area of cross-section in a plane at right angles to the lines of force.

Magnetic Dip.

The inclination from the horizontal assumed by a magnetic needle free to

move in the vertical plane. (See Magnetic Elements.) The angle of dip or

inclination is entirely a function of the earth, not of the needle.

Magnetic Discontinuity.

A break or gap in a magnetic circuit. To make a complete circuit the

iron or other core must be continuous. If the armature of a horseshoe

magnet is in contact with both poles the continuity is complete. If the

armature is not in contact magnetic continuity gives place to

discontinuity. It is an attribute of a paramagnetic substance only, and

is identical for permanent magnets, or for electro-magnets.

Magnetic Elements.

The qualities of the terrestrial magnetism at any place as expressed in

its action upon the magnetic needle. Three data are involved.

I. The Declination or Variation.

II. The Inclination or Dip.

III. The Force or Intensity.

I. The Declination is the variation expressed in angular degrees of the

magnetic needle from the true north and south, or is the angle which the

plane of the magnetic meridian makes with that of the geographical

meridian. It is expressed as east or west variation according to the

position of the north pole; east when the north pole of the needle is to

the east of the true meridian, and vice versa. Declination is different

for different places; it is at present west in Europe and Africa, and

east in Asia and the greater part of North and South America. The

declination is subject to (a) secular, (b) annual and (c) diurnal

variations. These are classed as regular; others due to magnetic storms

are transitory and are classed as irregular, (a) Secular variations. The

following table shows the secular variations during some three hundred

years at Paris. These changes are termed secular, because they require

centuries for their completion.

343

STANDARD ELECTRICAL DICTIONARY.

Table of Declination or Variation at Paris.

Year.   Declination.

1580   11º 30' E.

1663    0°

1700    8° 10' W.

1780   19º 55' W.

1785   22º 00' W.

1805   22º  5' W.

1814   22º 34' W.

1825   22° 22' W.

1830   22º 12' W.

1835   22º  4' W.

1850   20º 30' W.

1855   19º 57' W.

1860   19º 32' W.

1865   18º 44' W.

1875   17º 21' W.

1878   17º 00' W.

[Transcriber's note The value for 2008 is about  0° 48' W, changing by

0° 7' E/year.]

On scrutinizing these figures it will be seen that there is part of a

cycle represented and that the declination is slowly returning to the

zero point after having reached its maximum western variation in 1814.

Upwards of 300 years would be required for its completion on the basis

of what is known. In other places, notably the coast of Newfoundland,

the Gulf of the St. Lawrence and the rest of the North American seaboard

and in the British Channel, the secular variations are much more rapid

in progress. (b) Annual variations--These were first discovered in 1780

by Cassini. They represent a cycle of annual change of small extent,

from 15' to 18' only. In Paris and London the annual variation is

greatest about the vernal equinox, or March 21st, and diminishes for the

next three months, and slowly increases again during the nine following

months. It varies during different epochs. (c) Diurnal variations were

discovered in 1722 by Graham. A long needle has to be employed, or the

reflection of a ray of light, as in the reflecting galvanometer, has to

be used to observe them. In England the north pole of the magnetic

needle moves every day from east to west from sunrise until 1 or 2 P.

M.; it then tends towards the east and recovers its original position by

10 P. M. During the night the needle is almost stationary. As regards

range the mean amplitude of diurnal variations at Paris is from April to

September 13' to 15'; for the other months from 8' to 10'. On some days

it amounts to 25' and sometimes is no more than 5'. The amplitude of

diurnal variations decreases from the poles to the equator. Irregular

variations accompany earthquakes, the aurora borealis and volcanic

eruptions. In Polar regions the auroral variations may be very great;

even at 40° latitude they may be 1° or 2°. Simultaneous irregularities

sometimes extend over large areas. Such are attributed to magnetic

storms. II. The Inclination is the angle which the magnetic needle makes

with the horizon, when the vertical plane in which the needle is assumed

to be free to move coincides with the magnetic meridian. It is sometimes

called the dip of the needle. It varies as does the declination, as

shown in the following table of inclinations of London.

344   STANDARD ELECTRICAL DICTIONARY.

Table of Inclination or Dip at London

Year.   Inclination.

1576   71° 50'

1600   72°

1676   73° 30'

1723   74° 42'

1773   72° 19'

1780   72°  8'

1790   71° 33'

1800   70° 35'

1821   70° 31'

1828   69° 47'

1838   69° 17'

1854   68° 31'

1859   68° 21'

1874   67° 43'

1876   67° 39'

1878   67° 36'

1880   67° 35'

1881   67° 35'

III. Force or Intensity is the directive force of the earth. It varies

with the squares of the number of oscillations the magnetic needle will

make if caused to oscillate from a determined initial range. The

intensity is supposed to be subject to secular change. According to

Gauss the total magnetic intensity of the earth is equal to that which

would be exerted if in each cubic yard there were eight bar magnets,

each weighing one pound. This is, of course, a rough way of expressing

the degree of intensity. Intensity is least near the magnetic equator

and greatest near the magnetic poles; the places of maximum intensity

are termed the magnetic foci. It varies with the time of day and

possibly with changes in altitude.

Magnetic Elongation.

The elongation a bar of iron or steel undergoes when magnetized. By

magnetization it becomes a little longer and thinner, there being no

perceptible change in volume. The change is accompanied by a slight

sound--the magnetic tick. An exceedingly delicate adjustment of

apparatus is required for its observation.

Magnetic Equator.

A locus of the earth's surface where the magnet has no tendency to dip.

It is, approximately speaking, a line equally distant from the magnetic

poles, and is called also the aclinic line. It is not a great circle of

the earth.

345  STANDARD ELECTRICAL DICTIONARY.

Magnetic Field of Force.

The field of force established by a magnet pole. The attractions and

repulsions exercised by such a field follow the course of the electro-

magnetic lines of force. (See also Field of Force.) Thus the tendency of

a polarized needle attracted or repelled is to follow, always keeping

tangential to curved lines, the direction of the lines of force, however

sweeping they may be. The direction of magnetic lines of force is

assumed to be the direction in which a positive pole is repelled or a

negative one attracted; in other words, from the north pole of a magnet

to its south pole in the outer circuit. The direction of lines of force

at any point, and the intensity or strength of the field at that point,

express the conditions there. The intensity may bc expressed in terms of

that which a unit pole at unit distance would produce. This intensity as

unitary it has been proposed to term a Gauss. (See Weber.)

The direction of the lines of force in a magnetic field are shown by the

time-honored experiment of sprinkling filings of iron upon a sheet of

paper held over a magnet pole or poles. They arrange themselves, if the

paper is tapped, in more or less curved lines tending to reach from one

pole of the magnet to the other. Many figures may be produced by

different conditions. Two near poles of like name produce lines of force

which repel each other. (See Magnetic Curves.)

A magnetic and an electro-magnetic field are identical in all essential

respects; the magnetic field may be regarded as a special form of the

electro-magnetic field, but only special as regards its production and

its defined north and south polar regions.

Synonyms--Magnetic Spin (not much used).

Magnetic Field, Uniform.

A field of identical strength in all parts, such as the earth's magnetic

field. If artificially produced, which can only be approximately done,

it implies large cross-section of magnet pole in proportion to the

length of the magnetic needle affected by it, which is used in

determining its uniformity.

Magnetic Figures.

The figures produced by iron filings upon paper or glass held near

magnetic poles. By these figures the direction of lines of force is

approximately given, and a species of map of the field is shown. (See

Magnetic Field of Force--Magnetic Curves.)

Magnetic Filament.

The successive rows of polarized molecules assumed to exist in

magnetized iron. Each molecule represents an infinitely small magnet,

and its north pole points to the south pole of the next molecule. Such a

string or row is a theoretical conception based on the idea that the

molecules in a magnet are all swung in to parallelism in the magnetizing

process. A magnetic filament may be termed the longitudinal element of a

magnet. (See Magnetism, Hughes' Theory of.)

[Transcriber's note: This description parallels the modern

notion of electron spin as the basis of magnetism in materials.]

Magnetic Fluids.

A two-fluid theory of magnetism has been evolved, analogous to the

two-fluid theory of electricity. It assumes north fluid or "red

magnetism" and a south fluid or "blue magnetism." Each magnetism is

supposed to predominate at its own pole and to attract its opposite.

Before magnetization the fluids are supposed to neutralize each other

about each molecule; magnetization is assumed to separate them,

accumulating quantities of them at the poles.

Magnetic Flux.

Magnetic induction; the number of lines of force that pass through a

magnetic circuit.

Synonym--Magnetic Flow.

346   STANDARD ELECTRICAL DICTIONARY.

Magnetic Force.

The forces of attraction and repulsion exercised by a magnet. By

Ampere's theory it is identical with the forces of attraction and

repulsion of electric currents.

Magnetic Friction.

The damping effect produced on the movements of a mass of metal by

proximity to a magnet; the phenomenon illustrated in Arago's wheel, q.

v. When a mass of metal moves in the vicinity of a magnet it cuts the

lines of force emanating from its poles, thereby producing currents in

its mass; as the production of these currents absorbs energy a damping

effect is produced upon the movements of the mass.

Magnetic Gear.

Friction gear in which electro-magnetic adherence is employed to draw

the wheels together. (See Adherence, Electro-magnetic--Electro-magnetic

Friction Gear.)

Magnetic Inclination.

The inclination from the horizontal of a magnetic needle placed in the

magnetic meridian. (See Magnetic Element--Inclination Map.)

Synonym--Magnetic Dip.

Magnetic Induction.

The force of magnetization within an induced magnet. It is in part due

to the action of the surrounding particles of polarized material; in

part to the magnetic field. (See Magnetic Induction, Coefficient of.)

In a more general way it is the action of a magnet upon bodies in its

field of force. In some cases the magnetism induced causes the north

pole of the induced magnet to place itself as far as possible from the

north pole of the inducing magnet and the same for the south poles. Such

substances are called paramagnetic or ferromagnetic. They lie parallel

or tangential to the lines of force. In other cases the bodies lie at

right angles or normal to the lines of force. Such bodies are called

diamagnetic.

Some bodies are crystalline or not homogeneous in structure, and in them

the lines of magnetic induction may take irregular or eccentric paths.

(See AEolotropic.)

Synonym--Magnetic Influence.

Magnetic Induction, Apparent Coefficient of.

The apparent permeability of a paramagnetic body as affected by the

presence of Foucault currents in the material itself. These currents act

exactly as do the currents in the coils surrounding the cores of

electro-magnets. They produce lines of force which may exhaust the

permeability of the iron, or may, if in an opposite direction, add to

its apparent permeability.

Magnetic Induction, Coefficient of.

The number, obtained by dividing the magnetization of a body, expressed

in lines of force produced in it, by the magnetizing force which has

produced such magnetization, expressed in lines of force producible by

the force in question in air. It always exceeds unity for iron, nickel

and cobalt. It is also obtained by multiplying the coefficient of

induced magnetization by 4 PI (4 * 3.14159) and adding 1. (See Magnetic

Susceptibility--Magnetization, Coefficient of Induced.)

347   STANDARD ELECTRICAL DICTIONARY.

The coefficient of magnetic induction varies with the material of the

induced mass, and varies with the intensity of the magnetizing force.

This variation is due to the fact that as the induced magnetism in a

body increases, the magnetizing force required to maintain such

induction, increases in a more rapid ratio. The coefficient of magnetic

induction is the same as magnetic permeability, and in a certain sense

is the analogue of conductivity. It is also termed the multiplying power

of the body or core magnetized. It is the coefficient of induced

magnetization (see Magnetization, Coefficient of Induced) referred to a

mass of matter. For diamagnetic bodies the coefficient has a negative

sign; for paramagnetic bodies it has a positive sign.

Synonyms--Permeability--Multiplying Power--Magnetic Inductive Capacity.

Magnetic Induction, Dynamic.

The induction produced by a magnetic field which moves with respect to a

body, or where the body if moving moves at a different rate, or where

the body moves and the field is stationary. In the case where both move,

part of the induction may be dynamic and part static. (See Magnetic

Induction, Static.)

Magnetic Induction, Static.

Magnetic induction produced by a stationary field acting upon a

stationary body.

Magnetic Induction, Tube of.

An approximate cylinder or frustrum of a cone whose sides are formed of

lines of magnetic induction. (See Magnetic Induction, Lines of.) The

term tube is very curiously applied in this case, because the element or

portion of a magnetic field thus designated is in no sense hollow or

tubular.

Magnetic Inertia.

A sensible time is required to magnetize iron, or for it to part with

its magnetism, however soft it may be. This is due to its magnetic

inertia and is termed the lag. Permanent or residual magnetism is a

phase of it. It is analogous to self-induction of an electric circuit,

or to the residual capacity of a dielectric.

Magnetic Insulation.

Only approximate insulation of magnetism is possible. There is no

perfect insulator. The best ones are only 10,000 times less permeable

than iron. Hence lines of force find their way through air and all other

substance, being simply crowded together more in paths of iron or other

paramagnetic substance.

348   STANDARD ELECTRICAL DICTIONARY.

Magnetic Intensity.

The intensity of the magnetization of a body. It is measured by the

magnetic lines of force passing through a unit area of the body, such

area being at right angles to the direction of the lines of force.

Magnetic Lag.

In magnetism the tendency of hard iron or steel especially to take up

magnetism slowly, and to part with it slowly. (See Magnetic Inertia.)

The lag affects the action of a dynamo, and is a minor cause of those

necessitating the lead of the brushes.

Synonym--Magnetic Retardation.

Magnetic Latitude.

Latitude referred to the magnetic equator and isoclinic lines.

Magnetic Leakage.

The lines of force in a field magnet which pass through the air and not

through the armature are useless and represent a waste of field. Such

lines constitute magnetic leakage.

Magnetic Limit.

The temperature beyond which a paramagnetic metal cannot be magnetized.

The magnetic limit of iron is from a red to a white heat; of cobalt, far

beyond a white heat; of chromium, below a red heat; of nickel at about

350° C. (662°F.) of manganese, from 15° C. to 20° C. (59° to 68° F.)

Magnetic Lines of Force.

Lines of force indicating the distribution of magnetic force, which is

due presumably to whirls of the ether. A wire or conductor through which

a current is passing is surrounded by an electro-magnetic field of

force, q. v., whose lines of force form circles surrounding the

conductor in question. A magnet marks the existence of a similar

electro-magnetic field of force whose lines form circuits comprising

part of and in some places all of the body of the magnet, and which are

completed through the air or any surrounding paramagnetic or diamagnetic

body. They may be thought of as formed by the Ampérian sheet of current,

and analogous to those just mentioned as surrounding a conductor.

Fig. 223. MAGNETIC LINES OF FORCE, DIRECTION OF.

A magnetic line of force may be thought of as a set of vortices or

whirls, parallel to each other, and strung along the line of force which

is the locus of their centres.

If as many lines are drawn per square centimeter as there are dynes (per

unit pole) of force at the point in question, each such line will be a

unitary c. g. s. line of force.

349   STANDARD ELECTRICAL DICTIONARY.

Magnetic Mass.

A term for a quantity of magnetism. Unit mass is the quantity which at

unit distance exercises unit force.

Magnetic Matter.

Imaginary matter assumed as a cause of magnetism. Two kinds, one

positive and one negative, may be assumed as in the two fluid theory of

electricity, or only one kind, as in the single fluid theory of

electricity. Various theories of magnetic matter have been presented

whose value is only in their convenience.

[Transcriber's note: See "magnet" and Edward Purcell's explanation of

magnetism using general relativity.]

Magnetic Memory.

The property of retaining magnetism; coercive force; magnetic inertia;

residual magnetism.

[Transcriber's note: Small ferrite magnetic donuts were used as computer

main memory from 1950 to 1970.]

Magnetic Meridian.

A line formed on the earth's surface by the intersection therewith of a

plane passing through the magnetic axis. It is a line determined by the

direction of the compass needle. The meridians constantly change in

direction and correspond in a general way to the geographical meridians.

Magnetic Moment.

The statical couple with which a magnet would be acted on by a uniform

magnetic field of unit intensity if placed with its magnetic axis at

right angles to the lines of force of the field. (Emtage.) A uniformly

and longitudinally magnetized bar has a magnetic moment equal to the

product of its length by the strength of its positive pole.

Magnetic Needle.

A magnet with a cup or small depression at its centre and poised upon a

sharp pin so as to be free to rotate or oscillate in a horizontal plane.

The cup is often made of agate. Left free to take any position, it

places its magnetic axis in the magnetic meridian.

Magnetic Parallels.

Lines roughly parallel to the magnetic equator on all parts of each of

which the dip of the magnetic needle is the same; also called Isoclinic

Lines. These lines mark the places of the intersection of equipotential

surfaces with the earth's surface. They are not true circles, and near

the poles are irregular ellipses; the magnet there points toward their

centres of curvature. They correspond in a general way with the

Geographical Parallels of Latitude.

Magnetic Permeability.

The specific susceptibility of any substance, existing in a mass, for

magnetic induction. (See Magnetic Induction, Coefficient of, synonym for

Magnetic Permeability and Magnetization, Coefficient of Induced.)

Synonyms--Magnetic Inductive Capacity--Multiplying Power--Coefficient of

Magnetic Induction.

350   STANDARD ELECTRICAL DICTIONARY.

Magnetic Perturbations.

Irregular disturbances of the terrestrial magnetism, as by the aurora

and in electric storms.

Magnetic Poles.

The points where the equipotential surfaces of the terrestrial field of

force graze the earth's surface; the points toward which the north or

south poles of the magnetic needle is attracted. Over a magnetic pole

the magnetic needle tends to stand in a vertical position. There are two

poles, Arctic or negative, and Antarctic or positive. Magnetic needles

surrounding them do not necessarily point toward them, as they point to

the centres of curvature of their respective magnetic parallels. The

poles constantly change in position. The line joining them does not

coincide with anything which may be termed the magnetic axis of the

earth.

Magnetic Poles, False.

Poles on the earth's surface other than the two regular magnetic poles.

There seem by observation to be several such poles, while analogy would

limit true magnetic poles to two in number.

Magnetic Potential.

The potential at any point of a magnetic field is the work which would

be done by the magnetic forces of the field upon a positive unit of

magnetism as it moves from that point to an infinite distance. (Emtage.)

Magnetic Proof Piece.

A piece of iron used for testing magnets and the distribution of

magnetism in bars, by suspending or supporting above or near the magnet,

by detaching after adherence, and in other ways.

Magnetic Proof Plane.

An exploring coil used for testing the distribution of magnetism. It is

connected in circuit with a galvanometer, and exposed to alternation of

current, or to other disturbing action produced by the magnet or field

under examination. This affects the galvanometer, and from its movements

the current produced in the coil, and thence the magnetic induction to

which it was exposed, are calculated.

Synonym--Exploring Coil.

Magnetic Quantity.

The magnetism possessed by a body; it is proportional to the action of

similar poles upon each other, or to the field produced by the pole in

question. It is also called the strength of a pole.

The force exercised by two similar poles upon each other varies with

their product and inversely with the square of the distance separating

them; or it may be expressed thus (m * m) / (L^2). This is a force, and

the dimensions of a force are ML/(T^2). Therefore, (m^2)/(L^2) =

ML/(T^2) or m = (M^.5)*(L^1.5)/T.

351   STANDARD ELECTRICAL DICTIONARY.

Magnetic Reluctance.

The reciprocal of permeance; magnetic resistance; the relative

resistance to the passage of lines of force offered by different

substances. The idea is derived from treating the magnetic circuit like

an electric one, and basing its action on magneto-motive force acting

through a circuit possessing magnetic reluctance.

Magnetic Reluctivity.

The reciprocal of magnetic permeability, q. v.

Synonym--Magnetic Resistance.

Magnetic Retentivity.

The property of steel or hard iron by which it slowly takes up and

slowly parts with a magnetic condition--traditionally (Daniell) called

coercitive force.

Magnetic Rotary Polarization.

If a plane polarized beam of light is sent through a transparent medium

in a magnetic field its plane of polarization is rotated, and this

phenomenon is denoted as above. (Compare Refraction, Electric, and see

Electro-magnetic Stress.) This has been made the basis of a method for

measuring current. A field of force varies with the current; the

polarization produced by such field is therefore proportional to the

current. (Becquerel & Rayleigh.)

A plane polarized beam of light passing through the transparent medium

in the magnetic field by the retardation or acceleration of one of its

circular components has its plane of polarization rotated as described.

The direction of the lines of force and the nature of the medium

determine the sense of the rotation; the amount depends upon the

intensity of the field resolved in the direction of the ray, and on the

thickness and nature of the medium.

Magnetic Saturation.

The maximum magnetic force which can be permanently imparted to a steel

bar. A bar may be magnetized beyond this point, but soon sinks to it.

The magnetism produced in a bar is prevented from depolarization by the

retentivity or coercive force of the bar. The higher the degree of

magnetization the greater the tendency to depolarization.

It is also defined as the maximum intensity of magnetism produced in a

paramagnetic substance by a magnetic field as far as affected by the

permeability of the substance in question. The more lines of force

passed through such a substance the lower is its residual permeability.

It is assumed that this becomes zero after a certain point, and then the

point of saturation is reached. After this point is reached the addition

of any lines of force is referred entirely to the field and not at all

to the permeability of the substance. But such a zero is only definable

approximately.

Magnetic Screen.

A box or case of soft iron, as thick as practicable, for protecting

bodies within it from the action of a magnetic field. The lines of force

to a great extent keep within the metal of the box on account of its

permeability, and but a comparatively few of them cross the space within

it.

Such screens are used to prevent watches from being magnetized, and are

a part of Sir William Thomson's Marine galvanometer.

A magnetic screen may be a sphere, an infinite or very large plane, or

of the shape of any equipotential surface.

Synonym--Magnetic Shield.

352   STANDARD ELECTRICAL DICTIONARY.

Magnetic Self-induction.

The cause of a magnet weakening is on account of this quality, which is

due to the direction of the lines of force within a magnet from the

positive towards the negative pole. "A magnet thus tends to repel its

own magnetism and to weaken itself by self-induction." (Daniell.)

Magnetic Separator.

An apparatus for separating magnetic substances from mixtures. Such

separators depend on the action of electro-magnets. In one form the

material falls upon an iron drum, magnetized by coils. Any magnetic

substance adheres to the drum and is thereby separated. They are used by

porcelain makers for withdrawing iron particles from clay, by machinists

to separate iron filings and chips from brass, and for similar purposes.

Fig. 224. MAGNETIC SEPARATOR.

Magnetic Shell.

A theoretical conception of a cause of a magnetic field or of a

distribution of magnetism. If we imagine a quantity of very short

magnets arranged in contact with their like poles all pointing in the

same direction so as to make a metal sheet, we have a magnetic shell.

Its magnetic moment is equal to the sum of the magnetic moment of all

its parts. If the shell is of uniform strength the magnetic moment of a

unit area gives the strength of the shell; it is equal to the magnetic

quantity per unit of area, multiplied by the thickness of the shell.

If its strength is uniform throughout a magnetic shell is called simple;

if its strength varies it is termed complex.

Emtage thus defines it: A magnetic shell is an indefinitely thin sheet

magnetized everywhere in the direction normal to itself.

Magnetic Shell, Strength of.

The magnetic quantity per unit of area of the shell multiplied by the

thickness of the shell.

353   STANDARD ELECTRICAL DICTIONARY.

Magnetic Shield.

In general a magnetic screen, q. v. Sometimes a strong local field is

made to act as a shield, by its predominance overcoming any local or

terrestrial field to which the needle to be protected may be exposed.

Magnetic Shunt.

The conception of a magnetic circuit being formed, the shunt is a

corollary of the theory. It is any piece of iron which connects points

of a magnet differing in polarity, so as to divert part of the lines of

force from the armature or yoke. The shunt is especially applicable in

the case of horseshoe magnets. Thus a bar of iron placed across from

limb to limb a short distance back from the poles would act as a shunt

to the armature and would divert to itself part of the lines of force

which would otherwise go through the armature and would weaken the

attraction of the magnet for the latter. In dynamos a bar of iron used

as a magnetic shunt has been used to diminish the lines of force going

through the armature and hence to weaken the field and diminish the

electro-motive force. By moving the shunt nearer or further from the

poles the dynamo is regulated.

In the cut the projections between the yoke and poles of the magnet

shown act as a shunt to the yoke, taking some lines of force therefrom.

Fig. 225. MAGNETIC SHUNT.

Magnetic Storms.

Terrestrial magnetic disturbances sometimes covering very wide areas,

and affecting the magnetic declination and inclination. One such

disturbance was felt simultaneously at Toronto, Canada, the Cape of Good

Hope, Prague and Van Diemen's Land. (Sabine.)

354   STANDARD ELECTRICAL DICTIONARY.

Magnetic Strain.

The strain produced by magnetic lines of force in substances exposed to

their action. It is observed in substances placed between the poles of a

strong electro-magnet, and evinces itself in the alteration of the

optical properties of transparent substances.

Magnetic Stress.

The stress produced by magnetic lines of force on substances through

which they pass, evidenced in alteration of the optical properties of

transparent bodies thus treated.

Magnetic Susceptibility.

The specific intrinsic susceptibility of any material for magnetic

induction. It refers to the particle of matter, and not to the mass, as

in the latter its own particles react on each other and bring about what

is termed permeability, q. v. (See also Magnetization, Coefficient of

Induced, and Magnetic Induction, Coefficient of.)

Synonym--Coefficient of Induced Magnetization.

Magnetic Tick.

When a bar of iron is suddenly magnetized or demagnetized it emits a

slight sound, called the Page sound, or the magnetic tick. This has been

utilized in a telephone by Reiss. The telephone will receive sound, but

is very weak. It consists of a bar surrounded with a coil of insulated

wire. Variations in current produce sounds, which may be articulate if

the currents are produced by a telephonic transmitter.

Magnetic Twist.

A bar of iron held in the magnetic meridian and pointing to the pole and

twisted becomes to some extent permanently magnetized. Conversely a bar

when magnetized seems to have a twist set up in it. The latter is

magnetic twist.

Magnetic Variations.

Changes in the value of magnetic declination or inclination. (See

Magnetic Elements.)

Magnetism, Ampére's Theory of.

A theory accounting for magnetic phenomena by assuming the existence of

currents circulating around the molecules of permanent magnets. If such

currents so circulate and all in the same direction, the result is the

same as if the body of the magnet was enveloped in currents representing

those of an electro-magnet or solenoid. This is because in the interior

the current around one molecule would counteract the current around its

neighboring ones in part, so that the only virtual currents left would

be represented by those on the outer surfaces of the outer shell of

molecules, and these virtually resolve themselves into one general

current sheet, surrounding the magnet and coinciding with its surface.

The theory assumes that such currents permanently circulate around the

molecules of paramagnetic substances. Under ordinary conditions there is

no coincidence in their direction and no resultant current is produced.

When magnetized or polarized the molecules are brought into order, so

that the direction of their current coincides and the body becomes a

magnet.

355   STANDARD ELECTRICAL DICTIONARY.

Fig. 226. AMPÉRIAN CURRENTS IN MAGNETS.

At the north pole of the magnet the direction of the Ampérian currents

is the reverse of that of a watch when the observer faces the pole; the

reverse obtains for the south pole.

The attraction of opposite and repulsion of similar poles is explained

by the actions of the Ampérian currents upon each other. If north and

south pole are placed together these currents will coincide in direction

and hence will attract each other. If two like poles are put together

the currents will have opposite directions and will repel each other.

No energy is supposed to be required to maintain currents around or in a

single molecule.

Fig. 227. NORTH AND SOUTH POLES OF A MAGNET

SHOWING DIRECTION OF AMPÉRIAN CURRENTS.

Magnetism, Blue.

A term arising from the two fluid theory of magnetism; the magnetism of

the south pole of a magnet. (See Magnetic Fluids.) The magnetism of the

north pole is termed red magnetism. Both terms originated presumably in

the painting of magnets, and are little used.

Synonym--South Magnetic Fluid.

356   STANDARD ELECTRICAL DICTIONARY.

Magnetism, Components of Earth's.

The magnetic force of the earth acts in the plane of the magnetic

meridian and in direction generally lies oblique to the plane of the

horizon. It can be resolved into two components, one vertical, which has

no directive effect upon the magnetic needle, the other horizontal,

which represents the directive element for the usual compass needle. For

the dipping needle, q. v., the vertical component is the only active

one. A magnetic needle mounted on a universal joint at its centre of

gravity would be acted on by both components.

Magnetism, Creeping of.

The gradual increase of magnetism when a magnetic force is applied with

absolute steadiness to a piece of iron. It is a form of magnetic lag. It

may last for half an hour and involve an increase of several per cent.

of the total magnetism.

Synonym--Viscous Hysteresis.

Magnet, Iron Clad.

A magnet with a casing of iron connected at one end to the core. The

term is generally applied to electromagnets of this form.

Synonyms--Tubular Magnet--Jacketed Magnet.

Magnetism, Decay of.

The gradual loss of magnetism by permanent magnets, due to accidental

shocks, changes of temperature, slow spontaneous annealing of the iron

and other similar causes.

Magnetism, Discharge of.

The loosing of magnetization. Thus in a shunt-wound dynamo there is a

critical resistance for the outer circuit, below which the field ceases

to be magnetized, as enough current ceases to be shunted into it to

magnetize it. The machine is said to unbuild itself, and a discharge of

magnetism occurs from the field magnet.

Magnetism, Ewing's Theory of.

Ewing found by a model consisting of a number of pivoted magnetic

needles that the observed phenomena of magnetization could be

represented thereby. Thus there would be no need of assuming internal

frictional forces of Maxwell, nor the closed rings or chains of Hughes.

The theory retains the notion, however, of paramagnetic matter,

consisting of an assemblage of molecular magnets. The loss of energy by

hysteresis is represented in the model by the energy lost by the needles

in beating against the air.

357   STANDARD ELECTRICAL DICTIONARY.

Magnetism, Free.

The magnetism or magnetic field outside of a magnetic circuit. It is due

to escape of lines of force and to the magnetic leakage through the air.

The lines of force are never, under the most favorable circumstances,

confined to the metallic circuit of the magnet and armature. In a simple

magnet without armature all the lines of force have to follow an air

path, and the field is at its strongest. As the magnetism is strongest

at the surface near the poles, the term is sometimes understood as

applying to the surface attraction. In such case it is defined as the

distribution, on a magnetized bar or mass, of magnetic lines of force as

they emerge from its surface.

Synonym--Surface Magnetization.

Magnetism, Hughes' Theory of.

A theory accounting for magnetic phenomena by assuming that each

molecule is a magnet, and that in a polarized or magnetized body they

are all arranged with their poles in the same direction, while in an

unmagnetized body their poles, alternating in direction, neutralize each

other.

Magnetization consists in a partial rotation of the molecules so as to

make them agree in position, thus, as a resultant developing north and

south poles at the ends of the bar.

The theory is in a certain sense simpler than Ampere's theory, but is

not so generally adopted.

Magnetism, Lamellar Distribution of.

The distribution of magnetism in thin and uniform or "simple magnetic

shells," q. v. A given distribution is termed lamellar if the substance

in which it exists can be divided into simple magnetic shells, which

either form closed surfaces, or have their edges in the surface of the

substance. In lamellar distribution the polar area is very large

compared with the distance between opposite poles.

Magnetism of Gases.

Faraday experimented on this point by coloring gases with a little vapor

of iodine or other colored gas, and letting them flow between the two

poles of a powerful electromagnet. In this way he found some are

repelled, some attracted, and in the case of oxygen, it is attracted at

one temperature and repelled at another. At ordinary temperatures a

cubic yard of oxygen possesses the magnetism of 5.5 grains of iron and

when liquefied it is strongly attracted.

Magnetism or Magnetization, Temporary.

When a mass of iron is magnetized by a current, when the current ceases

the portion of its magnetism which disappears is the temporary

magnetism; the portion retained is the residual or permanent magnetism.

Magnetism, Red.

A term arising from the two fluid theory of magnetism; the magnetism of

the north pole of a magnet. (See Magnetic Fluids.) The magnetism of the

south pole is termed blue magnetism. Both terms originated in the

painting of magnets. They are but little used.

Synonym--North Magnetic Fluid.

358   STANDARD ELECTRICAL DICTIONARY.

Magnetic Remanence.

The residual magnetism left in a bar of steel or other paramagnetic

material after the application of a powerful magnet. It is distinguished

from coercive force, as the latter is the amount of negative magnetizing

or of demagnetizing force required to reduce the remanent magnetism to

zero.

Synonym--Remanence--Residual Magnetism.

Magnetism, Solenoidal Distribution of.

The distribution of magnetism in such a way that the poles are very far

apart in proportion to their area. The magnetization of a long thin bar

of steel illustrates solenoidal distribution.

Magnetism Sub-permanent.

The magnetism of a paramagnetic substance which presents a considerable

degree of permanency, but which gradually disappears, leaving the

permanent magnetism present. It is noticeable in iron or steel ships

whose magnetism gradually reduced in quantity, eventually becomes fully

permanent.

Magnetism, Weber's Theory of.

The molecules of a magnetizable material by this theory are supposed to

be magnets with their poles lying in every direction, and hence

neutralizing each other. By magnetization these are supposed to be

turned with their similar poles in the same direction, and their axis

parallel, hence acting like a group of magnets. It is practically

identical with Hughes' theory.

Magnetism, Terrestrial.

The magnetism of the earth. (See Magnetic Elements.)

Fig. 228. MAGNETIZATION BY DOUBLE TOUCH.

Magnetization by Double Touch.

The process of magnetizing a steel bar by simultaneously stroking it

with two poles of a horseshoe magnet or with two opposite poles of two

bar magnets. The poles must be close but not touching. A block of wood

may be placed between the ends if single magnets are used. The poles are

placed on the middle of the bar and carried back and forth to one end,

then to the other, and so on, ending at the middle of the bar in such

direction as to give each end the same number of strokes. The poles must

be close together or consequent poles will be produced. If bar magnets

are used they may be held inclined at an angle of 15º to 20º with the

horizontal bar to be magnetized. The ends of the latter may rest on

poles of two other magnets, each end on a pole of the same name as that

of the magnetizing magnet on its side. (See Magnetization, Hoffer's

Method.)

359    STANDARD ELECTRICAL DICTIONARY.

Magnetization by Separate Touch.

A method of magnetization. Two magnets are used. Held in an inclined

position two opposite poles are touched to the bar near its centre, and

are drawn off to the two ends. They are returned through the air and the

process is repeated.

Magnetization by Single Touch.

A method of polarizing or magnetizing steel bars, by stroking them

always in one direction with one pole of a magnet, returning it through

the air. The stroking is best done on both sides. The stroking may begin

at one end and end at the other, or it may be commenced in the center of

the bar and be carried to one end with one pole, and the same done for

the other half with the other pole.

Magnetization by the Earth.

The earth imparts magnetism to iron masses. If a rod of steel is held

parallel to the inclination and in the magnetic meridian it exhibits

polarity, which by jarring or hammering, can be made to some extent

permanent. A piece of soft iron held vertically, or still better in the

line of the dip as above, and which is twisted when in that position,

becomes magnetized with some degree of permanence. Many other instances

are cited, such as fire-irons, lamp-posts, iron gates, lathe turnings,

all of which often exhibit polarity, having been magnetized by the

earth's field.

[Transcriber's note: The earth's magnetic field is believed to originate

it electric currents in the moving molten core.]

Magnetization, Coefficient of Induced.

The coefficient (q. v.) expressing the relation between the specific

intensity of magnetization of a particle and the magnetizing force. The

magnetizing force is measured by the lines of force it can produce in a

field of air. The coefficient of induced magnetization is the factor by

which the intensity of a magnetizing field must be multiplied to produce

the magnetization imparted by it to a particle of any substance. This

coefficient varies for different substances, and is also called magnetic

susceptibility. It is distinguished from permeability as referring only

to a particle isolated from influence of a mass of surrounding particles

of its own kind. It is definable as the intensity of the magnetization

assumed by an exceedingly long and exceedingly thin bar placed in a unit

field. If a mass of metal were placed in such a field all its particles

would become affected and within the mass no unit field could exist.

Hence magnetic susceptibility (another name for this coefficient) does

not apply to the case of large cores of electro-magnets and

dynamo-armatures, but is really a theoretical rather than a practical

figure.

The sign of the coefficient of diamagnetic bodies is negative; of

paramagnetic bodies is positive.

Synonym--Magnetic Susceptibility.   \

360   STANDARD ELECTRICAL DICTIONARY.

Magnetization, Cycle of.

A cycle of positive or of positive and negative magnetization represents

the application of a magnetizing force beginning at a fixed value,

generally zero, rising to a maximum, or to a value of maximum distance

from the initial and then returning to the original basis. It is

virtually a full wave of magnetization and may extend on both sides of a

zero line giving positive and negative values.

Cycles of magnetization apply especially to transformers and other

apparatus of that character used with the alternating current system.

Magnetization, Hoffer's Method.

For horseshoe bars an armature is placed against the poles of the magnet

bar to be treated. The poles of a strong horseshoe magnet are stroked

over it from poles to bend and returned through the air, or vice versa.

In the first case the poles will be the same as those of the inducing

magnet; in the second case they will be opposite. A maximum effect is

produced in ten strokes. The stroking should be applied to both sides.

An electro-magnet may be used as inducer as shown, but an armature

should be used; in the cut it is omitted.

Fig. 229. MAGNETIZING A HORSESHOE MAGNET.

Magnetization, Intensity of.

The amount of magnetism induced in or present in a body. It is expressed

in Magnetic Lines of Force, q. v., per cross-sectional area.

Magnetization, Isthmus Method of.

A method used by Ewing in a research on the magnetization of iron in

very strong fields. He used samples of iron turned down in the centre to

a narrow neck, and thus concentrated the lines of force greatly.

Magnetization, Elias' Method.

The bar to be magnetized is surrounded by a magnetizing coil, q. v. A

strong current is passed through it, and the coil is moved back and

forth a few times.

Magnetization, Jacobi's Method.

For horseshoe bars. The bar is placed with its poles against those of a

horseshoe magnet. A bar of soft iron, long enough to reach from outside

to outside of the legs, is laid across near the junction and is drawn

along towards the bend of the new bar and away from it. This is repeated

a few times on both sides.

361   STANDARD ELECTRICAL DICTIONARY.

Magnetization, Limit of.

As the induction of magnetizing force increases, magnetization of

paramagnetic metals tends towards a limit, the increase in magnetization

being continually less and less as the metal becomes more highly

magnetized. In diamagnetic substances no limit is discernible.

Synonym--Maximum Magnetization.

Magnetization, Specific.

The magnetic moment per gram of a substance.

Magnet-keeper.

A bar of iron connecting the two poles of a permanent magnet. Often the

same bar serves as armature and keeper.

Magnet, Lamination of.

It is advantageous to make magnets of laminated construction, or of thin

plates of steel. The thin metal can be better tempered or hardened than

thick metal. A slight separation of the plates is advantageous from some

points of view. If in actual contact there is some danger that the

weaker members will have their polarity reversed by the stronger ones.

This is counteracted to some extent by separation.

Magnet, Long Coil.

A high resistance electro-magnet; one whose coil is of thin wire of

considerable length.

Magnet, Natural.

The lodestone, q. v.; a variety of magnetite or magnetic oxide of iron,

exhibiting permanent magnetism, attracting iron, and possessing north

and south poles.

Magnet, Neutral Line of.

A line at right angles to the magnetic axis of a magnet, q.v., and

nearly or quite at the centre, so situated with reference to the poles

on either end that it marks the locus of no polarity. It has been called

the equator of the magnet. It is defined by the intersection of the

plane of no magnetism with the surface of the bar.

Synonym--Magnetic Equator.

Magnet, Normal.

A bar or compound bar magnet, magnetized to such an extent that the

curves of the lines of force run into each other in the middle, is thus

termed by Jamin.

Magneto.

Abbreviation for Magneto-electric Generator. (See Magneto-electric

Generator.)

Magneto Call Bell.

A call operated by current from a magneto-electric generator. It is very

generally used in telephone systems.

362  STANDARD ELECTRICAL DICTIONARY.

Magneto-electric. adj.

Relating to induced electric effects due to the cutting of true magnetic

lines of force by, or equivalent action of or upon a conductor. These

effects are identical with electro-magnetic effects and are only

distinguished from them by the field being due to a permanent magnet

instead of an electromagnet.

Magneto-electric Brake.

A device for bringing to rest an oscillating galvanometer needle. It

consists essentially of a coil in circuit with a key and with the

galvanometer. On opening the circuit an inverse current is established

by induction, tending to bring the needle to rest.

Magneto-electric Generator.

A current generator operating by maintaining a potential difference at

its terminals, by reactions in a field of force, which field is

established by a permanent magnet.

The cut, Fig. 230, shows the general principle of construction of a

direct current generator. The armature is rotated between the poles of a

permanent magnet. Any of the regular types of dynamo armature can be

used. From its commutator the current is taken by brushes.

Fig. 230. MAGNETO-ELECTRIC GENERATOR.

Fig. 231. MAGNETO-ELECTRIC GENERATOR.

363   STANDARD ELECTRICAL DICTIONARY.

The cut, Fig. 231, shows an alternating current machine. In it a pair of

bobbins, wound in series, and both either right-handed or left-handed,

are rotated between permanent magnet poles. The current may be taken off

by two brushes bearing on two collecting rings on the axis of the

bobbins, the ends of the wire being connected thereto. Or if a shocking

current is desired, one of the brushes or springs may strike a series of

pins forming virtually a broken or interrupted collecting ring. This

gives a current for medical purposes.

Synonyms--Magneto-dynamo--Magneto-electric Machine.

Magnetograph.

An apparatus for recording variations in magnetic elements. One type

includes a magnetic needle to which a concave mirror is attached. The

light ray from the mirror is reflected upon sensitized paper where its

movements are photographically reproduced. The movements of the spot are

due to the movements of the needle and act as the record of the same.

Magneto-Inductor.

An instrument for use with a ballistic galvanometer to reproduce a

definite current impulse. Two magnets are fastened together in one

straight line, the north poles almost touching. This is mounted at the

end of a rod like a pendulum, the axis of the magnets transverse to the

rod. The magnets are carried by a frame and oscillate at the end of the

rod, back and forth within a fixed coil, which is one-half the length

of the double magnet. A bob is attached to the bottom of the frame by

which the whole can be swung. As the magnets are of fixed value, their

time of oscillation constant, and the coil fixed in size, the apparatus

provides a means of getting a definite instantaneous current of

identical value whenever needed.

Fig. 232. MAGNETO-INDUCTOR.

364   STANDARD ELECTRICAL DICTIONARY.

Magnetometer.

(a) A reflecting galvanometer, with heavy magnetic needle, dampened by a

copper frame. It was devised by Weber.

(b) An apparatus for measuring the intensity of magnetic force. It may

consist of a magnet suspended by bifilar or by torsion suspension. A

reflecting mirror and scale as in the reflecting galvanometer may be

used to act as indicator of its motions. It is used in investigations of

the intensity of the earth's field.

If the motions of the spot of light are received on a moving strip of

sensitized paper and are thereby reproduced photographically, the

instrument is self-recording. Such an apparatus is used in the Kew

Observatory, Eng., for recording the terrestrial magnetic elements.

Magnetometry.

The determination of the magnetic moment of a magnet.

It involves the determination by experiment of--( a) the product of the

magnetic moment, M, of the magnet by the horizontal component, H, of the

earth's magnetism; (b) the quotient of M divided by H. Knowing these two

quantities, M is given by the formula M = SquareRoot( )M * H) * (M/H) )

and if desired H is given by the formula H = SquareRoot( (M*H) / (M/H)).

M*H is determined by the method of vibrations. A very long, thin magnet

suspended by a torsion filament is caused to oscillate, and its period

is determined. Calling such period T and the moment of inertia of the

magnet I, we have the formula T= 2* PI * SquareRoot( I / (H*M) )  (a),

whence H*M is calculated, I of course being known or separately

determined.

Fig. 233 END-ON METHOD.

Fig. 234. BROADSIDE METHOD.

M/H is determined by the End-on deflection method, or the Broadside

deflection method. In both cases the deflection of a compass needle by

the magnet in question is the basis of the work.

In the end-on method AB is the magnet under examination; DE the compass

needle; a the angle of deflection; d  the distance between C and the

middle of AB, which should be considerable compared with the length of

DE; 2l, the length of AB. We then have the formula

tan a = (M/H) * (2d / (d^2 - l^2)^2),

which if 2l is small compared to d reduces to

tan a = M/Hd 3

(b), which gives M/H, a and d being known.

365   STANDARD ELECTRICAL DICTIONARY.

In the broadside method the line d is the magnetic meridian, and the

diagram shows the relative positions. We then have the formula

tan a = (M/H) / (d2 + l2)^1.5;

which if 1 is relatively small reduces to

tan a = M/(H * d3 )(C.)

[Transcriber's note: The image of the above paragraphs is included here.]

a and c or a and b can be combined giving M and H in C.G.S. measurement.

Magnetometer, Differential.

An apparatus, invented by Eickemeyer, for testing the magnetic qualities

of different samples of iron. It is very similar in construction and

principle to the magnetic bridge, q. v.

Magneto-motive Force.

The force producing a magnetic field or forcing lines of force around a

magnetic circuit. It is usually applied only to electro-magnets and is

expressible in turns of the wire winding multiplied by amperes of

current, or in ampere-turns.

Magnet Operation.

A term in surgery; the use of the electro-magnet or permanent magnet for

removing particles of iron from the eye.

Magnetoscope.

An apparatus for detecting the presence of magnetism, without measuring

its intensity. A simple magneto-scope consists of a magnetized bit of

watch-spring suspended in a vertical glass tube by a fine filament. A

bit of unmagnetized soft iron wire may be used in the same way. The

first has the advantage of indicating polarity; the latter merely shows

magnetic attraction. A cork may be used as base of the instrument.

Fig. 235. MAGNETOSCOPE.

366   STANDARD ELECTRICAL DICTIONARY.

Magnet, Permanent.

A bar of steel charged with residual magnetism. Steel possesses high

coercive force in virtue of which when once magnetized it retains part

of the magnetization.

Permanent magnets are generally straight bars or U shaped; they are

termed bar magnets, magnetic needles, horseshoe magnets, machine magnets

and otherwise, according to their shape or uses.

Magnet Pole.

The part of a magnet showing strongest polarity; the part which attracts

iron the most powerfully, and acts as the starting point for lines of

force.

Magnet Poles, Secondary.

Magnet poles are often not situated at the ends. Owing to inequality of

the material or other causes they may occupy intermediate positions on

the magnet. Such poles are called secondary poles.

Magnet Pole, Unit.

A unit magnet pole is one which exerts unit force on another unit pole

placed at unit distance from it. Unit force is the dyne; unit distance

is one centimeter.

Magnet, Portative Power of.

The power of sustaining a weight by attraction of its armature possessed

by a magnet. In general terms the adherence of the armature of a magnet

to the pole varies with the square of the number of lines of force which

pass through the point of contact. Hence an increased adherence of the

armature to a horseshoe electro-magnet is sometimes obtained by

diminishing the area of contact of one pole which concentrates the lines

of force. Steel magnets were frequently made with rounded ends to

increase the portative power.

Magnet, Simple.

A magnet made of one piece of metal, or at least magnetized as such; the

reverse of a compound magnet, which is magnetized piece by piece and

then fastened together.

Magnet, Solenoidal.

A magnet which is so uniformly magnetized and is so long in proportion

to its other dimensions that it virtually establishes two magnetic

poles, one at either end. It is a long thin bar so magnetized that all

its molecules would, considered as magnets, be absolutely equal.

(Daniell.) It acts like a solenoid, except that it is longer in

proportion than the solenoid generally is constructed.

Magnet, Sucking.

A magnet coil with movable or loose axial bar of soft iron.

The whole is usually mounted vertically. When a strong enough current is

passed the bar is drawn up into the coil as if by suction, whence the

name.

367   STANDARD ELECTRICAL DICTIONARY.

Magnet, Unipolar.

No such thing as a unipolar magnet is possible. The name is given to

poised or suspended magnets, one of whose poles lies in the axis of

suspension. It is obvious that such a magnet will act, as far as its

directive tendency and rotatory movements are concerned, as if it had

only one pole. As shown in the cut, the pole s in both magnets lies in

the axis of suspension or directly under the filament by which they are

suspended, while the other pole n is the active pole in causing rotation

or directive tendency; c c are counterweights or counterpoises.

Fig. 236. UNIPOLAR MAGNETS.

Magnetophone.

An apparatus for producing a loud sound, involving the principles of the

telephone. A rapidly alternating or make and break current being

produced by any means and being transmitted through the telephone gives

a loud note of pitch dependent on the current producing it. Sometimes a

perforated metallic disc is rotated in a magnetic field, and produces

the requisite type of current.

Magnus' Law.

A law of thermo-electricity. In a homogeneous circuit, however, the

temperature varies from point to point; there is no current.

Whatever potential differences may be established by the variations in

temperature it is evident that they must counteract each other and

reduce to zero.

Mains, Electric.

The larger conductors in a system of electric light or power

distribution.

Make. v.

To complete a circuit, as by closing a switch.

Make and Break Current.

A current which is continually broken or interrupted and started again.

It is applied only where the "makes" and "breaks" succeed each other

with great rapidity, as in the action of an induction coil or pole

changer, etc. It has had considerable importance in litigation affecting

the Bell telephone patents, the courts holding that the original Bell

patent (No. 174,465, of 1876,) covered the undulating current, for the

transmission of speech. Many efforts have been made by litigants to

prove that specific telephones have transmitted articulate speech by the

make and break current, but without success. If this could have been

proved the assumption is that the courts would have sustained the use of

such device as not infringing upon the claims of the Bell patent.

Malapterurus.

A fish, sometimes called the thunder fish, an inhabitant of African

rivers, occurring in the Nile and Senegal. It possesses considerable

electric power, similar to that of the gymnotus and torpedo, although

inferior in amount.

368   STANDARD ELECTRICAL DICTIONARY.

Fig. 237. MALAPTERURUS.

Man-hole.

The cistern-like depression in the ground for giving access to the ends

of tubes in electric conduits. (See Conduit, Electric Subway.)

Marked End or Pole.

The north pole or north seeking pole of a magnet, so called because it

is usually marked with a notch or scratch by the maker. The south pole

is called the unmarked end.

Mass.

The quantity of matter in a body. The C. G. S. unit of mass is the

quantity of matter in a gram. While weight varies with latitude and

other circumstances, mass is invariable.

The unit of mass is also defined as the quantity of matter which in a

balance will counterpoise a standard mass, the gram or pound. As the

gram is intended to be the mass of one cubic centimeter of water at

3.09º C. (39º F.), the C. G. S. unit of mass is really 1.000013 gram.

As a primary unit its dimensions are indicated by M.

Mass, Electric.

A term for quantity of electricity. The unit mass is such a quantity as

at unit distance will act with unit force.

Matter, Electric.

The imaginary substance constituting electricity; a conception used

purely as a matter of convenience.

[Transcriber's note: The electron was discovered five years after this

publication.]

Matter, Radiant.

Matter in the ultra-gaseous or so-called fourth state. In the gaseous

state the molecules of a gas are in perpetual kinetic motion, colliding

actually or virtually with each other, rebounding from such approach,

and striking also the walls of the containing vessel. But except for

these deflections, which are of enormous frequency, the paths of the

molecules would be perfectly straight.

In the radiant state matter exists in so high a vacuum that collisions

of the molecules rarely occur, and the molecules simply beat back and

forth in straight lines from side to side of the containing vessel.

A layer of gas in this condition is termed a Crookes' layer, from Prof.

William Crookes, who discovered and investigated these phenomena.

369   STANDARD ELECTRICAL DICTIONARY.

Luminous streams of the molecules are produced by electric high

potential discharges between electrodes. The course of the discharge is

normal, in general terms, to the surfaces of the electrodes, and reaches

from one to the other in a curve or straight line, as the case may be.

These luminous streams are deflected by a magnetic field; if brought to

a focus can heat refractory material in that focus to a full white heat,

and can develop phosphorescence. The latter is termed electric

phosphorescence. A great variety of experiments have been devised to

illustrate the phenomena of radiant matter. The vacuum is generally

produced in a hermetically sealed glass vessel into which the electrodes

are sealed, and which contain the phosphorescent substances or other

essentials for the experiments. The vessels are termed Crookes' Tubes.

[Transcriber's note: Crookes reported on "radiant matter" in 1879. It is

actually electrons, but he failed to distinguish them from ordinary

atoms. Thompson properly described electrons in 1897.]

Matteueci's Experiment.

An experiment for showing the inductive effect of the discharge of a

Leyden jar. Two glass plates are supported on standards in a vertical

position. Flat coils of wire are wound or coiled and secured to one

surface of each plate. One plate has much finer and longer wire than the

other. Metal handles are connected to the ends of the coarser wire coil.

The plates are placed with their coils facing each other. A Leyden jar

is discharged through the coarser coil, while the handles are grasped by

a person. The shock of the discharge is felt by him.

Matting, Electric Floor.

Matting or floor covering underlaid with burglar alarm contacts, so

arranged as to be closed by anyone walking on the matting. The contacts

are connected to a burglar alarm system. The object is to provide an

alarm if a burglar enters a house, in case he should enter a door or

window without sounding the bell. The latter can be done by cutting out

the window or part of the door instead of opening it.

Maxwell's Theory of Light.

A theory of light. It is due to J. Clerk Maxwell.

It supposes the phenomena of electric induction to be due to the ether,

q. v. It supposes the condition of the ether when conveying light to be

the same as if exposed to the induction of rapidly alternating currents

or discharges (in this case synonymous). It therefore is an

electro-magnetic effect if the theory is correct.

An electric stress such as one due to the induction of an

electrostatically charged body is not a wave-creating element or factor,

but is a simple stress. But let this stress be stopped and renewed and

at once it appears as a wave-forming agency.

This stoppage and renewal represents evidently a discharge succeeded by

a charge, or if repeated is equivalent to an intermittent current or an

alternating one.

370   STANDARD ELECTRICAL DICTIONARY.

Again the electrostatic stress kept constant may by being carried

through space carry with it a wave, just as a moving projectile carries

a wave of air in advance of itself.

Admitting this much the following consequences follow:

Since in non-conductors the displacement produces a restitution force,

which varies as the displacement which is requisite or is a criterion

for the propagation of waves, while in conductors no such force is

manifested and the electric energy appears as heat, it follows that

light vibrations are not possible in conductors, because

electro-magnetic waves do not exist in them when they are in circuit,

and conductors should be opaque, while the reverse is true for

non-conductors. (Daniell.)

This is carried out often enough to make a striking evidence in favor of

Maxwell's theory.

The velocity of propagation of an electro-magnetic disturbance in a

non-conductor should be equal to that of light. This constant is proved

by mathematical considerations, to be approximately the same as the

ratio of the electrostatic to the electromagnetic unit of intensity or

quantity. This ratio is 3E10 (30,000,000,000), which is almost exactly

the velocity of light.

It also follows from what has been said that if an electrostatically

charged body were whirled around a galvanometer needle at the rate of

3E10 revolutions per second it should affect it like a circulating

current. This rate of rotation cannot be attained, but Rowland has made

manifest the effect of a rotating statically charged body upon a

magnetic needle.

The above is the merest outline of Maxwell's theory. The full

development must be studied in his own and succeeding works.

Mayer's Floating Magnets.

An experiment due to Prof. Mayer. A number of sewing needles are

magnetized and thrust into bits of cork, almost all the way through,

with their like poles projecting. They are floated in a basin of water

and take, under the effects of attraction and repulsion, when approached

by a magnet pole, regular geometric positions, marking out the positions

of angles of polygons.

Measurements.

The determination of the value of quantities; determination of the

factor by which the unitary value must be multiplied to produce the

quantity under examination. Such are the measurement of the voltage of a

galvanic battery, or of the ohms of resistance of a conductor.

Electricity has been termed the science of measurement.

Meg or Mega.

A prefix, meaning one million times. A megohm is one million ohms; a

megerg is one million ergs; a megadyne is one million dynes.

371    STANDARD ELECTRICAL DICTIONARY.

Fig. 238. MAYER'S FLOATING MAGNETS.

Mercury.

A metal; one of the elements; symbol, Hg; atomic weight, 200 ;

equivalent, 200 or 100; valency, 1 and 2.

It is a conductor of electricity.

The following data are 0º C. (32º F.)

Relative Resistance,   62.73

Specific Resistance,   94.32   microhms.

Resistance of a wire,

(a) 1 foot long, weighing 1 grain,     18.51   ohms.

(b) 1 foot long, 1/1000 inch thick,   572.3     "

(c) 1 meter long, weighing 1 gram,     12.91    "

(d) I meter long, 1 millimeter thick    1.211   "

Resistance of  a 1 inch cube,   37.15   microhms.

Percentage increase of resistance per degree C. 1.8° F.

at about 20° C. (68° F.),   .72   per cent.

Electro-chemical equivalent (Hydrogen = .0105),   2.10   mgs.

1.05   "

372   STANDARD ELECTRICAL DICTIONARY.

Mercury Cup.

A cup of iron, wood or some material that does not amalgamate or is

unattacked by mercury, which is filled with mercury and made an

electrode of a circuit. By dipping the other terminal of the circuit

into the mercury a very good contact is obtained. It is well to cover

the mercury with alcohol. The cup may be filled so that the mercury

rises in a meniscus or semi-globule above its edges.

For some purposes this form is useful, as for contacts with the end of a

swinging wire or pendulum, because in such cases the contact can be made

without the contact point entering the cup. The point swings through the

projecting meniscus without touching the edges of the cup. A mercury cup

and contact constitute a mercury break.

Meridian, Astronomical.

The great circle passing through the north and south poles of the

celestial sphere. It lies in a plane with the corresponding geographical

or terrestrial meridian.

Meridian, Geographic.

The true north and south meridian; the approximate great circle formed

by the intersection of a plane passing through north and south poles of

the earth with the earth's surface.

373   STANDARD ELECTRICAL DICTIONARY.

Fig. 239. SCHALLENBERG'S ALTERNATING CURRENT METER.

Meter, Alternating Current.

A meter for measuring alternating current, as supplied to consumers,

from an alternating current system. Like most commercial meters its only

function is the measurement of quantity; the potential difference is

maintained at a constant figure by the generating plant.

The cut shows the Schallenberg meter. It is simply an alternating

current motor (see Motor, Alternating Current), with air vanes mounted

on its spindle. A main coil passes all the current. Within this is a

second coil complete in itself, and not touching or connecting with the

other. The latter is built up of copper rings. Within the two coils, and

concentric with both is a disc of copper carried by a vertical spindle.

The same spindle carries air vanes, and is free to rotate. As it does so

it moves the indicating machinery.

The current in the outer coil induces one in the inner coil. Owing to

lag, the current in the inner one differs in phase from that in the

outer one, and a rotatory field is produced. The copper disc acquires

induced polarity, and rotates with speed which normally would be in

proportion to the square of the current. But the object of the meter is

to register the current only. The air vanes effect this. The resistance

of the air to their motion causes the rate of rotation to vary directly

as the speed.

Meter Bridge.

A form of Wheatstone's bridge in which one lateral pair of arms is

represented by a straight wire. The other pair comprise a known

resistance, and the resistance to be determined. The galvanometer is

connected on one side between the known and unknown resistance. On the

other side its connection is moved back and forth along the straight

wire until the balance is secured and the galvanometer reads zero.

The relative lengths of wire intercepted between the two ends thereof

and the movable galvanometer connection are proportional to the

resistance of these parts and give the necessary data with the one known

resistance for determining the unknown resistance.

374   STANDARD ELECTRICAL DICTIONARY.

In the original meter bridge the wire was one meter long, whence its

name, and was stretched straight. In more recent examples the wire

varies in length and in one form is bent into a circle or spiral, so as

to make the instrument more compact.

The contact is not a sliding one, but is adjusted by trial. The contact

piece is slid along, but not touching the wire, and from time to time is

pressed down against the wire. This prevents wear of the wire. The wire

may be made of platinum or of platinum-iridium alloy. The latter is

very hard and not easily worn out.

Sometimes, as shown in the cut, three parallel wires are stretched along

the baseboard of the instrument, and arranged so that a single wire, two

wires or three wires in series can be used for the proportional sides of

the bridge, thus making it a two-meter or three-meter bridge as desired.

On the other hand some are made of restricted length, as a half or

quarter meter only.

Fig. 240. METER BRIDGE.

In the cut J K is the wire, traversed by the contact key. By moving the

contact C back and forth in the slot it can be brought over any of the

three divisions of the wire. H is the handle for depressing the key. S

is a flat spring, carrying the contact piece and holding it up from the

wires, except when pressed downwards. As shown in the cut, it is in use

for calibrating a voltmeter V, by Poggendorff's method, G being the

galvanometer and r1 and r2 being resistances.

Synonyms--Slide Bridge--Slide Balance.

Meter Candle.

A unit of illuminating power; the light given by one standard candle at

a distance of one meter. The ordinary units of illuminating power are

altogether relative; this one is definite.

375   STANDARD ELECTRICAL DICTIONARY.

Meter, Chemical Electric.

A current meter in which the current is determined by the amount of

chemical decomposition which it can effect. In the Edison meter the

solution is one of zinc sulphate. Two electrodes of zinc are immersed in

it, and a fractional part of the current is passed through it. The gain

in weight of one electrode and the loss in the other are proportional to

the current. Both electrodes are weighed periodically, one acting as

check upon the other.

Meter, Current.

An instrument for measuring the quantity of electricity in current form

supplied to consumers. It may be of various types. The general principle

involved is that in commercial installations for incandescent light and

power supply a fixed potential is usually maintained, the multiple arc

system being employed. Hence all that is requisite is to measure the

coulombs or the ampere-hours to know what quantity of energy has been

supplied.

Meter, Electro-magnetic.

A current meter in which the current is measured by its electro-magnetic

effects.

Meter-millimeter.

A unit of resistance. (See Resistance, Meter-millimeter.)

Meter, Thermal Electric.

A current meter in which the current is measured by the heat it imparts

to a conductor. In one meter a very light helix of mica is poised

horizontally over a conductor, and the whole is enclosed in a case. As

the wire is heated it causes an ascending current of air which rotates

the vane, and the latter moves delicate clockwork which moves indicating

hands. The hotter the wire the more rapidly the air ascends, and

consequently the speed of the vane is proportional to the current,

because the heat of the conductor is proportional thereto.

Meter, Time Electric.

An electric meter which measures the length of time during which current

is used. It assumes a constant current and potential. It is virtually a

clock, which is turned on when the current passes, and is turned off

with the current.

Meter, Watt.

A combined current and potential meter. It is constructed on the general

lines of a Siemens' Electro Dynamometer. If in it one coil is made of

coarse wire and is placed in series with the current conductor, and if

the other is wound with fine wire and is connected as a shunt from point

to point whose potential difference is to be determined, the instrument

becomes a watt meter.

Synonym--Energy Meter.

Methven Standard or Screen.

A standard of illuminating power. It is the light emitted by a

three-inch Argand gas flame through a rectangular aperture in a silver

plate carried by a screen. The aperture is of such size and so far

distant from the flame as to permit the passage of exactly two candles

illuminating power.

Fig. 241. METHVEN SCREEN

376   STANDARD ELECTRICAL DICTIONARY.

Mho.

A unit of conductance, not in very general use. It is the reciprocal of

the ohm. Thus a resistance of ten ohms is a conductance of one-tenth

mho.

Mica.

A natural mineral, a silicate of several oxides; muscovite. It is used

as an insulator and dielectric. Its resistance per centimeter cube after

several minutes electrification at 20º C. (68º F.) is 8.4E13 ohms

(Ayrton). Its specific inductive capacity is 5, air being taken at 1.

Mica, Moulded.

An insulating material, whose body is made of mica pulverized and

cemented together with heat and pressure and some suitable cement.

Shellac is often used as the cement.

Micro.

A prefix meaning "one-millionth of;" a micro-farad is one-millionth of a

farad.

Micrometer.

An instrument for measuring small distances or small differences. It

generally is based upon an accurate screw which may have a worm wheel

for head, actuated by a worm or helix with graduated head, so that

exceedingly small advances of the screw may be produced. The pitch of

the screw being known its actual advance is known.

Micrometer, Arc.

A micrometer for measuring the distance between voltaic arc electrodes.

Micron.

A unit of length. It is one-millionth of a meter or four

one-hundred-thousandths of an inch.

377   STANDARD ELECTRICAL DICTIONARY.

Microphone.

An apparatus which includes a contact of variable resistance; such

resistance can be varied in amount by slight vibrations, such as those

produced by sound waves. The apparatus in use forms part of a circuit

including a telephone and current generator. As the contact is varied

the resistance of the circuit and consequently the current intensity

changes and sounds are emitted by the telephone corresponding to such

changes. If the microphone is spoken to, the telephone will emit

corresponding sounds, reproducing the voice.

It has been found in practice that carbon gives the best microphone

contact. One of the simplest and earliest forms is shown in the cut. A

short rod or pencil of carbon, A, such as used in batteries, is

sharpened at the ends and rests loosely in a vertical position between

two blocks of carbon, C C, in each of which a hole is drilled to receive

one of the points. The blocks are carried on a standard and base D. The

blocks are connected with two terminals x, y, of a circuit, including a

telephone and battery. There are two contacts to be disturbed.

If delicately adjusted a fly walking over the base-board will disturb

the contacts enough to produce sounds in the telephone. These sounds are

possibly not due only to sound waves, but in part to absolute mechanical

disturbances.

The various forms of telephone transmitter are generally microphones.

Fig. 242. MICROPHONE.

Microphone Relay.

A combined microphone and telephone. A microphone is placed close to the

diaphragm of a telephone. The slight sound waves emitted by the

telephone affect the microphone and are repeated in its circuit. The

microphone circuit includes a local battery and telephone.

Microtasimeter.

An apparatus for indicating minute changes in temperature or atmospheric

moisture.

378   STANDARD ELECTRICAL DICTIONARY.

A button of compressed lampblack is placed in series with a battery and

galvanometer. A strip of some substance, affected in its length either

by heat or by moisture, is held pressing against the button. A slight

change in length of the strip varies the resistance of the button and

hence affects the galvanometer. In this way exceedingly slight changes

in heat or moisture may be indicated.

For heat indications vulcanite may be used. The heat of the hand held

near it is enough to affect the galvanometer. For moisture a slip of

gelatine is used. The moisture of a damp slip of paper two or three

inches distant is sufficient to affect the galvanometer.

In the cut, Fig. 2, shows the general distribution of the apparatus in

circuit with a battery and galvanometer. C is the base of the apparatus,

from which the standard, B, with adjusting screw, H, rises. The strip of

vulcanite is held between I and G. Within D is the carbon button (F in

Fig. 3) pressed between G and E; A is a standard to carry the parts last

described. In Fig. I it is shown as part of a Wheatstone bridge, a, b

and c being resistance coils; l the tasimeter, and g the galvanometer.

If a balance is secured, any variation in the resistance of the

tasimeter will disturb the galvanometer.

Synonym--Tasimeter.

Fig. 243. MICROTASIMETER.

379   STANDARD ELECTRICAL DICTIONARY.

Mil.

A unit of length; one-thousandth part of a lineal inch.

It is equal to

.025399 millimeter;

.000083 foot;

.001000 inch.

Mil, Circular.

A unit of area; employed in designating the cross-sectional area of

wires and other circular conductors.

It is equal to

.78540  square mil;

.000507 square millimeter;

7.8E-7 (.00000078) square inch.

If the diameter of a wire is given in mils, the square of its diameter

gives its cross-sectional area in circular mils.

Mil-foot.

A unit of resistance. (See Resistance, Mil-foot, Unit of).

Mil, Square.

A unit of area; one-millionth of a square inch.

It is equal to

.000645 square millimeter;

1.2733 circular mil;

.000001 square inch.

Milli.

A prefix; one-thousandth. Thus a milligram is one-thousandth of a gram;

a millimeter is one thousandth of a meter.

Milligram.

A unit of weight ; one-thousandth of a gram, q. v.

It is equal to

.015432 grain;

.000032 troy ounce.

Millimeter.

A unit of length; one-thousandth of a meter.

It is equal to

39.37079 mils;

.03937 inch;

.00109 yard.

380   STANDARD ELECTRICAL DICTIONARY.

Milli-oerstedt.

A proposed but not adopted unit of current; one-thousandth of an

oerstedt. It is equal to one-thousandth of an ampere.

[Transcriber's note: oersted: 1. CGS unit of magnetic intensity, equal

to the magnetic pole of unit strength when undergoing a force of one

dyne in a vacuum. 2. Formerly, the unit of magnetic reluctance equal to

the reluctance of a centimeter cube of vacuum between parallel

surfaces.]

mm.

Contraction for millimeters.

Molar.

Referring to phenomena of mass as gravitation. Mechanics

generally treats of molar laws and phenomena.

[Transcriber's note: Molar, or mole, often refers to a quantity of a

substance containing an Avagadro number (6.02E23) of molecules--a weight

equal to the atomic weight of the molecule. For example, a mole of

hydrogen (H2) is 2.015 grams; sodium chloride (NaCl) is 58.443 grams.]

Molar Attraction.

The attraction of mass for mass; gravitation. Synonyms--Mass

Attraction--Gravitation.

Molecular Affinity.

The attraction of molecules for each other as seen in the formation of

double salts, the combining of water of crystallization with a salt, and

in other cases; a phase of affinity belonging to chemistry, although

outside of true atomic attraction.

Molecular Attraction.

The attraction of molecules; physical affinity. Cohesion, the attraction

of similar molecules for each other, and adhesion, that of dissimilar

molecules, are examples. This should be distinguished from molecular

affinity, a phase of chemical force.

Molecular Bombardment.

When a gas contained in a vessel is brought to a sufficient state of

rarefaction the molecules cease to be subject to the laws of diffusion,

but move back and forth in straight lines from side to side of the

vessel. Their courses can be affected by electric discharge, which can

cause them to all impinge upon one of the electrodes, the positive one,

producing luminous effects. The path, if referred to the negative

electrode, tends to be normal to its surface, so that the resultant path

may be curved, as the stream of molecules go to the positive electrode.

The fanciful name of molecular bombardment is given to the phenomenon,

the luminous effect being attributed to the impinging of the molecules

against the positive electrode as they are projected from the positive.

The course of the molecules is comparable to the stream of carbon

particles from the positive to the negative electrode in an arc lamp.

(See Matter, Radiant.)

Molecular Chain.

The theoretical rows of molecules supposed to extend from anode to

cathode in an electrolytic cell (see Cell, Electric--Grothüss'

Hypothesis) are called molecular chains.

381   STANDARD ELECTRICAL DICTIONARY.

Molecular Rigidity.

The tendency of the molecules of a mass to retain their position in a

mass in resistance to polarizing or depolarizing force, the first being

the effect of a magnetic field. It is the theoretical cause of coercive

force, q. v., and of residual magnetism. (See Magnetism, Residual.)

Molecule.

The smallest particle of matter that can exist alone. It is made up of

atoms, but an atom can never exist alone, but only, with one or two

possible exceptions, combined with one or more other atoms as a

molecule. The molecules under present conditions are not in constant

contact with each other, but are perpetually vibrating through paths, in

solids probably in defined paths, in liquids and gases in perpetually

new paths. The molecules collide with each other and rebound. This

motion is the kinetic motion termed heat. At the absolute zero--minus

273.72° C. (-460.7° F.) the molecules would be in contact and quiescent.

In the gaseous state the molecules of most substances occupy the same

volume; those of a few elements occupy one-half and of others twice the

normal volume. The mean free path of the molecule of hydrogen is about

1/20,000 mm. (1/508,000 inch) (Maxwell) or twice this length (Crookes),

the collisions in hydrogen are about 17,750 millions per second; the

diameter is about 8/10,000,000 mm. (8/254,000,000 inch) ; A particle of

matter 1/4,000 mm. (1/102,000 inch) contains, it is supposed, about

40,000 molecules. The results of different authorities vary so widely as

to deprive the subject of much of its interest. A Sprengel pump, such as

used for exhausting Geissler tubes, or incandescent lamp bulbs, may

leave only one hundred-millionth (1/100,000,000,) of an atmosphere

present, giving the molecules a capability of an average free path of

vibration 33 feet long.

Moment.

When a force is applied so as to tend to produce rotation around a

point, the product of the force by the shortest distance from the point

of rotation to the extension of the line of the force. Such distance is

the perpendicular to the extension of the line through the point of

rotation.

Mordey Effect.

A phenomenon observed in dynamo armatures. At full loads the hysteresis

decreases. The effect is thus expressed by S. P. Thompson. "When an

armature core is rotated in a strong magnetic field, the magnetization

of the iron is being continually carried through a cycle, but in a

manner quite different from that in which it is carried when the

magnetizing force is periodically reversed, as in the core of a

transformer. Mordey has found the losses by hysteresis to be somewhat

smaller in the former case than in the latter."

Morse Receiver.

The receiving instrument formerly universally used in the Morse system.

It is now but little employed, the sounder having displaced it. Several

types were invented.

It consists of machinery which carries a reel of paper ribbon arranged

to be fed over a roller by clockwork. A pencil, inking roller, or

embossing stylus (for the latter the roller must have a groove) is

carried by an arm with restricted range of vibration just over the paper

and roller. The armature of an electro-magnet is attached to the arm.

When the magnet is excited the armature is attracted and the marking

device is pressed on the paper. If the clockwork is in operation the

marker will make a line as long as the armature is attracted. When

released no mark will be produced. In this way the dots and dashes of

the Morse code are made on a ribbon of paper.

As an inking arrangement a small roller is carried by the end of the

vibrating arm. The embosser, or dry point stylus, was very extensively

used. The clockwork was generally driven by descending weights.

Synonym--Morse Recorder.

382   STANDARD ELECTRICAL DICTIONARY.

Mortar, Electric.

An electric toy which may have various modifications. In the cut a

wooden mortar with recess to receive a ball is shown. Two wires enter

the base but do not touch. On placing the ball in position and passing a

spark from a Leyden jar across the interval between the wires, the heat

and disturbance are enough to project the ball. Gunpowder may be used,

the discharge being passed through a wet string to prolong the spark.

Fig. 244. ELECTRIC MORTAR.

Motor, Compound or Compound Wound.

A motor which has two windings on the field magnets, one in parallel

with that on the armature, the other in series therewith, exactly as in

a compound dynamo. (See Dynamo, Compound.)

Motor, Differential.

A differentially wound motor; with a compound wound field, whose series

coil and shunt coil are wound in opposition to each other. It is

virtually a compound wound dynamo. (See Dynamo, Compound Wound.)

Motor, Electric.

A machine or apparatus for converting electric energy into mechanical

kinetic energy. The electric energy is generally of the dynamic or

current type, that is to say, of comparatively low potential and

continuous or virtually continuous flow. Some electrostatic motors have,

however, been made, and an influence machine can often be operated as a

static motor.

Electric motors of the current type may be divided into two

classes--direct current and alternating current motors.

Direct current motors are generally based on the same lines of

construction as dynamos. One of the great discoveries in modern

electricity was that if a current is passed through a dynamo, the

armature will rotate. This fact constitutes the principle of the

reversibility of the dynamo.

383   STANDARD ELECTRICAL DICTIONARY.

Motors built on the dynamo model may be series wound, shunt wound, or

compound wound, or of the magneto type, in the latter case having a

fixed field irrespective of any current sent through them. The field may

be produced by an electro-magnet separately excited and unaffected by

the current sent through the motor.

A current passed through a magneto or motor with separately excited

field will turn it in the direction opposite to that required to produce

the same current from it were it worked as a generator.

A current passed through a series wound motor acts exactly as above.

Both these facts follow from Lenz's law, q. v.

A current passed through a shunt wound motor acts oppositely to the

above. The direction of rotation is the same as that required to produce

a current of the same direction. This is because the field being in

parallel with the armature the motor current goes through the magnet

coils in the direction the reverse of that of the current produced in

the armature when it is used as a dynamo. Hence this also carries out

Lenz's law.

The compound wound motor acts one way or the other according as its

shunt or series winding preponderates. The two may exactly balance each

other, when there will be no motion at all. The series connections of a

compound wound dynamo should therefore be reversed, making both series

and shunt work in unison, if the dynamo is to be used as a motor.

The general principles of the electric motor of the dynamo, or

continuous rotation type, can only be outlined here. The current passing

through the field magnets polarizes them and creates a field. Entering

the armature by the brushes and commutators it polarizes its core, but

in such a way that the north pole is away from the south pole of the

field magnet, and the same for the south pole. Hence the armature

rotates. As it does this the brushes connect with other commutator

sections, and the poles of the armature are shifted back. This action

continues indefinitely.

Another class of motors is of the reciprocating type. These are now very

little used. (See Motor, Reciprocating.)

One valuable feature of continuous rotation electric motors is the fact

that they absorb energy, to a great extent proportional in amount to the

work they have to do. The rotation of the armature in the field of the

motor involves the cutting of lines of force by its coils. This

generates an electro-motive force contrary in direction to that

producing the actuating current. The more rapid the rotation the greater

is this counter-electro-motive force. The motor armature naturally

revolves faster with diminished resistance to the motion of the

armature. This increases the counter-electromotive force, so that less

energy is absorbed. When the motor is called on to do work, the armature

rotates more slowly, and the counter-electro-motive force diminishes, so

that the machine absorbs more energy. (See Jacobi's Law.)

384   STANDARD ELECTRICAL DICTIONARY.

Motor Electro-motive Force.

The counter-electro-motive force of a motor. (F. J. Sprague.)

A motor rotates in virtue of the pull of the field magnet upon the poles

of the core of its armature. In responding to this pull the windings of

the armature cuts lines of force and hence generates a

counter-electro-motive force, for which the above term was suggested.

Motor-Generator.

A combined motor and generator used to lower the potential difference in

a portion of a circuit, e. g., that part within a building.

A motor-generator is a dynamo whose armature carries two commutators,

with two separate windings, one of fine wire of many turns, the other of

coarse wire of few turns. If the potential of the system is to be

lowered, the main current is passed through the fine winding. This

causes the armature to turn motor-fashion, and a potential difference is

generated by the rotation of the large coils in the field. This

potential difference is comparatively low and by properly proportioning

the windings may be lowered to as great a degree as required.

The same apparatus may be inverted so as to raise potential difference.

It acts for continuous current systems as the induction coil transformer

does for alternating current systems.

Synonym--Continuous Current Transformer.

Motor, Multiphase.

A motor driven by multiphase currents. It is arranged in general terms

for distribution of the multi phase currents in coils symmetrically

arranged around the circle of the field. These coils are wound on cores

of soft iron. A rotating field is thus produced, and a permanent magnet

or a polarized armature pivoted in such a field will rotate with the

field, its poles following the poles of the rotatory field.

The cut, Fig. 245, illustrates the principles of action of a four phase

current motor, connected to a four phase current dynamo or generator.

The generator is shown on the left hand of the cut and the motor on the

right hand. In the generator the armature N S is supposed to be turned

by power in the direction shown by the arrow. Each one of the pair of

coils is wound in the reverse sense of the one opposite to it, and the

two are connected in series with each other, and with a corresponding

pair in the motor. The connection can be readily traced by the letters A

A', a a' for one set of coils and B B' b b' for the other set.

385   STANDARD ELECTRICAL DICTIONARY.

For each rotation of the armature two currents, each in opposite

direction, are produced in A A', and the same is the case for B B'.

These currents which have an absolutely constant relation of phase, and

which it will be seen alternate four times for each rotation of the

armature, regulate the polarity of the field of the motor. The resultant

of their action is to keep the poles of the field magnet of the motor

constantly traveling around its circle. Hence the armature N S of the

motor, seen on the right hand of the cut, tends to travel around also

its north and south poles, following the south and north poles of the

rotatory field respectively.

Fig. 245. FOUR-PHASE CURRENT GENERATOR AND MOTOR.

It is not essential that the armature should be a magnet or polarized.

Any mass of soft iron will by induction be polarized and will be

rotated, although not necessarily synchronously, with the rotatory

field. Any mass of copper, such as a disc or cylinder, will have

Foucault currents induced in it and will also rotate. The only

components of such currents which are useful in driving the motor are

those which are at right angles to the lines of force and to the

direction of motion. A very good type of armature based on these

considerations is a core of soft iron wound with insulated copper wire

in one or more closed coils; and so wound as to develop the currents of

proper direction.

Such an armature is used in the Tesla alternating current motor. An

efficiency of 85 per cent. has been attained with some of the Tesla

motors.

Motor, Prime.

A machine used for producing mechanical motion against resistance. It

may operate by converting heat or any other form of kinetic or potential

energy into mechanical energy of the moving type. A steam-engine and a

water-wheel are examples of prime motors.

Motor, Reciprocating.

The early type of motor depending upon reciprocating motion, such as the

motion of a coil in a solenoid. These were based upon the lines of a

steam engine, and have been abandoned except for special purposes where

reciprocating motion is especially required, as in the case of rock

drills.

386   STANDARD ELECTRICAL DICTIONARY.

Fig. 246. RICORDON'S RECIPROCATING MOTOR.

In the cut, B is an electro-magnet; A is an armature; E a pole piece.

The current enters by the springs, b b, and by commutation is supplied

and cut off alternately, thus maintaining a reciprocating movement of

the armature and rotation of the fly-wheel.

Synonym--Pulsating Motor.

Motor, Series.

A motor whose winding on the armature is in series with the winding on

the field. It is similar to a series dynamo. (See Dynamo, Series.)

Motor, Shunt.

A motor whose winding on the armature is in parallel with the winding on

the field magnets. It is similar to a shunt wound dynamo. (See Dynamo,

Shunt.)

Fig. 247. MULTIPLE ARC CONNECTION.

Multiple.

A term expressing connection of electric apparatus such as battery

couples, or lamps in parallel with each other. In the ordinary

incandescent lamp circuits the lamps are connected in multiple.

Synonym--Multiple Arc.

387   STANDARD ELECTRICAL DICTIONARY.

Multiple Arc Box.

A resistance box arranged so that the coils may be plugged in multiple

instead of in series. Such can be used as a rheostat, as the resistance

can be very gradually changed by putting the coils one by one into

parallel with each other. Thus by adding in parallel with a 10 ohm coil

a 10,000 ohm coil the resistance is decreased to 9.999001 ohms, and thus

the resistance can be very slowly changed without sudden stops or abrupt

changes.

[Transcriber's note: The correct value is 9.99001]

Multiple Series.

Arrangements of electric apparatus in a circuit in a number of series,

which minor series are then arranged in parallel. The term may be used

as a noun, as "arranged in multiple-series," or as an adjective, as "a

multiple-series circuit."

Fig. 248. MULTIPLE SERIES CONNECTION.

Multiple Switch Board.

A switch board on whose face connecting spring jacks or other devices

are repeated for the same circuits, so that different operators have

each the entire set of connections repeated on the section of the board

immediately in front of and within their reach. This multiplication of

the same set of connections, giving one complete set to each operator,

gives the title "multiple" to the type of switch board in question. The

typical multiple switch board used in telephone exchanges is the best

example of this construction. The calling annunciators of the

subscribers are distributed along the bottom of the board extending its

full length. To each operator a given number is assigned, all within

reach of the right or left hand. This gives five or six feet length of

board to each, and an operator only responds to those subscribers within

his range. But anyone of his subscribers may want to connect with any of

the others in the entire central station. Accordingly in front of each

operator spring jacks are arranged, one for each of the entire set of

subscribers connected in that office. The operator connects as required

any of the calling subscribers, who are comparatively few, to any one of

the large number served by the central station. Thus the entire set of

subscribers' spring jacks are multiplied over and over again so as to

give one set to each operator.

388   STANDARD ELECTRICAL DICTIONARY.

Multiple Wire Method for Working Electro-magnets.

A method for suppressing sparking in working electro-magnets

intermittently. The magnet core is wound with a number (from four to

twenty) of separate layers of fine wire. A separate wire is taken for

each layer and all are wound in the same direction, from one end to the

other of the space or bobbin without returning. The ends are then joined

so as to bring all the wires in parallel. The effect of this is that as

the coils vary in diameter the time constants of each is different from

that of the others, the coefficient of self-induction being less, and

the resistance being greater for the coils farthest from the central

axis. Thus the extra currents run differently in the different coils,

and only a comparatively small spark can be produced owing to the

division of forces thus brought about.

Fig. 249. DIAGRAM ILLUSTRATING MULTIPLE WIRE WORKING.

Multiplex Telegraphy.

Any system of telegraphy transmitting more than four messages

simultaneously over a single wire. Properly it should apply to all

transmitting more than one, but conventionally has the above restricted

meaning, distinguishing it from duplex and quadruplex telegraphy.

Multiplying Power of a Shunt.

When a resistance is placed in parallel with a galvanometer on a circuit

the following relation obtains. Let s and g equal the resistances of the

shunt and galvanometer respectively, S and G the currents in amperes

passing through them, V the potential difference between their common

terminals, and A the whole current in amperes. Then we have

A = ( (s + g ) / s ) * G

and ( (s + g ) / s ) is termed the multiplying power of the shunt, as it

is the factor by which the current passing through the galvanometer must

be multiplied by to produce the total current.

Muscular Pile.

A species of voltaic battery, often termed Matteueci's pile, made up of

alternate pieces of muscle cut longitudinally and transversely

respectively. The different pieces represent the elements of a battery,

and their difference of potential is naturally possessed by the pieces.

Myria.

A prefix; one million times. Thus myriavolt means one million volts.

[Transcriber's note: Contemporary usage is mega, as in megavolt.]

389   STANDARD ELECTRICAL DICTIONARY.

N.

(a) Symbol for north pole or north-seeking pole of a magnet.

(b) Symbol for the number of lines of force in a magnetic circuit.

Nairne's Electrical Machine.

The cylinder electrical machine, q.v.

Napierian Logarithms.

A series of logarithms the base of whose system is 2.72818. They are

also called hyperbolic logarithms.

Nascent State.

An element just separating from a combination possesses at that time

higher affinities than after separation, and can effect more powerful

chemical changes.

It is sometimes attributed to a differential time of existence in the

atomic modification, before the freed atoms have united to form

molecules.

Natural Currents.

A term for earth currents. (See Current, Earth.)

Needle.

(a) A term applied to a bar magnet poised horizontally upon a vertical

point, or suspended in a horizontal position by a filament. Thus the

magnet in a mariner's compass, which may be a substantial bar magnet, is

called a magnetic needle.

(b) An indicator in general shape like the hand of a clock. (Sec

Annunciator, Needle- Telegraph, Needle.)

Needle of Oscillation.

The magnetic needle poised horizontally, and used for measuring the

intensity of the earth's magnetic field, or of an artificial magnetic

field, by the method of oscillations. The intensities of the field is

inversely as the square of the number of oscillations performed in a

given time.

Needle, Telegraphic.

The index in needle telegraphy (see Telegraph, Needle), whose motions

indicate the characters it is desired to transmit.

Negative Charge.

One of the two kinds of electric charges. The other is the positive.

By the double fluid hypothesis this is assumed to be a charge of a

particular kind of electricity--negative electricity.

By the single fluid hypothesis it is supposed to be caused by the

absence of part of the normal electricity of a surface. The reverse is

held by some theorists.

The subject is so purely theoretical that neither of the two hypotheses

is accepted as final.

[Transcriber's note: Current is a wire is the motion of negative

electrons. Current in a electrolyte is the motion of positive ions and

negative ions. Current in a plasma is the motion of electrons and

positive ions.]

390   STANDARD ELECTRICAL DICTIONARY.

Negative Electricity.

The kind of electricity with which a piece of amber is charged by

friction with flannel; resinous electricity. (See Electrostatic Series.)

In a galvanic battery the surface of the zinc plate is charged with

negative electricity.

According to the single fluid theory negative electrification consists

in a deficiency of electricity.

[Transcriber's note: Negative electrification is an excess of

electrons.]

Negative Element.

In a voltaic cell the plate not dissolved by the solution; the one which

is positively charged; the copper, platinum, or carbon plate in the

usual type of battery.

The current is assumed to flow from negative element to positive element

(the zinc plate) through the wire or other external conductor.

Nerve Currents.

Currents of electricity obtained from nerves. They are much more feeble

than those obtained from muscle, but are produced in the same general

ways.

Network.

Conductors in parallel and crossing each other, with connections at the

junctions.

The term is sometimes so loosely applied as to include parallel

conductors.

Neutral Line of Commutator.

The diameter of a commutator which connects its Neutral Points, q. v.;

sometimes termed the diameter of commutation; the diameter approximately

at right angles with the lines of force. The commutator brushes are

applied at the extremities of this diameter.

Neutral Point of a Commutator.

The points of a commutator at which no lines of force are cut; the

points at the extremities of a diameter which, except for the lag, would

be at right angles to the lines of force; the points at which the

brushes touch the commutator.

Neutral Point, Thermo-electric.

A temperature marking a point of no thermo-electric difference of

potential. If the junctions of a thermo-electric couple are at

temperatures, one a little over and the other an equal amount under the

neutral point, no current will be developed. At the neutral point the

thermo-electric polarities are reversed. Differences of temperature

above it give currents of reverse direction to those given by

corresponding differences below it. For an iron-copper couple the

neutral point is 274.5° C. (526° F.)

Synonym--Neutral Temperature.

Neutral Relay Armature.

An unpolarizable armature for use with a relay; an armature of soft iron

or iron wire; as distinguished from a polarized armature.

391   STANDARD ELECTRICAL DICTIONARY.

Neutral Wire.

The central wire in the three wire system, q. v., of electric

distribution; the wire connected to a point between the two dynamos, or

otherwise to the central point of the current generator.

Fig. 250. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE.

Neutral Wire Ampere Meter.

An ampere meter connected in the circuit of the neutral wire to

determine the current passing through it. Such determination is for the

purpose of ascertaining how much more work is being done by one of the

lateral leads than by the other.

Synonym--Balance Ampere Meter.

N. H. P.

Symbol or contraction for "nominal horse power." This is a basis for

rating the size of an engine.

Nickel.

A metal; one of the elements; atomic weight, 58.8 ; equivalent, 29.4;

valency, 2; specific gravity, 8.8. It is a conductor of electricity.

Relative resistance, annealed (Silver = 1),   8.285

Specific Resistance,                         12.47   microhms.

Resistance of a wire

(a) 1 foot long, weighing 1 grain,      15.206   ohms.

(b) 1 foot long, 1/1000 inch thick,     74.963    "

(c) 1 meter long, weighing 1 gram,       1.060    "

(d) 1 meter long, 1 millimeter thick,     .1587   "

Resistance of a 1-inch cube,             4.907   microhms.

Electro-chemical equivalent, (Hydrogen = .0105)   .3087   mgs.

It is strongly paramagnetic, but loses this quality at 350º C. (662º F.)

It is important as a constituent of German silver, an alloy much used

for resistance coils.

Nickel, Bath.

A bath for the electro-deposition of nickel. A great many

formulae have been given. Metallic nickel is dissolved in 1 vol.

sulphuric acid mixed with 2 vols. water. Neutralize with ammonia, and

add of ammonium sulphate one-half the weight of metallic nickel

originally used; 135 parts of nickel will be enough for a bath of 10,000

parts.

392   STANDARD ELECTRICAL DICTIONARY.

Other formulae are as follows:

Double nickel-ammonium sulphate,        4   parts.

Ammonium carbonate,                     3   "

Water                                 100   "

Nickel sulphate, nitrate or chloride,   1   "

Sodium bisulphate,                      1   "

Water,                                 20   "

Nickel anodes are used in the bath to maintain the strength. Too much

care cannot be exercised in the absolute cleanliness of the articles to

be plated. A too alkaline bath gives a disagreeable yellow color to the

deposit; too acid a bath gives badly adhering deposits.

Night Bell.

An alarm bell in a telegraph office, which bell is connected at night to

give a loud signal to attract the operator's attention. It is used in

telephone exchanges and is connected so as to ring as long as a

subscriber remains unanswered after calling.

Nobili's Rings.

When a dilute solution of copper acetate is placed on a bright silver

plate and a strip of zinc is touched to the silver beneath the copper, a

series of rings of copper are formed by electrolysis around the zinc.

These are Nobili's rings.

If for the copper acetate a solution of lead oxide in potassium hydrate

solution is substituted, and if the polished plate which may be German

silver is connected to the positive electrode of a battery, and a

platinum wire connected to the negative pole is immersed in the liquid,

it determines the formation of beautiful iridescent rings of lead

binoxide. The platinum wire is sometimes sealed in glass so that only

its point projects.

The colors are due to interference of light, the layers of lead oxide

being extremely thin.

The lead binoxide is formed by secondary reaction. Metallic lead is

first deposited on the negative pole. The oxygen which goes to the

positive pole formed by the polished plate produces lead binoxide which

is deposited there in rings. The reaction is comparable to that of a

storage battery.

Synonyms--Metallochromes--Electric Rings.

Nodular Deposit.

A deposit obtained in electroplating, characterized by irregular

thickness; due to too low density of current.

Non-conductor.

A material that does not conduct electricity except with great

difficulty; a substance of very high resistance.

Synonym--Insulator--Dielectric.

North Pole.

(a) The north-seeking pole of a magnet; the pole of a magnet which tends

to point to the north, and whence lines of force are assumed to issue on

their course to the other pole of the magnet.

(b) The North Pole of the earth. Treating the earth as a magnet, and

accepting the above nomenclature the north pole should be termed the

south pole. (See Austral Pole--Boreal Pole.)

393   STANDARD ELECTRICAL DICTIONARY.

North-seeking Pole.

The pole of a magnet which tends to point to the north; the north pole

of a magnet.

Null Method.

Any method of obtaining measurements or comparisons, in which the

measurement is correct when the deflection of the galvanometer or other

indicator is zero, nought or null. The Wheatstone Bridge (see Bridge,

Wheatstone) is an example of a null method.

Two obvious advantages attach to null methods in electric galvanometer

work. One is that an uncalibrated galvanometer can be employed. The

other is that a galvanometer of any high degree of sensitiveness can be

employed, there being no restriction as to its fineness of winding or

highness of resistance.

393   STANDARD ELECTRICAL DICTIONARY.

"Upper case Omega Graphic".

(Greek capital" Omega") symbol for megohm.

[Transcriber's note: Now used for ohms.]

"Lower case Omega Graphic".

(Greek omega) symbol for ohm.

[Transcriber's note: Now used for angular velocity, 2*PI*frequency.]

Occlusion.

An absorption of gases by metals. Palladium will, if used as the

hydrogen evolving electrode in decomposing water, absorb 980 times its

volume of hydrogen, which is said to be occluded. The metal may also be

heated in hydrogen and allowed to cool therein, when occlusion occurs.

Platinum will occlude 4 times its volume of hydrogen; iron, 4.15 times

its volume of carbon-monoxide; silver, 7 times its volume of oxygen.

Metals with occluded gases may serve as elements in a galvanic couple.

(See Gas Battery.) A metal expands in occluding a gas.

In the storage battery it is believed that occlusion plays a part,

hydrogen and oxygen being respectively absorbed by the two sets of

plates, and acting as they do in Groves' gas battery.

Oerstedt.

Name proposed for the unit of current strength, but not adopted. The

ampere is the accepted name.

394   STANDARD ELECTRICAL DICTIONARY.

Oerstedt's Discovery.

Oerstedt discovered in 1820 that a magnetic needle tended to place

itself at right angles to a current of electricity. This fundamental

experiment is the basis of the galvanometer.

Fig. 251. OERSTEDT'S DISCOVERY.

Ohm.

The practical unit of resistance; 1E9 C. G. S. electro-magnetic units.

The legal ohm is the resistance of a mercury column 1 square millimeter

in cross-sectional area and 106 centimeters in length. There has been

considerable confusion, owing to inaccuracy in early determinations, in

the valuation of the ohm. In this work the legal ohm is used. The

different ohms will be found defined in their place. Resistance units of

various names may also be consulted.

The following table gives the relative values of the different ohms.

Length of

Mercury                      Board of

Column in    True    B. A.    Trade     Legal

Centimetre.  Ohm.    Ohm.     Ohm.      Ohm.

True Ohm,           106.24    1.      1.0128    .9994    1.0022

B. A. Ohm,          104.9     .9874   1.        .9868     .9889

Board of Trade Ohm  106.3    1.00050  1.0133   1.        1.0028

Legal Ohm,          106.0     .9977   1.0112    .9971    1.

Ohmage.

The Resistance of a circuit expressed in ohms.

Ohm, B. A.

The British Association unit of resistance; the resistance of a column

of mercury 1 square millimeter in cross sectional area and 104.9

centimeters long; the B. A. Unit of Resistance.

Ohm, Board of Trade.

The approximate ohm as recommended by the British Board of Trade on the

advice of a committee (Sir W. Thomson, Dr. J. Hopkinson, Lord Rayleigh

and others). It is the resistance of a mercury column one square

millimeter in section, and 106.3 centimeters long at 0º C. (32º F.)

Synonym--New Ohm.

395   STANDARD ELECTRICAL DICTIONARY.

Ohmic Resistance.

True resistance as distinguished from spurious resistance, or

counter-electro-motive force.

Ohm, Legal.

The practical unit of resistance. The resistance of a column of mercury

one square millimeter in cross-sectional area and 106 centimetres long

at 0º C. (32º F.) The ohm used previously to 1884 is the B. A. Unit of

Resistance, q. v.

One legal ohm = 1.0112 B. A. Units, and I B. A. Unit = 0.9889 legal ohm.

The resistance of a copper wire 1 foot long and 1/1000 inch in diameter

is about 10 ohms. The resistance of 1 mile of iron wire 1/3 inch in

diameter is about 10 ohms.

Synonym--Congress Ohm.

396   STANDARD ELECTRICAL DICTIONARY.

Fig. 252. THEORY OF OHMMETER.

Fig. 253. OHMMETER.

Ohmmeter.

An instrument for measuring directly the resistance of a conductor or of

any part of a circuit through which a strong current is passing.  It is

the invention of Prof. W. E. Ayrton.

It contains two fixed coils at right angles to each other acting on the

same needle of soft iron. One coil is of thick wire and is placed in

series with the resistance to be measured. The other is of very thin

wire and is placed in parallel with the same resistance. One wire acts

by the total current, the other by the potential difference between the

ends of the resistance. The action on the soft iron needle is due to the

ratio of potential difference to total currents, or to the resistance

itself. By properly designing and proportioning the coils the angular

deflections of the needle are made proportional to the resistance.

In use the thick wire may be kept permanently in circuit. On connecting

the binding posts of the thin wire coil to any two parts of the circuit

its resistance is at once given by the deflection of the needle.

When no current is passing the needle rests in any position. A current

in the thick coil brings it to zero. A current simultaneously passing

through the thin high resistance coil brings about the deflection.

The instrument is a commercial rather than a scientific one.

Ohm's Law.

The fundamental law expressing the relations between current,

electro-motive force and resistance in an active electric circuit. It

may be expressed thus:

(a) The current strength is equal to the electro-motive force divided by

the resistance.

(b) The electro-motive force is equal to the current strength multiplied

by the resistance.

(c) The resistance is equal to the electro-motive force divided by the

current strength. All these are different forms of the same statement.

Algebraically the law is usually expressed thus, (a) C = E/R. It may

also be expressed thus: (b) E = C*R and (c) R= E/C, in which R denotes

resistance, C denotes current strength, and E denotes electro-motive

force.

Ohm, True.

The true ohm is the resistance of a column of mercury 1 square

millimeter in cross-sectional area, and 106.24 centimeters long. (See

Ohm.)

Synonym-Rayleigh Ohm.

Oil Insulation.

Oil insulation has received several applications in electrical work. It

has been proposed for use in underground conduits. These it was proposed

to fill with oil after the insertion of the conductors, the latter

properly wrapped with cotton or other covering. For induction coils it

has been very successfully used. Its principal utility depends on the

fact that it is liquid, so that if pierced by a spark it at once closes

again. A solid insulator if pierced is permanently injured. It is also

used in telegraph insulators (see Insulator, Liquid) to prevent surface

leakage.

397   STANDARD ELECTRICAL DICTIONARY.

Olefiant Gas.

A compound gas; C2H4; composed of carbon, 24; hydrogen, 4; molecular

weight, 28; specific gravity, .981.

It is a dielectric of about the resistance of air. Its specific

inductive capacity at atmospheric pressure is 1.000722 (Boltzman.)

Synonym--Ethene; heavy carburetted hydrogen.

[Transcriber's note: Also called ethylene. A primary use is polyethylene

plastic.]

Open. adj.

An electric circuit is said to be open when it is cut or broken so that

no current can pass through it. The term may be recollected by thinking

of a switch; when open no current can pass through it. The same

adjective is applied to magnetic circuits, an air gap implying an open

circuit.

Open Circuit Oscillation.

An oscillation of current in open circuit so that a spark discharge

accompanies it. It is produced by electric resonance in a simple circle

or loop of wire with ends placed near together but not touching, if the

circuit is of such size that its period of oscillation corresponds with

that of the inducing discharge. (See Resonance, Electric.) Its period

depends entirely on the self-induction of the circuit.

Ordinate.

In a system of plane co-ordinates (see Co-ordinates), the distance of

any point from the axis of abscissas measured parallel to the axis of

ordinates.

Ordinates, Axis of.

The vertical axis in a system of co-ordinates, q. v.

Synonym--Axis of Y.

Organ, Electric.

An organ in which the air blast is admitted or excluded from the

different pipes by electric mechanism.

The outlines of the system are a series of contacts worked by the keys

and stops, which cause, when operated by the organist, a current to pass

through electro-magnets, opening the valves of the different pipes. Thus

the manual may be at any distance from the organ, and a number of organs

may be worked upon the same manual. As many as five in a single

cathedral are thus connected to a manual in the chancel.

Orientation of a Magnetic Needle.

The acquirement by a magnetic needle of its position of rest, with its

magnetic axis in the magnetic meridian.

Origin of Co-ordinates.

In a system of linear co-ordinates the point of intersection of the

axes; the point whose co-ordinates are both zero.

398   STANDARD ELECTRICAL DICTIONARY.

Oscillating Needle.

A small light bar magnet suspended by a filament and employed in

determining the intensity of a magnetic field by the oscillations it

completes in a given time after a given disturbance.

Oscillations, Electric.

In static electricity the sudden and very rapid alternations in the

discharge of a static condenser. This discharge of the disruptive order

seems a single one, but is really composed of a number of discharges

alternating in direction and producing electro-magnetic ether waves,

probably identical with light waves except that they are longer and far

less rapid.

Oscillatory Electro-motive Force.

Electro-motive force rapidly changing in sense or in direction, so that

it presents an oscillatory character. The alternating current and the

telephone current as used in practice are actuated by this type of

electro-motive force.

Osmose, Electric.

When two liquids are separated by a porous diaphragm, and a strong

current of electricity is passed through from the liquid on one side,

through the diaphragm, to the liquid on the other side, the liquid on

the side towards which the current is passing rises in level. The

process is termed electric osmose. When a liquid is forced through a

diaphragm a current is produced; in other words electric osmose is

reversible. The current thus produced is termed a diaphragm current.

Oscillation, Electric.

The phase of discharge of a static condenser in one direction. It is

usually followed by a discharge in the opposite direction constituting a

second oscillation, and so on, so that a great number of exceedingly

short oscillations are comprised. Thus, in the discharge of the Leyden

jar a large number of oscillations of current back and forth are

produced, the current alternating like the swings of a pendulum.

These oscillations are supposed to affect the ether, producing waves in

it identical with light waves, except that we have not been able yet to

produce them short enough to affect the visual organs. The waves thus

produced can be reflected or refracted; some substances are transparent

for them and others opaque. There is a possibility that man may yet

succeed in producing electric oscillations of sufficient frequency to

bring about the direct production of light.

Oscillatory Displacement.

Hypothetical displacement currents of rapidly alternating direction

produced in the oscillatory discharge of a Leyden jar or static

condenser.

Oscillatory Induction.

Induction produced by sympathetic action of an oscillatory discharge or

by electric resonance. (See Oscillations, Electric--Resonance,

Electric--Resonator, Electric.)

399   STANDARD ELECTRICAL DICTIONARY.

Outlet.

The part of an electrolier or electric light fixture out of which the

wires are led for attachment of an incandescent light socket.

Output.

The rate of energy delivered or of work done by a machine. In the case

of a current generator it is the volt-coulombs per given second, or

better the volt-amperes delivered at its outer circuit terminals.

Output, Magnetic.

The analogue in a magnetic circuit of the output of an electric circuit.

It is the product of the magnetizing force by the induced magnetism.

Output, Unit of.

As a unit of output of a dynamo Prof. Sylvanus P. Thompson has proposed

1,000 watts, or one kilowatt. This unit is now frequently used. To

completely define the dynamo, however, the amperage or the voltage must

also be given, as a 10 kilowatt--110 volt machine, or a 10 kilowatt--99

ampere machine.

[Transcriber's note: 10 kilowatt at 110 volts is 91 amperes.]

Over-Compounding.

A proportioning of the series and shunt windings of a compound dynamo,

so that the voltage of the terminals rises with the load or output

enough to allow for the drop in mains, thus maintaining the potential

for full load at distant points in a district. It is carried out by an

increase of ampere-turns in the series winding.

Overload.

In an electric motor a mechanical load put upon it so great as to

prevent economical working. One effect of such a load is to make the

armature run so slowly as to unduly reduce the counter-electro-motive

force and hence to permit so much current to pass through the coils as

to heat them, perhaps injuriously. In this case the production of heat

implies the waste of energy.

Overtype Dynamo or Motor.

A dynamo or motor whose armature is placed above or in the upper part of

the field magnets, the yoke piece of the magnets being in or resting

upon the base of the machine.

Ozone.

An allotropic form of oxygen. It possesses much more energetic chemical

properties than oxygen. It is supposed to contain three atoms of oxygen

in its molecule, represented thus:

O

/ \

O---O

It is produced by electric discharges and it is its peculiar odor which

is noticed about an electric machine, and sometimes in a thunderstorm

near the path of a lightning flash.

In the electrolysis of water some ozone may be produced, thus

diminishing the volume of the oxygen or of the mixed gases given off.

This is a source of inaccuracy in a gas voltameter.

400   STANDARD ELECTRICAL DICTIONARY.

Pacinotti's Inductor.

The Pacinotti or Gramme Ring. (See Pacinotti's Ring.)

Pacinotti's Ring.

A ring of iron wire wound with coils of insulated wire at right angles

to its circular axis, and used as the armature of a dynamo or motor. A

number of connections are taken from the coils to a central commutator.

Fig. 254. PACINOTTI'S MACHINE, WITH RING ARMATURE.

If such a ring with its coils is rotated in a field, current can be

taken from points of the commutator on a line at right angles to the

lines of force entering the ring.

The ring was discovered in 1862 by Pacinotti, and later was

independently discovered by Gramme. It is often known as the Gramme

ring.

Pacinotti Teeth.

Projections on a cylindrical or drum armature, between which in the

grooves formed thereby, the wire is wound. The teeth being of iron tend

to diminish the reluctance or magnetic resistance of the interpolar

space, or interval between the poles of the field magnet.

Synonym--Pacinotti Projections.

Paillard Alloys.

Non-magnetic palladium alloys, invented by Paillard, of

Switzerland, used in anti-magnetic watches. The following are given as

the compositions of several such alloys:

I.                II.

Palladium,  60 to 75   parts   50 to 75  parts

Copper,     I5 to 25   "       20 to 30   "

Iron.        1 to 5    "       5 to 20   "

401   STANDARD ELECTRICAL DICTIONARY.

The following are more complex:

I.                II.

Palladium,   65 to 75   parts   45 to 50   parts

Copper,      15 to 25     "     15 to 25   "

Nickel,       1 to 5      "      2 to 5    "

Silver,       3 to 10     "     20 to 25   "

Gold,         1 to 2-1/2  "      2 to 5    "

Platinum,   1/2 to 2      "      2 to 5    "

Steel,        1 to 5      "      2 to 5    "

These alloys are used for balance springs, as well as for the balance

wheels and escapement parts of watches. The elasticity of recently

produced springs has been found to be very satisfactory.

Page Effect.

The sounds produced by magnetizing and demagnetizing a bar of iron or

steel; the magnetic tick. The sounds are strong enough to produce a

telephonic effect. (See Magnetic Tick.)

Palladium.

A metal of the platinum series. It has the highest power of occlusion,

q.v., of all metals. It is the characteristic ingredient of non-magnetic

watch alloys.

Palladium used as an electrode in the electrolysis of water will occlude

936 volumes of hydrogen, and the hydrogen-palladium alloy will exceed in

size the original electrode.

Fig. 255. LUMINOUS PANE.

Pane, Luminous.

A pane of glass, one side of which has pasted to it a long zigzag strip

of tinfoil. A design is made by cutting through the strip. On

discharging a Leyden jar or an electric machine through the strip sparks

appear where the tinfoil is severed, thus producing the design in a

luminous effect. Many variations can be employed in their construction.

402   STANDARD ELECTRICAL DICTIONARY.

Pantelegraphy.

A system of telegraphy for transmitting designs, maps, drawing, and the

like by telegraphy. (See Telegraphy, Facsimile.)

Paper Filaments.

Filaments of carbon for incandescent lamps made from paper.

This is one of the earliest materials practically used. The paper is cut

out of proper shape, and is carbonized in a close vessel, while embedded

in powdered charcoal or some other form of carbon to absolutely cut off

access of air. It is then placed in the lamp chamber and flashed or

subjected to the regular treatment.

Parabola.

A curve; one of the conic sections. It is approximately represented by a

small arc of a circle, but if extended becomes rapidly deeper than a

half circle.

If, from a point within called the focus, lines are drawn to the curve

and then other lines are drawn from these points parallel to the axis,

the angles of incidence will he equal to the angles of reflection as

referred to tangents at the points where the lines touch the curve.

[Transcriber's note; The general equation of a parabola is

A*x^2 + B*x*y + C*y^2 + D*x + E*y + F = 0

such that B^2 = 4*A*C, all of the coefficients are real, and A and C are

not zero. A parabola positioned at the origin and symmetrical on the y

axis is simplified to y = a*x^2 ]

Parabolic Reflector.

A reflector for a light, a paraboloid or surface of revolution whose

section is a parabola. A light placed at its focus has its rays

reflected parallel to each other.

Examples of parabolic reflectors are seen in electric search lights and

in locomotive head-lights. They are employed in electric search lights.

The arc light must be of such construction as to maintain its ignited

points always at the same point, the focus of the paraboloid.

Paraffine. v.

To coat or saturate with paraffine wax. Paper may be paraffined by

dipping in the wax, or by being sprinkled with fragments of wax,

subsequently melted in with a hot iron or otherwise. The tops of battery

carbons are often paraffined to prevent the acid from rising in the

pores by capillary attraction and rusting the connections.

403   STANDARD ELECTRICAL DICTIONARY.

Paraffine Wax.

A hydro-carbon composed principally of mixtures of the higher members of

the paraffine series C n H2 n + 2. It is made from cannel coal, coal

tar, or petroleum by distillation. It is an insulator. Its resistance at

46° C. (114.8° F.) per centimeter cube is 3.4E16 ohms, or about the

highest resistance known.

Its specific inductive capacity (for milky wax) is 2.47 (Schiller). For

clear wax it is given as follows by different authorities:

1.92  Ayrton.

1.96  Wüllner.

1.977 Gibson & Barclay.

2.32  Baltzmann.

It is extensively used in condensers and other electric apparatus as a

dielectric and insulator.

Paragrêles.

Protectors against hail; lightning rods used to guard fields against

hail; of little or no real utility.

Parallax.

The apparent change in position of an object when looked at from two

points of view. By looking at an object a few feet distant first with

one eye and then with the other, the shifting in apparent position is

seen.

In reading the position of an indicator or needle over a scale parallax

introduces an error unless the eye is held vertically over the needle.

By making the dial of looking- glass and holding the eye so that the

reflection of its pupil is bisected by the needle this verticality is

ensured.

Parallel.

(a) In the nomenclature of electric circuits two or more conductors

leading from one point to another, are said to be in parallel.

(b) When two or more conductors connect two main leads of comparatively

large size and low resistance they are said to be in parallel or in

multiple arc. This order is easiest pictured as the rungs of a ladder in

parallel connecting its two sides representing the main leads.

It may be used as a noun as "arranged in parallel," or as an adjective

as "a parallel circuit," the opposite of series, q. v.

Paramagnetic. adj.

Possessing paramagnetic properties; tending to occupy a position with

the longer axis parallel to the lines of force of a magnetic field;

having magnetism; attracted by a magnet.

"If a homogeneous isotropic substance is placed in a magnetic field it

becomes magnetized at every point in the direction of the magnetic

intensity at that point, and with an intensity of magnetization

proportional to the magnetic intensity. When the positive direction of

the induced magnetization is the same as that of the magnetic intensity

the substance is called Magnetic or Paramagnetic; when it is opposite,

the substance is called Diamagnetic." (Emtage.)

A paramagnetic substance has high permeability or multiplying power for

lines of force, hence in a magnetic field a bar of iron, etc., is in

unstable equilibrium unless its longer axis is parallel with the lines

of force in order to reduce as much as possible the reluctance of the

circuit.

404   STANDARD ELECTRICAL DICTIONARY.

Iron is the most paramagnetic of all substances. Other paramagnetic

metals are: Nickel, cobalt, manganese, platinum, cerium, osmium,

palladium. Diamagnetic metals are bismuth, antimony, zinc, tin, mercury,

lead, silver, copper, gold, arsenic. Bismuth is the most diamagnetic of

all metals.

Of gases oxygen is most paramagnetic. Becquerel calculated that a cubic

yard of oxygen condensed would act on a magnetic needle as powerfully as

5.5 grains of metallic iron. Liquefied oxygen will adhere to the poles

of a magnet.

Changes of temperature and of other conditions may affect a body's

magnetism. Thus hot oxygen is diamagnetic, and a substance paramagnetic

in a vacuum may be diamagnetic in air.

Of liquids, solutions of iron or cobalt are paramagnetic; water, blood,

milk, alcohol, ether, oil of turpentine and most saline solutions are

diamagnetic.

Paramagnetism.

(a) The science or study of paramagnetic substances and phenomena.

(b) The magnetic property of a paramagnetic substance; that of being

attracted by a magnet, and of arranging itself with its longer axis

parallel with the lines of force of a magnetic field.

Parchmentizing.

If cellulose is treated with a mixture of two parts of sulphuric acid

and one part of water perfectly cold, it becomes like parchment. It

should at once be washed with water, and then with ammonia and water.

The Swan incandescent light fibres are made of parchmentized cotton

thread, which is afterward carbonized.

Partial Earth.

A fault in a conductor caused by imperfect connection with the earth,

where insulation from the earth is desired.

Passive State.

A state of a substance in virtue of which it is unattacked by a solvent

which ordinarily would dissolve or attack it. Iron in strong nitric acid

is unattacked or assumes the passive state. This particular case is

supposed to be due to a coating of magnetic oxide, so that there would

be properly speaking no question of a passive state, but only one of

superficial protection.

The existence of a true passive state of any substance is very doubtful.

P. D.

Abbreviation for potential difference or difference of potential, or for

electro-motive force.

405   STANDARD ELECTRICAL DICTIONARY.

Peltier Effect.

The thermal effect produced by the passage of a current through the

junction of two unlike conductors. Such junction is generally the seat

of thermo-electric effects, and a current is generally produced by

heating such a junction. If an independent current is passed in the same

direction as that of the thermoelectric current, it cools the junction,

and warms it if passed in the other direction. In general terms,

referring to thermo-electric couples, if passed through them it tends to

cool the hot and heat the cool junction. The phenomenon does not occur

in zinc-copper junctions.

Peltier's Cross.

A bar of bismuth and a bar of antimony soldered centre to centre at

right angles, being notched or halved there to receive or to set into

each other. It is used to demonstrate the Peltier effect, q. v. To one

pair of ends are connected the terminals of a battery circuit; to the

other pair are connected the terminals of a galvanometer.

The galvanometer by its deflections in one and then in the other

direction indicates that the junction is heated when the current passes

from antimony to bismuth and vice versa. It thus illustrates the heating

and cooling of a thermo-electric junction by a current of electricity.

The current from the battery by the Peltier effect either heats or cools

the junction, as the case may be. This heating or cooling them produces

a thermo-electric current in the galvanometer circuit. The battery has

no direct influence on the galvanometer.

Pendant Cord.

A double conductor or pair of conductors, insulated from each other and

covered with a worsted, silk, or cotton covering and used to suspend

incandescent lamps and at the same time to conduct the current to them.

It is also used for other similar service, such as acting as conductors

for small motors. Often each conductor is composed of a number of thin

wires laid together. This gives flexibility to the cord.

Synonym--Flexible Cord.

Pendulum, Electric.

(a) A pendulum operated by the intermittent action of an electro-magnet,

whose circuit is opened and closed by the pendulum itself. A point at

the lower end of the pendulum swinging through a globule of mercury may

close and open the circuit. Various other methods of accomplishing the

same end are employed ..

(b) A pith ball suspended by a thread from an insulating stand. It is

used to show the attraction exercised by a piece of sealing wax or other

substance excited by rubbing.

406   STANDARD ELECTRICAL DICTIONARY.

Pen, Electric.

A stylus for producing a series of perforations in paper, so that the

paper may act as a stencil for the reproduction of a great number of

copies of the original matter. Various kinds of electric pens have been

invented. One kind, invented by Edison, consists of a handle carrying an

electric motor actuating a needle, which is driven in and out of the

other end of the handle with high rapidity. It is used by being held

vertically on the paper with the needle end downward, and is moved so as

to describe perforated letters or designs. The paper is then used as a

stencil with an ink roller to reproduce the writing or design ad

libitum. A simpler kind dispenses with the motor and depends on the

perforations produced by the electric spark. As shown in the cut the

stylus is one terminal of an induction coil circuit. The support on

which the paper rests is the other terminal and must be a conductor. In

use the induction coil is started, and the stylus is moved over the

paper; a series of sparks pass through the paper from stylus to the

supporting tablet, perforating the paper and producing a stencil to be

used for reproduction.

Fig. 256. ELECTRIC PEN.

Pentane Standard, Harcourt's.

A standard of illuminating power; in it the combustible substance is a

gas made by mixing one cubic foot of air with three cubic inches of

liquid pentane, measured at 60° F. or, if measured as gases, 20 volumes

of air to 7 of pentane. It is burned at the rate of 0.5 cubic foot per

hour from a cylindrical tube one inch in diameter, closed at the top by

a disc 0.5 inch thick with a hole 0.25 inch in diameter, through which

the gas issues. It gives a flame 2.5 inches high.

The pentane used is the distillate of petroleum which boils at 50° C.

(122° F.) ; it has a specific gravity at 15° C. (60° F.) of from 0.628

to 0.631. It is almost pure pentane (C5H12).

As long as the rate of consumption is between 0.48 and 0.52 cubic foot

per hour the flame gives practically the same light.

407   STANDARD ELECTRICAL DICTIONARY.

Perforator.

An apparatus used in automatic high speed telegraphy for perforating

strips of paper. These are then used by drawing between a roller and

contact spring for making and breaking the telegraphic circuit for the

production of a record, such as the Morse record, at the distant

receiving station.

The perforated strip has different classes of holes punched in it to

represent dots or dashes. It is fed by machinery very rapidly, so that

the message is transmitted with the highest speed. Several operators may

simultaneously prepare the paper strips, and thus in conjunction with

its rapid feeding in the transmitter, far surpass the time of ordinary

direct transmission.

Fig. 257. PERFORATOR FOR

WHEATSTONE'S AUTOMATIC TELEGRAPH.

Perforators may be entirely mechanical but are sometimes pneumatic,

compressed air being used to operate them. The holes they make are on

different levels of the paper strip, as shown in the cut.

Period.

The time required for the completion of one complete element of periodic

motion. This may be a complete alternation (See Alternation, Complete)

of an alternating current, or of an oscillatory discharge.

Periodicity.

The rate of succession of alternations or of other fixed phases; the

rate of recurrence of phenomena.

408   STANDARD ELECTRICAL DICTIONARY.

Permanency.

In electric current conductors the property of possessing conductivity

unaffected by lapse of time. Generally the permanency of conductors is

very high. In some cases a slow annealing takes place which causes a

gradual change with the lapse of time. Annealed German silver wire has

been found to increase in conductivity at about .02 per cent. in a year.

(Matthiessen.) Wire, whether annealed or not, is left in a strained

condition after the drawing operations, and such a change is consonant

with this fact. The figure only applies to the samples tested by

Matthiessen.

Permanent State.

In a telegraph line or other current conductor, the condition when a

uniform current strength obtains over the whole line. When a current is

started it advances through the line with a sort of wave front gradually

increasing in strength. At the further end some time may elapse before

it attains its full intensity. When its does the permanent state

prevails. Until then the variable state, q. v., exists in the line.

Permeameter.

An apparatus for determining the permeability of samples of iron. It

consists of a large slotted block of iron. A coil is placed within the

slot. A hole is drilled through one end, and a rod of the iron to be

tested is passed through this hole and through the coil to the bottom of

the slot. The lower end of the rod must be accurately faced off. The

current is turned on, upon which the rod adheres to the bottom of the

slot. The force required to detach it is determined with a spring

balance. The permeation through its face is proportional to the square

of the force required.

Fig. 258. PERMEAMETER.

Permeance.

The multiplying or the conducting power for magnetic lines of force

possessed by a given mass of material. It varies with the shape and size

of the substance as well as with the inducing force. It is distinguished

from permeability, as the latter is a specific quality proper to the

material, and expressed as such; the permeance is the permeability as

affected by size and shape of the object as well as by its material.

409   STANDARD ELECTRICAL DICTIONARY.

Pflüger's Law.

A law of electro-therapeutics. It states that stimulation of a nerve is

only produced by successive appearance of the kathelectrotonic state,

and disappearance of the anelectrotonic state.

Phantom Wires.

The extra transmission circuits obtained in multiplex telegraph systems.

A single line arranged for four separate simultaneous transmissions by

quadruplex apparatus is said to establish three phantom wires.

Phase.

In wave motion, oscillating motion, simple harmonic motion, or similar

periodic phenomena, the interval of time passed from the time the moving

particle moved through the middle point of its course to the instant

when the phase is to be stated.

Pherope.

An apparatus for the electric transmission of pictures. (See Telephote.)

[Transcriber's note: Precursor of the contemporary Fax and scanner.]

Philosopher's Egg.

An ellipsoidal vessel mounted with its long axis vertical and with two

vertical electrodes, the upper one sliding, and arranged to be attached

to an air pump. A discharge through it when the air is exhausted takes

the general shape of an egg.

Phonautograph.

An apparatus for registering the vibrations of a stylus, which is

mounted on a diaphragm and is acted on by sound waves.

It is virtually a resonating chamber, over one of whose ends a parchment

diaphragm is stretched. To the centre of the parchment a needle or

stylus is attached. A cylinder covered with soot is rotated in contact

with the point of the stylus. As the chamber is spoken into the

diaphragm and stylus vibrate and the vibrations are marked on the

cylinder. It is of some electric interest in connection with telephony.

Phone.

Colloquial abbreviation for telephone.

Phonic Wheel.

A form of small motor of very simple construction. It consists of a

toothed wheel of soft iron. A bar electro-magnet is fixed with one pole

facing the teeth of the wheel. By a tuning fork make and break a

succession of impulses of rapid frequency and short duration are sent

through the magnet. The teeth act as armatures and are successively

attracted by the magnet. The regulated speed is one tooth for each

impulse, but it may rotate at one-half the speed, giving two teeth for

each impulse, or at certain other sub-multiples of its regular speed. It

is the invention of Paul Lecour.

410   STANDARD ELECTRICAL DICTIONARY.

Phonograph.

An apparatus for reproducing articulate speech. It is not electric,

except as it may be driven by electricity.

It consists of a cylinder of wax-like material which is rotated and

moved slowly, longitudinally, screw fashion, at an even speed. A glass

diaphragm carrying a needle point is supported with the point barely

touching the wax. If the diaphragm is agitated, as by being spoken

against, the needle is driven back and forwards cutting a broken line or

groove following the direction of the thread of a screw in the wax, the

depth of which line or groove continually varies.

This imprints the message. If the needle is set back and the cylinder is

rotated so as to carry the needle point over the line thus impressed,

the varying depth throws the needle and diaphragm into motion and the

sound is reproduced.

The cylinder is rotated often by an electric motor, with a centrifugal

governor.

[Transcriber's note; Due to T. A. Edison, 1877, fifteen years before

this book.]

Phonozenograph.

An apparatus for indicating the direction of the point where a sound is

produced. It operates by a microphone and telephone in conjunction with

a Wheatstone bridge to determine the locality.

Phosphorescence.

The emission of light rays by a substance not heated, but whose

luminosity is due to the persistence of luminous vibration after light

has fallen upon it.

A phosphorescent body, after exposure to light, is luminous itself.

Phosphorescence may be induced by rubbing or friction, by heat, by

molecular bombardment, as in Crookes' tubes, and by static discharge of

electricity, as well as by simple exposure to light.

Another form of phosphorescence may be due to slow chemical combustion.

This is the cause of the luminosity of phosphorous.

Phosphorous, Electrical Reduction of.

Phosphorous is reduced from bone phosphate by the heat of the electric

arc. The phosphate mixed with charcoal is exposed to the heat of the

voltaic are, and reduction of the phosphorous with its volatilization at

once ensues. The phosphorous as it volatilizes is condensed and

collected.

Photo-electricity.

The development of electrical properties by exposure to light. Crystals

of fluor spar are electrified not only by heat (see Pyro-electricity)

but also by exposure to sunlight or to the light of the voltaic arc.

[Transcribers note: Although first observed in 1839 by Becquerel, it

was not explained until 1905 by Albert Einstein with the introduction of

photons.]

Photo-electric Microscope.

A projection, solar or magic-lantern microscope worked by the electric

light.

Photo-electro-motive Force.

Electro-motive force produced in a substance by the action of light.

411   STANDARD ELECTRICAL DICTIONARY.

Photometer.

An apparatus for measuring the intensity of light emitted by a given

lamp or other source of illuminating power. They may be classified into

several types.

Calorimetric or Heat Photometers act by measuring relatively the heat

produced by the ether waves (so-called radiant heat) emitted by the

source. The accuracy of the instrument is increased by passing the rays

through an alum solution. A thermopile, or an air thermometer, may be

used to receive the rays.

Chemical Photometers. In these the light falls upon sensitized

photographic paper. The depth of coloration is used as the index of

illuminating power.

Direct Visual Photometers. These include Rumford's Shadow Photometer,

Bunsen's Bar Photometer, and Wheatstone's Bead Photometer, in which the

light is estimated by direct visual comparison of its effects.

Optical Photometers. These include Polarization Photometers, in which

the light is polarized; Dispersion Photometers, in which a diverging

lens is placed in the path of the rays of light so as to reduce the

illuminating power in more rapid ratio than that of the square of the

distance.

Selenium Photometers, in which the variations in resistance of selenium

as light of varying intensity falls upon it is used as the indicator of

the intensity of the light.

Jet Photometers, for gas only, in which the height of a flame under

given conditions, or the conditions requisite to maintain a flame of

given height, is used to indicate the illuminating power.

The subject of photometers has acquired more importance than ever in

view of the extensive introduction of the electric light. (See Candle,

Standard--Carcel--Violé's Standard--and Photometers of various kinds.)

Photometer, Actinic.

A photometer whose registrations are produced by the action of the light

being tested upon sensitized paper or plates, such as used in

photography. Some efforts at self-registering photometers have been

based on actinic registration of the height of a flame of the gas to be

tested.

Photometer, Bar.

A photometer in which the two lights to be compared are fixed at or

opposite to the ends of a bar or scale of known length, generally 60 or

100 inches. The bar is divided by the rule of the inverse square of the

distances, so that if a screen is placed on any part of the bar where it

receives an equal amount of light from both sources, the figure on the

bar will indicate the relative illuminating power of the larger lamp or

light in terms of the smaller. The divisions of the bar are laid out on

the principle that the illuminating power of the two sources of light

will vary inversely with the square of their distance from the screen.

412   STANDARD ELECTRICAL DICTIONARY.

The screen used is sometimes the Bunsen disc. This is a disc of paper

with a spot of paraffine wax in the centre melted thoroughly into the

paper or with a ring of paraffine wax surrounding the untouched centre.

When this disc is equally illuminated on both sides the spot is nearly

invisible. Inequality of illumination brings it out more visibly.

Sometimes a Leeson disc is used. This consists of three pieces of paper,

two thin ones between which a thicker piece, out of which a star is cut,

is laid. When equally illuminated on both sides the star appears equally

bright on both sides.

The bar photometer is the standard form. A candle or pair of candles may

be burned at one end and an incandescent lamp at the other, or a gas

flame may first be rated by candles and used as a standard.

Synonyms--Bunsen's Photometer--Translucent Disc Photometer.

Fig. 259. BAR PHOTOMETER.

Photometer. Calorimetric.

A photometer in which the radiant energy, so called radiant heat, is

used as the measurer of the light.

In one type a differential air thermometer is used, one of whose bulbs

is blackened. On exposing this bulb to a source of light it will become

heated, and if lights of the same character are used the heating will be

in proportion to their illuminating power quite closely. The heating is

shown by the movements of the index. By careful calibration the

instrument may be made quite reliable.

Photometer, Dispersion.

A photometer in which the rays from one of the lights under comparison

are made more divergent by a concave lens. In this way a strong light,

such as all arc lamp can be photometered more readily than where only

the natural divergence of the beam exists. The law of the variation of

the intensity of light with the square of the distance is abrogated for

a law of more rapid variation by the use of a concave lens.

The diagram, Fig. 260, illustrates the principle. E represents a

powerful light, an arc light, to be tested. Its distance from the screen

is e. Its light goes through the concave lens L and is dispersed as

shown over an area A1, instead of the much smaller area A, which the

same rays would otherwise cover. Calling l the distance of the lens from

the screen, f its focus, and c the distance of the standard candle from

the screen when the shadows are of equal intensity, we have the

proportion.

Illuminating power of lamps: ditto of standard candle::

(l (e-l) + fe)2 : (c f)2

413   STANDARD ELECTRICAL DICTIONARY.

Fig. 260. DIAGRAM OF PRINCIPLE

OF THE DISPERSION PHOTOMETER.

The cut, Fig. 261, gives a perspective view of Ayrton's Dispersion

Photometer. C is the standard candle, L the concave lens, R the rod for

producing the two shadows on the screen S.

Fig. 261. AYRTON'S DISPERSION PHOTOMETER.

The mirror M is fixed at an angle of 45° with the stem on which it

rotates. The light of the arc lamp is received by the mirror and is

reflected through the lens. The candle holder slides along a graduated

bar C, and at D is an index plate to show the angle at which the spindle

carrying the mirror is set.

414   STANDARD ELECTRICAL DICTIONARY.

Dr. J. Hopkinson in his dispersion photometer uses a double convex lens.

This gives a focal image of the arc-lamp between the lens and screen,

whence the rays diverge very rapidly, thus giving the desired dispersion

effect.

It is principally for arc lamps that dispersion photometers are used.

Photometer, Shadow.

A photometer in which the relative intensity of the two lights is

estimated by the intensity or strength of shadows of the same object

which they respectively cast.

Fig. 262. RUMFORD'S SHADOW PHOTOMETER.

Fig. 263. RUMFORD'S SHADOW PHOTOMETER ARRANGED FOR TESTING

INCANDESCENT LAMPS.

415   STANDARD ELECTRICAL DICTIONARY.

A rod is supported in a vertical position. Back of it is a screen of

white paper. The two lights to be compared are arranged in front of the

rod and at a little distance from each other. They are shifted about

until the two shadows appear of equal darkness. The relative intensity

of the lights varies inversely with the square of their distances from

the shadows cast respectively by them on the screen.

The cut, Fig. 262, shows the simplest type of the shadow photometer. In

the cut, Fig. 263, a shadow photometer for testing incandescent lamps is

shown. In it E is the lamp under trial supported by a clamp H. A is an

ampere meter in circuit with the lamp, and V is a voltmeter. A candle C

can be moved along a graduated scale G G. R is the vertical rod, and S

is the screen on which the shadows fall.

Photophore.

An instrument for medical examination of the cavities of the body. It

includes an incandescent lamp mounted in a tube with a concave mirror

and convex lens.

Photo-voltaic Effect.

The change in resistance of some substances effected by light. Selenium,

of all substances, is most susceptible to this effect. (See Selenium.)

Piano, Electric.

A piano whose manual or key-board operates to close electric circuits,

whereby electro-magnets are caused to operate to drive the hammers

against the strings.

Pickle.

An acid solution for cleaning metal surfaces before electro-plating,

galvanizing or other deposition of metal upon them.

Picture, Electric.

A picture produced by passing a strong discharge through a piece of gold

leaf clamped or firmly pressed upon a sheet of paper. The gold leaf is

cut out of the desired shape, or else a stencil of paper overlays it.

The discharge dissipates the gold, and produces a purple colored

reproduction of the design upon the paper. The design is due to the

deposition of an exceedingly thin film of metallic gold.

Synonym--Electric Portrait.

Pile.

A galvanic or voltaic battery. It is sometimes restricted to a number of

voltaic couples connected. It should be only applied to batteries with

superimposed plates and no containing vessel such as the Dry Pile, q.

v., or Volta's Pile, q. v.

Pilot Transformer.

In alternating current distribution a small transformer placed at any

part of the system and connected to a voltmeter in the central station,

to indicate the potential difference of the leads.

Pilot Wires.

Wires brought from distant parts of electric light or power mains, and

leading to voltmeters at the central station, so that the potential of

distant parts of the system can be watched. The wires can be very small,

as they have but little current to transmit.

416   STANDARD ELECTRICAL DICTIONARY.

Pistol, Electric.

An experimental apparatus for exhibiting the power of electric

incandescence or of the electric spark. A tube is mounted with a handle

like a pistol. A plug is provided to screw in and out of its side. The

plug carries two wires connected on its inner side by a fine platinum

wire, or else disconnected but with their ends brought near together to

act as terminals for the production of a spark. To use it the tube is

filled with a mixture of air and gas, the latter either hydrogen,

hydro-carbon or other combustible gas. The tube when full is corked. The

wire is heated to incandescence by a current, or a spark is passed from

a Leyden jar or other source of electrostatic excitation. The mixture,

if properly proportioned, explodes and expels the cork violently.

Fig. 264. ELECTRIC PISTOL.

Pith.

A light and soft cellular tissue forming the central core of exogenous

trees and plants. In the older parts of the tree the woody tissue often

encroaches in and partly obliterates it.

For electrical pith-balls, the pith of the elder, of corn, or, best of

all, of sun-flower stems is used.

Pith-balls.

Ball made of pith. They are used in the construction of electroscopes

and for other experiments in static electricity.

They are cut out with a sharp knife and their shape may be improved by

gentle rolling in the hand or between the fingers.

Pivot Suspension.

Suspension poising or supporting of an object on a sharp pivot. This is

used for the needle in the ordinary compass. A cavity or inverted cup,

which may be made of agate, is attached to the middle of the needle

which has a hole for its reception. The centre of gravity of the needle

comes below the bottom of the cup.

Pivot suspension is not perfect, as it has considerable friction. There

is no restitution force, as with torsion filaments.

417   STANDARD ELECTRICAL DICTIONARY.

Plant.

The apparatus for commercial manufacturing or technical works. An

electric lighting plant includes the boilers, engines and dynamos for

producing the current, and the electric mains and subsidiary apparatus.

Plant Electricity.

Electricity manifested by plant life. By means of a galvanometer

potential differences are found to exist in different parts of trees or

fruits. The roots and interior portions are negative, and the flowers,

smaller branches and fruit are positive.

In some cases a contraction of the tissue of plants can be produced by

an electric current. The sensitive plant and others exhibit this

phenomenon, exactly analogous to the action of muscular tissue.

Plate, Arrester.

In a lightning arrester the plate connected to the circuit. Sometimes

both plates are designated arrester plates.

Plate Condenser.

A static condenser having a flat plate of glass for dielectric. (See

Epinus' Condenser.)

Plate Electrical Machine.

A frictional electric machine, in which a circular plate of glass is

excited by friction with the cushions. It is the most recent type of

frictional machine and has superseded the old cylinder machines. In its

turn it is superseded by influence machines, really plate machines, but

not so termed in practice.

Plate, Ground.

In a lightning arrester, the plate connected to the earth.

Plate, Negative.

In a voltaic battery, either primary or secondary, the plate which is

unattacked by the oxygen or negative radical or element of the fluid. It

corresponds to the carbon plate in the ordinary voltaic battery, and is

the one charged with positive electricity.

Plate, Positive.

In a voltaic battery, either primary or secondary, the plate which is

dissolved or attacked by the oxygen or negative radical or element of

the fluid. It is the plate corresponding to the zinc plate in the

ordinary voltaic battery, and is the one charged with negative

electricity.

Plating Balance.

A balance or scales to which articles in an electroplater's bath are

suspended. A weight exceeding by a known amount that of the article as

immersed overbalances the article. When the plating is being deposited

as soon as it exceeds the excess of weight of the counterpoise the

balance tips, the article descends a little, the electric circuit is

broken and the plating ceases. Thus the plating is automatically stopped

when a predetermined amount of metal is deposited.

418   STANDARD ELECTRICAL DICTIONARY.

Plating Bath.

A vessel of solution for the deposition of metal by electrolysis as used

in electro-plating.

Plating, Electro-.

The deposition of metal by electrolysis so as to coat the conducting

surface of objects therewith. The full details of the many processes are

very lengthy and cannot be given here.

The general principle includes a battery or source of electric current.

The object to be plated is connected to the negative terminal and is

immersed in the solution. Thus with a battery the object is in

electrical connection with the zinc plate. To the other terminal a

metallic plate is connected. The object and the plate termed the anode

being introduced into a suitable bath, the metal whose solution is in

the bath is deposited upon the surface of the object.

The bath is a solution of the metal in some form that will lend itself

to the electrolytic action. The anode is often a plate of the metal of

the bath, so that it dissolves as fast as metal is deposited on the

object, thus keeping up the strength of the solution.

The objects to be plated must be scrupulously clean, and great care must

be taken to keep the bath uncontaminated.

When the object has a non-conducting surface, it is made conducting by

being brushed over with plumbago q.v. In addition iron dust is sometimes

dusted over it. This acts by precipitating the metal of the bath

directly and thus giving a conducting basis for the metal to deposit on.

To avoid getting iron in a bath the object may be dipped in copper

sulphate solution. This precipitates copper in place of the iron and

leaves the article in good shape for silver or other plating.

Electro-plating, if made thick enough, gives a reverse of the article

when separated therefrom. A direct copy can be got by a second plating,

on the first plating after separation, or a wax impression can be

employed.

Under the different metals, formulae for the baths will be found. (See

also Quicking--

Steeling--Plating Balance.)

Platinoid.

An alloy of copper, nickel, zinc in the proportions of German silver

with 1 or 2 per cent of tungsten. It is used for resistances. It has a

specific resistance (or resistance per centimeter cube) of about 34

microhms. Its percentage variation in resistance per degree C. (1.8° F.)

is only about .021 per cent., or less than half that of German silver.

This is its most valuable feature.

419   STANDARD ELECTRICAL DICTIONARY.

Platinum.

A metal; one of the elements; symbol, Pt; atomic weight, 197.4;

equivalent, 49.35; valency, 4; specific gravity, 21.5.

It is a conductor of electricity.

The following data refer to the annealed metal at 0° C. (32° F.)

Relative Resistance (Silver annealed = 1),   6.022

Specific Resistance,   9.057   microhms.

Resistance of a wire,

(a) 1 foot long, weighing 1 grain,     2.779   ohms.

(b) 1 foot long, 1/1000 inch thick,   54.49     "

(c) 1 meter long, weighing 1 gram,     1.938    "

(d) 1 meter long, 1 millimeter thick,   .1153   "

Resistance of a 1 inch cube,   3.565

Electro-chemical equivalent (Hydrogen = .0105),   0.5181.

The coefficient of expansion by heat is almost the same as that of

glass. It can be passed through holes in glass and the latter can be

melted about it so as to hermetically seal its place of passage through

the glass. It is used in incandescent lamps for leading-in wires and

other similar uses.

Platinum Black.

Finely divided platinum. It is made by boiling a solution of platinic

chloride with excess of sodium carbonate and a quantity of sugar, until

the precipitate is perfectly black and the supernatant liquid is

colorless. It seems to possess a great power of occluding oxygen gas.

When heated to redness it becomes spongy platinum. The negative plates

of a Smee battery are coated with platinum black.

Platinum-silver Alloy.

An alloy of 1 part platinum and 2 parts silver, used for resistance coils.

Relative Resistance (silver annealed = 1 ),   16.21   microhms.

Specific Resistance at 0°C. (32° F.),        24.39

Resistance of a wire,

(a) 1 foot long, weighing 1 grain,         4.197   ohms.

(b) 1 foot long, 1/1000 inch diameter,   146.70     "

(c)  1 meter long weighing 1 gram,         2.924    "

(d) 1 meter long, 1 millimeter diameter,   0.3106   "

Resistance of a 1 inch cube,   9.603   microhms.

Percentage Variation per degree C. (1.8° F.)

at about 20° C. (68° F.), 0.031 per cent.

Synonym--Platinum Alloy.

Platinum Sponge.

Finely divided platinum obtained by igniting platinum black, q.v., and

also by igniting salts of platinum. It has considerable power of

condensing or occluding oxygen. It will, if in good condition, set fire

to a jet of hydrogen impinging upon it.

Plow.

Contact arms projecting downwards from the motors, trucks, or bodies of

electric street cars, which enter the underground conduit through the

slot and carry contact pieces or brushes, to take the current for

driving the motors from the leads within the conduit.

420   STANDARD ELECTRICAL DICTIONARY.

Plücker Tubes.

A special form of Geissler tube designed for the production of

stratification and for observing the effects produced in the space

surrounding the negative electrode.

Plug.

(a) A piece of metal with a handle and a somewhat tapered end, used to

make connections by insertions between two plates or blocks of metal

slightly separated and with grooves to receive it.

(b) A plug or wedge with two metallic faces, insulated from each other

with a separate wire connected to each one. It is used in spring-jacks

q. v., to introduce a loop in a circuit.

Synonym--Wedge.

Plug. v.

To connect by inserting a plug, as in a resistance box.

Fig. 265. PLUGS FOR RESISTANCE COIL BOX.

Fig. 266. PLUG SWITCH.

Plug, Double.

A spring-jack plug or wedge with two pairs of insulated faces, one

behind the other, so as to simultaneously introduce two loops into a

circuit.

Plug, Grid.

A piece or mass of lead oxide, inserted into the holes in the lead

plates of storage batteries. The holes are often dovetailed or of uneven

section to better retain the plugs.

Plug Infinity.

In a box-bridge or resistance box, a plug whose removal from between two

disconnected discs opens the circuit. All the other discs are connected

by resistance coils of various resistance.

Plug Switch.

A switch composed of two contact blocks, not touching each other and

brought into electrical connection by the insertion of a metallic plug.

The latter is usually provided with an insulating handle, and a seat is

reamed out for it in the two faces of the contact blocks.

421   STANDARD ELECTRICAL DICTIONARY.

Plumbago.

Soft lustrous graphite, a native form of carbon; sometimes chemically

purified. It is used in electro-plating to give a conducting surface to

non-conducting objects, such as wax moulds. The surface, after coating

with plumbago, is sometimes dusted over with iron dust, which

precipitates the metal of the bath and starts the plating. It is

sometimes plated with copper, silver or gold, and is then termed

coppered, silvered, or gilt plumbago. It is gilded by moistening with

etherial solution of gold chloride and exposing to the air, and drying

and igniting.

Plunger.

A movable core which is used in connection with a so-called solenoid

coil, to be drawn in when the coil is excited. (See Coil and Plunger.)

Fig. 267 COIL AND PLUNGER WITH

SCALES TO SHOW ATTRACTION.

P. O.

Abbreviation for Post Office, q.v.

Poggendorf's Solution.

An acid depolarizing and exciting fluid for zinc-carbon batteries. The

following is its formula: Water, 100 parts; potassium bichromate, 12

parts; concentrated sulphuric acid, 25 parts. All parts by weight. Use

cold.

Point, Neutral.

(a) On a commutator of a dynamo the points at the ends of the diameter

of commutation, or where the brushes rest upon the surface of the

commutator, are termed neutral points. At these points there is no

generation of potential, they marking the union of currents of opposite

direction flowing from the two sides of the armature into the brushes.

(b) In electro-therapeutics, a place in the intra-polar region of a

nerve so situated with reference to the kathode and electrode as applied

in treatment, that its condition is unaffected.

Synonym--Indifferent Point.

(c) In a magnet the point of no attraction, situated between the two

poles, at about an equal distance from each, so as to mark the centre of

a magnet of even distribution of polarity.

(d) In thermo-electricity the point of temperature where the

thermo-electric powers of two metals are zero; in a diagram the point

where the lines representing their thermo-electric relations cross each

other; if the metals are arranged in a thermo-electric couple, one end

at a temperature a given amount above, the other at a temperature the

same amount below the neutral point, no current or potential difference

will be produced.

422   STANDARD ELECTRICAL DICTIONARY.

Point, Null.

A nodal point in electrical resonators; a point where in a system of

waves or oscillations, there is rest, the zero of motion being the

resultant of oppositely directed and equal forces. In electrical

resonators it is to be sought for in a point symmetrically situated,

with reference to the spark gap, or in a pair of points, which pair is

symmetrically placed.

The null point in resonators is found by connecting a lead from one of

the secondary terminals of an induction coil to different parts of the

resonator. The null point is one where the connection does not give rise

to any sparks between the micrometer knobs or spark gap, or where the

sparks are of diminished size.

The whole is exactly comparable to loops and nodes in a vibrating string

or in a Chladni plate as described in treatises on sound and acoustics.

(See Resonance, Electrical--Resonator, Electrical.)

Synonym--Nodal Point.

Point Poles.

Magnet poles that are virtually points, or of no magnitude. A long thin

magnet with little leakage except close to the ends may be supposed to

have point poles within itself a short distance back from the ends.

Points, Consequent.

In a magnet with consequent poles, the points where such poles are

situated.

Points, Corresponding.

In bound electrostatic charges the points of equal charges of opposite

potentials; the points at opposite extremities of electrostatic lines of

force. This definition implies that the bound charges shall be on equal

facing areas of conductors, as otherwise the spread or concentration of

the lines of force would necessitate the use of areas of size

proportionate to the spreading or concentrating of the lines of force.

At the same time it may figuratively be applied to these cases, the

penetration of the surface by a single line of force including the area

fixed by its relation to the surrounding lines.

Points, Isoelectric.

In electro-therapeutics, points of equal potential in a circuit.

423   STANDARD ELECTRICAL DICTIONARY.

Points of Derivation.

The point where a single conductor branches into two or more conductors,

operating or acting in parallel with each other.

Polar Angle.

The angle subtended by one of the faces of the pole pieces of the field-

magnet of a dynamo or motor. The centre of the circle of the angle lies

in the axis of the armature.

Synonym--Angle of Polar Span.

Polar Extension.

An addition made of iron to the poles of magnets. Various forms have

been experimented with. The pole pieces of dynamo field magnets are

polar extensions.

Synonyms--Pole Piece--Polar Tips.

Polarity, Diamagnetic.

The induced polarity of diamagnetic substances; it is the reverse of

paramagnetic polarity, or of the polarity of iron. A bar of diamagnetic

material held parallel with the lines of force in a magnetic field has a

like pole induced in the end nearest a given pole of the field magnet,

and vice versa. This theory accounts for the repulsion by a magnet of a

diamagnetic substance. The existence of this polarity is rather an

assumption. It originated with Faraday.

Polarity, Paramagnetic.

The induced polarity of paramagnetic substances, such as iron, nickel,

or cobalt.

When such a substance is brought into a magnetic field the part nearest

a specific pole of a magnet acquires polarity opposite to that of such

pole and is thereby attracted.

Another way of expressing it, in which the existence of a pole in or

near to the field is not implied, is founded on the conventional

direction of lines of force. Where these enter the substance a south

pole is formed and where they emerge a north pole is formed.

Such polarity tends always to be established in the direction of

greatest length, if the body is free to rotate.

424   STANDARD ELECTRICAL DICTIONARY.

Polarization.

(a) The depriving of a voltaic cell of its proper electro-motive force.

Polarization may be due to various causes. The solution may become

exhausted, as in a Smee battery, when the acid is saturated with zinc

and thus a species of polarization follows. But the best definition of

polarization restricts it to the development of counter-electro-motive

force in the battery by the accumulation of hydrogen on the negative

(carbon or copper) plate. To overcome this difficulty many methods are

employed. Oxidizing solutions or solids are used, such as solution of

chromic acid or powdered manganese dioxide, as in the Bunsen and

Leclanché batteries respectively; a roughened surface of platinum black

is used, as in the Smee battery; air is blown through the solution to

carry off the hydrogen, or the plates themselves are moved about in the

solution.

(b) Imparting magnetization to a bar of iron or steel, thus making a

permanent magnet, is the polarization of the steel of which it is made.

Polarization may be permanent, as in steel, or only temporary, as in

soft iron.

(c) The strain upon a dielectric when it separates two oppositely

charged surfaces. The secondary discharge of a Leyden jar, and its

alteration in volume testify to the strain put upon it by charging.

(d) The alteration of arrangement of the molecules of an electrolyte by

a decomposing current. All the molecules are supposed to be arranged

with like ends pointing in the same direction, positive ends facing the

positively-charged plate and negative ends the negatively-charged one.

(e) The production of counter-electro-motive force in a secondary

battery, or in any combination capable of acting as the seat of such

counter-electro-motive force. (See Battery, Secondary--Battery, Gas.)

The same can be found often in organized cellular tissue such as that of

muscles, nerves, or of plants. If a current is passed through this in

one direction, it often establishes a polarization or potential

difference that is susceptible of giving a return current in the

opposite direction when the charging battery is replaced by a conductor.

Polarization Capacity.

A voltaic cell in use becomes polarized by its negative plate

accumulating hydrogen, or other cause. This gradually gives the plate a

positive value, or goes to set up a counter-electro-motive force. The

quantity of electricity required to produce the polarization of a

battery is termed its Polarization Capacity or Capacity of Polarization.

Polarization of the Medium.

The dielectric polarization, q. v., of a dielectric, implying the

arrangement of its molecules in chains or filaments; a term due to

Faraday. He illustrated it by placing filaments of silk in spirits of

turpentine, and introduced into the liquid two conductors. On

electrifying one and grounding (or connecting to earth) the other one,

the silk filaments arranged themselves in a chain or string connecting

the points of the conductors.

Polar Region.

That part of the surface of a magnet whence the internal magnetic lines

emerge into the air. (S. P. Thompson.) As such lines may emerge from

virtually all parts of its surface, the polar regions are indefinite

areas, and are properly restricted to the parts whence the lines emerge

in greatest quantity.

Polar Span.

A proportion of the circle which represents the transverse section of

the armature space between the pole pieces of the field magnet in a

dynamo or motor; it is the proportion which is filled by the faces of

the pole pieces.

425   STANDARD ELECTRICAL DICTIONARY.

Pole, Analogous.

The end of a crystal of a pyroelectric substance, such as tourmaline,

which end when heated become positively electrified. On reduction of

temperature the reverse effect obtains.

Pole, Antilogous.

The end of a crystal of a pyroelectric substance, such as tourmaline,

which end, while increasing in temperature, becomes negatively

electrified. During reduction of its temperature the reverse effect

obtains.

Pole Changer.

(a) An automatic oscillating or vibrating switch or contact-breaker

which in each movement reverses the direction of a current from a

battery or other source of current of fixed direction, as such current

goes through a conductor.

(b) A switch moved by hand which for each movement effects the above

result.

Pole, Negative.

(a) In a magnet the south pole; the pole into which the lines of force

are assumed to enter from the air or outer circuit.

(b) In a current generator the pole or terminal into which the current

is assumed to flow from the external circuit. It is the negatively

charged terminal and in the ordinary voltaic battery is the terminal

connected to the zinc or positive plate.

Pole Pieces.

The terminations of the cores of field or other electro-magnets, or of

permanent magnets. These terminations are variously shaped, sometimes

being quite large compared to the core proper of the magnet.

They are calculated so as to produce a proper distribution of and

direction of the lines of force from pole to pole. As a general rule the

active field should be of uniform strength and the pole pieces may be of

contour calculated to attain this end.

Pole, Positive.

(a) In a magnet the north pole; the pole from which lines of force are

assumed to emerge into the air.

(b) In a current generator the pole or terminal whence the current is

assumed to issue into the outer circuit. It is the positively charged

terminal, and in the ordinary voltaic battery is the terminal connected

to the copper or carbon plate, termed the negative plate.

Poles.

(a) The terminals of an open electric circuit, at which there

necessarily exists a potential difference, produced by the generator or

source of electro-motive force in the circuit.

(b) The terminals of an open magnetic circuit; the ends of a magnetized

mass of steel, iron or other paramagnetic substance.

(c) The ends in general of any body or mass which show electric or

magnetic properties more developed than those of the central sections of

the body.

426   STANDARD ELECTRICAL DICTIONARY.

Pole, Salient.

In dynamo and motor field magnets, salient poles are those projecting

from the base or main body of the field magnet, as distinguished from

consequent poles formed by coils wound on the main body itself.

Fig. 268. SALIENT POLES OF FIELD MAGNET.

Poles, Compensating.

A device for avoiding the cross-magnetizing effect on the commutator

core due to the lead of the brushes. It consists in maintaining a small

bar electro-magnet perpendicularly between the pole pieces. This

compensates the cross-magnetizing effect.

Poles of Intensity.

The locus of highest magnetic force on the earth's surface. One such

pole is in Siberia, another is about lat. 52° N., long. 92° W.

[Transcriber's note: 52° N., long. 92° W is about 250 miles Northeast of

Winnipeg.]

Poles of Verticity.

The magnetic poles of the earth. (See Magnetic Poles.)

Pole Tips.

The extreme ends of the expanded poles of a field magnet. In some

machines some of the pole tips are made of cast iron, to alter the

distribution of the lines of force and resulting magnetic pull upon the

armatures. This is done to take off the weight of the armature from its

bearings.

Pole, Traveling.

A term applied to the poles produced in the action of a rotatory field,

whose poles constantly rotate around the circle of the field. (See

Field, Rotatory.)

417   STANDARD ELECTRICAL DICTIONARY.

Porous Cup.

A cup of pipe clay, unglazed earthenware or other equivalent material

used in voltaic cells to keep two liquids separate and yet to permit

electrolysis and electrolytic conduction.

They are necessarily only an expedient, as their porous nature permits

considerable diffusion, and were they not porous electrolytic action

would be impossible.

Synonym--Porous Cell.

Porret's Phenomenon.

In electro-physiology, an increase in the diameter of a nerve produced

by the positive pole of a voltaic circuit, when placed in contact with

the tissue and near to the nerve in question, the other pole being

connected to a more or less remote part of the body.

Portelectric Railroad.

A railroad worked by solenoidal attraction, the car forming the core of

the solenoids. It includes a series of solenoids or hollow coils of

copper wire distributed all along the road and inclosing within

themselves the track. On this a cylindrical car with pointed ends moves

on wheels. Current is supplied to the solenoid in advance of the car,

and attracts it. As it advances it breaks the contacts of the attracting

solenoid and turns the current into the one next in advance. This

operation is repeated as the car advances.

The solenoids are placed close together, each including in the trial

track 630 turns of No. 14 copper wire. The car was of wrought iron, 12

feet long, 10 inches in diameter and weighing 500 lbs. It was proposed

to employ the system for transportation of mail matter and similar uses.

Position Finder.

An instrument for determining the position of objects which are to be

fired at from forts. It is designed for use from forts situated on the

water.

Fiske's position finder may be thus generally described. On a chart the

channel is divided into squares, and the position finder determines the

square in which a vessel lies. For each square the direction and

elevation of the guns is calculated beforehand. The enemy can therefore

be continuously located and fired at, although from smoke or other cause

the object may be quite invisible to the gunner.

It comprises two telescopes situated at distant extremities of as long a

base line as is obtainable. These telescopes are kept directed upon the

object by two observers simultaneously. The observers are in constant

telephonic communication. As each telescope moves, it carries a contact

over an arc of conducting material. Below each telescope is an arm also

moving over an arc of conducting material. These arcs enter into a

Wheatstone bridge and are so connected that when the arm and the distant

telescope are at the same angle or parallel a balance is obtained. Thus

each observer has the power of establishing a balance. A chart is

provided for each of them, and over it the arm connected with the

distant telescope and an arm or indicator attached to the telescope at

that station move so that as long as both telescopes point at the object

and each observer maintains the electric balance, the intersection of

the arms shows the position on the chart.

The Position Finder is a simplification and amplification of the Range

Finder, q. v. In practice the observers may be placed far from the

forts, and may telephone their observations thereto. It has been found

accurate within one-third of one per cent.

428   STANDARD ELECTRICAL DICTIONARY.

Positive Direction.

The direction which lines of force are assumed to take in the air or

outer circuit from a positive to a negative region. It applies to

electrostatic, to magnetic and to electro-magnetic lines of force.

Positive Electricity.

The kind of electricity with which a piece of glass is charged when

rubbed with silk; vitreous electricity.

In a galvanic cell the surface of the copper or carbon plate is charged

with positive electricity. (See Electrostatic Series.)

According to the single fluid theory positive electrification consists

in a surplus of electricity.

[Transcriber's note: "Positive electricity" is a deficiency of electrons.]

Post Office. adj.

Many pieces of electric apparatus of English manufacture are thus

qualified, indicating that they are of the pattern of the apparatus used

by the British Post Office in its telegraph department.

Potential.

Potential in general may be treated as an attribute of a point in space,

and may express the potential energy which a unit mass would have if

placed at that point.

This conception of potential is that of a property attributable to a

point in space, such that if a unit mass were placed there the forces

acting upon it would supply the force factor of energy, while the body

would supply the mass factor. This property is expressible in units,

which produce, if the supposed mass is a unit mass, units of work or

energy, but potential itself is neither.

Thus taking gravitation, a pound mass on the surface of the earth

(assuming it to be a sphere of 4,000 miles radius) would require the

expenditure of 21,120,000 foot pounds to remove it to an infinite

distance against gravity. The potential of a point in space upon the

surface of the earth is therefore negative and is represented by

-21,120,000*32.2 foot poundals (32.2 = acceleration of gravity). (See

Poundal.) In practice and conventionally all points on the earth's

surface are taken as of zero potential.

[Transcriber's note; 21,120,000 foot pounds is about 8 KWh.]

429   STANDARD ELECTRICAL DICTIONARY.

Potential, Absolute.

The absolute electrical potential at a point possesses a numerical value

and measures the tendency which the existing electric forces would have

to drive an electrified particle away from or prevent its approach to

the point, if such a particle, one unit in quantity, were brought up to

or were situated at that point. It is numerically equal to the number of

ergs of work which must be done to bring a positive unit of electricity

from a region where there is absolutely no electric force up to the

point in question. (Daniell.) Two suppositions are included in this. The

region where there is an electric force has to be and only can be at an

infinite distance from all electrified bodies. The moving of the

particle must take place without any effect upon the distribution of

electricity on other particles.

Potential, Constant.

Unchanging potential or potential difference.

The ordinary system of incandescent lighting is a constant potential

system, an unvarying potential difference being maintained between the

two leads, and the current varying according to requirements.

Potential Difference, Electric.

If of any two points the absolute potentials are determined, the

difference between such two expresses the potential difference.

Numerically it expresses the quantity of work which must be done to

remove a unit of electricity from one to the other against electric

repulsion, or the energy which would be accumulated in moving it the

other way.

A positively charged particle is driven towards the point of lower

potential. A negatively charged body is driven in the reverse direction.

Potential Difference, Electro-motive.

A difference of potential in a circuit, or in part of a circuit, which

difference produces or is capable of producing a current, or is due to

the flow of such current.

It may be expressed as the fall in potential or the electro-motive force

included between any two points on a circuit. The current in an active

circuit is due to the total electro-motive force in the circuit. This is

distributed through the circuit in proportion to the resistance of its

parts. Owing to the distribution of electro-motive force throughout a

circuit including the generator, the terminals of a generator on closed

circuit may show a difference of potential far lower than the

electro-motive force of the generator on closed circuit. Hence potential

difference in such a case has been termed available electro-motive

force.

Potential, Electric Absolute.

The mathematical expression of a property of a point in space, measuring

the tendency which existing electric forces would have to drive an

electrified unit particle away from or prevent its approach to the point

in question, according to whether the point was situated at or was at a

distance from the point in question.

Potential is not the power of doing work, although, as it is expressed

always with reference to a unit body, it is numerically equal to the

number of ergs of work which must be done in order to bring a positive

unit of electricity from a region where there is no electric

force--which is a region at an infinite distance from all electrified

bodies--up to the point in question. This includes the assumption that

there is no alteration in the general distribution of electricity on

neighboring bodies. (Daniell.)

In practice the earth is arbitrarily taken as of zero electric potential.

430   STANDARD ELECTRICAL DICTIONARY.

Potential, Fall of.

The change in potential between any two points on an active circuit. The

change in potential due to the maintenance of a current through a

conductor.

The fall in potential multiplied by the current gives work or energy

units.

The fall of potential in a circuit and its subsequent raising by the

action of the generator is illustrated by the diagram of a helix. In it

the potential fall in the outer circuit is shown by the descent of the

helix. This represents at once the outer circuit and the fall of

potential in it. The vertical axis represents the portion of the circuit

within the battery or generator in which the potential by the action of

the generator is again raised to its original height.

In a circuit of even resistance the potential falls evenly throughout

it.

A mechanical illustration of the relation of fall of potential to

current is shown in the cut Fig. 269. A vertical wire is supposed to be

fixed at its upper end and a lever arm and cord at its lower end, with

weight and pulley imparts a torsional strain to it. The dials and

indexes show a uniform twisting corresponding to fall of potential. For

each unit of length there is a definite loss of twisting, corresponding

to fall of potential in a unit of length of a conductor of uniform

resistance. The total twisting represents the total potential

difference. The weight sustained by the twisting represents the current

maintained by the potential difference. For a shorter wire less twisting

would be needed to sustain the weight, as in a shorter piece of the

conductor less potential difference would be needed to maintain the same

current.

Fig. 269. MECHANICAL ILLUSTRATION OF

FALL OF POTENTIAL AND CURRENT STRENGTH.

431   STANDARD ELECTRICAL DICTIONARY.

Fig. 270. ILLUSTRATION OF THE FALL AND

REDEVELOPMENT OF POTENTIAL IN AN ELECTRIC CIRCUIT.

The fall of potential in a circuit in portions of it is proportional to

the resistance of the portions in question. This is shown in the

diagram. The narrow lines indicate high and the broad lines low

resistance. The fall in different portions is shown as proportional to

the resistance of each portion.

Fig. 271. DIAGRAM OF FALL OF POTENTIAL IN A

CONDUCTOR OF UNEVEN RESISTANCE.

Potential, Magnetic.

The magnetic potential at any point of a magnetic field expresses the

work which would be done by the magnetic forces of the field on a

positive unit of magnetism as it moves from that point to an infinite

distance therefrom. The converse applies to a negative unit.

It is the exact analogue of absolute electric potential.

The potential at any point due to a positive pole m at a distance r is

m/r;. that due to a negative pole - m at a distance r' is equal to

-m/r';. that due to both is equal to m/r - m/r' or m(1/r - 1/r').

Like electric potential and potential in general, magnetic potential

while numerically expressing work or energy is neither, although often

defined as such.

432   STANDARD ELECTRICAL DICTIONARY.

Potential, Negative.

The reverse of positive potential. (See Potential, Positive.)

Potential, Positive.

In general the higher potential. Taking the assumed direction of lines

of force, they are assumed to be directed or to move from regions of

positive to regions of negative potential. The copper or carbon plate of

a voltaic battery is at positive potential compared to the zinc plate.

Potential, Unit of Electric.

The arbitrary or conventional potential--or briefly, the potential of a

point in an electric field of force--is, numerically, the number of ergs

of work necessary to bring a unit of electricity up to the point in

question from a region of nominal zero potential--i. e., from the

surface of the earth. (Daniell.) This would give the erg as the unit of

potential.

Potential, Zero.

The potential of the earth is arbitrarily taken as the zero of electric

potential.

The theoretical zero is the potential of a point infinitely distant from

all electrified bodies.

Fig. 272. DIAGRAM OF POTENTIOMETER CONNECTIONS.

Potentiometer.

An arrangement somewhat similar to the Wheatstone Bridge for determining

potential difference, or the electro-motive force of a battery. In

general principle connection is made so that the cell under trial would

send a current in one direction through the galvanometer. Another

battery is connected, and in shunt with its circuit the battery under

trial and its galvanometer are connected, but so that its current is in

opposition. By a graduated wire, like that of a meter bridge, the

potential of the main battery shunt can be varied until no current

passes. This gives the outline of the method only.

433   STANDARD ELECTRICAL DICTIONARY.

In the cut A B is the graduated potentiometer wire through which a

current is passed in the direction of the arrow. E is the battery under

trial, placed in opposition to the other current, with a galvanometer

next it. Under the conditions shown, if the galvanometer showed no

deflection, the E. M. F. of the battery would be to the E. M. F. between

the ends of the potentiometer wire, 1 . . . . .10, as 1.5 the distance

between the points of connection, A and D of the battery circuit, is to

10, the full length of the potentiometer wire.

Poundal.

The British unit of force; the force which acting on a mass of one pound

for one second produces an acceleration of one foot.

[Transcriber's note: The force which acting on a mass of one pound

produces an acceleration of ONE FOOT PER SECOND PER SECOND.]

Power. Activity;

the rate of activity, of doing work, or of expending energy. The

practical unit of electric power is the volt-ampere or watt, equal to

1E7 ergs per second. The kilowatt, one thousand watts or volt-amperes,

is a frequently adopted unit.

Power, Electric.

As energy is the capacity for doing work, electric energy is represented

by electricity in motion against a resistance. This possesses a species

of inertia, which gives it a species of kinetic energy. To produce such

motion, electro- motive force is required. The product of E. M. F. by

quantity is therefore electric energy. (See Energy, Electric.)

Generally the rate of energy or power is used. Its dimensions are

( ( (M^.5)*(L^.5) ) / T )  *   ( ( (M^.5) *(L^1.5) )/( T^2) )

(intensity or current rate)   *   (electro-motive force or potential)

= (M * (L^2) ) / (T^3),

which are the dimensions of rate of work or activity. The practical unit

of electric rate of energy or activity is the volt-ampere or watt. By

Ohm's law, q. v., we have C = E/R (C = current; E = potential difference

or electro-motive force; R = resistance.) The watt by definition = C*E.

By substitution from Ohm's formula we deduce for it the following

values: ((C^2) * R) and ((E^2) /R). From these three expressions the

relations of electric energy to E.M.F., Resistance, and Current can be

deduced.

Power of Periodic Current.

The rate of energy in a circuit carrying a periodic current. In such a

circuit the electro-motive force travels in advance of the current it

produces on the circuit. Consequently at phases or intervals where,

owing to the alternations of the current, the current is at zero, the

electro-motive force may be quite high. At any time the energy rate is

the product of the electro-motive force by the amperage. To obtain the

power or average rate of energy, the product of the maximum

electro-motive force and maximum current must be divided by two and

multiplied by the cosine of the angle of lag, which is the angle

expressing the difference of phase.

[Transcriber's note; The voltage phase will lead if the load is

inductive. The current phase will lead if the load is capacitive.

Capacitors or inductors may be introduced into power lines to correct

the phase offset introduced by customer loads.]

434   STANDARD ELECTRICAL DICTIONARY.

Pressel.

A press-button often contained in a pear-shaped handle, arranged for

attachment to the end of a flexible conductor, so as to hang thereby. By

pressing the button a bell may be rung, or a distant lamp may be

lighted.

Pressure.

Force or stress exerted directly against any surface. Its dimensions are

force/area or ((M*L)/(T^2)) / (L^2) = M/(L* (T^2)).

Pressure, Electric.

Electro-motive force or potential difference; voltage. An expression of

metaphorical nature, as the term is not accurate.

Pressure, Electrification by.

A crystal of Iceland spar (calcium carbonate) pressed between the

fingers becomes positively electrified and remains so for some time.

Other minerals act in a similar way. Dissimilar substances pressed

together and suddenly separated carry off opposite charges. This is

really contact action, not pressure action.

Primary.

A term used to designate the inducing coil in an induction coil or

transformer; it is probably an abbreviation for primary coil.

Primary Battery.

A voltaic cell or battery generating electric energy by direct

consumption of material, and not regenerated by an electrolytic process.

The ordinary voltaic cell or galvanic battery is a primary battery.

Prime. vb.

To impart the first charge to one of the armatures of a Holtz or other

influence machine.

Fig. 273. PRIME CONDUCTOR AND PROOF PLANE.

435   STANDARD ELECTRICAL DICTIONARY.

Prime Conductor.

A metal or metal coated sphere or cylinder or other solid with rounded

ends mounted on insulating supports and used to collect electricity as

generated by a frictional electric machine.

According to whether the prime conductor or the cushions are grounded

positive or negative electricity is taken from the ungrounded part.

Generally the cushions are grounded, and the prime conductor yields

positive electricity.

Probe, Electric.

A surgeon's probe, designed to indicate by the closing of an electric

circuit the presence of a bullet or metallic body in the body of a

patient.

Two insulated wires are carried to the end where their ends are exposed,

still insulated from each other. In probing a wound for a bullet if the

two ends touch it the circuit is closed and a bell rings. If a bone is

touched no such effect is produced. The wires are in circuit with an

electric bell and battery.

Projecting Power of a Magnet.

The power of projecting its lines of force straight out from the poles.

This is really a matter of magnetic power, rather than of shape of the

magnet. In electromagnets the custom was followed by making them long to

get this effect. Such length was really useful in the regard of getting

room for a sufficient number of ampere turns.

436   STANDARD ELECTRICAL DICTIONARY.

Fig. 274. PRONY BRAKE.

Prony Brake.

A device for measuring the power applied to a rotating shaft. It

consists of a clamping device to be applied more or less rigidly to the

shaft or to a pulley upon it. To the clamp is attached a lever carrying

a weight. The cut shows a simple arrangement, the shaft A carries a

pulley B to which the clamp B1 B2 is applied. The nuts C1 C2 are used

for adjustment.

A weight is placed in the pan E attached to the end of the lever D. The

weight and clamp are so adjusted that the lever shall stand horizontally

as shown by the index E. If we call r the radius of the pulley and F the

friction between its surface and the clamp, it is evident that r F, the

moment of resistance to the motion of the pulley, is equal to the weight

multiplied by its lever arm or to W*R, where W indicates the weight and

R the distance of its point of application from the centre of the pulley

or r*F = R*W. The work represented by this friction is equal to the

distance traveled by the surface of the wheel multiplied by the

frictional resistance, or is 2*PI*r*n*F, in which n is the number of

turns per minute. But this is equal to 2*PI*R*W. These data being known,

the power is directly calculated therefrom in terms of weight and feet

per minute.

Proof-plane.

A small conductor, usually disc shaped, carried at the end of an

insulating handle. It is used to collect electricity by contact, from

objects electrostatically charged. The charge it has received is then

measured (see Torsion Balance) or otherwise tested. (See Prime

Conductor.)

Proof-sphere.

A small sphere, coated with gold-leaf or other conductor, and mounted on

an insulated handle. It is used instead of a proof-plane, for testing

bodies whose curvature is small.

Fig. 275. BOX BRIDGE.

437   STANDARD ELECTRICAL DICTIONARY.

Proportionate Arms.

In general terms the arms of a Wheatstone bridge

whose proportion has to be known to complete the measurement. There is a

different system of naming them. Some designate by this title the two

arms in parallel with each other branching at and running from one end

of the bridge to the two galvanometer connections. In the cut of the Box

Bridge, A C and A B are the proportionate arms. The third arm is then

termed the Rheostat arm. (Stewart & Gee.)

Others treat as proportionate arms the two side members of the bridge in

parallel with the unknown resistance and third or rheostat arm.

Synonym--Ratio Arms.

Prostration, Electric.

Too great exposure to the voltaic arc in its more powerful forms causes

symptoms resembling those of sunstroke. The skin is sometimes affected

to such a degree as to come off after a few days. The throat, forehead

and face suffer pains and the eyes are irritated. These effects only

follow exposure to very intense sources of light, or for very long

times.

[Transcriber's note: Arcs emit ultraviolet rays.]

Protector, Comb.

A lightning arrester, q. v., comprising two toothed plates nearly

touching each other.

Protector, Electric.

A protective device for guarding the human body against destructive or

injurious electric shocks. In one system, Delany's, the wrists and

ankles are encircled by conducting bands which by wires running along

the arms, back and legs are connected. A discharge it is assumed

received by the hands will thus be short circuited around the body and

its vital organs. India rubber gloves and shoe soles have also been

suggested; the gloves are still used to some extent.

Pull.

A switch for closing a circuit when pulled. It is used instead of a push

button, q.v., in exposed situations, as its contacts are better

protected than those of the ordinary push button.

Pump, Geissler.

A form of mercurial air pump. It is used for exhausting Geissler tubes,

incandescent lamp bulbs and similar purposes.

Referring to the cut, A is a reservoir of mercury with flexible tube C

connected to a tube at its bottom, and raised and lowered by a windlass

b, the cord from which passes over a pulley a. When raised the mercury

tends to enter the chamber B, through the tube T. An arrangement of

stopcocks surmounts this chamber, which arrangement is shown on a larger

scale in the three figures X, Y and Z. To fill the bulb B, the cocks are

set in the position Z; n is a two way cock and while it permits the

escape of air below, it cuts off the tube, rising vertically from it.

This tube, d in the full figure connects with a vessel o, pressure gauge

p, and tube c, the latter connecting with the object to be exhausted.

The bulb B being filled, the cock m is closed, giving the position Y and

the vessel A is lowered until it is over 30 inches below B.

438   STANDARD ELECTRICAL DICTIONARY.

This establishes a Torricellian vacuum in B. The cock n is now turned,

giving the position X, when air is at once exhausted from the vessel

connected to C. This process is repeated until full exhaustion is

obtained. In practice the first exhaustion is often effected by a

mechanical pump. By closing the cock on the outlet tube c but little air

need ever find its way to the chambers o and B.

Fig. 276. GEISSLER AIR PUMP.

439   STANDARD ELECTRICAL DICTIONARY.

Pumping.

In incandescent lamps a periodical recurring change in intensity due to

bad running of the dynamos, or in arc lamps to bad feeding of the

carbons.

Fig. 277. SPRENGEL AIR PUMP.

Pump, Sprengel.

A form of mercurial air pump. A simple form is shown in the cut. Mercury

is caused to flow from the funnel A, through c d to a vessel B. A side

connection x leads to the vessel R to be exhausted. As the mercury

passes x it breaks into short columns, and carries air down between

them, in this way exhausting the vessel R. In practice it is more

complicated. It is said to give a better vacuum than the Sprengel pump,

but to be slower in action.

440   STANDARD ELECTRICAL DICTIONARY.

Pump, Swinburne.

A form of mechanical air pump for exhausting incandescent lamp bulbs.

Referring to the cut, A is a bulb on the upper part of a tube G; above A

are two other bulbs C and D. From the upper end a tube runs to the bulb

E. Through the cock L, and tube F connection is made with a mechanical

air pump. The tube H leads to a drying chamber I, and by the tube J

connects with the lamp bulbs or other objects to be exhausted. The tube

G enters the bottle B through an airtight stopper, through which a

second tube with stopcock K passes. In use a vacuum is produced by the

mechanical pumps, exhausting the lamp bulbs to a half inch and drawing

up the mercury in G. The bent neck in the bulb E, acts with the bulb as

a trap to exclude mercury from F. When the mechanical pumps have

produced a vacuum equal to one half inch of mercury, the cock L is

closed and K is opened, and air at high pressure enters. This forces the

mercury up to the vessel D, half filling it. The high pressure is now

removed and the mercury descends. The valve in D closes it as the

mercury falls to the level G. Further air from the lamps enters A, and

by repetition of the ascent of the mercury, is expelled, through D. The

mercury is again lowered, producing a further exhaustion, and the

process is repeated as often as necessary.

Fig. 278. SWINBURNE'S AIR PUMP.

Push-Button.

A switch for closing a circuit by means of pressure applied to a button.

The button is provided with a spring, so that when pushed in and

released it springs back. Thus the circuit is closed only as long as the

button is pressed. The electric connection may be made by pressing

together two flat springs, each connected to one of the wires, or by the

stem of the button going between two springs, not in contact, forcing

them a little apart to secure good contact, and thereby bridging over

the space between them.

441   STANDARD ELECTRICAL DICTIONARY.

Pyro-electricity.

A phenomenon by which certain minerals when warmed acquire electrical

properties. (Ganot.) The mineral tourmaline exhibits it strongly. It was

originally observed in this mineral which was found to first attract and

then to repel hot ashes.

The phenomenon lasts while any change of temperature within certain

limits is taking place. In the case of tourmaline the range is from

about 10º C. (50º F.) to 150º C. (302º F.) Above or below this range it

shows no electrification.

The effect of a changing of temperature is to develop poles, one

positive and the other negative. As the temperature rises one end is

positive and the other negative; as the temperature becomes constant the

polarity disappears; as the temperature falls the poles are reversed.

If a piece of tourmaline excited by pyro-electricity is broken, its

broken ends develop new poles exactly like a magnet when broken.

The following minerals are pyro-electric: Boracite, topaz, prehnite,

zinc silicate, scolezite, axenite. The following compound substances are

also so: Cane sugar, sodium- ammonium racemate and potassium tartrate.

The list might be greatly extended.

The phenomenon can be illustrated by sifting through a cotton sieve upon

the excited crystal, a mixture of red lead and flowers of sulphur. By

the friction of the sifting these become oppositely electrified; the

sulphur adheres to the positively electrified end, and the red lead to

the negatively electrified end. (See Analogous Pole-Antilogous Pole.)

Pyromagnetic Motor.

A motor driven by the alternation of attraction and release of an

armature or other moving part, as such part or a section of it is

rendered more or less paramagnetic by heat.

Thus imagine a cylinder of nickel at the end of a suspension rod, so

mounted that it can swing like a pendulum. A magnet pole is placed to

one side to which it is attracted. A flame is placed so as to heat it

when in contact with the magnet pole. This destroys its paramagnetism

and it swings away from the magnet and out of the flame. It cools,

becomes paramagnetic, and as it swings back is reattracted, to be again

released as it gets hot enough. This constitutes a simple motor.

A rotary motor may be made on the same lines. Nickel is particularly

available as losing its paramagnetic property easily.

442   STANDARD ELECTRICAL DICTIONARY.

Various motors have been constructed on this principle, but none have

attained any practical importance. Owing to the low temperature at which

it loses its paramagnetic properties nickel is the best metal for

paramagnetic motors.

In Edison's motor, between the pole pieces of an electro-magnet a

cylinder made up of a bundle of nickel tubes is mounted, so as to be

free to rotate. A screen is placed so as to close or obstruct the tubes

farthest from the poles. On passing hot air or products of combustion of

a fire or gas flame through the tubes, the unscreened ones are heated

most and lose their paramagnetism. The screened tubes are then attracted

and the armature rotates, bringing other tubes under the screen, which

is stationary. Then the attracted tubes are heated while the others

cool, and a continuous rotation is the result.

Fig. 279. EDISON'S PYROMAGNETIC MOTOR.

Pyromagnetic Generator.

A current generator producing electric energy directly from thermal

energy by pyromagnetism.

Edison's pyromagnetic generator has eight electro-magnets, lying on

eight radii of a circle, their poles facing inward and their yokes

vertical. Only two are shown in the cut. On a horizontal iron disc are

mounted eight vertical rolls of corrugated nickel representing

armatures. On each armature a coil of wire, insulated from the nickel by

asbestus is wound. The coils are all in series, and have eight

connections with a commutator as in a drum armature. There are two main

divisions to the commutator. Each connects with an insulated collecting

ring, and the commutator and collecting rings are mounted on a spindle

rotated by power. Below the circle of vertical coils is a horizontal

screen, mounted on the spindle and rotating with it.

A source of heat, or a coal stove is directly below the machine and its

hot products of combustion pass up through the coils, some of which are

screened by the rotating screen. The effect is that the coils are

subjecting to induction owing to the change in permeability of the

nickel cores, according as they are heated, or as they cool when the

screen is interposed. The two commutator segments are in constant

relation to the screen, and current is collected therefrom and by the

collecting rings is taken to the outside circuit.

443   STANDARD ELECTRICAL DICTIONARY.

Pyromagnetism.

The development of new magnetic properties or alteration of magnetic

sensibility in a body by heat. Nickel and iron are much affected as

regards their paramagnetic power by rise of temperature.

Fig. 280. PYROMAGNETIC GENERATOR.

Pyrometer, Siemens' Electric.

An instrument for measuring high temperatures by the variations in

electric resistance in a platinum wire exposed to the heat which is to

be measured.

443   STANDARD ELECTRICAL DICTIONARY.

Q.

Symbol for electric quantity.

Quad.

(a) A contraction for quadrant, used as the unit of inductance; the henry.

(b) A contraction for quadruplex in telegraphy.

[Transcriber's note: A modern use of "quad" is a unit of energy equal to

1E15  (one quadrillion) BTU, or 1.055E18 joules. Global energy

production in 2004 was 446 quad.]

Quadrant.

A length equal to an approximate earth quadrant, equal to 1E9

centimeters. It has been used as the name for the unit of inductance,

the henry, q. v.

Synonym--Standard Quadrant.

444   STANDARD ELECTRICAL DICTIONARY.

Quadrant, Legal.

The accepted length of the quadrant of the earth, 9.978E8 instead of 1E9

centimeters; or to 9,978 kilometers instead of 10,000 kilometers.

Quadrature.

Waves or periodic motions the angle of lag of one of which, with

reference to one in advance of it, is 90°, are said to be in quadrature

with each other.

[Transcriber's note: If the voltage and current of a power line are in

quadrature, the power factor is zero (cos(90°) = 0)  and no real power

is delivered to the load.]

Qualitative.

Involving the determination only of the presence or absence of a

substance or condition, without regard to quantity. Thus a compass held

near a wire might determine qualitatively whether a current was passing

through the wire, but would not be sufficient to determine its quantity.

(See Quantitative.)

Quality of Sound.

The distinguishing characteristic of a sound other than its pitch; the

timbre.

It is due to the presence with the main or fundamental sound of other

minor sounds called overtones, the fundamental note prevailing and the

other ones being superimposed upon it. The human voice is very rich in

overtones; the telephone reproduces these, thus giving the personal

peculiarities of every voice.

Synonym--Timbre.

Quantitative.

Involving the determination of quantities. Thus a simple test would

indicate that a current was passing through a wire. This would be a

qualitative test. If by proper apparatus the exact intensity of the

current was determined, it would be a quantitative determination. (See

Qualitative.)

Quantity.

This term is used to express arrangements of electrical connections for

giving the largest quantity of current, as a quantity armature, meaning

one wound for low resistance.

A battery is connected in quantity when the cells are all in parallel.

It is the arrangement giving the largest current through a very small

external resistance.

The term is now virtually obsolete (Daniell); "in surface," "in

parallel," or "in multiple arc" is used.

Quantity, Electric.

Electricity may be measured as if it were a compressible gas, by

determining the potential it produces when stored in a defined

recipient. In this way the conception of a species of quantity is

reached. It is also measured as the quantity of current passed by a

conductor.

Thus a body whose surface is more or less highly charged with

electricity, is said to hold a greater or less quantity of electricity.

It may be defined in electrostatic or electro-magnetic terms. (See

Quantity, Electrostatic--Quantity, Electro-magnetic.)

445   STANDARD ELECTRICAL DICTIONARY.

Quantity.

Electro-magnetic. Quantity is determined electro-magnetically by the

measurement of current intensity for a second of time: its dimensions

are therefore given by multiplying intensity or current strength by

time. The dimensions of intensity are

( (M^.5) * (L^.5) ) / T

therefore the dimensions of electro-magnetic quantity are

( ( (M^.5) * (L^.5) ) / T ) * T = ( (M^.5) * (L^.5) )

Quantity, Electro-magnetic, Practical Unit of.

The quantity of electricity passed by a unit current in unit time; the

quantity passed by one ampere in one second; the coulomb.

It is equal to 3E9 electrostatic absolute units of quantity and to 0.1

of the electro- magnetic absolute unit of quantity.

One coulomb is represented by the deposit of

.00111815 gram, or .017253 grain of silver,

.00032959 gram, or .005804 grain of copper,

.0003392 gram,  or .005232 grain of zinc.

If water is decomposed by a current each coulomb is represented by the

cubic centimeters of the mixed gases (hydrogen and oxygen) given by the

following formula.

( 0.1738 * 76 * (273 + Cº ) ) / ( h * 273 )

in which Cº is the temperature of the mixed gases in degree centigrade

and h is the

pressure in centimeters of mercury column; or by

( 0.01058 * 30 (491 + Fº - 32)  ) / (h * 491 )

for degrees Fahrenheit and inches of barometer.

[Transcriber's note: 6.24150962915265E18 electrons is one coulomb.]

Quantity, Electrostatic.

Quantity is determined electro-statically by the repulsion a charge of

given quantity exercises upon an identical charge at a known distance.

The force evidently varies with the product of the two quantities, and

by the law of radiant forces also inversely with the square of the

distance. The dimensions given by these considerations is Q * Q/(L*L).

This is the force of repulsion. The dimensions of a force are

(M * L) /(T^2). Equating these two expressions we have:

(Q^2)/(L^2) = (M*L)/(T^2)

or

Q = ((M^.5)*(L^1.5)) / T

which are the dimensions of electrostatic quantity.

Quantity, Meter.

An electric meter for determining the quantity of electricity which

passes through it, expressible in coulombs or ampere hours. All

commercial meters are quantity meters.

446   STANDARD ELECTRICAL DICTIONARY.

Quartz.

A mineral, silica, SiO2. It has recently been used by C. V. Boys and

since by others in the making of filaments for torsion suspensions. The

mineral is melted, while attached to an arrow or other projectile. It is

touched to another piece of quartz or some substance to which it adheres

and the arrow is fired off from the bow. A very fine filament of

surpassingly good qualities for galvanometer suspension filaments is

produced.

As a dielectric it is remarkable in possessing but one-ninth the

residual capacity of glass.

Quicking.

The amalgamating of a surface of a metallic object before silver

plating. It secures better adhesion of the deposit. It is executed by

dipping the article into a solution of a salt of mercury. A solution of

mercuric nitrate 1 part, in water 100 parts, both by weight, is used.

446   STANDARD ELECTRICAL DICTIONARY.

R.

(a) Abbreviation and symbol for Reamur, as 10º R., meaning 10º by the

Reamur thermometer. (See Reamur Scale.)

(b) Symbol for resistance, as in the expression of Ohm's Law C=E/R.

(rho, Greek r) Symbol for specific resistance.

Racing of Motors.

The rapid acceleration of speed of a motor when the load upon it is

removed. It is quickly checked by counter-electro-motive force. (See

Motor, Electric.)

Radian.

The angle whose arc is equal in length to the radius; the unit angle.

Radiant Energy.

Energy, generally existing in the luminiferous ether, kinetic and

exercised in wave transmission, and rendered sensible by conversion of

its energy into some other form of energy, such as thermal energy.

If the ether waves are sufficiently short and not too short, they

directly affect the optic nerve and are known as light waves; they may

be so short as to be inappreciable by the eye, yet possess the power of

determining chemical change, when they are known as actinic waves; they

may be also so long as to be inappreciable by the eye, when they may be

heat-producing waves, or obscure waves.

Other forms of energy may be radiant, as sound energy dispersed by the

air, and gravitational energy, whose connection with the ether has not

yet been demonstrated.

Radiation.

The traveling or motion of ether waves through space.

[Transcriber's note: The modern term corresponding to this definition is

photons. The modern concept of radiation also includes particles--

neutrons, protons, alpha (helium) and beta (electrons) rays and other

exotic items.]

Radicals.

A portion of a molecule, possessing a free bond and hence free to

combine directly. A radical never can exist alone, but is only

hypothetical. An atom is a simple radical, an unsaturated group of atoms

is a compound radical.

447   STANDARD ELECTRICAL DICTIONARY.

Radiometer.

An instrument consisting of four vanes poised on an axis so as to be

free to rotate, and contained in a sealed glass vessel almost perfectly

exhausted. The vanes of mica are blackened on one side.

On exposure to light or a source of heat (ether waves) the vanes rotate.

The rotation is due to the beating back and forth of air molecules from

the surface of the vanes to the inner surface of the glass globe.

Radiometer, Electric.

A radiometer in which the motion of the molecules of air necessary for

rotation of the vane is produced by electrification and not by heating.

Radio-micrometer.

An instrument for detecting radiant energy of heat or light form. It

consists of a minute thermopile with its terminals connected by a wire,

the whole suspended between the poles of a magnet. A minute quantity of

heat produces a current in the thermopile circuit, which, reacted on by

the field, produces a deflection. A convex mirror reflecting light is

attached so as to move with the thermopile. The instrument is of

extraordinary sensitiveness. It responds to .5E-6 of a degree Centigrade

or about 1E-6 degree Fahrenheit.

Radiophony.

The production of sound by intermittent action of a beam of light upon a

body. With possibly a few exceptions all matter may produce sound by

radiophouy.

Range Finder.

An apparatus for use on shipboard to determine the distance of another

ship or object. It is designed for ships of war, to give the range of

fire, so as to set the guns at the proper elevation. The general

principle involved is the use of the length of the ship if possible, if

not of its width, as a base line. Two telescopes are trained upon the

object and kept trained continuously thereon. The following describes

the Fiske range finder.

The range finder comprises two fairly powerful telescopes, each mounted

on a standard, which can be rotated round a vertical axis, corresponding

with the center of the large disc shown in the engraving. One-half of

the edge of this disc is graduated to 900 on either side of a zero

point, and below the graduation is fixed a length of platinum silver

wire. This wire only extends to a distance of 81.10 on either side of

zero, and is intended to form two arms of a Wheatstone bridge. The

sliding contact is carried by the same arm as the telescope standards,

so that it moves with the telescope. The two instruments are mounted at

a known distance apart on the ship, as shown diagrammatically in the

cut. Here A and B are the centers of the two discs, C and D the arms

carrying the telescopes, and E and F the platinum silver wires. Suppose

the object is at T, such that A B T is a right angle, then

AT=AB/sin(ATB).

448   STANDARD ELECTRICAL DICTIONARY.

If the two sectors are coupled up as shown, with a battery, h, and a

galvanometer, by the wires, a b and c d, then since the arm, e, on being

aligned on the object takes the position c1 while d remains at zero, the

Wheatstone bridge formed by these segments and their connections will be

out of balance, and a current will flow through the galvanometer, which

may be so graduated as to give the range by direct reading, since the

current through it will increase with the angle A T B.

Fig. 281. RANGE FINDER.

In general, however, the angle A B T will not be a right angle, but some

other angle. In this case AT = AB / sin(A T B) * sin( A B T), and hence

it will only be necessary to multiply the range reading on the

galvanometer by the sine of the angle A B T, which can be read directly

by the observer at B. This multiplication is not difficult, but by

suitably arranging his electrical appliances Lieutenant Fiske has

succeeded in getting rid of it, so that the reading of the galvanometer

always gives the range by direct reading, no matter what the angle at B

may be. To explain this, consider the two telescopes shown in the cut in

the positions C and D; the whole current then has a certain resistance.

449   STANDARD ELECTRICAL DICTIONARY.

Next suppose them, still remaining parallel, in the positions C1 and D1.

The total resistance of the circuit is now less than before, and hence

if C1, one of the telescopes, is moved out of parallel to the other,

through a certain angle, the current through the galvanometer will be

greater than if it were moved through an equal angle out of a parallel

when the telescopes were in the positions C and D. The range indicated

is, therefore, decreased, and by properly proportioning the various

parts it is found that the range can always be read direct from the

galvanometer, or in other words the multiplication of A B/sin( A T B )

by sin( A B T ) is to all intents and purposes performed automatically.

There is, it is true, a slight theoretical error; but by using a small

storage battery and making the contents carefully it is said to be

inappreciable. Each telescope is fitted with a telephone receiver and

transmitter, so that both observers can without difficulty decide on

what point to align their telescopes. It will be seen that it is

necessary that the lines of sight of two telescopes should be parallel

when the galvanometer indicates no current. It has been proposed to

accomplish this by sighting both telescopes on a star near the horizon,

which being practically an infinite distance away insures the

parallelism of the lines of sight.

Rate Governor.

An apparatus for securing a fixed rate of vibration of a vibrating reed.

It is applied in simultaneous telegraphy and telephoning over one wire.

The principle is that of the regular make and break mechanism, with the

feature that the contact is maintained during exactly one-half of the

swing of the reed. The contact exists during the farthest half of the

swing of the reed away from the attracting pole.

Fig. 282. LANGDON DAVIRS' RATE GOVERNOR.

In the left hand figure of the cut, K is the key for closing the

circuit. A is the base for attachment of the reed. V is the

contact-spring limited in its play to the right by the screw S. C is the

actuating magnet. By tracing the movements of the reed, shown on an

exaggerated scale in the three right hand figures, it will be seen that

the reed is in electric contact with the spring during about one-half

its movement. The time of this connection is adjustable by the screw S.

Synonym--Langdon Davies' Rate Governor or Phonophone.

450   STANDARD ELECTRICAL DICTIONARY.

Ray, Electric. Raia torpedo.

The torpedo, a fish having the same power of giving electric shocks as

that possessed by the electric eel, q. v. (See also Animal Electricity.)

Fig. 283. TORPEDO OR ELECTRIC RAY

Reaction of Dynamo, Field and Armature.

A principle of the dynamo current generator, discovered by Soren Hjorth

of Denmark.

When the armature is first rotated it moves in a field due to the

residual magnetism of the field magnet core. This field is very weak,

and a slight current only is produced. This passing in part or in whole

through the field magnet cores slightly strengthens the field, whose

increased strength reacts on the armature increasing its current, which

again strengthens the field. In this way the current very soon reaches

its full strength as due to its speed of rotation.

The operation is sometimes termed building up.

Sometimes, when there is but a trace of residual magnetism, it is very

hard to start a dynamo.

Reading Telescope.

A telescope for reading the deflections of a reflecting galvanometer.

A long horizontal scale is mounted at a distance from the galvanometer

and directly below or above the centre of the scale a telescope is

mounted. The telescope is so directed that the mirror of the

galvanometer is in its field of view, and the relative positions of

mirror, scale and telescope are such that the image of the scale in the

galvanometer mirror is seen by the observer looking through the

telescope.

Under these conditions it is obvious that the graduation of the scale

reflected by the mirror corresponds to the deflection of the

galvanometer needle.

The scale may be straight or curved, with the galvanometer in the latter

case, at its centre of curvature.

Reamur Scale.

A thermometer scale in use in some countries of Continental Europe. The

temperature of melting ice is 0°; the temperature of condensing steam

is 80°; the degrees are all equal in length. For conversion to

centigrade degrees multiply degrees Reamur by 5/4. For conversion to

Fahrenheit degrees multiply by 9/4 and add 32 if above 0° R., and if

below subtract 32. Its symbol is R., as 10° R.

451   STANDARD ELECTRICAL DICTIONARY.

Recalescence.

A phenomenon occurring during the cooling of a mass of steel, when it

suddenly emits heat and grows more luminous for an instant. It is a

phase of latent heat, and marks apparently the transition from a

non-magnetizable to a magnetiz  able condition.

Receiver.

In telephony and telegraphy, an instrument for receiving a message as

distinguished from one used for sending or transmitting one.

Thus the Bell telephone applied to the ear is a receiver, while the

microphone which is spoken into or against is the transmitter.

Receiver, Harmonic.

A receiver including an electro-magnet whose armature is an elastic

steel reed, vibrating to a particular note. Such a reed responds to a

series of impulses succeeding each other with the exact frequency of its

own natural vibrations, and does not respond to any other rapid series

of impulses. (See Telegraph Harmonic.)

Reciprocal.

The reciprocal of a number is the quotient obtained by dividing one by

the number. Thus the reciprocal of 8 is 1/8.

Applied to fractions the above operation is carried out by simply

inverting the fraction. Thus the reciprocal of 3/4 is 4/3 or 1-1/3.

Record, Telephone.

Attempts have been made to produce a record from the vibrations of a

telephone disc, which could be interpreted by phonograph or otherwise.

Fig. 284. MORSE RECORDER OR EMBOSSER.

452   STANDARD ELECTRICAL DICTIONARY.

Recorder, Morse.

A telegraphic receiving apparatus for recording on a strip of paper the

dots and lines forming Morse characters as received over a telegraph

line. Its general features are as follows:

A riband or strip of paper is drawn over a roller which is slightly

indented around its centre. A stylus or blunt point carried by a

vibrating arm nearly touches the paper. The arm normally is motionless

and makes no mark on the paper. An armature is carried by the arm and an

electro-magnet faces the armature. When a current is passed through the

magnet the armature is attracted and the stylus is forced against the

paper, depressing it into the groove, thus producing a mark. When the

current ceases the stylus is drawn back by a spring.

Fig. 285. INKING ROLLER MECHANISM OF MORSE RECORDER.

In some instruments a small inking roller takes the place of the stylus,

and the roller is smooth. The cut, Fig. 285, shows the plan view of the

ink-roller mechanism. J is the roller, L is the ink well, Cl is the arm

by which it is raised or lowered by the electro-magnet, as in the

embosser. S S is the frame of the instrument, and B the arbor to which

the arm carrying the armature is secured, projecting to the right. A

spring is arranged to rub against the edge of the inking roller and

remove the ink from it.

The paper is fed through the apparatus by clockwork. At the present day

sound reading has almost entirely replaced the sight reading of the

recorder.

Recorder, Siphon.

A recording apparatus in which the inked marks are made on a strip of

paper, the ink being supplied by a siphon terminating in a capillary

orifice.

In the cut N S represents the poles of a powerful electro-magnet. A

rectangular coil bb of wire is suspended between the coils. A stationary

iron core a intensifies the field. The suspension wire f f 1 has its

tension adjusted at h. This wire acts as conductor for the current.

453   STANDARD ELECTRICAL DICTIONARY.

The current is sent in one or the other direction or is cut off in

practice to produce the desired oscillations of the coil b b. A glass

siphon n l works upon a vertical axis l. One end l is immersed in an ink

well m. Its longer end n touches a riband of paper o o. The thread k

attached to one side of the coil pulls the siphon back and forth

according to the direction of current going through the electro-magnet

cores. A spiral spring adjusted by a hand-screw controls the siphon. In

operation the siphon is drawn back and forth producing a zigzag line.

The upward marks represent dots, the downward ones dashes. Thus the

Telegraphic Code can be transmitted on it. To cause the ink to issue

properly, electrification by a static machine has been used, when the

stylus does not actually touch the paper, but the ink is ejected in a

series of dots.

Fig. 286. SIPHON RECORDER.

Reducteur for Ammeter.

A resistance arranged as a shunt to diminish the total current passing

through an ammeter. It is analogous to a galvanometer shunt. (See

Multiplying Power of Shunt.)

Reducteur for Voltmeter.

A resistance coil connected in series with a Voltmeter to diminish the

current passing through it. Its resistance being known in terms of the

resistance of the voltmeter it increases the range of the instrument so

that its readings may cover double or more than double their normal

range.

Reduction of Ores, Electric.

Treatment of ores by the electric furnace (see Furnace, Electric.) The

ore mixed with carbon and flux is melted by the combined arc and

incandescent effects of the current and the metal separates. In another

type the metal is brought into a fusible compound which is electrolyzed

while fused in a crucible. Finally processes in which a solution of a

salt of the metal is obtained, from which the metal is obtained by

electrolysis, may be included. Aluminum is the metal to whose extraction

the first described processes are applied.

454   STANDARD ELECTRICAL DICTIONARY.

Refraction, Electric Double.

Double refraction induced in some materials by the action of either an

electrostatic, magnetic or an electro-magnetic field.

The intensity or degree of refracting power is proportional to the

square of the strength of field.

Refreshing Action.

In electro-therapeutics the restoration of strength or of nerve force by

the use of voltaic alternatives, q. v.

Region, Extra-polar.

In electro-therapeutics the area or region of the body remote from the

therapeutic electrode.

Region, Polar.

In electro-therapeutics the area or region of the body near the

therapeutic electrode.

Register, Electric.

There are various kinds of electric registers, for registering the

movements of watchmen and other service. Contact or press buttons may be

distributed through a factory. Each one is connected so that when the

circuit is closed thereby a mark is produced by the depression of a

pencil upon a sheet or disc of paper by electro-magnetic mechanism. The

paper is moved by clockwork, and is graduated into hours. For each

push-button a special mark may be made on the paper. The watchman is

required to press the button at specified times. This indicates his

movements on the paper, and acts as a time detector to show whether he

has been attending to his duty.

Register, Telegraphic.

A term often applied to telegraph recorders, instruments for producing

on paper the characters of the Morse or other alphabet.

Regulation, Constant Current.

The regulation of a dynamo so that it shall give a constant current

against any resistance in the outer circuits, within practical limits.

It is carried out in direct current machines generally by independent

regulators embodying a controlling coil with plunger or some equivalent

electro-magnetic device inserted in the main circuit and necessarily of

low resistance. In some regulators the work of moving the regulator is

executed mechanically, but under electrical control; in others the

entire work is done by the current.

A typical regulator or governor (Golden's) of the first class comprises

two driven friction wheels between which is a driving friction wheel,

which can engage with one driven wheel only at once. It is brought into

engagement with one or the other by a solenoid and plunger.

455   STANDARD ELECTRICAL DICTIONARY.

As it touches one wheel it turns it in one direction. This moves a

sliding contact in one direction so as to increase a resistance. This

corresponds to a motion of the plunger in one direction. As the driving

wheel moves in the opposite direction by a reverse action it diminishes

the resistance. Thus the increase and decrease of resistance correspond

to opposite movements of the solenoid plunger, and consequently to

opposite variations in the current. The whole is so adjusted that the

variations in resistance maintain a constant amperage. The resistance is

in the exciting circuit of the dynamo.

In Brush's regulator, which is purely mechanical, a series dynamo is

made to give a constant current by introducing across the field magnets

a shunt of variable resistance, whose resistance is changed by an

electro-magnet, whose coils are in circuit with the main current. Carbon

resistance discs are used which the electro-magnet by its attraction for

its armature, presses with varying intensity. This alters the

resistance, decreasing it as the current increases and the reverse. As

the connection is in shunt this action goes to maintain a constant

current.

Regulation, Constant Potential.

The regulation of constant potential dynamos is executed on the same

lines as that of constant current dynamos. If done by a controlling

coil, it must for constant potential regulation be wound with fine wire

and connected as a shunt for some part of the machine.

Regulation of Dynamos.

The regulation of dynamos so that they shall maintain a constant

potential difference in the leads of their circuit for multiple arc

systems or shall deliver a constant current in series systems. Hence two

different systems of regulation are required, (a) constant potential

regulation--(b) constant current regulation. The first named is by far

the more important, as it concerns multiple arc lighting, which is the

system universally used for incandescent lighting.

S. P. Thompson thus summarizes the methods of governing or regulating

dynamos. Premising that alteration of the magnetic flux is the almost

universal way of control, it can be done in two ways; first, by varying

the excitation or ampere turns of the field, and second by varying the

reluctance of the magnetic circuit. The excitation or magnetic flux may

be varied

(a) by hand, with the aid of rheostats and commutators in the exciting

circuit;

(b) automatically, by governors, taking the place of the hand;

(c) by compound windings. The magnetic circuit may have its reluctance

caused to vary in several ways;

(d) by moving the pole pieces nearer to or further from the armature;

(e) by opening or closing some gap in the magnetic circuit (field-magnet

core);

(f) by drawing the armature endways from between the pole pieces;

(g) by shunting some of the magnetic lines away from the armature by a

magnetic shunt.

The latter magnetic circuit methods d, e, f, and g, have never met with

much success except on small machines or motors. Method e is adopted in

the Edison motor, the yoke being withdrawn or brought nearer the cores

of the coils. (See Regulation, Constant Current-Regulation, constant

Potential.)

456   STANDARD ELECTRICAL DICTIONARY.

Reguline. adj.

Having the characteristics of a piece of metal, being flexible,

adherent, continuous, and coherent. Applied to electrolytic deposits.

Relative.

Indicating the relation between two or more things without reference to

absolute value of any one of them. Thus one lamp may be of relatively

double resistance compared to another, but this states nothing of the

resistance in ohms of either lamp.

Relay.

A receiving instrument which moves in accordance with impulses of

currents received, and in so moving opens and closes a local circuit,

which circuit may include as powerful a battery as required or

desirable, while the relay may be on the other hand so delicate as to

work with a very weak current.

Fig. 287. RELAY.

The typical relay includes an electro-magnet and armature. To the latter

an arm is attached and the lower end of the arm works in pivots. As the

armature is attracted the arm swings towards the magnet. When the

current is cut off, the armature and arm are drawn back by a spring.

When the arm swings towards the magnet its upper end touching a contact

screw closes the local circuit. When it swings back it comes in contact

with a second screw, with insulated point, and opens the circuit as it

leaves the first named screw.

One terminal connects with the arm through the pivots and frame. The

other connects with the contact screw through the frame carrying it.

Synonym--Relay Magnet.

457   STANDARD ELECTRICAL DICTIONARY.

Relay Bells.

Bells connected by relay connection to a main line for acoustic

telegraphy. A stroke on one bell indicates a dot and on the other a

dash. The system is now nearly extinct.

Relay, Box-sounding.

A relay which is surrounded by or mounted on a resonator or wooden box

of such proportions and size as to reinforce the sound. This enables a

relay to act as a sounder, its weak sounds being virtually magnified so

as to be audible.

Relay Connection.

A connection used in telegraphy, including a local battery, with a short

circuit normally open, but closed by a switch and a sounder or other

appliance. The latter is made very sensitive so as to be worked by a

feeble current, and is connected to the main line. A very slight current

closes the switch and the local battery comes into operation to work a

sounder, etc. When the current ceases on the main line the switch opens

and throws the local battery out of action. The switch is termed a

relay, q. v. A long main line may thus produce strong effects at distant

stations, the intensity of action depending on the local battery.

Fig. 288. RELAY OR LOCAL CIRCUIT.

Relay, Differential.

A relay containing two coils wound differentially, and of the same

number of turns and resistance. If two equal currents pass through the

coils they counteract each other and no action takes place. If there is

a difference in the currents the relay acts as one coil preponderates.

The coils may be wound for uneven currents with different resistance and

number of turns.

Relay, Microphone.

A relay connection applied to a telephone circuit. It consists of a

microphone mounted in front of the diaphragm of a telephone receiver. In

circuit with the microphone is a battery and second telephone receiver.

The microphone is supposed to intensify the sounds of the first

telephone.

458   STANDARD ELECTRICAL DICTIONARY.

Relay, Polarized.

A relay whose armature is of steel, and polarized or permanently

magnetized, or in which a permanent magnet is used as the basis for the

electro-magnets. In the relay shown in the cut the coils shown are

mounted on cores carried on the end of a powerful bent permanent magnet.

Thus when no current passes their upper poles are both of the same sign,

and the horizontally vibrating tongue is held by the magnetic attraction

against one or the other pole piece. If a current is sent through the

electro-magnet it gives opposite polarity to the two polar extensions.

As the end of the vibrating tongue is of polarity determined by the

permanent magnet it is attracted to one pole and  repelled from the

other. On cessation of current it remains attached by the permanent

magnetism. If now a current is sent in the opposite direction the two

poles again acquire opposite polarity, the reverse of the former, and

the tongue flies across to the opposite side. On cessation of current it

remains attached as before by the permanent magnetism.

In its movements to and fro the relay tongue opens and closes a contact,

so as to work a sounder or other apparatus. The polarized relay is of

high sensibility, and requires little or no change of adjustment.

Fig. 288. POLARIZED RELAY

Reluctance.

In a magnetic circuit or portion thereof, the resistance offered to the

flow of lines of force. The magnetic circuit as has already been stated

is treated like an electric circuit, and in it reluctance occupies the

place of resistance in the electric circuit. It is the reciprocal of

permeance. S. P. Thompson expresses the law thus:

Total number of magnetic lines = (magneto-motive force) / (magnetic

reluctance)

Synonyms--Magnetic Reluctance-Magnetic Resistance.

Reluctance, Unit of.

The reluctance of a circuit through which unit magnetizing power

(magneto-motive force) can produce a unit of induction or one line of

force. This value is very high; the reluctance of ordinary magnetic

circuits ranges from 1E-5 to 1E-8 unit of reluctance.

Reluctivity.

Specific reluctance; the reluctance of a cube of material whose edge

measures one centimeter in length. It is a quality bearing the same

relation to reluctance that permeability does to permeance.

It is defined as the reciprocal of magnetic permeability. (Kenelly.) If

plotted as a curve for different values of the magnetizing force it is

found to be nearly a straight line, a linear function of the magnetizing

force, H with the equation a + b H. Reluctivity is the property of a

substance; reluctance is the property of a circuit.

459   STANDARD ELECTRICAL DICTIONARY.

Remanence.

The residual magnetism left after magnetic induction, expressed in lines

of force per square centimeter.

Repeater.

In telegraphy an instrument for repeating the signals through a second

line. It is virtually a relay which is operated by the sender, and which

in turn operates the rest of the main line, being situated itself at

about the middle point of the distance covered. In the simpler forms of

repeater two relays are used, one for transmission in one direction the

other for transmission in the other. An attendant switches one or the

other in as required.

Thus a common relay is virtually a repeater for its local circuit. If

such a relay is placed half way down a line, and if the line beyond it

is connected as its local, it becomes a repeater.

Some forms of repeaters are automatic, and repeat both ways without the

need of an attendant.

It is the practice to somewhat prolong the signals sent through a

repeater.

Replenisher, Sir William Thomson's.

A static accumulating influence machine contained in Thomson's quadrant

electrometer and used to change the quadrants. The cut shows the

horizontal section and construction of the apparatus.

It contains two gilt brass inductors A B, and two eccentric sectors or

carriers, C, D, which are mounted on an ebonite spindle, which is spun

around by the fingers. The springs s s1 connect each with its inductor;

the springs S S1 connect only each other, and touch the sectors as they

turn around.

One of the inductors may be always assumed to be of slightly higher

potential than that of the other one. When the carriers are in contact

with the springs S S1 they are each charged by induction with

electricity opposite in sign to that of the nearest quadrant. As they

leave the springs S S1 in their rotation, they next touch the springs s

s1, but of the recently opposite inductor. They share each a portion of

its charge with the inductors building up their charges. The action is

repeated over and over again as they rotate.

Fig. 289. DIAGRAM OF THOMSON'S REPLENISHER.

Fig. 290. THOMSON'S REPLENISHER.

460   STANDARD ELECTRICAL DICTIONARY.

Reservoir, Common.

A term applied to the earth, because all electrified bodies discharge

into it if connected thereto.

Residual Atmosphere.

The air left in a receiver after exhaustion by an air pump. The

quantity, where good air pumps are used, is very minute.

Residue, Electric.

The residual charge of a condenser. (See Charge, Residual.)

Resin.

(a) The product obtained by non-destructive distillation of the juice of

the pitch pine. It is the solid residue left after the turpentine has

been evaporated or distilled. It is a mixture of abietic acid C44 H64 O5

and pinic acid C20 H30 O2. It is an insulator; its specific inductive

capacity is 2.55. (Baltzmann.)

Synonyms--Colophony--Rosin.

(b) The name is also generally applied to similar substances obtained

from the sap of other trees; thus shellac is a resin. The resins are a

family of vegetable products; the solid portions of the sap of certain

trees. Common resin, lac, dragons blood, are examples. They are all

dielectrics and sources of resinous or negative electricity when rubbed

with cotton, flannel, or silk. (See Electrostatic Series.)

461   STANDARD ELECTRICAL DICTIONARY.

Resinous Electricity.

Negative electricity; the electricity produced upon the surface of a

resinous body by rubbing it; such a body is shellac or sealing wax;

flannel and other substances may be used as the rubbing material. (See

Electrostatic Series.)

Resistance.

(a) The quality of an electric conductor, in virtue of which it opposes

the passage of an electric current, causing the disappearance of

electro-motive force if a current passes through it, and converting

electric energy into heat energy in the passage of a current through it.

If a current passes through a conductor of uniform resistance there is a

uniform fall of potential all along its length. If of uneven resistance

the fall in potential varies with the resistance. (See Potential, Fall

of.)

The fall of potential is thus expressed by Daniell. "In a conductor, say

a wire, along which a current is steadily and uniformly passing, there

is no internal accumulation of electricity, no density of internal

distribution; there is, on the other hand, an unequally distributed

charge of electricity on the surface of the wire, which results in a

potential diminishing within the wire from one end of the wire to the

other."

Resistance varies inversely with the cross section of a cylindrical or

prismatic conductor, in general with the average cross-section of any

conductor, and in the same sense directly with its true or average or

virtual length. It varies for different substances, and for different

conditions as of temperature and pressure for the same substance. A rise

of temperature in metals increases the resistance, in some bad

conductors a rise of temperature decreases the resistance.

462   STANDARD ELECTRICAL DICTIONARY.

Approximately, with the exception of iron and mercury, the resistance of

a metallic conductor varies with the absolute temperature. This is very

roughly approximate.

Except for resistance energy would not be expended in maintaining a

current through a circuit. The resistance of a conductor may be supposed

to have its seat and cause in the jumps from molecule to molecule, which

the current has to take in going through it. If so a current confined to

a molecule would, if once started, persist because there would be no

resistance in a molecule. Hence on this theory the Ampérian currents

(see Magnetism, Ampere's Theory of) would require no energy for their

maintenance and Ampére's theory would become a possible truth.

When metals melt their resistance suddenly increases.

Light rays falling on some substances, notably selenium, q. v., vary the

resistance.

Longitudinal stretching of a conductor decreases it, it increases with

longitudinal compression, and increases in iron and diminishes in tin

and zinc when a transverse stress tends to widen the conductor.

(b) The term resistance is used to express any object or conductor used

in circuit to develop resistance.

[Transcriber's note: At room temperatures, the thermal motion of ions in

the conductor's crystal lattice scatters the electrons of the current.

Imperfections of the lattice contribute slightly. At low temperatures

superconductivity (zero resistance) can occur because an energy gap

between the electrons and the crystal lattice prevents any interaction.

At the time of this book, none of this was known. "Jumps from molecule

to molecule" is a good guess.]

Resistance, Apparent.

Impedance; the virtual resistance of a circuit including the spurious

resistance due to counter-electromotive force. It may be made up of true

resistance and partly of an inductive reaction, as it represents the net

factor, the entire obstruction to the passage of a current, and not

merely a superadded resistance or counter-electro-motive force.

Synonym--Impedance.

[Transcriber's note: Impedance can also have a component due to

capacitance.]

Resistance, Asymmetrical.

Resistance which varies in amount in different directions through a

conductor. It implies a compound or composite conductor such as the

human system. The presence of counter-electro-motive force in different

parts of a conductor may bring about asymmetrical resistance.

Resistance, B. A. Unit of.

The British Association Ohm. (See Ohm, B. A.)

463   STANDARD ELECTRICAL DICTIONARY.

Resistance Box.

A box filled with resistance coils. The coils are connected in series so

that a circuit including any given number has their aggregate resistance

added to its own. The terminals of consecutive coils are connected to

short blocks of brass which are secured to the top of the box, lying

flatwise upon it, nearly but not quite in contact with each other. Plugs

of brass are supplied which can go in between pairs of blocks, which

have a pair of grooves reamed out to receive them. Such plugs short

circuit the coil below them when in position. The cut shows how such

coils are connected and the use of plugs to short circuit them. The

diagram shows the top of a Wheatstone bridge, q. v., resistance box with

connections for determining resistances.

Fig. 291. RESISTANCE BOX.

Resistance Box, Sliding.

A resistance box whose coils are set in a circle. Two metal arms with

handles are pivoted at the centre of the circle and by moving them

around they make and break contacts so as to throw the coils in and out

of circuit. The object is to permit an operator to adjust resistance

without looking at the box--an essential in duplex telegraphy.

Resistance, Breguet Unit of.

The same in origin as the Digney Unit. (See Resistance, Digney Unit of.)

It is equal to 9.652 Legal Ohms.

Resistance, Carbon.

A resistance, a substitute for a resistance coil; it is made of carbon,

and is of various construction. In the Brush dynamo regulator a set of

four vertical piles of plates of retort carbon, q. v., is used as a

resistance, whose resistance is made to vary by changing the pressure.

This pressure automatically increases as the current strength increases,

thus reducing the resistance.

464   STANDARD ELECTRICAL DICTIONARY.

Resistance Coil, Standard.

A standard or resistance issued by the Electric Standard Committee of

Great Britain. The cut shows the standard ohm. It is formed either of

German silver, or of an alloy of silver, 66.6 per cent. and platinum,

33.4 per cent. The wire is insulated and doubled before winding as

described before. (See Coil, Resistance.) The two ends of the wire are

soldered, each one to a heavy copper wire or rod r. The whole coil is

enclosed in a brass case, and is enclosed with paraffine melted in at A.

A place for a thermometer is provided at t. By immersing the lower part

of the case B in water of different degrees of heat any desired

temperature can be attained.

Fig. 292. STANDARD OHM COIL.

Resistance, Combined.

The actual resistance of several parallel conductors starting from the

same point and ending at the same point. If the individual resistance be

a b c d .. and the combined resistance be x then we   have

x = 1 / (( 1/a)  + (1/b) + (1/c) + (1/d) + …)

Synonym--Joint Resistance.

Resistance, Critical.

In a series wound dynamo the resistance of the outer circuit above which

the machine will refuse to excite itself.

Resistance, Dielectric.

The mechanical resistance of a dielectric to the tendency to perforation

or to the strains due to electrification. This is a phase of mechanical

resistance, and is distinct from the electrical or ohmic resistance of

the same substance.

Resistance, Digney Unit of.

The resistance of an iron wire, 1 kilometer long, 4 millimeters

diameter, temperature unknown.

It is equal to 9.163 legal ohms.

Resistance, Electrolytic.

The resistance of an electrolyte to the passage of a current decomposing

it. It is almost entirely due to electrolysis and is added to by

counter- electro-motive force, yet it is not treated specifically as

such, but as an actual resistance. When a current of a circuit of too

low voltage to decompose an electrolyte is caused by way of immersed

terminals to pass through an electrolyte the resistance appears very

high and sometimes almost infinite. If the voltage is increased until

the electrolyte is decomposed the resistance suddenly drops, and what

should be termed electrolytic resistance, far lower than the true

resistance, appears.

465   STANDARD ELECTRICAL DICTIONARY.

Resistance, English Absolute or Foot-Second Unit of.

A unit based on the foot and second. It is equal to (( foot / second ) *

1E7) , being based on these dimensions.

It is equal to 0.30140 legal ohm.

Resistance, Equivalent.

A resistance equivalent to other resistances, which may include

counter-electro-motive force.

Resistance, Essential.

The resistance of the generator in an electric circuit; the same as

internal resistance.

Resistance, External.

In an electric circuit the resistance of the circuit outside of the

generator, or battery.

Synonym--Non-essential Resistance.

Fig. 293. RESISTANCE FRAME.

Resistance Frame.

An open frame filled with resistance coils of iron, or German silver

wire. It is used as a resistance for dynamos and the larger or working

class of plant. The coils are sometimes connected so that by a switch

moving over a row of studs one or more can be thrown into series

according to the stud the switch is in contact with.

Resistance, German Mile Unit of.

The resistance of 8,238 yards of iron wire 1/6 inch in diameter. It is

equal to 56.81 legal ohms.

466   STANDARD ELECTRICAL DICTIONARY.

Resistance, Hittorf's.

A high resistance, often a megohm, composed of Hittorf's solution, q. v.

It is contained in a vertical glass tube near whose upper and lower ends

are electrodes of metallic cadmium attached to platinum wires. The

cadmium is melted in glass tubes, the platinum wire is inserted into the

melted metal and the tube is broken after all is solid. The resistance

should show no polarization current.

Fig. 294. HITTORF'S RESISTANCE

Resistance, Inductive.

A resistance in which self-induction is present; such as a coil of

insulated wire wound around an iron core.

Resistance, Insulation.

The resistance of the insulation of an insulated conductor. It is stated

in ohms per mile. It is determined by immersing a section of the line in

water and measuring the resistance between its conductor and the water.

The section must be of known length, and its ends must both be above the

liquid.

Resistance, Internal.

The resistance of a battery, or generator in an electric circuit as

distinguished from the resistance of the rest of the circuit, or the

external resistance.

Synonym--Essential Resistance.

Resistance, Jacobi's Unit of.

The resistance of a certain copper wire 25 feet long and weighing 345

grains.

It is equal to 0.6296 legal ohm.

Resistance, Matthiessen's Meter-gram Standard.

The resistance of a pure hard drawn copper wire of such diameter that

one meter of it weighs one gram. It is equal to .1434 Legal Ohms at 0º

C. (32º F.)

Resistance, Matthiessen's Unit of.

The resistance of a standard mile of pure annealed copper wire 1/16 inch

diameter, at a temperature of 15.5º C. (60º F.).

It is equal to 13.44 legal ohms.

467   STANDARD ELECTRICAL DICTIONARY.

Resistance, Meter-millimeter Unit of.

The resistance of a wire of copper one meter long and one square

millimeter in section. It is equal to .02057 ohms at 0º C. (32º F.) The

term may also be applied to the resistance of similar sized wire of

other metals.

Resistance, Mil-foot Unit of.

The resistance of a foot of copper wire one-thousandth of an inch in

diameter. It is equal to 9.831 ohms at 0º C. (32º F.) The term may also

be applied to the resistance of similar sized wire of other metals.

Resistance, Non-essential.

The resistance of the portion of an electric circuit not within the

generator; the same as external resistance.

Synonym--External Resistance.

Resistance, Non-inductive.

A resistance with comparatively little or negligible self-induction.

Resistance of Human Body.

The resistance of the human body is largely a matter of perfection of

the contacts between its surface and the electrodes. It has been

asserted that it is affected by disease. From 350 to 8,000 ohms have

been determined as resistances, but so much depends on the contacts that

little value attaches to the results.

Resistance, Ohmic.

True resistance measured in ohms as distinguished from

counter-electro-motive force, q. v. The latter is called often spurious

resistance.

Synonym--True Resistance.

[Transcriber's note: "True" vs. "spurious" are interesting terms,

considering that today we define impedance as a combination of "real"

resistance and "imaginary" capacitive and inductive reactance.]

Resistance, Reduced.

The resistance of a conductor reduced to ohms, or to equivalent lengths

of a column of mercury, 1 square millimeter in cross area.

Resistance, Siemen's Unit of.

The resistance of a column of mercury 1 meter long and 1 square

millimeter cross-sectional area at 0º C. (32º F.)

It is equal to .9431 legal ohm.

Resistance, Specific.

The relative resistance of a substance. It is expressed as the actual

resistance of a cube of the substance which is one centimeter on each

edge. For metals it is usually expressed in microhms, for liquids in

ohms.

The resistances of a specified length of wire of specified diameter of

different substances is often given, and is really a particular way of

stating specific resistances.

Synonym--Specific Conduction Resistance.

Resistance, Spurious.

The counter-electro-motive force, q. v., operating to prevent a current

being produced of what should be its full strength were the true

resistance and actuating electro-motive force only concerned. Such

counter-electro-motive force may be treated as a spurious resistance and

such a value in ohms assigned to it as would correspond to its proper

effect.

468   STANDARD ELECTRICAL DICTIONARY.

In its effect on opposing a current and in resisting its formation it

differs from true resistance. The latter in diminishing current strength

absorbs energy and develops heat; spurious resistance opposes and

diminishes a current without absorption of energy or production of heat.

[Transcriber's note: "Spurious resistance" is now called reactance,

consisting of capacitive reactance and inductive reactance. The

combination of reactance and (Ohmic/true) resistance is called

impedance. The calculation of impedance requires complex algebra, not

just real values used in DC circuit analysis.]

Resistance, Steadying.

When arc lamps are connected in parallel or multiple arc a small

resistance coil is sometimes placed in series with each lamp for

steadying purposes. It reduces the percentage of variation of resistance

in each lamp, which may be caused by a change in the position of the

carbons.

Resistance, Swiss Unit of.

A unit constructed by the "Administration Suisse," based on the same

data as the Breguet and the Digney Units. (See Resistance, Digney Unit

of)

It is equal to 10.30 legal ohms.

Resistance, Thomson's Unit of.

A unit of resistance based on the foot and second.

It is equal to 0.3166 legal ohm.

Resistance, Unit.

Unit resistance is that of a conductor in which unit current is produced

by unit electro-motive force.

Resistance, Varley's Unit of.

The resistance of a standard mile of a special copper wire 1/16 inch

diameter.

It is equal to 25.33 ohms.

Resistance, Weber's Absolute Unit.

A metric system unit; (meter / second) * 1E7

It is equal to 0.9089 legal ohm.

Resonance, Electric.

A set of phenomena known as the Hertz experiments are grouped under this

title, which phenomena are incidents of and depend on the propagation of

electric waves through wires or current conductors, as well as through

the ether. Ordinarily a wire is only a seat of current, and is in its

nature inconsistent with wave propagation through its mass. Such waves

are virtually confined to the exterior of the wire. The point is that

the current-producing force is supposed to enter the wire at all points

from without, the current not being produced by an end-push. Hence in

rapidly recurring waves which are produced by a rapidly pulsatory or

alternating current, no time is afforded for the current-producing

force, in this case the wave-producing force, to penetrate into the

substance of the wire. In one of his experiments Dr. Hertz surrounded a

wire by a glass tube chemically silvered. The coating was so thin as to

be translucent. Through this metallic layer a current could be induced

in the wire in its interior. Any mechanical layer of metal took up the

induction itself, and protected the central wire. This gave a clue to

the thickness of metal penetrated by the rapid induced waves used by Dr.

Hertz.

469   STANDARD ELECTRICAL DICTIONARY.

Fig. 295. ELECTRICAL RESONANCE EXCITER.

The method used for the production of rapid oscillations is the

following. To the terminals of an induction coil two metal spheres AA1

are connected as shown. This apparatus is termed the exciter; in its

discharge a series of isochronous discharges takes place, alternating in

direction. The period of duration T of a single one is given by the

formula T= 2* PI * squareRoot( LC ),  in which C is the capacity and L

is the self-induction. The spheres may be 30 centimeters (11.8 inches)

in diameter, connected each to conductors 0.5 centimeter (.2 inch) in

diameter and 40 centimeters (15.7 inches) long each. For the length of

an undulation the formula gives for this apparatus 4.8 meters (15.75

feet) as the length of a wave, assuming for them the velocity of

propagation equal to that of light. The exciter may have 10,000 times

the rate of oscillation possessed by the plain induction coil.

When this apparatus is worked it produces induced waves in every

neighboring conductor. The resonance effects appear in the size of the

spark induced. Thus a wire bent into a circle with its ends nearly

touching will give a spark, but if made of proper electrostatic

capacity, corresponding with the particular waves employed, the spark

will be very much larger. The ring, with its spark gap is termed a

resonator. It is used as an explorer to trace the waves.

Waves thus produced are transmitted by stone walls and nonconductors in

general. A plate of zinc reflects part and transmits part. The reflected

waves can be traced by the resonator, their angle of reflection being

equal to their angle of incidence. They can be received by one parabolic

reflector, reflected to another and brought to a focus. They can be

reflected so as to produce interference or loops and nodes, and the

loops and nodes can be traced by the resonator. By a prism of asphalt

they are refracted exactly like light.

From all this it is concluded that an additional proof is furnished of

the identity of light and electro-magnetic waves, and a very strong

experimental proof of Maxwell's theory of light is furnished.

Synonym--Hertz's Experiments.

470   STANDARD ELECTRICAL DICTIONARY.

Fig. 296. ELECTRICAL RESONATOR.

Resonator, Electric.

A small open electric circuit, with ends nearly touching. When exposed

to electric resonance, or to a sympathetic electric oscillatory

discharge, a spark passes from across the gap. The production of this

spark is altogether a matter of the inductance of the resonator. The

simplest form is a circle of copper wire with its ends nearly touching.

The length of the gap is adjustable by bending. A screw adjustment may

also be provided. Another form is shown in the cut, Fig. 296. Here

sheets of tinfoil are used to regulate the electrostatic capacity, while

at m is shown the finger piece for regulating the size of the spark gap

a.

Synonym--Spark Micrometer.

Resultant.

The line indicating the result of the application of two or more forces

to a point. Its direction and length give the elements of direction and

intensity. (See Forces, Resolution of Forces, Composition of

Components.)

Resultant Polarity.

The magnetic polarity imparted to a mass of iron acted on by two or more

separate inducing forces or currents. It appears in dynamos and motors.

The final polarity is the resultant of the inducing effect of the field

magnet poles and of the windings.

Retardation.

In telegraphy a retardation of the rate of transmission of signals. It

is due to several causes.

(a) The self-induction of the circuit, especially if it includes many

electro-magnets, produces extra currents (see Currents, Extra.) These

are opposed to the main current on closing it and hence retard the

action. They are in the same direction on opening it and hence again

retard the action.

(b) Every line has a certain static capacity. This is affected by the

proximity of the lines to the earth. For each signal electricity has to

be charged upon the line until the line is charged to its end with a

certain proportion of the initial density. This charging takes time and

hence introduces retardation.

(c) The cores of the electro-magnets of the relays or sounders are not

instantly magnetized and demagnetized. This magnetic lag, q. v.,

introduces retardation.

471   STANDARD ELECTRICAL DICTIONARY.

Retardation of Phase.

The fractional lagging behind of waves or alternating currents; by

lagging behind a portion of a wave length the corresponding phases, as

of full amplitude, are kept back or retarded. The phase of current

intensity may be retarded with reference to the electro-motive force by

the introduction of transformers of high capacity with high resistance

on open secondary circuits.

[Transcriber's note: Capacitors are used to correct current phase lag.]

Retentivity.

Coercitive or coercive force; by virtue of which steel retains its

magnetism. It is the more modern name, "coercive force" as a term being

rejected by many.

Synonyms--Coercive Force--Coercitive Force.

Retort Carbon.

Carbon deposited in coal gas retorts from decomposition of the

hydrocarbons. It is a very hard, pure form, and is of graphitic

modification. Owing to its great hardness it is little used for

electrical purposes, the molded carbons being easier to make. The

deposition occurs in the regular gas-making process, and is a

disadvantage to the working.

Return.

A line or conductor which is supposed to carry current back to its

starting point, after it has traversed a line. It may be a wire or the

grounding of the ends of a line [or] may make the earth act as a return,

termed ground- or earth-return. The best distinction of a return is to

so term the portion of a circuit on which no apparatus is placed.

Reversibility.

The principal in virtue of which a device for producing a given form of

energy can absorb the same and do work. The reversibility of the dynamo

is its quality in virtue of which it can act as a current generator,

thereby converting mechanical energy into electric energy, or if a

current is passed through it, it rotates, doing work, and thereby

converting electric energy into mechanical energy. The knowledge of this

principle can be traced back to Jacobi in 1850.

Reversible Bridge.

A form of Wheatstone's Bridge adapted for reversal of the positions or

interchange of the proportionate arms, v., so that the accuracy of the

coils can be tested.

Rheochord.

An apparatus by means of which variable quantities of wire are thrown

into the circuit; a rheostat using wire. (See Rheostat, Wheatstone's.)

Rheometer.

A galvanometer. (Obsolete.)

472   STANDARD ELECTRICAL DICTIONARY.

Rheomotor.

A source of current; a current generator; a producer of potential

difference. (Obsolete.)

Rheophore.

The portion of an active circuit capable of deflecting a magnetic

needle. This properly includes all of the metallic conductor of a

circuit. (Obsolete.)

Rheoscope.

A galvanoscope; an instrument for qualitatively detecting potential

difference, fall or rise. (See Galvanoscope.)

Rheostat.

An adjustable resistance; an apparatus for changing the resistance

without opening the circuit. Its action may depend on the introduction

of variable lengths of mercury column, of some other liquid, or of wire

into a circuit. (See Rheostat, Wheatstone's.)

Rheostat Arm.

The third arm of known resistance in a Wheatstone bridge. (See

Proportionate Arms.)

Rheostatic Machine.

An apparatus for increasing potential difference. It consists of a

number of static condensers. They are charged in multiple arc or in

parallel, and are discharged in series. Secondary batteries may be used

for the charging; thus a static effect is produced from a galvanic

battery.

Rheostat, Wheatstone's.

This apparatus consists of two cylinders, one, A, made of brass, the

other, B, of wood, with a spiral groove. At its end is a copper ring a.

A fine brass wire has one end attached to this ring. Its other end is

fastened at e, and it is wound as shown; n and o are binding screws

connected, one with the cylinder-ring a, the other with the brass

cylinder, A. The current entering at o, traverses the wire on B, as

there the windings are insulated by the grooves, thence it passes to m

and by A, whose metal short circuits all the wire on it, to the

binding-post n. The handle, d, is turned one way or the other to

regulate the length of the wire through which the current must pass. On

each cylinder there is a square head, one of which is shown at c, so

that the handle can be shifted from one to the other as required; to A

if the wire is to be wound on that cylinder, to B if the reverse is

desired.

Fig. 297. WHEATSTONE'S RHEOSTAT.

473   STANDARD ELECTRICAL DICTIONARY.

Rheotome.

An automatic circuit breaker, one which rapidly opens and closes a

circuit, as in the case of the primary of an induction coil an

interrupter. (Obsolete.)

Rheotrope.

A pole changer, current reverser, or commutator, g., such as the

commutator of an induction coil. (Obsolete.)

Rhigolene.

A petroleum product; a hydrocarbon of low boiling point. Its vapor is

used in flashing (q. v.) carbon filaments for incandescent lamps.

Rhumbs.

In a mariners' compass, the thirty-two points, designated, north, north

by east, north north east, etc. (See Compass Mariner's-Compass, Points

of the.)

Rhumkorff Coil.

The induction coil, q. v.

Rigidity, Molecular.

The tendency of molecules to resist rotation or change of position; the

assumed cause of magnetic coercive force, or retentivity.

Ring Contact.

A contact formed by a terminal clip in the shape of a ring, split or cut

at one point so that its ends tend to spring together. The other

terminal is a bar which passes into the cut and is tightly pressed by

the elastic ring.

Fig. 298. SWITCH WITH RING CONTACTS.

474   STANDARD ELECTRICAL DICTIONARY.

Ring, Faraday.

A closed ring of iron used as the core of a transformer or induction

coil. The term is derived from Faraday's classic experiment with such an

apparatus when he produced a spark by induction in a secondary circuit.

Roaring.

A term applied to the noise sometimes produced in a voltaic arc, when

the electrodes are close together and a heavy current is passing.

Rocker.

In a dynamo the movable piece, mounted concentrically with the

commutator, and carrying the rocker-arms and brush-holders. By moving it

the brushes are adjusted for proper lead.

Rocker Arms.

The arms projecting from a rocker and each carrying one of the

brush-holders.

Roget's Spiral.

An experimental apparatus for illustrating the mutual attraction of

currents going in like direction. A cylindrical helix or spiral of wire

is suspended by one end. Its lower end just dips into a mercury cup. An

active circuit is connected, one terminal to the upper end, the other

terminal to the mercury cup, bringing the apparatus in series into the

circuit. The current as it passes causes the coil to shorten, each

spiral attracting its neighbors. This breaks the circuit by drawing the

lower end out of the mercury cup. The current being cut off the coils

cease to attract each other, and the end dips into the mercury cup

again. This closes the circuit, the coils again attract each other and

the same sequence follows and is repeated over and over again. A bright

spark is produced at each break of the mercury contact.

Rotation of Liquids, Electro-dynamic.

By passing a current through a liquid, such as dilute sulphuric acid, it

rotates if exposed to the induction of a current flowing at right angles

to it. The condition resolves itself into a liquid traversed by

horizontal currents from centre to circumference or vice versa, rotated

by a current passing through a circular conductor below it.

475   STANDARD ELECTRICAL DICTIONARY.

Rotation of Liquids, Electro-magnetic.

The rotation produced in a liquid carrying centripetal or centrifugal

currents by an electromagnet. It is practically an intensification of

electro-dynamic rotation. (See Rotation of Liquids, Electro-dynamic.)

Rubber.

In a frictional electric machine the cushion of leather which is pressed

against the plate as it rotates.

475   STANDARD ELECTRICAL DICTIONARY.

S.

(a) Symbol for second.

(b) Symbol for space, or length; L is preferable.

(c) Symbol for south-seeking pole of a magnet.

Saddle Bracket.

A bracket carried on the top of telegraph poles, carrying an insulator

for the upper wire.

Safety Device.

(a) A device to prevent overheating of any portion of a circuit by

excess of current. It generally consists of a slip of fusible metal

which if the current attains too much strength melts and opens the

circuit. To ensure its breaking a weight is sometimes suspended from the

strip. In one form an insulated German silver wire is wrapped around the

end of the fusible strip a number of times and its end is connected to

it. The other end of the German silver wire connects with the main lead,

so that all the current goes through both in series. If the German

silver wire becomes heated from excess of current the coil wrapped

tightly around the end of the fusible strip melts it and opens the

circuit.

(b) Lightning arresters, q. v., may be cited under this heading.

Synonyms--Automatic Cut Out--Safety Fuse, Plug, or Strip.

Fig. 299. COCKBURN SAFETY FUSE.

Safety Fuse.

A strip of metal inserted so as to form part of a circuit and of such

size that a smaller current [than] would heat the regular wire of the

circuit dangerously, so as to cause a conflagration for instance, would

melt the fuse and open the circuit. As it sometimes happens that a

safety fuse melts without parting a weight is sometimes hung upon it, so

as to break it as it softens.

Salt.

A salt is a chemical compound containing two atoms of two radicals,.

which saturate each other. One atom or radical is electro-positive

referred to the other, which is electro-negative. By electrolysis salts

are decomposed, the atoms or radicals separating and uniting to form new

molecules.

476   STANDARD ELECTRICAL DICTIONARY.

Saturated. adj.

A liquid is saturated with a substance when it has dissolved all that it

can, while an excess is present in the liquid. It is possible, by

dissolving some salts in hot water and allowing the solution to cool

without access of air, to obtain a supersaturated solution. On

introduction of a crystal of the salt, or often on mere access of air,

the solution forms crystals and the liquid left is saturated.

Saw, Electric.

A platinum coated steel wire mounted and connected to be raised to

incandescence for cutting purposes.

Schweigger's Multiplier.

An old term for the galvanometer as invented by Schweigger soon after

Oerstedt's discovery.

Scratch Brushes.

Brushes for cleaning the surface of articles to be electroplated to give

a good metallic surface suitable for deposition. They have often wire

instead of bristles.

477   STANDARD ELECTRICAL DICTIONARY.

Fig. 300. WIRE GAUZE ELECTRIC SCREEN.

Screen, Electric.

A large plate or a hollow case or cage of conducting material connected

with the earth, and used to protect any body placed within it from

electrostatic influences.

If within a hollow conducting sphere an electrified body is placed, the

inner surface of the sphere will be charged with electricity of opposite

kind to that of the sphere, and the outer surface with the same kind as

that of the sphere. Thus the sum of the electricities called into action

by induction is zero. The two inner charges are bound to each other. The

induced charge on the outer surface of the sphere is all that has any

effect on objects in the outer air.

If the outer surface is connected to the earth it becomes discharged,

and however highly electrified the body introduced into the sphere and

the inner surface of such sphere may be, they produce no external

effects, as they are bound one to the other.

If the sphere is connected to the earth and an unelectrified object is

placed within it, such object will be perfectly shielded from the

effects of an outer electrostatic field. Perforated tinfoil or wire

gauze has just as good a result. A large plate of metal connected to the

earth has the same effect. The screen whether plane or hollow simply

retains a bound charge due to the field of force, thereby neutralizing

it, and the electricity of the opposite sign escapes to the earth. Thus

a true shielding or screening effect is produced.

In the cut an experiment is shown in which an electric screen is carried

by a Leyden jar. Pith balls are suspended outside and inside of it. By

the approach of an electrified body the outer pith balls will diverge,

while no effect is produced upon the inner ones.

Secondary Actions.

In electrolysis the direct products of the electrical decomposition are

not always obtained at the electrodes, but products due to their

reaction on the water and other chemicals may appear. These constitute

secondary actions. Thus if a solution of copper sulphate is electrolyzed

with platinum electrodes, metallic copper appears at one pole and

sulphuric acid and oxygen gas at the other. But the products of

electrolysis by the current are copper (Cu) and sulphion (SO4). The

latter reacting on water sets free oxygen gas and forms sulphuric acid.

The latter is a secondary action.

Secondary Generator.

(a) An alternating current converter generating a so-called secondary

current.

(b) A secondary battery, q. v., may be thus termed.

Secondary, Movable.

The term movable secondaries has been applied to rings, spheres and

discs of conducting material, such as copper, whose behavior when near

the pole of an electro-magnet traversed by an alternating current, have

been studied by Elihu Thomson. Such masses are subjected to very

peculiar movements and mutual reactions. As the phenomena are due to

induced currents the above term has been applied to the masses in which

the currents are induced.

478   STANDARD ELECTRICAL DICTIONARY.

Secondary Plates, Colors of.

In a secondary battery of the lead plate type, the color of the plates

is a good indication of the condition of the battery. The negative plate

should be brown or deep-reddish, the other should be slate-colored.

Secondary Poles.

Poles sometimes found in magnets existing in positions intermediate

between the end or true poles.

Synonym--Consequent Poles.

Seebeck Effect.

The production of a current by heating the junction of two different

metals forming part of a circuit, or the thermo-electric production of

current, is stated as the Seebeck effect, having been discovered by that

investigator.

Selenium.

A non-metallic element. It is interesting electrically on account of the

changes its electric resistance undergoes when it is subjected to light.

In one set of experiments it was found that diffused light caused the

resistance to fall in the ratio of 11 to 9. Full sunlight reduced it to

one-half. Of the spectrum colors red was most powerful and the ultra red

region still more strongly affected its resistance.

The effect produced by exposure to light is instantaneous, but on

removal to the dark only slowly disappears.

A vessel of hot water was found to have no effect, showing that short

ether waves are essential to the effect.

Selenium Cell.

A selenium resistance box. Vitreous selenium is made by keeping ordinary

selenium for some hours at a temperature of about 220º C. (428º F.)

after fusing. It is placed in an electric circuit as part of the

conductor.

Its resistance can then be determined. It decreases in sunlight to about

one-half its resistance in the dark.

The selenium cell is used in the Photophone, q. v. Otherwise it is

little more than a subject of experiment.

Selenium Eye.

A model eye in which selenium in circuit with a battery and galvanometer

takes the place of the retina of the human eye.

Self-repulsion.

When a body is electrified each molecule repels its neighbor and the

condition in question is thus designated. An electrified soap-bubble

expands in virtue of self-repulsion.

Semi-conductors.

Substances which conduct static electricity poorly, but quite

appreciably and beyond the extent of leakage. The following are

examples: Alcohol and ether, powdered glass, flowers of sulphur, dry

wood, paper, ice at 0º C. (32º F.)

479   STANDARD ELECTRICAL DICTIONARY.

Sensibility.

The measure of the effect of a current upon a galvanometer,

or any similar case.

Sensitiveness, Angle of Maximum.

Every galvanometer has its angle of maximum sensitiveness, which is the

angle of deflection at which a small increment of current will produce

the greatest deflection. For every tangent galvanometer 45° is the angle

in question. In using a galvanometer for direct reading methods it is an

object to have it work at its angle of maximum sensitiveness.

Separately Excited Dynamo.

A dynamo-electric machine whose field magnet is excited from an outside

source, which may be another dynamo or a battery. Alternating current

dynamos are often of this description.

Separate Touch.

In magnetism a method of inducing magnetism in a steel bar. The opposite

poles of two magnets are applied at the center of the bar to be

magnetized, but without touching each other, and are drawn apart to its

ends. They are returned through the air and the process is repeated a

number of times and on both sides of the bar if necessary.

Separation of Electricities.

Under the double fluid theory of electricity the action of

electrification in accumulating positive electricity in one conductor

and negative on the other of the excited surfaces of two conductors.

Separator.

India rubber bands or other forms used in batteries to keep the plates

from touching in the cell; especially applied to secondary batteries,

where the plates are so near together as to require separators to

prevent short circuiting.

Fig. 301. SERIES CONNECTION.

Series.

(a) Arranged in succession as opposed to parallel. Thus if a set of

battery jars are arranged with the zinc of one connected to the carbon

of the next one for the entire number, it is said to be arranged in

series. When incandescent lamps are arranged in succession so that the

current goes through one after the other they are arranged in series.

The opposite of parallel, q. v., or multiple arc, q. v.; it may be used

as a noun or as an adjective.

(b) See Electro-Chemical Series;

(c) Thermo-Electric Series

(d) Electrostatic Series;

(e) Electro-motive Series.

Synonym--Cascade Connection (but little used.)

480   STANDARD ELECTRICAL DICTIONARY.

Series-multiple.

Arrangement of electric apparatus, in which the parts are grouped in

sets in parallel and these sets are connected in series. It is used as a

noun, as "arranged in series-multiple," or as an adjective, as "a

series-multiple circuit or system."

Fig. 302. SERIES-MULTIPLE CONNECTION.

Service Conductors.

In electric distribution the equivalents of service pipes in the

distribution of gas; wires leading from the street mains to the houses,

where current is to be supplied.

Serving.

The wrapping or winding of a cable composed of small size wire, laid

closely and smoothly with a tool called a serving mallet, or serving

block, or by machinery. It serves to protect the cable from wear.

Shackle.

In telegraph lines a swinging insulator bracket for use where wires make

an angle with the pole. A journal box is attached to the pole, like half

of a gate hinge. To this a short iron arm is pivoted so as to be free to

swing through a considerable angle. At its end an insulator is carried

to which the wire is attached. The shackle swings into line with the

wire, or takes a position for two wires corresponding to the resultant

of their directions of pull.

Fig. 303. DOUBLE SHACKLE

Shadow. Electric.

A term applied to a phenomenon of high vacua. If an electric discharge

is maintained in a Crookes' tube the glass opposite the negative

electrode tends to phosphoresce. A plate of aluminum, used also as the

positive electrode, protects the glass directly behind it so as to

produce the effect of a shadow.

Synonym--Molecular Shadow.

[Transcriber's note: The effect is due to the "shadowing" of the

electrons streaming past the plate.]

481   STANDARD ELECTRICAL DICTIONARY.

Sheath for Magnet Coils.

In 1867 C. E. Varley proposed the use of a copper sheath surrounding a

magnet core to diminish self-induction. It has since been used by Brush

and others. Sometimes metallic foil is laid between the successive coils

of wire.

Synonym--Mutual Induction Protector.

Sheath for Transformers.

A protective sheath of copper, interposed between the primary and

secondary circuits of an alternating current transformer. It is

connected to the earth. If the primary coil loses its insulation before

it can leak to the secondary it is grounded. This protects the secondary

circuit from the high electro-motive force of the primary circuit.

Shellac.

A resin; produced as an exudation upon the branches of certain Asiatic

trees, such as the banyan (Ficus religiosa). It is due to punctures in

the bark of the trees in question, which punctures are made by the

female of the insect coccus ficus or c. lacca.

Commercial shellac contains about 90 per cent. of resinous material, the

rest is made up of wax, gluten, coloring matter and other substances.

Shellac is soluble in alcohol, and in aqueous solutions of ammonium

chloride, of borax and in strong ammonia solution. Long standing is

required in the case of the last named solvent. Dilute hydrochloric and

acetic acids dissolve it readily; nitric acid slowly; strong sulphuric

acid is without action on it. Alkalies dissolve it.

In electric work it is used as an insulator and dielectric. Its

alcoholic solution is used to varnish glass plates of influence

machines, for the coils of induction coils and similar purposes.

Resistance in ohms per centimeter cube at 28° C. (82.4 F.)--(Ayrton),

9.0E15

Specific Inductive Capacity (Wüllner),   2.95 to 3.73

The same substance in less pure forms occurs in commerce, as stick lac,

lump lac, seed lac, button lac.

Shellac Varnish.

Solution of shellac in alcohol; methylic alcohol (wood alcohol or wood

naphtha) is often used as solvent.

Dr. Muirhead recommends button lac, dissolved in absolute alcohol, and

the top layers decanted. For highest insulation he dissolves the lac in

ordinary alcohol, precipitates by dropping into water, collects the

precipitate, dries and dissolves in absolute alcohol.

Shielded. adj.

An electric measuring instrument of the galvanometer type is shielded

when it is so constructed that its indications are not seriously

affected by the presence of neighboring magnets or by fields of force.

Shielding can be effected by using a very strong permanent magnet to

produce a field within which the magnetic needle moves and which reacts

upon it, or by enclosing the instrument in a thick iron box.

482   STANDARD ELECTRICAL DICTIONARY.

S. H. M.

Symbol or abbreviation for "simple harmonic motion."

Shock, Break.

A term in electro-therapeutics; the shock received when an electric

circuit, including the patient in series, is broken or opened.

Synonym--Opening Shock.

Shock, Electric.

The effect upon the animal system of the discharge through it of

electricity with high potential difference. Pain, nervous shock, violent

muscular contortions accompany it. Of currents, an alternating current

is reputed worse than a direct current; intermediate is the pulsatory

current.

The voltage is the main element of shock, amperage has also some direct

influence.

Shock, Static.

A term in electro-therapeutics. The application of static discharges

from small condensers or Leyden jars to a patient who is insulated from

the ground with one electrode applied to the conducting surface on which

he rests, while the other, a spherical electrode, is brought near the

body so as to produce a disruptive or spark discharge.

Short Circuit.

A connection between two parts of a circuit, which connection is of low

resistance compared to the intercepted portion. The term is used also as

a verb, as "to short circuit a lamp."

Fig. 304. DIAGRAM ILLUSTRATING SHORT CIRCUIT WORKING.

Short Circuit Working.

A method of working intermittently an electro-magnet so as to avoid

sparking. It consists in providing a short circuit in parallel with the

magnetic coils. This short circuit is of very low resistance. To throw

the magnet into action the short circuit is opened; to throw it out of

action the short circuit is closed. The shunt or short circuit must be

of negligibly small resistance and inductance.

483   STANDARD ELECTRICAL DICTIONARY.

Shovel Electrodes.

Large plate electrodes used in a medical bipolar bath. (See Bath,

Bipolar.)

Shunt.

In a current circuit a connection in parallel with a portion of the

circuit. Thus in a dynamo a special winding for the field may have its

ends connected to the bushes, from which the regular external circuit

also starts. The field is then wound in shunt with the armature. In the

case of a galvanometer a resistance coil may be put in parallel with it

to prevent too much current going through the galvanometer; this

connection is a shunt.

The word is used as a noun, as "a shunt," or "a connection or apparatus

in shunt with another," and as an adjective, as "a shunt connection," or

as a verb, as "to shunt a battery."

Shunt Box.

A resistance box designed for use as a galvanometer shunt. (See Shunt,

Galvanometer.) The box contains a series of resistance coils which can

be plugged in or out as required.

Shunt, Electro-magnetic.

In telegraphy a shunt for the receiving relay consisting of the coils of

an electro-magnet. It is placed in parallel with the relay. Its poles

are permanently connected by an armature. Thus it has high

self-induction.

On opening and closing the circuit by the sending key, extra currents

are produced in the shunt. The connections are so arranged that on

making the circuit the extra current goes through the relay in the same

direction as the principal current, while on breaking the circuit the

induced current goes in the opposite direction.

Thus the extra currents accelerate the production and also the cessation

of signalling currents, tending to facilitate the operations of sending

despatches.

Shunt, Galvanometer.

A resistance placed in parallel with a galvanometer, so as to short

circuit its coils and prevent enough current passing through it to

injure it. By knowing the resistance of the shunt and of the

galvanometer coils, the proportion of current affecting the galvanometer

is known. This gives the requisite factor for calculation. (See

Multiplying Power of Shunt.)

Shunt Ratio.

The coefficient expressing the ratio existing between the current in a

shunt and in the apparatus or conductor in parallel with it. (See

Multiplying Power of/ Shunt.)

Shunt Winding.

A dynamo or motor is shunt-wound when the field magnet winding is in

shunt or in parallel with the winding of the armature.

Shuttle Current.

A current alternating in direction; an alternating current.

484   STANDARD ELECTRICAL DICTIONARY.

Side-Flash.

A bright flashing lateral discharge from a conductor conveying a current

due to a static discharge.

Sighted Position.

In an absolute electrometer (see Electrometer, Absolute) the position of

the balanced arm carrying the movable disc or plate, when the disc and

guard plate are in one plane. The cross-hair on the lever-end is then

seen midway between two stops, or some other equivalent position is

reached which is discerned by sighting through a magnifying glass or

telescope.

Silver.

A metal; one of the elements; symbol Ag.; atomic weight, 108; valency, 1;

equivalent, 108; specific gravity, 10.5. It is a conductor of electricity.

Relative resistance, annealed,   1.0

Specific Resistance, annealed, at 0° C. (32° F.)   1.504 microhms.

Resistance of a wire at 0° C. (32° F.), Annealed.   Hard Drawn.

(a) 1 foot long, weighing 1 grain,      .2190 ohms   .2389 ohms.

(b) 1 foot long, 1/1000 inch thick,    9.048   "    9.826    "

(c) 1 meter long, weighing 1 gram,      .1527  "     .1662   "

(d) 1 meter long, 1 millimeter thick,   .01916 "     .02080  "

Resistance annealed of a 1-inch cube, at 0° C. (32°F.) .5921 microhms.

Percentage increase in resistance per degree C.

(1.8 F.) at about 20° C. (68° F.), annealed,   0.377 per cent.

Electro-chemical equivalent, (Hydrogen = .0105)   .1134 mgs.

Silver Bath.

A solution of a salt of silver for deposition in the electroplating

process.

The following is a typical formula:

Water,              10.0   parts by weight.

Potassium Cyanide,   5       "        "

Metallic Silver,     2.5     "        "

The silver is first dissolved as nitrate and converted into cyanide and

added in that form, or for 2.5 parts metallic silver we may read:

Silver cyanide,   3   parts by weight.

While many other formulas have been published the above is

representative of the majority. Other solvents for the silver than

potassium cyanide have been suggested, such as sodium hyposulphite, but

the cyanide solution remains the standard.

Silver Stripping Bath.

Various baths are used to remove silver from old electroplated articles.

Their composition depends upon the base on which the metal is deposited.

Silvered iron articles are placed as anodes in a solution of 1 part

potassium cyanide in 20 parts of water. As kathode a silver anode or a

copper one lightly oiled may be used. From the latter the silver easily

rubs off. For copper articles a mixture of fuming sulphuric acid and

nitric acid (40º Beaumé) may be used. The presence of any water in this

mixture will bring about the solution of the copper. Or fuming sulphuric

acid may be heated to between 300º and 400º F., some pinches of dry

pulverized potassium nitrate may be thrown in and the articles at once

dipped. These methods effect the solution of the silver, leaving the

copper unattacked.

485   STANDARD ELECTRICAL DICTIONARY.

Simple Substitution.

A method of obtaining a resistance equal to that of a standard. The

standard is put in circuit with a galvanometer and the deflection is

noted. For the standard another wire is substituted and its length

altered until the same deflection is produced. The two resistances are

then evidently identical. The standard can be again substituted to

confirm the result.

Sine Curve.

If we imagine a point moved back and forth synchronously with a

pendulum, and if such point made a mark upon paper, it would trace the

same line over and over again. If now the paper were drawn steadily

along at right angles to the line of motion of the point, then the point

would trace upon it a line like the profile of a wave. Such line is a

sine curve. It derives its name from the following construction. Let a

straight line be drawn, and laid off in fractions, such as degrees, of

the perimeter of a circle of given diameter. Then on each division of

the line let a perpendicular be erected equal in height to the sine of

the angle of the circle corresponding to that division; then if the

extremities of such lines be united by a curve such curve will be a sine

curve.

In such a curve the abscissas are proportional to the times, while the

ordinates are proportional to the sines of angles, which angles are

themselves proportional to the times. The ordinates pass through

positive and negative values alternately, while the abscissas are always

positive.

Any number of sine curves can be constructed by varying the diameter of

the original circle, or by giving to the abscissas a value which is a

multiple of the true length of the divisions of circle. If the pendulum

method of construction were used this would be attained by giving a

greater or less velocity to the paper as drawn under the pendulum.

A species of equation for the curve is given as follows: y = sin( x )

In this x really indicates the arc whose length is x, and reference

should be made to the value of the radius of the circle from which the

curve is described. It will also be noticed that the equation only

covers the case in which the true divisions of the circle are laid off

on the line. If a multiple of such divisions are used, say n times, or

1-n times, then the equation should read

y = n sin( x ) or y = sin( x ) / n

Synonyms--Curve of Sines--Sinusoidal Curve--Harmonic Curve.

486   STANDARD ELECTRICAL DICTIONARY.

Sine Law.

The force acting on a body is directly proportional to the sine of the

angle of deflection when--

I. The controlling force is constant in magnitude and direction; and

II. The deflecting force, although variable in its direction in space,

is fixed in direction relatively to the deflecting body.

Single Fluid Theory.

A theory of electricity. Electricity, as has been said, being

conveniently treated as a fluid or fluids, the single fluid theory

attributes electrical phenomena to the presence or absence of a single

fluid. The fluid repels itself but attracts matter; an excess creates

positive, a deficiency, negative electrification; friction, contact

action or other generating cause altering the distribution creates

potential difference or electrification. The assumed direction (see

Direction) of the current and of lines of force are based on the single

fluid theory. Like the double fluid theory, q. v., it is merely a

convenience and not the expression of a truth. (See Fluid, Electric, and

Double Fluid Theory.)

Synonym--Franklin's Theory.

Single Fluid Voltaic Cell.

A galvanic couple using only a single fluid, such as the Smee or Volta

cell.

Simple Harmonic Motion.

Motion of a point or body back and forth along a line; the motion of a

pendulum, as regards its successive swings back and forth, is an example

of harmonic motion.

Sinistrotorsal. adj.

The reverse of dextrotorsal, q. v. A helix with left-handed winding, the

reverse of an ordinary screw, such as a wood-screw or corkscrew.

Skin Effect.

A current of very brief duration does not penetrate the mass of a

conductor. Alternating currents for this reason are mainly conducted by

the outer layers of a conductor. The above is sometimes called the skin

effect.

Sled.

A contact for electric cars of the conduit system. It is identical with

the plow, q.v., but is drawn after the cars instead of being pushed

along with them.

Slide Meter Bridge.

A name for a Slide Bridge one meter long. There are also slide half

meter and slide quarter meter bridges and others. (See Meter Bridge.)

S. N. Code.

Abbreviation for single needle code, the telegraphic alphabet used with

the single needle system.

Soaking-in-and-out.

A term for the phenomena of the residual electrostatic charge; the

gradual acquirement or loss by a condenser of a portion of its

electrostatic charge.

487   STANDARD ELECTRICAL DICTIONARY.

Soldering, Electric.

(a) Soldering in which the solder is melted by means of electricity;

either current incandescence or the voltaic arc may be used. It is

identical in general with electric welding. (See Welding, Electric.)

(b) The deposition by electric plating of a metal over the ends of two

conductors held in contact. This secures them as if by soldering. It is

used in connecting the carbon filament of an incandescent lamp with the

platinum wires that pass through the glass. Copper is the metal usually

deposited.

Solenoid.

The ideal solenoid is a system of circular currents of uniform

direction, equal, parallel, of equal diameter of circle, and with their

centers lying on the same straight line, which line is perpendicular to

their planes.

Fig. 305. EXPERIMENTAL SOLENOID.

The simple solenoid as constructed of wire, is a helical coil, of

uniform diameter, so as to represent a cylinder. After completing the

coil one end of the wire is bent back and carried through the centre of

the coil, bringing thus both ends out at the same end. The object of

doing this is to cause this straight return member to neutralize the

longitudinal component of the helical turns. This it does approximately

so as to cause the solenoid for its practical action to correspond with

the ideal solenoid.

Instead of carrying one end of the wire through the centre of the coil

as just described, both ends may be bent back and brought together at

the centre.

A solenoid should always have this neutralization of the longitudinal

component of the helices provided for; otherwise it is not a true

solenoid.

Solenoids are used in experiments to represent magnets and to study and

illustrate their laws. When a current goes through them they acquire

polarity, attract iron, develop lines of force and act in general like

magnets.

A solenoid is also defined as a coil of insulated wire whose length is

not small as compared with its diameter.

488   STANDARD ELECTRICAL DICTIONARY.

Sonometer, Hughes'.

A sound measurer; a modification of a portion of Hughes' induction

balance, used for testing the delicacy of the ear or for determining the

relative intensity of sounds. (See Hughes' Induction Balance.) It is the

arrangement of three coils, two mounted one at each of the ends of a

graduated bar, and the third one between them and free to slide back and

forth thereon.

Sonorescence.

The property of producing sounds under the influence of momentary light

radiations rapidly succeeding each other. It is the property utilized in

the photophone, q. v.

Fig. 306. MORSE SOUNDER.

Sounder.

In telegraphy an instrument consisting of an electromagnet with armature

attached to an oscillating bar, the range of whose movements is

restricted by adjusting screws. The armature is drawn away from the

magnet by a spring. When a current is sent through the magnet the

armature is drawn towards the poles and produces a sound as the bar

strikes a striking piece or second adjusting screw. When the current

ceases the bar and armature are drawn back, striking the first mentioned

screw with a distinct sound, the back stroke.

The sounder is used to receive Morse and analogous character messages.

The forward strokes correspond to the beginnings of the dots or dashes

of the code, the back strokes to beginnings of the intervals. The

distinction between dots and dashes is made by observing the interval

between forward and back stroke.

Various devices are used to increase the sound. Sometimes a resonance

box is used on which the sounder is mounted.

In practice sounders are generally placed on local circuits and are

actuated by relays.

489   STANDARD ELECTRICAL DICTIONARY.

Sound Reading.

The art or method of receiving telegraph messages by ear. It is now

universally used by all expert Morse operators. It can only be applied

to telegraph systems producing audible sounds; in some cases, as in

needle telegraphy, it may be quite inapplicable.

Space, Clearance.

The space between faces of the pole pieces and the surface of the

armature in a dynamo. It is really the air gap, but in calculating

dynamo dimensions the thickness of the insulated copper wire windings of

the commutator are counted in as part of the air gap, because copper is

almost the same as air in impermeability. Clearance space is a

mechanical factor; the air gap is an electric or magnetic factor.

Synonym--Inter-air Space.

Space, Crookes' Dark.

In an exhausted tube, through which an electric discharge is caused to

pass, the space surrounding the negative electrode of the tube. This

space is free from any luminous effect, and by contrast with the light

of the discharge appears dark. The vacuum may be made so high that the

dark space fills the whole space between the electrodes. It is less for

a less vacuum and varies for other factors, such as the temperature of

the negative electrode from which it originates, the kind of residual

gas present, and the quality of the spark.

Space, Faraday's Dark.

The space in an exhausted tube between the luminous glows about the two

electrodes.

Space, Interferric.

A term for the air-gap in a magnetic circuit. It is etymologically more

correct than air-gap, for the latter is often two-thirds or more filled

with the insulating material and copper wire of the armature windings.

(See Space, Clearance.)

Spark Arrester.

A screen of wire netting fitting around the carbons of an arc lamp above

the globe to prevent the escape of sparks from the carbons.

Spark Coil.

A coil for producing a spark from a source of comparatively low

electro-motive force. It consists of insulated wire wound round a core

of soft iron, best a bundle of short pieces of wire. Such a coil may be

eight inches long and three inches thick, and made of No. 18-20 copper

wire, with a core one inch in diameter. On connecting a battery

therewith and opening or closing the circuit, a spark is produced by

self-induction, q. v. It is used for lighting gas.

490   STANDARD ELECTRICAL DICTIONARY.

Spark, Duration of Electric.

Wheatstone determined the duration of the spark given by a Leyden jar as

1/24000 second. Feddersen by interposing a tube of water 9 millimeters

(.36 inch) long in its path found that it lasted 14/10000 second, and

with one 180 millimeters (7.2 inches) long, 188/10000 second. Lucas and

Cazin for a 5 millimeter (.2 inch) spark, with different numbers of

Leyden jars, found the following:

Number of jars.   Duration of Spark.

2           .000026 second

4           .000041 "

6           .000045 "

8           .000047 "

The duration increases with the striking distance, and is independent of

the diameter of the balls between which it is produced.

Spark Gap.

The space left between the ends of an electric resonator (see Resonator,

Electric) across which the spark springs. Its size may be adjustable by

a screw, something like the arrangement of screw calipers.

Sparking.

In dynamo-electric machines, the production of sparks at the commutator

between the brushes and commutator sections. The sparks are often true

voltaic arcs, and in all cases are injurious if in any quantity, wearing

out the commutator and brushes.

Sparking, Line or Points of Least.

In a dynamo or electric motor the diameter of the commutator

determining, or the points on the commutator marking the position of the

brushes where the sparking is a minimum. Field magnets powerful in

proportion to the armature are a preventative cause. The direction of

the line fixes the angle of lead to be given to the brushes.

Sparking, Resistance to.

The resistance to disruptive discharge through its substance offered by

a dielectric or insulator. It does not depend on its insulating

qualities, but on its rigidity and strength.

Spark, Length of.

The length of the spark accompanying the disruptive discharge is counted

as the distance from one electrode to the other in a straight line. It

is longer for an increased potential difference between the two

electrodes. If the gas or air between the electrodes is exhausted the

length increases, until the vacuum becomes too high, when the length

begins to decrease, and for a perfect vacuum no spark however small can

be produced. The shape of the conductor which is discharged, the

material of the electrodes, and the direction of the current are all

factors affecting the length of spark producible.

491   STANDARD ELECTRICAL DICTIONARY.

Spark Tube.

A tube used as a gauge or test to determine when the exhaustion of the

vacuum chamber or bulb of an incandescent lamp is sufficiently high.

The interior of the tube is connected with the interior of the bulb or

chamber of the lamps in process of exhaustion, and hence shares their

degree of exhaustion. From time to time connections with an induction

coil are made. When the exhaustion is carried far enough no discharge

will take place through the vacuum. As long as the tube acts like a

Geissler tube the exhaustion is not considered perfect.

Specific Heat of Electricity.

The heat absorbed or given out by a fluid in passing from one

temperature to another depends on its specific heat. In the Peltier and

the Thomson effects. q. v., the electric current acts as the producer of

a change of temperature, either an increase or decrease as the case may

be. This suggests an absorption of and giving out of heat which amount

of heat corresponding to a current of known amount is determinable, and

may be referred to any unit of quantity such as the coulomb. This or

some equivalent definite quantity of heat it has been proposed (Sir

William Thomson) to term the Specific Heat of Electricity.

Spent Acid.

Acid which has become exhausted. In a battery the acid becomes spent

from combination with zinc. It also loses its depolarizing power, if it

is a chromic acid solution or of that type, and then may be said to be

spent.

Spent Liquor.

The liquor of a plating bath which has become exhausted from use, the

metal it contained being all or partly deposited.

Sphygmograph, Electric.

An electric apparatus for recording the beat of the pulse, both as

regards its rate and strength.

Sphygmophone.

An apparatus for examination of the pulse by the microphone and

telephone.

Spiders.

Core-discs of a dynamo or motor armature are sometimes perforated with a

large central aperture, are fastened together with insulated bolts, and

the whole mass is secured to the shaft by three- or four-armed spiders.

These are like rimless wheels, the ends of their arms being secured to

the hollow cylinder constituting the armature core, and a central

aperture in their hub receiving the shaft.

492   STANDARD ELECTRICAL DICTIONARY.

Spiral.

This term is sometimes used instead of coil, as the primary spiral or

secondary spiral of an induction coil or transformer.

Spiral Winding.

The winding used on ring armatures. This may diagrammatically be

represented by a spiral carried around the ring shaped core. With two

field poles it gives two collecting points, positive and negative, with

four field poles it gives four collecting points, alternately positive

and negative.

Splice Box.

A box in which the splices in underground cables and electric lines are

contained. The splicing is generally done in the boxes with the cables

in place. They may be two-way for straight lines, or be four-way for two

side or lateral connections.

Spluttering.

A term applied to a sound sometimes produced in a voltaic arc, perhaps

caused by impure or insufficiently baked electrodes. (Elihu Thomson.)

Spring Control.

Control of or giving the restitutive force to the needle of a

galvanometer, core of a solenoid ammeter or moving part of any similar

instrument by a spring. As an example see Ammeter, Ayrton's.

Fig. 307. SPRING JACKS.

Spring Jack.

An arrangement for effecting, at one insertion of a species of plug, the

opening or breaking of a circuit and for the simultaneous connection to

the terminals formed by the breaking of two terminals of another system

or loop. Thus let a line include in its circuit two springs pressing

against each other, thereby completing the circuit. If a plug or wedge

of insulating material were inserted between the springs so as to press

them apart it would break the circuit and the whole would constitute a

spring jack cut-out. If each side of the plug had a strip of brass or

copper attached to it, and if the ends of another circuit were connected

to these strips, then the insertion of the plug would throw the new line

into the circuit of the other line.

493   STANDARD ELECTRICAL DICTIONARY.

Spring Jack Cut-out.

A cut-out, of the general construction of a spring jack, q. v., except

that a simple insulating plug or wedge is used in place of the

metal-faced wedge with its connections of the regular spring jack. The

insertion of an insulating wedge opens the circuit, which on its removal

is closed. The regular spring jack wedge will operate in the same way,

if its connections are kept open.

Spurious Voltage.

The voltage in excess of that developed by a secondary battery which is

required in the charging process. It is about .25 volt.

Square Wire.

Wire whose cross-section is a square. It has been used of iron for

building up the cores of armatures for dynamos or motors, for which it

is peculiarly suitable, and also of copper as a winding for armatures.

Staggering. adj.

When the brushes of a dynamo are set, one a little in advance of the

other on the surface of the commutator, they are said to be set

staggering. It is used to get over a break in the armature circuit.

State, Electrotonic.

A term expressing an abandoned theory. Faraday at one time proposed the

theory that a wire had to be in the electrotonic state to produce

electro-motive force by movement through an electric field. Any such

idea was ultimately abandoned by Faraday.

Static Breeze.

The electric breeze obtained by the silent discharge of high tension

electricity.

Static Electricity.

Electricity at rest or not in the current form ordinarily speaking. The

term is not very definite and at any rate only expresses a difference in

degree, not in kind. The recognition of the difference in degree has now

to a great extent also disappeared.

Station, Central.

The building or place in which are placed electrical apparatus, steam

engines and plant supplying a district with electric energy.

Station, Distant.

The place at the further end of a telegraph line, as referred to the

home station.

Station, Home.

The end of a telegraph line where the operators using the expression are

working.

494   STANDARD ELECTRICAL DICTIONARY.

Station, Transforming.

In alternating current distribution, a building or place where a number

of transformers are worked, so that low potential or secondary circuits

are distributed therefrom.

Steel.

A compound of iron with carbon. The carbon may range from a few

hundredths of one per cent. up to two per cent. For magnets, tool steel

drawn to a straw color or a little lower is good. All shaping and filing

should be done before magnetization.

Steeling.

The deposition of iron on copper plates by electrolysis. In

electrotyping a thin deposit of iron is thus given the relief plates

before printing from them. The deposit is very hard and exceedingly

thin, so that it does not interfere with the perfection of the

impression in the printing process. As the iron becomes worn it can be

dissolved off with hydrochloric acid, which does not dissolve the

copper, and a new deposit can be given it. Thus the plate may last for

an indefinite number of impressions.

The iron bath may be prepared by immersing in a solution of ammonium

chloride, two plates of iron, connected as anode and kathode in a

circuit. One plate dissolves while hydrogen is given off from the other.

The solution thus produced is used for a bath.

The hardness of the deposit, which is really pure iron, gives the name

of "steeling."

Synonym--Acierage.

St. Elmo's Fire.

Luminous static discharge effects sometimes seen on objects elevated in

the air. They are especially noticed on ships' masts. The sailors term

them corpusants (holy bodies). They resemble tongues or globes of fire.

Step-by-step Telegraphy.

A system of telegraphy in which in the receiving instrument a hand is

made to move step-by-step, with an escape movement around a dial. For

each step there is a letter and the hand is made to stop at one or the

other letter until the message is spelled out. (See Dial Telegraph.)

Step-down. adj.

A qualification applied to a converter or transformer in the alternating

current distribution, indicating that it lowers potential difference and

increases current from the secondary.

Step-up. adj.

The reverse of step-down; a qualification of a transformer or converter

indicating that it raises the potential and decreases the current in the

secondary.

Sticking.

The adherence, after the current is cut off, of the armature to the

poles of a magnet. In telegraphy it is a cause of annoyance and

obstructs the working. It may, in telegraphy, be due to too weak a

spring for drawing back the armature, or to imperfect breaking of the

contact by the despatcher's key or by the receiver's relay.

495   STANDARD ELECTRICAL DICTIONARY.

Stopping Off.

In electroplating the prevention of deposition of the plating metal on

any desired portions of the object. It is effected by varnishing the

places where no coating is desired. An article can be plated with

silver, stopped off in any desired design, and the unvarnished portions

may then be plated with gold in another bath. Various effects can be

produced by such means.

Storage Capacity.

A term for the ampere-hours of electricity, which can be taken in

current form from a storage battery.

Storage of Electricity.

Properly speaking electricity can only be stored statically or in static

condensers, such as Leyden jars. The term has been popularly applied to

the charging of secondary or storage batteries, in which there is really

no such thing as a storage of electricity, but only a decomposition and

opposite combination brought about, which leave the battery in a

condition to give a current.

Storms, Electric.

Wide-spread magnetic and electric disturbances, involving the

disturbance of the magnetic elements and other similar phenomena. (See

Magnetic Storms.)

Strain.

The condition of a body when subjected to a stress. Various consequences

may ensue from strain in the way of disturbance of electric and other

qualities of the body strained.

Stratification Tube.

A Geissler tube, q. v., for showing the stratification of the electric

discharge through a high vacuum.

The stratifications are greatly intensified by the presence of a little

vapor of turpentine, alcohol, bisulphide of carbon and other substances.

Stray Field.

In a dynamo or motor the portion of the field whose lines of force are

not cut by the armature windings.

Stray Power.

The proportion of the energy wasted in driving a dynamo, lost through

friction and other hurtful resistances.

Streamlets, Current.

A conception bearing the same relation to an electric current that lines

of force do to a field of force; elementary currents. If evenly

distributed the current is of uniform density; if unevenly distributed,

as in alternating currents, the current density varies in different

parts of the cross section of the conductor. This evenness or unevenness

may be referred to the number of streamlets per unit of area of

cross-section.

[Transcriber's note: Streamlets per unit of area is redundant with

current density.]

Stress.

Force exercised upon a solid tending to distort it, or to produce a

strain.

496   STANDARD ELECTRICAL DICTIONARY.

Stress, Dielectric.

The condition of a dielectric when maintaining a charge; its two

extremities are in opposite states of polarity, or are under permanent

potential difference. As the two opposite polarities tend to unite a

condition of stress is implied in the medium which separates them.

Stress, Electro-magnetic.

The stress produced upon transparent substances in an electro-magnetic

field of force. It is shown in the modified optical properties of glass

and similar substances placed between the poles of a strong

electro-magnet.

Stress, Electrostatic.

The stress produced upon substances in an electrostatic field of force;

the exact analogue of electro-magnetic stress, and affecting transparent

substances in the same general way.

Striae, Electric.

In Geissler tubes the light produced by the electric discharge is filled

with striae, bright bands alternating with dark spaces; these may be

termed electric striae.

Striking Distance.

The distance that separates two conductors charged with electricity of

different potential, when a spark starts between them.

Striking Solution.

In silver-plating a bath composed of a weak solution of silver

cyanide-with a large proportion of free potassium cyanide. It is used

with a strong current and a large silver anode. This gives an

instantaneous deposition of metallic silver over the surface of the

article which goes to insure a perfect coating in the silver bath

proper. After a few seconds in the striking solution, the article is at

once removed to the plating bath.

Stripping.

The removal of electroplating from an object. It may be effected in

several ways. An object whose plating is to be removed is placed in a

plating bath of the solution of the metal with which it is coated. It is

connected as the anode to the positive plate of the battery or

corresponding terminal of the generator. A kathode connected to the

other terminal being placed in the bath, the coating is dissolved by

electrolytic action. Sometimes simple treatment with acid is employed.

Different stripping baths are described under the heads of the different

metals.

S. U.

Symbol or abbreviation for Siemens' Unit of Resistance. (See Resistance,

Siemens' Unit of.)

Sub-branch.

A branch or lead of wire taken from a branch lead: a term used in

electric distribution.

Sub-main.

In electric distribution a conductor connected directly to a main; a

branch.

497   STANDARD ELECTRICAL DICTIONARY.

Subway, Electric.

A subterranean system of conduits for electric cables. As generally

constructed in this country it includes manholes, q. v., at the street

corners connected by ducts or pipes. These pipes are large enough to

hold a cable. To introduce a cable into a duct, which latter may be two

or three inches in diameter, and from two hundred to six or seven

hundred feet long, a wire or rope is first passed through the duct. This

is done by a set of short wooden rods with screws at the end so as to be

screwed together. Each rod must be shorter than the diameter of the

manhole. A rod is thrust in, another is screwed to it and thrust in, and

thus a set of rods is made to extend as far as desired. In pulling them

out a rope is attached and drawn through. This rope or a larger one is

used in drawing the cable through the duct. A windlass is employed to

draw the rope with cable attached through the ducts.

Sulphating.

In storage battery cells, the formation of a hard white basic lead

sulphate, Pb2 S05. Its formation is due to over-exhaustion of the cells.

As long as the voltage is not allowed to fall below 1.90 volts per cell

little of it forms. As it accumulates it is apt to drop off the plate

and fall to the bottom, thus weakening the plate possibly, and depriving

it of active material, and clogging up the cell. If it carries a film of

metallic lead with it, there is danger of short circuiting the cell.

The presence of some sodium sulphate in the solution is said to tend to

prevent sulphating, or to diminish it.

Sulphur Dioxide.

A compound gas, S O2; composed of

Sulphur,            32

Oxygen,             32

Molecular weight,   64

Specific gravity,    2.21.

It is a dielectric of about the same resistance as air. Its specific

inductive capacity at atmospheric pressure is: 1.0037 (Ayrton).

Synonyms--Sulphurous Acid--Sulphurous Acid Gas.

Sunstroke, Electric.

Exposure to the arc light sometimes produces the effects observed in

cases of sunstroke. It is said that, in the case of workmen at electric

furnaces, these effects are very noticeable. (See Prostration,

Electric.)

[Transcriber's note: Effects are due to ultraviolet light.]

Supersaturated. adj.

A liquid is supersaturated when it has dissolved a substance at a

temperature favorable to its solubility and its temperature has been

allowed to change, the liquid being kept free from agitation or access

of air, provided crystallization or precipitation has not taken place.

It expresses the state of a liquid when it holds in solution more than

the normal quantity of any substance soluble in it.

Surface.

A galvanic battery is arranged in surface when all the positive plates

are connected together and all the negative plates are also connected.

This makes it equivalent to one large cell, the surface of whose plates

would be equal to the aggregate surface of the plates of the battery. It

is also used as an adjective, as "a surface arrangement of battery."

498   STANDARD ELECTRICAL DICTIONARY.

Surface Density.

The relative quantity of an electric charge upon a surface.

Surface, Equipotential.

A surface over all of which the potential is the same. In a general

sense equipotential surfaces are given by planes or surfaces which cut

lines of force at right angles thereto, or which are normal to lines of

force. The conception applies to electrostatic and electro-magnetic

fields of force, and for current conductors the planes normal to the

direction of the current are equipotential surfaces.

The contour of an equipotential surface of a field of force which is

drawn or represented by delineations of its lines of force can be

obtained by drawing a line normal thereto. This line will ordinarily be

more or less curved, and will be a locus of identical potentials.

An electric equipotential surface may be described as electro-static,

electro- magnetic, or magnetic; or may be an equipotential surface of a

current conductor. Besides these there are mechanical and physical

equipotential surfaces, such as those of gravitation.

Surface Leakage.

Leakage of current from one part of an insulating material to another by

the film of moisture or dirt on the surface.

Suspension.

This term is applied to methods of supporting galvanometer needles,

balance beams, magnetic compass needles and similar objects which must

be free to rotate. (See Suspension, Bifilar--Fibre and Spring

Suspension--Fibre Suspension--Knife Edge Suspension--Pivot

Suspension--Suspension, Torsion.)

Fig. 308. DIAGRAM OF BIFILAR SUSPENSION.

Suspension, Bifilar.

Suspension by two vertical parallel fibres, as of a galvanometer needle.

The restitution force is gravity, the torsion being comparatively slight

and negligible. Leaving torsion out of account the restitution force is

(a) proportional to the distance between the threads;. (b) inversely

proportional to their length; (c) proportional to weight of the needle

or other object suspended; (d) proportional to the angle of

displacement.

499   STANDARD ELECTRICAL DICTIONARY.

Assume two masses A and B at the end of a weightless rod, suspended by

the parallel cords a A, b B. Let the rod be rotated through an angle

theta. Consider the cord a A. Its lower end is swung through the angle

theta, as referred to the center O; the cord is deflected from the

vertical by an angle psi, such that a A tang(psi)= O A 2 sin (theta/2).

The component of gravitation tending to restore A to A, acting towards A

is equal to m g tan(psi). Its moment around O is equal to (m g tan(psi))

* (O A cos(theta/2). The whole moment of the couple is 2 m g  tan(psi).

0 A. cos(theta/2) = 2 m g (O A2/ a A) 2 sin(theta/2). Cos(theta/2) =

2mgl(OA2/aA) sin(theta). The moment of the restoring force is thus

proportional to the sine of the angle of deflection, and the

oscillations of such a system are approximately simple harmonic.

(Daniell.)

If the twisting is carried so far as to cause the threads to cross and

come in contact with each other the suspension ceases to be a bifilar

suspension, but assumes the nature of a torsional suspension.

[Transcriber's note: This is the image of the first paragraph.]

Swaging, Electric.

Mechanical swaging in which the objects to be swaged are heated by an

electric current as in electric welding.

S. W. G.

Abbreviation for Standard Wire Gauge.

Fig. 309. SIMPLE SWITCH.

Switch.

A device for opening and closing an electric circuit.

A simple type is the ordinary telegrapher's switch. A bar of metal is

mounted horizontally by a pivot at one end, so as to be free to rotate

through an arc of a circle. In one position its free end rests upon a

stud of metal. One terminal of a circuit is attached to its journal, the

other to the stud. Resting on the stud it closes the circuit, in other

positions it opens the circuit.

500   STANDARD ELECTRICAL DICTIONARY.

Switch, Automatic.

A switch opened and closed by the electric current. It is used for

lighting distant incandescent lamps. It includes one or two

electro-magnets operated by two push buttons. In the usual arrangement

one button is black and the other white, for extinguishing and lighting

respectively. When the white button is pushed it causes a current to

pass through one of the electro-magnets. This attracts its armature,

thereby making a contact and throwing the lamps into the lighting

circuit. Then they remain lighted until the black button is pressed.

This excites the other magnet, which attracts its armature, breaks the

contact and extinguishes the lights.

The object of the automatic switch is to enable distant lamps to be

lighted without the necessity of carrying the electric leads or wires to

the place whence the lighting is to be done. A very small wire will

carry enough current to operate the magnets, and open circuit batteries,

such as Leclanché batteries, may be used as the source of current for

the switch, but generally the lighting current is used for the purpose.

A single magnet may do the work. When the lighting button is pressed the

magnet is excited, attracts its armature and holds it attracted, until

by pressing the black button the current is turned off from it. In this

case the lighting current is used to excite the magnet.

Switch Board.

A board or tablet to which wires are led connecting with cross bars or

other switching devices, so as to enable connections among themselves or

with other circuits to be made.

Switch, Circuit Changing.

A switch whose arm in its swing breaks one contact and swinging over

makes another. It is employed to change the connections of circuits from

one dynamo to another.

Synonyms--Changing Switch--Changing Over Switch.

Switch, Double Break.

A form of switch in which double contact pieces are provided to give a

better contact. One form consists of a hinged bar whose end swings down

between two pairs of springs. Both pairs are connected to one terminal,

and the bar to the other terminal of a circuit.

Switch, Double Pole.

A heavy switch for central station work, that connects and disconnects

two leads simultaneously.

Switch, Feeder.

A heavy switch, often of double contact type, for connecting and

disconnecting feeders from bus bars in central stations.

501   STANDARD ELECTRICAL DICTIONARY.

Switch, Knife.

A switch whose movable arm is a narrow, deep bar of copper or brass, and

which in making contact is forced in edgeways between two springs

connected to one terminal. The bar is connected to the other terminal.

Synonyms--Knife Break Switch--Knife Edge Switch.

Switch, Multiple.

A switch which in the swing of its bar connects one by one with a number

of contacts so that ultimately the end of its bar is in contact with all

at once. It is used to throw lights in and out in succession, and it

can, if the multiple contacts connect with resistances, make them

operate as a rheostat.

Switch, Pole Changing.

A switch for changing the direction of the current in a circuit.

Switch, Reversing.

A switch, often of the plug type (see Plug Switch) for changing the

direction of current passing through a galvanometer.

Switch, Snap.

A switch constructed to give a quick, sharp break. It has a spiral

spring interposed between the handle and arm. As the handle is drawn

back to open it the spring is first extended, the bar being held by the

friction of the contacts, until the spring suddenly jerks it up, thus

breaking the contact.

Switch, Storage Battery Changing.

A switch for changing storage battery connections from series to

multiple and back again.

Switch, Three Way.

A switch, so constructed that by turning its handle connection can be

made from one lead to either of two other leads, and also so that

connection can be completely cut off.

Sympathetic Vibration.

The establishment of periodic movement in one body by impulses of the

same period communicated to it from another body in motion. Thus if two

tuning forks are of the same pitch and one is sounded the other will

begin to sound by sympathy, the sound waves communicating the necessary

periodic impulses to it.

Sympathetic vibrations are utilized in harmonic telegraphy. (See

Harmonic Receiver--Telegraph, Harmonic.)

501   STANDARD ELECTRICAL DICTIONARY.

T.

Symbol of time.

Tailings.

(a) In high speed transmission of telegraph signals by the automatic

system, the definiteness of the signal marks is sometimes interfered

with by retardation. Wrong marks are thus produced called tailings.

(b) The prolongation of the current at the distant receiving station of

a telegraph line due to the discharge of the line and to self-induction.

Synonyms--Tailing--Tailing Current.

502   STANDARD ELECTRICAL DICTIONARY.

Tamidine.

Reduced nitro-cellulose. Nitro-cellulose is dissolved in a proper

solvent and is obtained by evaporation as a translucent solid mass. By

ammonium sulphide or other reagent it is reduced so as to be virtually

cellulose. It is cut into shape for filaments of incandescent lamps,

which shapes are carbonized and flashed.

Tangent Law.

In a galvanometer the tangents of the angles of deflection of the needle

are proportional to the deflecting force--

I.  When the controlling force is unaltered in absolute magnitude and

direction by the motion of the needle.

II. When the deflecting force acts at right angles always to the

controlling force.

These conditions are usually secured by having the actuating coil

through which the current passes flat and of large diameter compared to

the length of the needle; by using the uniform field of the earth as the

control; by having a short needle; by placing the coil with its plane in

the magnetic meridian.

For best proportions of tangent galvanometer coils see Bobbins.

Fig. 310. GRAPHIC CONSTRUCTION OF TANGENT SCALE.

Tangent Scale.

An arc of a circle in which the number of graduations in any arc

starting from zero are proportional to the tangent of the angle

subtended by such arc. The system is for use with tangent galvanometers.

Thus if for 45° a value of 100 is taken and marked on the scale then for

the arc 26° 33' + a value of 50 should be marked on the scale because

such are the relative values of the tangents.

Thus the scale instead of being divided into degrees is divided into

arcs of varying length, growing shorter as they are more distant from

the zero point, of such length that the first division being subtended

by a tangent of length 1, the first and second divisions added or taken

together as one arc are subtended by a tangent of length 2, and so on.

In the cut a simple method of graphically laying out a tangent scale is

shown. In it C is the centre of the arc, and H the radius running to the

zero of the instrument. From C a circle is described and on H a vertical

line tangent to the arc is erected. Taking any part of the tangent, as

the length shown ending at D, it is divided into any number of equal

parts. Radii of the circle are now drawn whose prolongations pass

through the divisions on the tangent. These radii, where they intersect

the arc of the circle, determine equal divisions of the tangent scale,

which, as is evident from the construction, are unequal angular

divisions of the arc.

503   STANDARD ELECTRICAL DICTIONARY.

Tanning, Electric.

The tanning of hides in the manufacture of leather by the aid of

electrolysis. A current of electricity is maintained through the tanning

vats in which regular tanning liquor is contained. Very extraordinary

claims are made for the saving of time in the tanning process. What is

ordinarily a process of several months, and sometimes of a year, is said

to be reduced to one occupying a few days only. The action of

electrolysis is the one relied on to explain the results.

Tapper.

The key used in single needle telegraph transmitters. It comprises two

flat springs L, E, each with a handle, normally pressed upward against

one contact bar Z, and when pressed down by the operator making contact

against a lower bar C when messages are to be transmitted. A double

tapper, such as shown, is used for each instrument.

Synonyms--Double Tapper Key--Pedal Key.

Fig. 311. TAPPER.

Target, Electric.

A target registering or indicating electrically upon an annunciator the

point of impact of each bullet.

Taste, Galvanic.

The effect produced upon the gustatory nerves by the passage of an

electric current, or by the maintenance of potential difference between

two portions of the tongue. It is very simply produced by placing a

silver coin above, and a piece of zinc below the tongue, or the reverse,

and touching their edges. A sour, peculiar taste is at once perceived.

It cannot be due to any measurable quantity of current or of

electrolytic decomposition, because the couple can do little more than

establish a potential difference. With a strong current the taste

becomes too strong for comfort, and if on a telegraph line the extra

currents produced by the signaling make the operation of tasting the

current a very unpleasant one. It is said that messages have been

received in this way, the receiver placing one terminal of the line on

his tongue, and a terminal attached to a grounded wire below it, and

then receiving the Morse characters by taste.

504   STANDARD ELECTRICAL DICTIONARY.

Teazer.

Originally a fine wire coil wound on the field magnets of a dynamo in

shunt with the regular winding to maintain the magnetism. It was

originally used in electroplating machines to prevent inversion of the

magnetism, but has since developed into a component part of the winding

of the compound dynamo. (See Dynamo, Compound.)

Tee, Lead.

A lead pipe of T shape used for connecting branches to electric cables.

The tee is soldered by wiped joints to the lead sheathings of the cable

and branches after the wires have been connected, and the junctions

coated with insulating tape or cement, or both.

It is sometimes made in two halves, and is known as a split tee.

Tel-autograph.

A telegraph for reproducing the hand-writing of the sender at the

receiving end of the line. To save time a special spelling is sometimes

used.

Teleautograph.

The special spelling used with the Tel-Autograph telegraph.

Tele-barometer, Electric.

A barometer with electric attachment for indicating or recording at a

distance the barometric readings.

Telegraph, ABC.

This term is applied to alphabet telegraphs indicating the message by

the movements of a pointer on a dial marked with the characters to be

sent. In England the Wheatstone ABC system is much employed.

Telegraph, Automatic.

A telegraph system based on the operation of the transmitting instrument

by a perforated strip of paper drawn through it. The perforations made

by an apparatus termed a perforator, are so arranged as to give

telegraphic characters of the Morse or International Code in the

transmitting instrument. (See Perforator.) Bain in the year 1846 was the

originator of the system. He punched a fillet of paper with dots and

dashes, and drew it between two terminals of the line, thus sending over

the line a corresponding series of short and long currents which were

received by his chemical receiver. (See Chemical Receiver.) The method

was not successful. Its modern development, the Wheatstone Automatic

Telegraph, is highly so. The perforated paper by its perforations

controls the reciprocating movement of two rods, which pass through each

hole in two rows, corresponding to the two rods respectively as the

holes come opposite to the ends of the rods. The rods are kept

constantly moving up and down. If unperforated paper is above them their

upward motion is limited. This gives three positions for the rods, (a)

both down, (b) one up and the other down, (c) both up. These positions

of the rods work a pole changing key by which dots, spaces, and dashes

are transmitted to the receiving instrument, which is an exceedingly

delicate ink-printer. The latter can have its speed adjusted to receive

from 200 to 450 words per minute.

505   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Dial.

A telegraph in which as receiver a dial instrument is used. A pointer or

index hand moves around a dial. The dial is marked with letters of the

alphabet. The movements of the pointer are controlled by the

transmitting operator at a distant station. He by the same actions moves

a pointer on a duplicate instrument before him and the two are

synchronized to give identical indications. Thus a message is spelled

out letter by letter on both dials simultaneously. The motions of the

index are generally produced by what is virtually a recoil escapement.

The scape wheel is carried by the axle of the index, and a pallet or

anchor is vibrated by an electro-magnet whose armature is attached to

the stem of the pallet. As the pallet is vibrated it turns the wheel and

index one tooth for each single movement. There are as many teeth in the

wheel as there are characters on the dial. The two instruments being in

duplicate and synchronized, the pallets move exactly in unison, so that

identical readings of the dials are given. The pallets may be moved by

any kind of make and break mechanism, such as an ordinary telegraph key.

The index moves by steps or jerks, so that the system is sometimes

called step-by-step telegraphy.

Fig. 312. DIAL TELEGRAPH.

In the cut the make and break transmitter is shown at v v, with its

handle and contacts g and t. This mechanism sends impulses of current by

F and Z to the receiving magnet l. This attracts and releases its

armature K from contact into the position indicated by the dotted lines.

This works the rocker n on the pin o, and actuates the double or anchor

pawl s r, which turns the pallet or scrape wheel m.

The system is dropping into disuse, being supplanted by the telephone.

Synonym--Step-by-step Telegraph.

506   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Double Needle.

A telegraph system in which the message is read by the motions of two

vertical needles on the face of the instrument in front of the receiving

operator. An identical instrument faces the transmitting operator. By

two handles, one for each hand, the needles are caused by electric

impulses to swing to right and to left so as to give a telegraphic code.

It has been generally superseded by the single needle telegraph.

Telegraph, Duplex.

A telegraph capable of transmitting simultaneously two messages over one

wire. The methods of effecting it are distinct from those of multiplex

telegraphy. This term is used as a distinction from diode multiplex

telegraphy, in which the work is done on other principles. There are two

systems of duplex telegraphy, the differential and the bridge systems.

Telegraph, Duplex Bridge.

A system of duplex telegraphy employing the principle of the Wheatstone

bridge. The other or differential system depends on equality or

difference of currents; the bridge method on equality or difference of

potentials. The cut shows the system known as Steam's Plan.

At the ends of the line wire are two cross connections like duplicate

galvanometer connections in a Wheatstone bridge, each including a

receiving relay. The rest of the connections are self-explanatory.

When A depresses his key the current splits at the point indicating the

beginning of the bridge. One portion goes through the line to B and to

earth, the other goes to earth at A through the rheostats indicated by

the corrugated lines.

On reaching B's end the current divides at the cross-connection and part

goes through the receiving relay shown in the center of that

cross-connection.

Thus if A sends to B or B to A it is without effect on the home

receiving instrument. Now suppose that both simultaneously are sending

in opposite directions. If the connections be studied it will be seen

that every movement of the transmitting key will affect the balance of

the distant or receiving end of the bridge and so its instrument will

record the signals as they are sent.

As shown in the cut the sending keys are on local circuits, and work

what are known as duplex transmitters. These are instruments which send

line signals without breaking the connection.

Fig. 313. STEARN'S PLAN OF DUPLEX BRIDGE TELEGRAPHY.

In Stearn's plan condensers are introduced as shown. By this plan

different receiving instruments can be used. The inventor once worked a

Morse instrument at one end of the line, and a Hughes' instrument at the

other end.

507   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Duplex, Differential.

A system of duplex telegraphy employing the differential action of two

exciting or magnetizing coils. The general principles are the following.

Suppose that at each of two stations, there is a magnet working as a

sounder or relay. Each magnet is differentially wound, with two coils of

opposite direction, of identical number of turns.

When the sending key at a station A is depressed two exactly equal

currents go through the magnet in opposite directions. One called the

compensation current goes to the earth at the stations. The other called

the line current goes through the line, through the line coil of the

distant station E, thereby actuating the relay or sounder armature.

The instrument of the sender A is unaffected because he is sending

opposite and equal currents through its two coils. A special resistance

is provided on the compensation circuit for keeping the currents exactly

equal in effect. Nothing the sender at A does affects his own

instrument.

Now suppose E desires to telegraph back at the same time that A is

telegraphing to his station. He works his key. This does not affect his

own instrument except by sending the equal and opposite currents through

its coils. When his key is depressed and A's key is untouched, he works

A's receiving instrument.

508   STANDARD ELECTRICAL DICTIONARY.

When A's key is depressed simultaneously with B's key, the two line

currents are in opposition and neutralize each other. This throws out

the balance in the instruments and both armatures are attracted by the

compensation currents left free to act by the neutralization of the line

currents.

Fig. 314. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM

Suppose that B is sending a dash, and it begins while A's key is raised.

The line and compensation currents in B's receiving instrument

neutralize each other and no effect is produced, while A's receiving

instrument begins to register or indicate a dash. Now suppose A starts

to send a dash while B's is half over. He depresses his key. This sends

the two opposite currents through his magnet. His line current

neutralizes B's working current so that the compensation currents in

both receiving instruments hold the armatures attracted for the two

dashes. Meanwhile A's dash ends and he releases his key. At once his

line current ceases to neutralize B's line current, his receiving

instrument is actuated now by B's line current, while B's receiving

instrument ceases to be actuated by the compensation current.

Two assumptions are made in the above description. The line currents are

assumed to be equal in strength and opposite in direction at each

station. Neither of these is necessary. The line current received at a

station is always weaker than the outgoing line current, and it is the

preponderance of the compensation current over the partly neutralized

line current that does the work. As this preponderance is very nearly

equal to the line current received from the distant station, the signals

are actuated by almost the same current, whether it is compensation or

line current.

509   STANDARD ELECTRICAL DICTIONARY.

Both line currents may coincide in direction. Then when the two keys are

depressed, a line current of double strength goes through both receiving

instruments and both work by preponderance of the double line current

over the compensation current. In other respects the operation is the

same as before described.

Fig. 315. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM.

Fig. 316. DIFFERENTIAL DUPLEX TELEGRAPH CONNECTIONS.

The cut shows a diagram of the operation of one end of the line. R and R

are resistances, E and E are earth contacts, and the two circles show

the magnet of the receiving instrument wound with two coils in

opposition. The battery and key are also shown. It also illustrates what

happens if the key of the receiver is in the intermediate position

breaking contact at both 1 and 2. The sender's line current then goes

through both coils of the receiving instrument magnet, but this time in

series, and in coincident direction. This actuates the instrument as

before. Owing to the resistance only half the normal current passes, but

this half goes through twice as many coils or turns as if the receiver's

key was in either of the other two positions.

In actual practice there are many refinements. To compensate for the

varying resistance of the line a rheostat or resistance with sliding

connection arm is connected in the compensation circuit so that the

resistance can be instantly changed. As the electro-static capacity of

the line varies sectional condensers are also connected in the

compensation circuits.

510   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Facsimile.

A telegraph for transmitting facsimiles of drawing or writing. The

methods employed involve the synchronous rotation of two metallic

cylinders, one at the transmitting end, the other at the receiving end.

On the transmitter the design is drawn with non-conducting ink. A tracer

presses upon the surface of each cylinder and a circuit is completed

through the two contacts. In operation a sheet of chemically prepared

paper is placed over the surface of the receiving cylinder. The two

cylinders are rotated in exact synchronism and the tracers are traversed

longitudinally as the cylinders rotate. Thus a number of makes and

breaks are produced by the transmitting cylinder, and on the receiving

cylinder the chemicals in the paper are decomposed, producing marks on

the paper exactly corresponding to those on the transmitting cylinder.

Synonyms--Autographic Telegraph--Pantelegraphy.

Telegraph, Harmonic Multiplex.

A telegraph utilizing sympathetic vibration for the transmission of

several messages at once over the same line. It is the invention of

Elisha Gray. The transmitting instrument comprises a series of vibrating

reeds or tuning-forks, each one of a different note, kept in vibration

each by its own electro-magnet. Each fork is in its own circuit, and all

unite with the main line so as to send over it a make and break current

containing as many notes superimposed as there are tuning forks. At the

other end of the line there are corresponding tuning forks, each with

its own magnet. Each fork at this end picks up its own note from the

makes and breaks on the main line, by the principle of sympathetic

vibration.

To each pair of operators a pair of forks of identical notes are

assigned. As many messages can be transmitted simultaneously as there

are pairs of forks or reeds.

The movements of a telegraph key in circuit with one of the transmitting

reeds sends signals of the Morse alphabet, which are picked out by the

tuning fork of identical note at the other end of the line.

511   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Hughes'.

A printing telegraph in very extensive use in continental Europe. Its

general features are as follows:

The instruments at each end of the line are identical. Each includes a

keyboard like a piano manual, with a key for each letter or character.

On each machine is a type wheel, which has the characters engraved in

relief upon its face. With the wheel a "chariot" as it is termed also

rotates. The type wheels at both stations are synchronized. When a key

is depressed, a pin is thrown up which arrests the chariot, and sends a

current to the distant station. This current causes a riband of paper to

be pressed up against the face of both type wheels so as to receive the

imprint of the character corresponding to the key. The faces of the

wheels are inked by an inking roller.

Fig. 317. ELECTRO-MAGNET OF HUGHES' PRINTING TELEGRAPH.

The most characteristic feature is the fact that the current sent by

depressing a key does not attract an armature, but releases one, which

is then pulled back by a spring. The armature is restored to its

position by the mechanical operation of the instrument. The magnet used

is a polarized electro-magnet. Coils are carried on the ends of a strong

powerful magnet. The coils are so connected that a current sent through

them by depressing a key is in opposition to the magnetism of the

permanent magnet so that it tends to release the armature, and in

practice does so. This release permits the printing mechanism to act.

The latter is driven by a descending weight, so that very slight

electric currents can actuate the instruments.

Synonym--Hughes' Type Printer.

Telegraphic Code.

(a) The telegraphic alphabet, as of the Morse System. (See Alphabet,

Telegraphic.)

(b) A code for use in transmitting messages either secretly, or

comprising several words or short sentences in one word, in order to

economize in transmission. Such codes are extensively used in commercial

cable messages.

512   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Magneto-electric.

A telegraph in which the current is produced by magneto-electric

generators. It has been applied to a considerable extent in England. The

Wheatstone ABC or dial telegraph is operated by a magneto-generator

turned by hand.

In this country the magneto-electric generator by which the calling bell

of a telephone is rung is an example. The magneto-electric key (See Key,

Magneto-electric) is for use in one kind of magneto-electric

telegraphing.

Telegraph, Morse.

A telegraph, characterized by the use of a relay, working a local

circuit, which circuit contains a sounder, or recorder for giving dot

and dash signals constituting the Morse alphabet. The signals are sent

by a telegraph key, which when depressed closes the circuit, and when

released opens it. The two underlying conceptions of the Morse Telegraph

system are the use of the dot and dash alphabet, and the use of the

local circuit, which circuit includes a receiving instrument, and is

worked by a relay, actuating a local battery. It would be difficult to

indicate any invention in telegraphy which has had such far-reaching

consequences as the one known as the Morse telegraph.

In other places the principal apparatus of the system will be found

described. The cut Fig. 318, repeated here gives the general disposition

of a Morse system. (See Circuit, Local.)

Fig. 318. DIAGRAM OF MORSE SYSTEM.

513   STANDARD ELECTRICAL DICTIONARY.

The key by which the messages are transmitted is shown in Fig. 319. M is

a base plate of brass. A is a brass lever, mounted on an arbor G carried

between adjustable set screws D. C is the anvil where contact is made by

depressing the key by the finger piece B of ebonite. E, Fl are adjusting

screws for regulating the vertical play of the lever. H is the switch

for opening or closing the circuit. It is opened for transmission, and

closed for receiving. By screws, L L, with wing nuts, K K, the whole is

screwed down to a table.

Fig. 319. MORSE TELEGRAPH KEY.

In the United States the simplest disposition of apparatus is generally

used. The main line is kept on closed circuit. In it may be included a

large number of relays at stations all along the line, each with its own

local circuit. There may be fifty of such stations. Battery is generally

placed at each end of the line. Very generally gravity batteries are

used, although dynamos now tend to supplant them in important stations.

As relays the ordinary relay is used. Its local circuit includes a

sounder and local battery. The latter is very generally of the gravity

type, but oxide of copper batteries (See Battery, Oxide of Copper) are

now being introduced. At main or central offices, the terminals of the

lines reach switch boards, where by spring-jacks and plugs, any desired

circuits can be looped into the main circuit in series therewith.

In European practise the main line is kept on open circuit. Polarized

relays are used to work the local circuits. The currents for these have

to be alternating in direction. When the line is not in use its ends are

connected to earth at both ends, leaving the battery out of circuit.

Each intermediate station has its own main, or line battery for use when

it desires to send a message. In the American system as first described,

it will be seen that the main batteries are at most two in number.

For the details of the different apparatus, the following definitions

may be consulted: Embosser, Telegraphic--Recorder, Morse--Relay--Relay

Connection--Sounder.

514   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Multiplex.

A system of telegraphy by which a number of messages can be transmitted

in both directions over a single wire. The principles underlying the

systems are the following:

Suppose that at the two extremities of a telegraph line two arms are

kept in absolute synchronous rotation. Let the arms in their rotation,

press upon as many conducting segments as there are to be transmissions

over the line. A transmitting and receiving set of instruments may be

connected to one segment at one end of the line, and another set to the

corresponding segment at the distant station. For each pair of segments

two sets can be thus connected. Then if the arm rotates so rapidly that

the contacts succeed each other rapidly enough each pair of sets of

instruments can be worked independently of the others. In practice this

rapid succession is effected by having a number of contacts made for

each pair during a single rotation of the arm or equivalent.

The multiplex system has been perfected by the use of La Cour's phonic

wheel (see Phonic Wheel), and brought into a practical success by

Patrick B. Delany, of New York.

Two phonic wheels rotate at each end of the line. They are kept in

synchronous motion by two vibrating steel reeds of exactly the same

fundamental note, and the axle of each wheel carries an arm whose end

trails over the contacts or distributor segments already spoken of. The

reeds are adjusted to vibrate at such speed that the trailer is in

contact with each segment about 1/500 second. The number of groups of

segments required for each working is determined by the retardation of

the signals owing to the static capacity of the line. To convert the

rapidly recurring impulses of current into practically a single current,

condensers are connected across the coils of the relay. One battery

serves for all the arms.

Multiplex telegraphy can effect from two to six simultaneous

transmissions over one wire. For two or four transmissions the method

only distinguishes it from duplex or quadruplex telegraphy. The terms

diode, triode, tetrode, pentode and hexode working are used to indicate

respectively the simultaneous transmission of two, three, four, five, or

six messages over one wire.

It will be seen that the multiplex process really assigns to each

transmission separate times, but divides these times into such short and

quickly recurring intervals that the work is executed as if there was

continuous contact. In no case is there the popular conception of the

sending of several messages actually simultaneously over one wire. Each

signal in reality has its own time assigned it, divided into short

periods of high frequency, and only utilizes the line when it is free.

515   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Over-house.

An English term for telegraph lines led over houses and supported on

standards on the roofs.

Telegraph Pole Brackets.

Arms for carrying insulators, which arms are attached to telegraph poles

or other support. They vary in style; sometimes they are straight bars

of wood gained into and bolted or spiked in place; sometimes they are of

iron.

Telegraph, Printing.

Various telegraphs have been invented for printing in the ordinary

alphabet the messages at the receiving end of the line.

Representative instruments of this class are used for transmitting

different market and stock reports to business offices from the

exchanges. The type faces are carried on the periphery of a printing

wheel, which is rotated like the hand of a dial telegraph, and against

whose face a paper riband is pressed whenever the proper letter comes

opposite to it. As each letter is printed the paper moves forward the

space of one letter. Spacing between words is also provided for. In the

recent instruments two lines of letters are printed on the paper one

above the other.

In England, and on the continent of Europe, printing instruments have

received considerable use for ordinary telegraphic work. Hughes' type

printer and Wheatstone's ABC telegraph meet with extensive use there for

ordinary transmission.

Telegraph, Quadruplex.

Duplex telegraphy is the sending of two messages in opposite directions

simultaneously through the same wire. Duplex telegraphy is the sending

of two messages simultaneously in the same direction. The two combined

constitute quadruplex telegraphy. [SIC]

The system was suggested by Stark of Vienna and Bosscha of Leyden in

1855; the successful problem was solved by Edison in 1874.

The principle is based on the two orders of difference in electric

currents; they may vary in strength or in direction. Thus we may have

one instrument which works with change of strength of current only, the

other with change of direction only. The two can be worked together if

the direction of the current can be altered without alteration of

strength, and if strength can be altered without alteration of

direction. Double current and single current working are so combined

that one relay works by one system of currents and another relay by the

other system. A current is constantly maintained through the line. The

relay operated by change in direction is a simple polarized relay which

works by change of direction of current. The relay operated by change in

strength is the ordinary unpolarized relay.

516   STANDARD ELECTRICAL DICTIONARY.

For the following description and the cuts illustrating it we are

indebted to Preece and Sivewright. The cut shows the arrangement of the

apparatus and connections for terminal offices.

"Sufficient table room is provided to seat four clerks. The apparatus is

arranged for the two senders to sit together in the centre, the messages

to be forwarded being placed between them. The section on the left of

the switch Q is known as the 'A' side, that on the right as the 'B' side

of the apparatus.

K1 the reversing key, reverses the direction of the current. K2 is a

simple key, known as the increment key; it is used simply to increase

the strength of the current.

Fig. 320. QUADRUPLEX TELEGRAPH CONNECTIONS.

The way in which the keys K1 and K2 combine their action is shown by

Fig. 321. E1 and E2 are the line batteries, the one having two and

one-third (2-1/3) the number of cells of the other, so that if E1 be the

electro-motive force of the smaller, that of the whole combined battery

will be 3.3 E1. The negative pole of E1 is connected to z and z1 of  K1

and the positive pole of E2 to a of K2 through a resistance coil s. A

wire, called the 'tap' wire, connects the positive pole of E1 and the

negative pole of E2 to b of K2. This wire has in it a resistance coil

r2. The springs c and c1 of Kl are connected to the lever L of K2. Now,

when both keys are at rest, the negative pole of E1 is to line through

z, and the positive pole of E1 to earth through b of K2 and c of K1; the

positive pole of E2 being insulated at a of K2.

517   STANDARD ELECTRICAL DICTIONARY.

There is thus a weak negative current flowing to line. When K1 alone is

worked, the current of E1 is reversed. When K2 is worked alone, c of K1

is transferred from b to a, and the strength of the negative current

going to line is increased through the increase of the electro-motive

force from E1 to 3.3 E1 for the whole battery is brought into play. When

K1 and K2 are depressed together, then the negative pole of E1 goes to

earth through Z1; and the positive pole of E2 to line through a of K2

and c1 of K1 and a positive current, due to the whole electro-motive

force 3.3 E1 goes to line. Hence the effect of working K1 is simply to

reverse the current, whatever its strength, while that of K2 is to

strengthen it, whatever its direction.

The resistance coil s, of 100° resistance, is called a spark coil,

because it prevents the high electro-motive force of the whole battery

from damaging the points of contact by sparking or forming an arc across

when signals are sent; and the resistance r2 is made approximately equal

to the combined resistance of E2 and the spark coil, so that the total

resistance of the circuit may not be altered by the working of the

apparatus.

Fig. 321. QUADRUPLEX TELEGRAPH.

A1 and B1 (Fig. 320) are the relays which are used to respond to the

changes in the currents sent by the keys K1 and K2 at the distant

station.

A, is a simple polarized relay wound differentially, each wire having a

resistance of 200 [omega], and so connected up as to respond to the working of

the reversing key K1 of the distant station. It acts independently of

the strength of the current, and is therefore not affected by the

working of the increment key K2. It is connected up so as to complete

the local circuit of the sounder S1 and the local battery l1 and forms

the receiving portion of the 'A' side.

B, is a non-polarized relay also wound differentially, each coil having

a resistance of 200 [omega]. It responds only to an increase in the

strength of the current, and therefore only to the working of the

increment key K2 of the distant station.

[Transcriber's note: In current usage upper case omega indicates ohms and

lower case omega denotes angular frequency, 2*PI*f.]

518   STANDARD ELECTRICAL DICTIONARY.

The relay spring is so adjusted that the armatures are not actuated by

the weak current sent from E by the key K1.

In its normal position this relay completes the circuit of the local

battery through the sounder S. This sounder S, called the uprighting

sounder, acts as a relay to a second sounder, S2, called the reading

sounder, which is worked by another local battery, l2. Of course,

normally, the armature of S is held down and that of S2 is up, but when

the tongue t moves, as it does when the increment key K2 is depressed so

as to send the whole current to line, then the current from l is

interrupted, and the circuit of l2 is completed by the rising of the

armature of S, causing the reading sounder S2 to work. This is the 'B'

side.

R is a rheostat for balancing the resistance of the line, as used in

duplex working.

C is a condenser used for compensating the static charge of the line. It

is provided with an adjustable retardation coil, R1, to prolong the

effect of the compensating current from the condenser.

G is a differential galvanometer, used for testing, and for facilitating

adjustment and balancing.

Q is a switch for putting the line to earth, either for balancing, or

for any other purpose. There is on the earth wire leading from Q a

resistance coil, r1, equalling approximately the resistance of the whole

battery, 3.3 E1, and the resistance s.

The connections shown in Fig. 321, are for an 'up' office. At a 'down'

office it is necessary to reverse the wires on the two lower terminals

of the galvanometer and the two battery wires on the reversing key K1.

The keys K1 and K2 are, for repeaters, replaced by transmitters.

The adjustment of this apparatus requires great care and great accuracy.

Its good working depends essentially on technical skill that can only be

acquired by patience and perseverance.

Faults in working generally arise from careless adjustments, dirty

contacts, loose connections, battery failures, and the ordinary line

interruptions, but there are no troubles that are beyond the reach of

ordinary skill, and it can be safely said that, within moderate

distances, wherever and whenever duplex working is practicable, then

quadruplex working is so too."

The above is a typical quadruplex bridge system. There is also a

differential system, the full description of which, in addition to what

has been given, is outside of the scope of this work.

519   STANDARD ELECTRICAL DICTIONARY.

Telegraph Repeater.

An extension of the relay system, adopted for long lines. A repeating

station comprises in general terms duplicate repeating apparatus. One

set is connected for messages in one direction, the other for messages

in the opposite direction. The general operation of a repeating set is

as follows. The signals as received actuate a relay which by its local

circuit actuates a key, which in ordinary practise would be the sounder,

but in the repeater its lever opens and closes a circuit comprising a

battery and a further section of the line.

Repeaters are placed at intervals along the line. Each repeater repeats

the signals received for the next section of line with a new battery. It

represents an operator who would receive and repeat the message, except

that it works automatically.

The Indo-European line from London to Teheran, 3,800 miles long, is

worked directly without any hand retransmission, it being carried out by

five repeaters. This gives an average of over 500 miles for each

repeater.

[Transcriber's note: … 650 miles for each repeater.]

Repeaters introduce retardation, and each repeater involves a reduction

in the rate of working. Yet in many cases they increase the speed of a

line greatly, as its speed is about equal to that of its worst section,

which may be far greater than that of the whole line in one.

Synonym--Translater.

Telegraph Signal.

In the telegraph alphabet, a dot, or dash; the signal or effect produced

by one closing of the circuit. A dash is equal in length to three dots.

The space between signals is equal to one dot; the space between letters

to three dots; and the space between words to six dots.

Telegraph, Single Needle.

A telegraph system in which the code is transmitted by the movements of

a needle shaped index which oscillates to right and left, the left hand

deflection corresponding to dots, the right hand deflection to dashes.

The instruments for sending and receiving are combined into one. The

needles are virtually the indexes of vertical galvanometers. In one form

by a tapper key (see Tapper), in another form by a key worked by a

drop-handle (the drop handle instrument), currents of opposite

directions are sent down the line. These pass through both instruments,

affecting both needles and causing them to swing to right or left, as

the operator moves his key.

As galvanometer needle or actuating needle a soft iron needle is

employed, which is polarized by the proximity of two permanent magnets.

This avoids danger of reversal of polarity from lightning, a trouble

incident to the old system.

520   STANDARD ELECTRICAL DICTIONARY.

The cut, Fig. 322, shows a single needle telegraph instrument of the

tapper form. The action of the tapper can be understood from the next

cut.

Fig. 322. SINGLE NEEDLE TELEGRAPH INSTRUMENT, DOUBLE

TAPPER FORM.

Fig. 323. DOUBLE TAPPER KEY FOR SINGLE NEEDLE TELEGRAPH.

C and Z are two strips of metal to which the positive and negative poles

of the battery are respectively connected. E and L are two metallic

springs; E is connected to earth, L is connected to the line; at rest

both press against Z. If L is depressed so as to touch C, the current

from the battery goes to the line by the key L, goes through the coils

of the distant instrument and deflects the needle to one side, and then

goes to the earth. If the key E is depressed, L retaining its normal

position, the direction of the current is reversed, for the other pole

of the battery is connected to the earth and the reverse current going

through the coils of the distant instrument deflects the galvanometer

needle to the other side.

In the drop-handle type an analogous form of commutator worked by a

single handle produces the same effects.

521   STANDARD ELECTRICAL DICTIONARY.

Telegraph, Wheatstone, A. B. C.

A magneto-electric telegraph of the dial system. An alternating current

magneto-generator is turned by hand and by depressing keys its current

is admitted to or cut off from the line and receiver's instrument. The

message is received by a dial instrument working by the escapement

motion described under Telegraph, Dial.

Telegraph, Writing.

A telegraph in which the message is received in written characters. The

transmitter includes a stylus which is held in the hand and whose point

bears against the upper end of a vertical rod. The rod is susceptible of

oscillation in all directions, having at its base a spring support

equivalent to a universal joint.

The stylus is moved about in the shape of letters. As it does this it

throws a series of resistances in and out of the circuit.

At the receiving end of the line the instrument for recording the

message includes two electro-magnets with their cores at right angles to

each other and their faces near together at the point of the angle. An

armature is supported between the faces and through it a vertical rod

carried by a spring at its bottom rises. These magnets receive current

proportional to the resistances cut in and out by the motions of the

other rod at the transmitting end of the line. These resistances are

arranged in two series at right angles to each other, one for each

magnet. Thus the movements of the transmitting stylus and rod are

repeated by the end of the rod in the receiving instrument. A species of

pen is carried at the end of the rod of the receiving instrument, which

marks the letters upon a riband of paper which is fed beneath it.

Telemanometer. Electric.

A pressure gauge with electric attachment for indicating or recording

its indications at a distance.

It is applicable to steam boilers, so as to give the steam pressure in

any desired place.

Telemeter, Electric.

An apparatus for electrically indicating or recording at a distance the

indications of any instrument such as a pressure gauge, barometer or

thermometer, or for similar work. The telemanometer applied to a boiler

comes into this class of instrument.

Telephotography.

The transmission of pictures by the electric current, the requisite

changes in the current being effected by the action of light upon

selenium. The picture is projected by a magic lantern. Its projection is

traversed by a selenium resistance through which the current passes.

This is moved systematically over its entire area, thus constituting the

transmitter, and synchronously with the motion of the selenium a contact

point at the other end of the line moves systematically over a sheet of

chemically prepared paper. The paper, which may be saturated with a

solution of potassium ferrocyanide and ammonium nitrate, is stained by

the passage of the current, and by the variation in intensity of

staining, which variation is due to variations in the current, produced

by the effects of the light upon the selenium, the picture is

reproduced.

522   STANDARD ELECTRICAL DICTIONARY.

Telepherage.

An electric transportation system, hitherto only used for the carrying

of ore, freight, etc. Its characteristic feature is that the electric

conductors, suspended from poles, supply the way on which carriages

provided with electric motors run. The motors take their current

directly from the conductors.

There are two conducting lines, running parallel with each other,

supported at the opposite ends of transverse brackets on a row of

supporting poles. At each pole the lines cross over so that right line

alternates with left, between consecutive pairs of poles.

The cars are suspended from pulleys running on one or the other of the

conductors. A train of such cars are connected and the current is taken

in near one end and leaves near the other end of the train. These

current connections are so distant, their distance being regulated by

the length of the train, that they are, for all but an instant at the

time of passing each of the poles, in connection with segments of the

line which are of opposite potential. To carry out this principle the

distance between contacts is equal to the distance between poles. Owing

to the crossing over of the lines the contacts are in connection as

described and thereby the actuating current is caused to go through the

motors.

Cars running in one direction go on the electric conductors on the one

side, those running in the other direction go on the other conductor.

A great many refinements have been introduced, but the system has been

very little used.

Telephone.

An instrument for the transmission of articulate speech by the electric

current. The current is defined as of the undulatory type. (See Current,

Undulatory.)

The cut shows what may be termed the fundamental telephone circuit. A

line wire is shown terminating in ground plates and with a telephone in

circuit at each end. The latter consists of a magnet N S with a coil of

insulated wire H surrounding one end. Facing the pole of the magnet is a

soft iron diaphragm D, held in a frame or mouthpiece T. Any change of

current in the line affects the magnetism of the magnet, causing it to

attract the diaphragm more or less. The magnet and diaphragm really

constitute a little electric motor, the diaphragm vibrating back and

forth through an exceedingly short range, for changes in the magnetic

attraction.

The principle of the reversibility of the dynamo applies here. If the

magnet is subjected to no change in magnetism, and if the diaphragm is

moved or vibrated in front of its poles, currents will be induced in the

wire bobbin which surrounds its end. If two such magnets with bobbins

and diaphragms are arranged as shown, vibrations imparted to one

diaphragm will send currents through the line which, affecting the

magnetism of the distant magnet, will cause its diaphragm to vibrate in

exact accordance with the motions of the first or motor diaphragm. In

the combination one telephone represents a dynamo, the other a motor.

If the vibrations of the diaphragm are imparted by the voice, the voice

with all its modulations will be reproduced by the telephone at the

distant end of the line.

523   STANDARD ELECTRICAL DICTIONARY.

Fig. 324. DIAGRAM OF BELL TELEPHONES

AND LINE WITH EARTH CONNECTIONS.

Fig. 325. SECTION OF BELL TELEPHONE.

The above gives the essential features of the Bell telephone. In

practice the telephone is used only as the receiver. As transmitter a

microphone is employed. To give the current a battery, generally of the

open circuit type, is used, and the current in the line is an induced or

secondary one.

The microphone which is talked to, and which is the seat of the current

variations which reproduce original sound, is termed the transmitter,

the telephone in which the sounds are produced at the distant end of the

line is termed the receiver.

Fig. 325 shows the construction of the Bell telephone in universal use

in this country as the receiver. M is a bar magnet, in a case L L. B B

is a bobbin or coil of insulated wire surrounding one end of the magnet.

D is the diaphragm of soft iron plate (ferrotype metal), and E is the

mouthpiece. The terminals of the coil B B connect with the binding

screws C C. The wire in the coil is No. 36, A. W. G., and is wound to a

resistance of about 80 ohms.

524   STANDARD ELECTRICAL DICTIONARY.

As typical transmitter the Blake instrument may be cited. It is a carbon

microphone. It is shown in section in the cut; a is the mouthpiece and e

is a diaphragm of iron plate, although other substances could be used; f

is a steel spring, with a platinum contact piece at its end. One end

bears against the diaphragm, the other against a carbon block k. The

latter is carried by a brass block p, and pressure is maintained between

these contacts by the spring g and weight of the piece c, which by

gravity tends to press all together. The current passes by way of the

spring f, carbon button k and spring g through the circuit indicated.

A battery is in circuit with these parts. If a telephone is also in

circuit, and the transmitter is spoken against, the diaphragm vibrating

affects the resistance of the carbon-platinum contact, without even

breaking the contact, and the telephone reproduces the sound. The heavy

piece of metal C acts by its inertia to prevent breaking of the contact.

The position of this piece c, which is carried by the brass plate m, is

adjusted by the screw n.

Fig. 326. SECTION OF BLAKE TRANSMITTER.

In practice the transmitter and battery are usually on a local circuit,

which includes the primary of an induction coil. The line and distant

receiving telephone are in circuit with the secondary of the induction

coil, without any battery.

Telephone, Bi-.

A pair of telephones carried at the ends of a curved bar or spring so

that they fit the head of a person using them. One telephone is held

against each ear without the use of the hands.

525   STANDARD ELECTRICAL DICTIONARY.

Telephone, Capillary.

A telephone utilizing electro-capillarity for the production of

telephonic effects. The following describes the invention of Antoine

Breguet.

The point of a glass tube, drawn out at its lower end to a capillary

opening dips vertically into a vessel. This vessel is partly filled with

mercury, over which is a layer of dilute sulphuric acid. The end of the

immersed tube dips into the acid, but does not reach the mercury. One

line contact is with mercury in the tube, the other with the mercury in

the vessel. The arrangement of tube and vessel is duplicated, giving one

set for each end of the line. On introducing a battery in the circuit

the level of the mercury is affected by electro-capillarity. The tubes

are closed by plates or diaphragms at their tops, so as to enclose a

column of air. It is evident that the pressure of this air will depend

upon the level of the mercury in the tube, and this depends on the

electro-motive force. On speaking against the diaphragm the sound waves

affect the air pressure, and consequently the level, enough to cause

potential differences which reproduce the sound in the other instrument.

Fig. 327. BREGURT'S CAPILLARY TELEPHONE.

Telephone, Carbon.

A telephone transmitter based on the use of carbon as a material whose

resistance is varied by the degree of pressure brought to bear upon it.

Undoubtedly the surface contact between the carbon and the other

conducting material has much to do with the action. Many carbon

telephones have been invented. Under Telephone the Blake transmitter is

described, which is a carbon telephone transmitter. The Edison carbon

transmitter is shown in section in the cut. E is the mouth piece and D

the diaphragm. I is a carbon disc with adjusting screw V. A platinum

plate B B, with ivory button b, is attached to the upper surface of the

carbon disc. C C is an insulating ring. The wire connections shown bring

the disc into circuit. It is connected like a Blake transmitter. It is

now but little used.

Fig. 328. SECTION OF EDISON CARBON TRANSMITTER.

526   STANDARD ELECTRICAL DICTIONARY.

Telephone, Chemical.

A telephone utilizing chemical or electrolytic action in transmitting or

receiving. The electro-motograph is an example of a chemical receiver.

(See Electro-motograph.)

Telephone, Electrostatic.

A telephone utilizing electrostatic disturbances for reproduction of the

voice. In the cut D and C are highly charged electrophori. The

diaphragms A and B when spoken to affect the potential of the

electrophorus so as to produce current variations which will reproduce

the sound. Dolbear and others have invented other forms of transmitters

based on electrostatic action. Receivers have also been constructed. A

simple condenser may be made to reproduce sound by being connected with

a powerful telephone current.

Fig. 329. DIAGRAM OF EDISON'S ELECTROSTATIC TELEPHONE.

Telephone Induction Coil.

The induction coil used in telephone circuits for inducing current on

the main line. It is simply a small coil wound with two separate

circuits of insulated wire. In the Edison telephone the primary coil, in

circuit with the transmitter, is of No. 18 to 24 wire and of 3 to 4 ohms

resistance. The secondary in circuit with the line and receiving

instrument is of No. 36 wire and of 250 ohms resistance. The Bell

telephone induction coil has its primary of No. 18 to 24 wire wound to a

resistance of 1/2 ohm, and its secondary of No. 36 wire, and of 80 ohms

resistance.

527   STANDARD ELECTRICAL DICTIONARY.

Telephone, Reaction.

A form of telephone containing two coils of insulated wire, one of which

is mounted on the disc, and the other on the magnet pole in the usual

way. These coils react upon each other so as to strengthen the effect.

Telephone, Thermo-electric.

A telephone transmitter including a thermo-electric battery, placed in

circuit with the line. A plate of vulcanite faces it. When the sound

waves strike the vulcanite they move it backward and forward. These

movements, owing to the elasticity of the vulcanite, produce minute

changes of temperature in it, which affecting the thermo-electric pile

produce in the circuit currents, which passing through a Bell telephone

cause it to speak. This type of instrument has never been adopted in

practice.

Telephote.

An apparatus for transmitting pictures electrically, the properties of

selenium being utilized for the purpose.

Synonym--Pherope.

Teleseme.

An annunciator, displaying on a dial the object wanted by the person

using it. It is employed to transmit messages from rooms in a hotel to

the office, or for similar functions.

Tele-thermometer.

A thermometer with electric attachment for indicating or recording its

indications at a distance.

Tempering, Electric.

A process of tempering metals by electrically produced heat. The article

is made part of an electric circuit. The current passing through it

heats it, thereby tempering it. For wire the process can be made

continuous. The wire is fed from one roll to another, and if required

one roll may be immersed in a liquid bath or the wire between the rolls

may be led therein. The current is brought to one roll and goes through

the wire to the other. As it does this the wire is constantly fed from

one roll to another. The bath may be used as described to cool it after

the heating. The amount of heating may be regulated by the rate of

motion of the wire.

528   STANDARD ELECTRICAL DICTIONARY.

Ten, Powers of.

This adjunct to calculations has become almost indispensable in working

with units of the C. G. S. system. It consists in using some power of 10

as a multiplier which may be called the factor. The number multiplied

may be called the characteristic. The following are the general

principles.

The power of 10 is shown by an exponent which indicates the number of

ciphers in the multiplier. Thus 10^2 indicates 100; 10^3 indicates 1,000

and so on.

The exponent, if positive, denotes an integral number, as shown in the

preceding paragraph. The exponent, if negative, denotes the reciprocal

of the indicated power of 10. Thus 10^-2 indicates 1/100; 10^-3 indicates

1/1000 and so on.

The compound numbers based on these are reduced by multiplication or

division to simple expressions. Thus: 3.14 X 10^7 = 3.14 X 10,000,000 =

31,400,000. 3.14 X 10^-7 = 3.14/10,000,000 or 314/1000000000. Regard must

be paid to the decimal point as is done here.

To add two or more expressions in this notation if the exponents of the

factors are alike in all respects, add the characteristics and preserve

the same factor. Thus:

(51X 10^6) + (54 X 10^6) = 105 X 10^6.

(9.1 X 10^-9) + (8.7 X 10^-9) = 17.8 X 10^-9.

To subtract one such expression from another, subtract the

characteristics and preserve the same factor. Thus:

(54 X 10^6) - (51 X 10^6) = 3 X 10^6.

If the factors have different exponents of the same sign the factor or

factors of larger exponent must be reduced to the smaller exponent, by

factoring. The characteristic of the expression thus treated is

multiplied by the odd factor. This gives a new expression whose

characteristic is added to the other, and the factor of smaller exponent

is preserved for both,

Thus:

(5 X 10^7) + (5 X10^9) = (5 X 10^7) + (5 X 100 X 10^7) = 505 X 10^7.

The same applies to subtraction. Thus:

(5 X 10^9) - (5 X 10^7) = (5 X 100 X 10^7) - (5 X 10^7) = 495 X 10^7.

If the factors differ in sign, it is generally best to leave the

addition or subtraction to be simply expressed. However, by following

the above rule, it can be done. Thus:

Add

5 X 10^-2 and 5 X 10^3.

5 X 10^3 = 5 X 10^5 X 10^-2

(5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2

This may be reduced to a fraction 500000/100 = 5000.05.

To multiply add the exponents of the factors, for the new factor, and

multiply the characteristics for a new characteristic. The exponents

must be added algebraically; that is, if of different signs the

numerically smaller one is subtracted from the other one, and its sign

is given the new exponent.

Thus;

(25 X 10^6) X (9 X 10^8) = 225 X 10^14.

(29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1

(9 X 10^8) X (98 X 10^2) = 882 X 10^1

529    STANDARD ELECTRICAL DICTIONARY.

To divide, subtract (algebraically) the exponent of the divisor from

that of the dividend for the exponent of the new factor, and divide the

characteristics one by the other for the new characteristic. Algebraic

subtraction is effected by changing the sign of the subtrahend,

subtracting the numerically smaller number from the larger, and giving

the result the sign of the larger number.

(Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2.)

Thus;

(25 X 10^6) / (5 X 10^8) = 5 X 10^-2

(28 X 10^-8) / (5 X 10^3) = 5.6 X 10^-11

[Transcriber's note: I have replaced ordinary exponential notation by

the more compact and simpler "programming" representation. The last two

example would be:

25E6 / 5E8  = 5E-2

28E-8 / 5E3 = 5.6E-11

]

Tension.

Electro-motive force or potential difference in a current system is

often thus termed. It is to be distinguished from intensity or current

strength, which word it too greatly resembles.

Tension, Electric.

(a) The condition an electrified body is brought into by

electrification, when each molecule repels its neighbor. The condition

is described as one of self-repulsion.

(b) The voltage or potential difference of a circuit is also thus

termed.

Terminal.

The end of any open electric circuit, or of any electric apparatus; as

the terminals of a circuit, dynamo, or battery.

Terminal Pole.

In telegraph line construction the last pole of a series; one beyond

which the line is not carried. Such pole, as the pull of the wires is

all in one direction, requires special staying or support. The regular

line poles are free from this strain, as the wire pulls in both

directions.

Tetanus, Acoustic.

A term in electro-therapeutics. An effect produced on a nerve by very

rapidly alternating induced currents. The currents are produced by an

induction coil with a vibrator giving a musical note. This is a species

of gauge of proper frequency of alternations.

Theatrophone.

An apparatus worked by automatic paying machinery by which a telephone

connection is made with a theatre or opera by the deposition of a coin

in a slot.

Therm.

A unit of heat. It has been proposed by the British Association and

amounts to a redefinition of the smaller calorie. It is the amount of

heat required to raise the temperature of one gram of water one degree

centigrade, starting at the temperature of maximum density of water.

530   STANDARD ELECTRICAL DICTIONARY.

Thermaesthesiometer.

An electro-therapeutic instrument for testing the sensitiveness of the

surface of the body to changes of temperature. Vessels of mercury are

provided with thermometers to indicate their temperature. One vessel is

surrounded by an electric conductor wound in a number of turns. The

temperature is raised by passing a current through this. By successive

applications of the vessels to the same spot upon the skin the power of

differentiating temperatures is determined.

Thermo Call.

(a) An electric alarm or call bell operated by thermo-electric currents.

It may serve as a fire alarm or heat indicator, always bearing in mind

the fact that differential heat is the requisite in a thermo-electric

couple.

(b) See Thermo-electric Call.

Thermo-chemical Battery.

A voltaic battery in which the electro-motive force is generated by

chemical action induced by heat.

The chemical used generally is sodium nitrate or potassium nitrate. The

positive plate is carbon. On heating the battery the nitrate attacks the

carbon, burning it and produces potential difference. For negative plate

some metal unattacked by the nitrate may be employed.

Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY.

Thermo-electric Battery or Pile.

A number of thermo-electric couples q. v., connected generally in

series.

In Nobili's pile the metals are bismuth and antimony; paper bands

covered with varnish are used to insulate where required. In Becquerel's

pile copper sulphide (artificial) and German silver, (90 copper, 10

nickel) are the two elements. The artificial copper sulphide is made

into slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about).

Water is used to keep one set of junctions cool, and gas flames to heat

the other set. In Fig. 331, c, d represent the binding screws. The

couples are mounted on a vertical standard, with adjusting socket and

screw B, so that its lower end can be immersed in cold water, or raised

therefrom as desired.

531   STANDARD ELECTRICAL DICTIONARY.

FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES.

Fig. 332 shows one couple of the battery. S is artificial antimony

sulphide; M is German silver; m is a protecting plate of German silver

to save the sulphide from wasting in the flame.

Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES.

Clamond's pile has been used in practical work. The negative element is

an alloy of antimony, 2 parts, zinc, 1 part. The positive element is tin

plate. Mica in some parts, and a paste of soluble glass and asbestus in

other parts are used as insulators. They are built up so as to form a

cylinder within which the fire is maintained. The air is relied on to

keep the outer junctions cool. The temperature does not exceed 200° C.

(392° F.)

Sixty such elements have an electro-motive force of 300 volts and an

internal resistance of 1.5 ohms. Such a battery requires the consumption

of three cubic feet of gas per hour. (See Currents, Thermo-electric. )

532   STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Call.

A thermostat arranged to ring a bell or to give some indication when the

temperature rises or falls beyond certain points. It may be a compound

bar of brass and steel fixed at one end and free for the rest of its

length. Its end comes between two adjustable contacts. As the

temperature rises it bends one way (away from the brass side) and, if

hot enough, touching a contact gives one signal. If the temperature

falls it curves the other way, and if cold enough touches the other

contact, giving another signal. (See Thermostat, Electric.)

Thermo-electric Couple.

If two dissimilar conductors form adjacent parts of a closed circuit,

and their junction is at a different temperature than that of the rest

of the circuit, a current will result. Such pair of conductors are

called a thermo-electric couple. They may be joined in series so as to

produce considerable electro-motive force. (See Thermo-electricity and

other titles in thermo-electricity.)

The efficiency of a thermo-electric couple according to the second law

of thermo-dynamics is necessarily low--not over 10 per cent.

Thermo-electric Diagram.

A diagram indicating the change in potential difference for a fixed

difference of temperature between different metals at different

temperatures. It is laid out with rectangular co-ordinates. On one axis

temperatures are laid off, generally on the axis of abscissas. On the

other axis potential differences are marked. Different lines are then

drawn, one for each metal, which show the potential difference, say for

one degree centigrade difference of temperature between their junctions,

produced at the different temperatures marked on the axis of abscissas.

Fig. 333. THERMO-ELECTRIC DIAGRAM,

GIVING POTENTIAL DIFFERENCE IN C. G. S. UNITS.

Thus taking copper and iron we find at the temperature 0° C. (32° F.) a

difference of one degree C. (1.8° F.) in their junctions will produce a

potential difference of 15.98 micro volts, while at 274.5° C. (526.1°

F.) the lines cross, and zero difference of potential is indicated.

Taking the lead line on the same diagram it crosses the iron line a

little above 350° C. (662° F.), indicating that if one junction is

heated slightly above and the other is heated slightly below this

temperature no potential difference will be produced. Lead and copper

lines, on the other hand, diverge more and more as the temperature

rises.

533   STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Inversion.

The thermo-electric relations of two conductors vary at different

temperatures. Sometimes at a definite point they have no electro-motive

force and after passing this point the positive plate becomes a negative

one and vice versa. This is inversion, or reversal. (See Thermo-electric

Diagram.)

Synonym-- Thermo-electric Reversal.

Thermo-electricity.

Electric energy, electro-motive force or electrification produced from

heat energy by direct conversion. It is generally produced in a circuit

composed of two electric conductors of unlike material, which circuit

must possess at least two junctions of the unlike substances. By heating

one of these to a higher temperature than that of the other, or by

maintaining one junction at a different temperature from that of the

other a potential difference is created accompanied by an electric

current.

In many cases differential application of heat to an identical material

will develop potential difference. This effect, the converse of the

Thomson effect, is not used to produce currents, as in a closed circuit

the potential differences due to differential heating would neutralize

each other.

Thermo-electric Junction.

A junction between two dissimilar conductors, which when heated or

cooled so as to establish a differential temperature, as referred to the

temperature of the other junction, produces potential difference and an

electric current.

Thermo-electric Pile, Differential.

A thermo-electric pile arranged to have opposite faces subjected to

different sources of heat to determine the identity or difference of

temperature of the two sources of heat. It corresponds in use to a

differential air thermometer.

Thermo-electric Power.

The coefficient which, multiplying the difference of temperature of the

ends of a thermo-electric couple, gives the potential difference,

expressed in micro-volts. It has always to be assigned to a mean or

average temperature of the junctions, because the potential difference

due to a fixed difference of temperature between two metals varies with

the average temperature of the two junctions. (See Thermo-electric

Diagram.)

For bismuth and antimony at 19.5° C. (67.1° F.) it is 103 microvolts per

degree Centigrade (1.8° F.). This means that if one junction is heated

to 19° C. and the other to 20° C. (66.2° F. and 68.0° F.) a potential

difference of 103 micro-volts will be produced.

The potential difference is approximately proportional to the difference

of temperature of the two junctions if such difference is small. Hence

for large differences of potential the thermo-electric power coefficient

does not apply.

As a differential function it is thus deduced by Sir William Thomson,

for expressing the E. M. F. in a thermo-electric circuit: If a circuit

is formed of two metals with the junctions at indefinitely near

temperatures, t and t + dt, and dE is the E. M. F. of the circuit, then

the differential coefficient dE/dt is called the thermo-electric power

of the two metals for the temperature t.

534   STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Series.

The arrangement of possible thermoelectric elements, q. v., in a table

in the order of their relative polarity. Bismuth and antimony form a

couple in which when their junction is heated the bismuth acts as the

positive or negatively charged element and antimony as the negative or

positively charged. Between these two extremes according to Seebeck the

series runs as follows:

Antimony,   Silver,      Copper,

Arsenic,    Gold,        Platinum,

Iron,       Molybdenum,  Palladium,

Steel,      Tin,         Cobalt,

Cadmium,    Lead,        Nickel,

Tungsten,   Mercury,     Bismuth.

Zinc,       Manganese,

A differential temperature of 1° C. (1.8° F.) in a bismuth-antimony

couple maintains a potential difference of 103 micro-volts.

Matthiessen gives a different series; it is arranged in two columns; the

first column has positive coefficients annexed the second has negative.

On subtracting the greater one from the lesser, which, if the two

elements are in different columns, of course amounts to adding after

changing the negative sign, the relative potential difference due to the

combination is obtained.

+                         -

Bismuth    25      Gas Coke          0.1

Cobalt      9      Zinc              0.2

Potassium   5.5    Cadmium           0.3

Nickel      5      Strontium         2.0

Sodium      3.     Arsenic           3.8

Lead        1.03   Iron              5.2

Tin         1      Red Phosphorous   9.6

Copper      1      Antimony          9.8

Silver      1      Tellurium       179.9

Platinum    0.7    Selenium        290

Thus the relative E. M. F. of a bismuth-nickel couple, as both are in

the + column, would be 25 - 5 = 20; that of a cobalt-iron couple, one

being in the + column the other in the - column, would be 9 + 5.2 =

14.2. Alloys are not always intermediate to their constituents, and

small amounts of impurities affect the results largely. This may account

for the discrepancies of different observers. Other compounds could be

introduced into the series.

Artificial silver sulphide has been used by Becquerel in a

thermo-electric battery.

535   STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Thermometer.

A species of differential thermometer. It consists of two

thermo-electric junctions connected in opposition with a galvanometer in

the circuit. Any inequality of temperature in the two ends or junctions

produces a current shown by the galvanometer. It may be used to

determine the temperature of a distant place, one of the junctions being

located there and the other being under control of the operator. If the

latter junction is heated until no current is produced its temperature

is evidently equal to that of the distant couple or junction. The

heating may be done with hot water or mercury, or other melted metal.

The temperature of the water, or other substance, gives the temperature

of the distant place.

Thermolysis.

Decomposition by heat; dissociation. All compound bodies are

decomposable by heat if it is intense enough. Hence at very elevated

temperatures there can be no combustion.

Synonym--Dissociation.

Thermometer.

An instrument for indicating the intensity of heat. Three scales of

degrees of heat are used in practise, the Fahrenheit, Réamur, and

Centigrade, each of which is described under its own title. (See Zero,

Thermometric-Zero, Absolute.) The ordinary thermometer depends on the

expansion of mercury; in some cases alcohol is used. Besides these the

compound bar principle as used in the thermostat (see Thermostat,

Electric) is employed.

Thermometer, Electric.

(a) A thermometer whose indications are due to the change of resistance

in conductors with change of temperature. Two exactly similar resistance

coils maybe electrically balanced against each other. On exposing one to

a source of heat, its resistance will change and it will disturb the

balance. The balance is restored by heating the other coil in a vessel

of water when the temperature of the water gives the temperature of both

coils. The coils are enclosed in water-tight metallic cases.

Synonym--Electric Resistance Thermometer.

(b) A differential thermometer may be made by connecting with a pair of

conductors, two thermo-electric couples in opposition to each other, and

including a galvanometer in series. On heating the junction of one

couple more than that of the other a current at once goes through the

galvanometer.

(c) (See Thermometer, Kinnersley's.)

Synonym--Thermo-electrometer.

536   STANDARD ELECTRICAL DICTIONARY.

Fig. 334. KINNERSLEY'S THERMOMETER.

Thermometer, Kinnersley's.

A thermo-electrometer. A large glass tube is mounted on a standard and

communicates with a small tube parallel to it. Water is poured in so as

to rise in the small tube. Two wires terminating in bulbs enter the

large tube by its top and bottom. The upper wire can be adjusted by

moving up and down through a stuffing box. On discharging a Leyden jar

through the space between the knobs on the two wires the water for a

moment rises in the small tube. There is little or no accuracy in the

instrument. It is allied to the electric mortar (see Mortar, Electric)

as a demonstrative apparatus.

Synonyms--Electric Thermometer--Thermo-electrometer.

Thermo-multiplier.

A thermo-electric battery including a number of couples. The term is

generally applied to a small battery with its similar junctions facing

in one direction and used for repeating Melloni's experiments on radiant

energy, or so-called radiant heat.

537   STANDARD ELECTRICAL DICTIONARY.

Thermophone.

An apparatus for reproducing sounds telephonically by the agency of

heat; a receiving telephone actuated by heat. Thus a wire may be

attached to the centre of a diaphragm and kept in tension therefrom, and

the transmitting telephone current may be caused to pass through it. The

wire changes in temperature and consequently in length with the pulses

of current going through it and vibrates the diaphragm, reproducing the

sound. It is to be distinguished from the thermo-electric telephone

which involves the action of potential difference produced by

thermo-electric action.

Thermostat, Electric.

A thermostat or apparatus, similar to a thermometer in some cases, for

closing an electric circuit when heated. It is used in connection with

automatic fire alarms to give warning of fire. For this use a

temperature of 52° C. (125° F.) is an approved one for setting one at,

to complete the circuit. It is also applied to regulation of

temperature, as in incubators.

(a) One kind of thermostat consists of a compound bar wound into a

spiral and fastened at one end, to which a terminal of a circuit is

connected. The bar may be made of two strips of brass and iron riveted

together, and wound into a spiral. When such a bar is submitted to

changes of temperature it bends in different directions, because brass

expands and contracts more under changes of temperature than does iron.

A contact point, to which the other terminal is connected, is arranged

to make contact with the spiral at any desired degree of temperature,

thus closing an electric circuit and ringing a bell, opening or closing

a damper, or doing anything else to notify an attendant or to directly

change the temperature.

If the brass forms the outside of the spiral, increase of temperature

makes the bending of the spiral bring the coils still closer. If the

brass forms the inside, increase of temperature makes the spiral tend to

become less close. As shown in the cut, the brass should lie along the

inside of the spiral.

Sometimes a straight compound bar is used, one of whose ends is fastened

and the other is free. As the temperature changes such a bar curves more

or less, its free end moving to and fro. Two contact screws are

provided, one on each side of its free end. If the temperature falls it

makes contact with one of these; if the temperature rises, it makes

contact with the other. Thus it may close one of two circuits, one for a

fall and the other for a rise in temperature.

It is well to introduce a third bar between the brass and iron ones,

made of some material of intermediate coefficient of expansion.

(b) Another kind of thermostat comprises a vessel of air or other gas,

which, expanding by heat, actuates a piston or other device and closes

an electric circuit. Synonym--Electro-pneumatic Thermostat.

(c) Another form utilizes the expansion of mercury. The mercury is made

part of an open electric circuit. As it expands it comes in contact with

the other terminal of the circuit, thus completing it, when the current

gives an alarm or does as is provided for in the apparatus employed.

Thermostats may be worked on either open or closed circuits; normally

the circuit may be open as described and may close on rise of

temperature, or it may be normally closed and open as the temperature

rises.

Fig. 335. ELECTRIC THERMOSTAT.

538   STANDARD ELECTRICAL DICTIONARY.

Thomson Effect.

In an unequally heated conductor the differential heating is either

increased as in iron, or diminished as in copper by a current. In lead

the phenomenon does not occur. It is termed the Thomson effect. It is

intimately related to the Peltier effect.

In a thermo-electric couple a heated junction is the source of

electro-motive force, if heated more than other parts of the circuit.

The current in a copper-iron junction flows from the copper to the iron

across the heated junction. A hot section of an iron conductor next to a

cold section of the same is a source of thermoelectricity, in the sense

that the hot section is negative to the colder. A current passing from

the hot to the cold iron travels against rising potentials, and cools

the iron in the cooler parts. As it passes to the hotter parts it

travels against falling potentials and hence heats the iron in these

parts. In this way a current intensifies differential heating in an iron

conductor.

In copper the reverse obtains. In it the thermo-electric relations of

hot and cold copper are the reverse of those of iron, and a current

tends to bring all parts of a differentially heated copper conductor to

an identical temperature.

As a current travels in iron from hot to cold it absorbs heat; in copper

traveling from cold to hot it absorbs heat.

The convection of heat by a current of electricity in unequally heated

iron is negative, for it is opposed to that convection of heat which

would be brought about by the flow of water through an unequally heated

tube. In copper, on the other hand, the electric convection of heat is

positive. (Daniell.)

The above effects of the electric current upon an unequally heated

conductor are termed the Thomson effects. In iron, at low red heat, they

are reversed and are probably again reversed at higher temperatures.

539   STANDARD ELECTRICAL DICTIONARY.

Three Wire System.

A system of distribution of electric current for multiple arc or

constant potential service. It is the invention of Thomas A. Edison.

It includes three main wires which start from the central station or

generating plant, and ramify with corresponding reduction in size,

everywhere through the district or building to be lighted. As ordinarily

carried out when dynamos are used, the dynamos are arranged in groups of

two. One lateral lead starts from the negative binding post of one

dynamo. The positive terminal of this dynamo connects to the negative of

the other. Between the two dynamos the central or neutral lead is

connected. The other lateral lead starts from the positive binding post

of the second dynamo.

The lamps or other appliances are calculated for the potential

difference of a single dynamo. They are arranged between the neutral

wire and the laterals, giving as even a disposition as possible to the

two laterals.

Fig. 336. DIAGRAM OF THREE WIRE SYSTEM

SHOWING NEUTRAL WIRE.

If evenly arranged and all burning or using current, no current goes

through the neutral wire. If all the lamps situated on one lateral are

on open circuit all the current goes through the neutral wire. In other

cases the neutral wire receives the excess of current only.

The advantages of the system are that it uses smaller wire than the two

wire system for lamps of the same voltage. If lamps of double the

voltage were used the two wire system would be most economical.

540   STANDARD ELECTRICAL DICTIONARY.

Four wire and five wire systems have been more or less used, based on

identical considerations, and involving in each case the coupling of

three or of four dynamos respectively, or else employing a dynamo with

special armature connections to give the requisite three-fold or

four-fold division of total potential. In the five wire system the total

voltage is four times that of a single lamp, the lamps are arranged four

in series across the leads and the central wire is the only one that can

be considered a neutral wire. When lamps are burning entirely from three

side-leads they constitute a sort of three wire system by themselves,

and their central wire may for the time be a neutral wire.

In some of the three wire mains, especially in the larger sizes, the

neutral wire is made of much smaller section than that of a lateral

conductor, because in extensive districts it is practically impossible

that the current should be concentrated in the neutral wire.

Throw.

In a galvanometer the instantaneous deflection of the needle when the

contact or closing of the circuit is instantaneous, or when the

discharge is completed before the needle begins to move. The throw of

the needle is the datum sought when the ballistic galvanometer is used.

Synonym--Elongation.

Throw-back Indicator.

A drop annunciator, whose shutter or drop is electrically replaced.

Thrust-bearings.

Bearings to support the end-thrust or push of a shaft. In disc armatures

where the field-magnets attract the armatures in the direction of their

axis of rotation, thrust-bearings have to be provided. In ordinary

cylinder or drum armatures end-thrust is not applied, as a little end

motion to and fro is considered advantageous as causing more even wear

of the commutator surface.

Thunder.

The violent report which, as we hear it, succeeds the lightning flash in

stormy weather. It is really produced simultaneously with the lightning

and is supposed to arise from disturbance of the air by the discharge.

The rolling noise has been attributed to successive reflections between

clouds and earth, and to series of discharges reaching the ear from

different distances and through air of varying density. The subject is

obscure. By timing the interval from lightning flash to the report of

the thunder an approximate estimate of the distance of the seat of

discharge can be made. The first sound of the thunder should be timed.

An almost concurrence of thunder and lightning indicates immediate

proximity of the discharge.

[Transcriber's note: The speed of sound at sea level is about 5 seconds

per mile.]

Ticker.

A colloquial name for a stock or market report automatic printing

telegraph, which prints its quotations and messages on a long tape.

541   STANDARD ELECTRICAL DICTIONARY.

Time Constant.

(a) When current is first turned into a circuit of considerable

self-induction it is resisted rather by the inductance than by the

resistance. It is governed by the ratio of resistance and self-induction

and this factor represents the time which it takes for the current to

reach a definite fraction of its final strength. This fraction is

(2.7183 - 1)/2.7183  or 0.63. 2.7183 is the base of the Napierian system

of logarithms. Thus if in any circuit we divide the inductance in

henries by the resistance in ohms, the ratio gives the time-constant of

the circuit, or it expresses the time which it will take for the current

to reach 0.63 of its final value.

(b) In a static condenser the time required for the charge to fall to

1/2.7183th part of its original value.

Time Cut-outs.

Cut-outs which automatically cut storage batteries out of the charging

circuit when they are sufficiently charged.

Time-fall.

In a secondary battery the decrease with use of electromotive force

maintained by a primary or secondary battery. As the battery becomes

spent its voltage falls. The conditions of the fall are represented by

its discharging curve. (See Curve, Discharging.)

Time-reaction.

A term in electro-therapeutics; the period of time occupied in the

passage of the effects of an electric current from nerve to muscle.

Time-rise.

In a secondary battery the increase of electromotive force produced

during the charging process. Its rate and conditions are graphically

shown in the charging curve. (See Curve, Charging.)

Tin.

A metal; one of the elements; symbol, Sn; atomic weight, 117.8;

equivalent, 58.9 and 29.5; valency, 2 and 4; specific gravity, 7.3.

It is a conductor of electricity.

Relative resistance, compressed, (Silver = 1)   8.784

Specific resistance at 0° C. (32° F.),   13.21   microhms.

Resistance of a wire at 0° C. (32° F.),

(a) 1 foot long, weighing 1 grain,       1.380   ohms.

(b) 1 foot long, 1/1000 inch thick,     79.47     "

(c) 1 meter long, weighing 1 gram,        .9632   "

(d) 1 meter long, 1 millimeter thick,     .1682   "

Resistance of a 1 inch cube at 0° C. (32° F.),   5.202   microhms.

Percentage of variation in resistance

per degree C. (1.8° F.), at about 20° C. (68° F.),  .0365

Electro-chemical equivalent (hydrogen = .0105),   .619   mgs.

.310   "

542   STANDARD ELECTRICAL DICTIONARY.

Tinnitus, Telephone.

A nervous affection of the ear, of the order of professional cramp; it

is attributed to too much use of the telephone.

Tin Sounders.

A recent addition to the single needle telegraph. (See Telegraph, Single

Needle.) It consists of small tin plates, cut and bent, and so fitted in

pairs to the instrument, that the needle as deflected strikes one or the

other on its right and left hand movements. The sounders can be made to

give sufficiently distinctive sounds to make sound-reading, q. v.,

possible. Commercial tin plate, which is really tinned iron, seems to

give the best results.

Fig. 337. TIN SOUNDERS.

Tissandier's Solution.

A solution for bichromate batteries. It is composed as follows:

Water,                100 parts by weight

potassium bichromate,  16 parts

66° sulphuric acid,    37 parts.

Tongue of Polarized Relay.

The German silver extension of the vibrating or oscillating member of a

polarized relay, corresponding to the armature of an ordinary relay.

Tongue of Polarized Relay, Bias of.

In a Siemens' polarized relay the pole pieces are adjustable so that

they may be brought nearer to or withdrawn from the tongue. One of the

poles is adjusted so as to be nearer the tongue. This one-sided

adjustment is the bias. Its effect is that when the relay is unexcited

this pole attracts the armature so that it normally is drawn towards it.

This ensures the normal contact of the tongue either with the contact

point, or with the insulated stop piece or adjustment screw. Without

bias the armature remains in contact with or drawn towards whichever

pole it was last attracted to. In its usual use a bias is given it.

Top, Magnetic.

A toy illustrating magnetic attraction. It consists of a disc or body of

lead or other material, through which a magnetized steel spindle pointed

at its lower end is thrust. A number of short pieces of iron wire are

used with it. It is spun like an ordinary top upon the point of the

spindle and one of the pieces of iron wire is laid by the side of its

point. As it turns the magnetic adherence causes the piece of wire to be

carried along in one direction by the rotation of the spindle, until the

end is reached, when it goes over to the other side of the spindle and

travels back again.

By using bent pieces of wire of various shapes the most curious effects

are produced. Circles and S shaped pieces give good effects. To increase

the mysterious effect covered iron wire (bonnet wire) may be employed.

Fig. 338. MAGNETIC TOP.

543   STANDARD ELECTRICAL DICTIONARY.

Torpedo, Electric.

(a) A fish, the Raia Torpedo, which possesses the power of giving

electric shocks. (See Ray, Electric.)

(b) An instrument of war; a torpedo whose operations include electrical

discharge or other electric function or factor of operation.

Torpedo, Sims-Edison.

A torpedo driven by an electric motor, and also steered by electricity.

Its motions are all controlled from the shore. The torpedo proper is

carried some distance below the surface of the water by a vessel

immediately above it, from which it is suspended by two rigid bars. In

the torpedo is a cable reel on which the conducting cable is disposed.

An electric motor and controlling gear are also contained within the

torpedo. In its front the explosive is placed. It is driven by a screw

propeller actuated by the electric motor. As it moves it pays out cable

so that it has no cable to draw after it through the water, the cable

lying stationary in the water behind it. This avoids frictional

resistance to its motion. The maintenance of the torpedo at a proper

depth is one of the advantages of the system.

544   STANDARD ELECTRICAL DICTIONARY.

Torque.

A force tending to produce torsion around an axis. An example is the

pulling or turning moment of an armature of an electric motor upon its

shaft. It is often expressed as pounds of pull excited at the end of a

lever arm one foot long.

The expression is due to Prof. James Thompson, then of the University of

Glasgow.

"Just as the Newtonian definition of force is that which produces or

tends to produce motion (along a line), so torque may be defined as that

which produces or tends to produce torsion (around an axis). It is

better to use a term which treats this action as a single definite

entity than to use terms like 'couple' and 'moment,' which suggest more

complex ideas." (S. P. Thompson.)

A force, acting with radius r gives a torque equal to f X r ;  f and r

may be expressed in any units. S. P. Thompson gives the following

equivalents :

To reduce

dyne-centimeters to gram centimeters, divide by   981

dyne-centimeters to meter-kilograms   divide by   981E5

dyne-centimeter, to pound-feet        divide by   13.56E6

pound-feet to meter-kilograms         divide by   7.23

In each of these compound units the first unit is the force and the

second unit is the radius or lever arm of the torque.

Synonyms--Turning Moment--Moment of Couple--Axial Couple--Angular

Force--Axial Force.

Torsion Balance, Coulomb's.

Originally an apparatus in which electrostatic attraction or repulsion

is measured against the torsion of a filament, often of silk-worm cocoon

fibre. It consists in one form of a cylindrical glass vessel in which a

light shellac needle is suspended horizontally by a fibre. This needle

carries at one end a gilded disc or sphere and is suspended by a fine

wire, or filament. A proof plane, q. v., is excited by touching it to

the body under trial; it is then inserted in the case. The disc on the

needle is first attracted and then repelled. The position finally taken

by the needle is noted. The force of torsion thus produced is determined

by twisting the filament by the torsion head on the top of the apparatus

so as to move the needle a certain distance towards the proof plane. The

more the torsion-head has to be turned to carry the needle through a

specified arc the greater is the torsion effected or the greater is the

repulsion exerted, The torsional force of a wire is proportional to the

angle of torsion; this gives the basis for the measurement.

With magnetic needle it is used to measure magnetic repulsion and

attraction. The best material for the filament is quartz, but the

instrument is not very much used.

Torsion Galvanometer.

A galvanometer in which the torsion required to bring the index back to

zero, when the current tends to displace it, is made the measure of the

current strength or of the electro-motive force. It involves the use of

a torsion head, q. v., or its equivalent.

545   STANDARD ELECTRICAL DICTIONARY.

Torsion Head.

The handle and disc from whose undersurface the filament depends to

which the needle or magnet is attached. It is turned to measure the

torsional effect, the edge of the disc being marked or graduated so as

to give the angle of deflection required to overcome the effect of the

torque of the needle.

Torsion Suspension.

Suspension by one or more wires, fibres, or ribands, involving the

restitutive force of torsion. Thus fibre suspension, q. v., is a variety

of torsion suspension.

Often a single riband of steel stretched horizontally and secured at

both ends is used, the suspended object, e. g., a balance beam, being

attached at its own centre to the centre of the stretched riband. Quite

sensitive balances are constructed on this principle. It is peculiarly

available where an electric current is to be transmitted, as absolute

contact is secured, as in William Thomson's ampere balances.

Touch.

A term applied to methods of magnetization, as "single touch," "double

touch," or "separate touch," indicating how the poles of the inducing

magnet or magnets are applied to the bar to be magnetized. Under the

titles of Magnetization the different methods are described.

Tourmaline.

A mineral; a subsilicate; characterized by the presence of boric

trioxide, which replaces aluminum oxide. It is notable for possessing

pyro-electric properties. (See Pyro-electricity.)

Tower, Electric.

The tower used in the tower system, q. v., of arc light illumination.

Tower System.

In electric lighting the system of lighting extended areas by powerful

arc lamps placed on high towers, generally of iron or steel frame-work.

The lights are thus maintained at a high elevation, giving greater

uniformity of illumination than if they were lower, but at the expense

of considerable light which is lost. Sometimes wooden masts are employed

instead of towers.

The principle involved is that the intensity of light at any place given

by a source of illumination varies with the square of its distance from

the place in question. Hence in using strong arc lights it is an object

to have the distances of all parts of the area illuminated at as nearly

uniform distances from the light as possible. An approximation to

uniformity is secured by placing the lamps at a very high elevation.

546   STANDARD ELECTRICAL DICTIONARY.

Transformer.

In alternate current lighting the induction coil by which the primary

current with high initial electro-motive force is caused to produce a

secondary current with low initial electromotive force.

A typical transformer consists of a core of thin iron sheets. The

primary is of comparatively thin wire and often of ten or more times as

many turns as the secondary. The latter is of thicker wire. Where the

ratio of 10 to 1 as regards number of turns in the primary and secondary

obtains, the initial E. M. F. of the secondary is one-tenth that of the

primary circuit.

The cores are laminated, as described, to avoid the formation of

Foucault currents.

The counter-electro-motive force of the transformer when the secondary

circuit is open, prevents any but the slightest current from passing

through the primary. In proportion as the secondary is closed and its

resistance diminished, as by lighting more lamps in parallel, the

counter-electro-motive force of the transformer falls and more current

passes through the primary.

Fig. 339. FERRANTI'S TRANSFORMER.

The economy of the apparatus is in the fact that counter-electromotive

force reduces current through a conductor without absorbing any energy.

A resistance coil cuts down a current, but absorbs energy equal to the

current multiplied by the potential difference between the terminals of

the coil. This electric energy is converted into heat energy and is

wasted. But the counter-electromotive force of a transformer is exerted

to reduce current without production of heat and with little waste of

energy. This is one of the advantages of the alternating current system

of distribution of electric energy.

The object of a transformer being to secure safety to the person or to

life by the separation of the high potential primary or street circuit,

and the low potential house circuit, any contact of the two circuits in

the converter is a source of danger. Special care should be taken to

ensure absence of leakage, as it is termed. Mica or other insulation is

sometimes employed to prevent the wires from coming in contact by

piercing or sparking with the core and with each other.

547   STANDARD ELECTRICAL DICTIONARY.

Transformer, Commuting.

A type of continuous current transformer, resembling a dynamo with

armature and field both stationary, but with revolving commutator, by

which the magnetic polarity of a double wound armature is made to

rotate. This secures the desired action, of a change or lowering of

potential.

Transformer, Continuous Alternating.

An apparatus for transforming a continuous into an alternating current

or the reverse. The combination of a continuous current dynamo with an

alternating current one is sometimes employed. It is a form of motor

dynamo.

Another type is a regular dynamo with ordinary commutator and with, in

addition thereto, two, three or four contact rings, connecting to as

many symmetrically disposed points in the winding of the armature. This

will give out or receive alternating currents of two, three or four

phases according to the number of collecting rings. One winding serves

for both alternating and continuous currents.

Transformer, Continuous Current.

A machine of the dynamo type for changing the potential of a circuit. In

one form two armatures are mounted on one shaft in a single field or in

separate fields; one is a motor armature driven by the original current;

the other generates the new current. This is a motor dynamo. In 1874

Gramme constructed a machine with ring armature with two windings, of

coarse and fine wire respectively, and with independent commutators.

Such dynamo could transform currents up or down.

Continuous current transformers have attained an efficiency of 83 per

cent. at full load, and of 75 per cent. at half load. Owing to the

balancing of the self-inductions of the two windings these machines do

not spark. As the driven and driving parts are contained in one rotating

part their friction is very slight.

Transformer, Core.

A transformer wound upon an enclosed core, such as the hedgehog

transformer (see Transformer, Hedgehog), or common induction coil.

548   STANDARD ELECTRICAL DICTIONARY.

Transformer, Hedgehog.

An induction coil transformer whose iron core is composed of a bundle of

iron wires, which after the wire windings are in place have their ends

spread out to reduce to some extent the reluctance of the circuit, which

at the best is high, as the air acts as the return circuit.

This transformer has a low degree of hysteresis; and its efficiency for

very small loads or for no load is superior to that of the closed

magnetic circuit transformer.

Fig. 340. SWINBURNE'S HEDGEHOG TRANSFORMER.

Transformer, Multiple.

A transformer connected in parallel with others between the two leads of

the primary circuit. The term refers to the connection only and not to

any peculiarity of the transformer itself.

Transformer, Oil.

A transformer with oil insulation. The advantage of this insulation is

that if pierced it at once closes, so that no permanent injury ensues.

It is a self-healing form of insulation.

Transformer, Series.

Transformers connected in series upon the primary circuits. The term,

like "multiple transformers," only applies to the connection, not to the

transformer. Series transformers are but little used.

Transformer, Shell.

A transformer with its iron core entirely outside of and enclosing the

primary and secondary winding. It may be made by the use of outer iron

wire windings as core.

Transformer, Welding.

The transformer used for electric welding. (See Welding, Electric.) It

is a transformer with very long primary and exceedingly short and thick

secondary. It is used with the alternating current in the primary, and

produces in the secondary circuit which includes the bars to be welded a

very low potential difference.

Owing to the very low resistance of the secondary circuit this low

electro-motive force produces a very strong current, which develops the

requisite heat. The same type of transformer is used for brazing and

similar purposes.

549   STANDARD ELECTRICAL DICTIONARY.

Transmitter.

In general electric phraseology, any instrument which produces signals

to be transmitted through a line or circuit is a transmitter. Thus the

Morse key in telegraphy or the Blake transmitter in telephony are

examples of such.

Transmitter, Carbon.

A form of microphone used as a telephone transmitter. (See Carbon

Telephone.)

Transposing.

A method of laying metallic circuits for telephoning. The wires at short

intervals are crossed so that alternate sections lie on opposite sides

of each other. It is done to avoid induction.

Transverse Electro-motive Force.

Electro-motive force in a substance in which electric displacement is

taking place, produced by a magnetic field. It is sometimes assigned as

the cause of the Hall effect, q. v.

Trimmer, Brush.

A shears for cutting off evenly and squarely the ends of copper dynamo

brushes. The brushes when uneven from wear are removed from the brush

holders, and their ends are sheared off in the trimmer.

Trolley.

A grooved metallic pulley or set of pulleys which runs along an active

wire of a circuit, a lead from which trolley goes to earth or connects

with another wire, so that the trolley takes current generally for

operating a street car motor placed upon the circuit leading from it; a

rolling contact with an electric lead.

Trolleys are principally used on electric railroads, and are now

universally of the sub-wire system, being at the end of a pole which is

inclined backward and forced upward by springs, so as to press the

trolley against the bottom of the wire. Thus the trolley does not

increase the sagging of the wire, but tends to push it up a little in

its passage.

Trolley, Double.

A trolley with two rollers or grooved wheels, placed side by side, and

running on two parallel leads of wire. It is adapted to systems

employing through metallic trolley lines with the motors in multiple

arc, connecting or across the two leads.

Trolley Section.

An unbroken or continuous section of trolley wire.

Trouvé's Solution.

An acid exciting and depolarizing solution for a zinc-carbon battery.

Its formula is as follows: Water, 80 parts; pulverized potassium

bichromate, 12 parts; concentrated sulphuric acid, 36 parts; all parts

by weight. The pulverized potassium bichromate is added to the water,

and the acid is added slowly with constant stirring. As much as 25 parts

potassium bichromate may be added to 100 parts of water. The heating

produced by the acid and water dissolves nearly all the potassium salt.

Use cold.

550   STANDARD ELECTRICAL DICTIONARY.

True Contact Force.

A species of electro-motive force whose existence is supposed to be

proved by the Peltier effect. The lowering in temperature of a contact

of dissimilar metals is attributed to a force that helps the current on

its way if in the direction of thermo-current proper to the junction and

opposing it if in the reverse. The true contact force is taken to

explain this phenomenon; thermo-electric force cannot, as there is no

heat or cold applied to the junction.

Trumpet, Electric.

An apparatus consisting of a vibrating tongue, kept in motion by

electricity as in the buzzer, q. v., placed in the small end of a

trumpet-shaped tube.

Trunking Switchboard.

A telephone switchboard arranged in sections, which sections are

connected by trunk lines, through which trunk lines the desired

connections

are made.

Trunk Lines.

In telephone distribution systems, the lines connecting different

stations, or different sections of a switch-board and used by anyone

requiring such connections; one trunk line answers for a number of

subscribers.

Tube, Electric.

A tube of glass around which is pasted a series of tinfoil circles,

diamonds, or little squares, or other form of interrupted conductor. The

pieces generally are placed in the line of a spiral. When a static

discharge of electricity takes place along the conductor a row of bright

sparks is produced at the breaks in the conductor. These by reflection

are multiplied apparently, and a beautiful effect of intersecting or

crossing spirals of sparks is presented.

The experiment is in line with the luminous pane and lightning jar, and

is used merely as a demonstration, or lecture experiment.

Synonym--Luminous Tube.

Tubular Braid.

A braid woven of tissue or worsted, and tubular or hollow. Its object is

to provide a covering which can be drawn over joints in covered wires.

In making the joint the ends of the wires are necessarily bared, and a

short piece of tubular braid is used for covering them. It is drawn by

hand over the joint.

Turns.

An expression applied to the convolutions of wire in a solenoid,

electro-magnet, or other apparatus or construction of that kind. A turn

indicates a complete encircling of the core or axis of the object. Thus

a wire wound five times around a bar gives five turns.

While this is its primary meaning the term if compounded may refer to

virtual turns. Thus an ampere-turn means one ampere passing through one

turn. But ten ampere-turns may mean ten amperes passing through ten

turns, five amperes passing through two turns, and so on. This use is

analogous to a dimension of length in a compound word, as foot-pound.

[Transcriber's note: "But ten ampere-turns may mean ten amperes passing

through ONE turn or one ampere through ten turns, and so on."]

There may be a number of kinds of turns qualified by descriptive

adjectives, as series-turns, the turns of wire in a series circuit of a

compound dynamo. In the same way there are shunt-turns. If series

ampere-turns or shunt ampere-turns are meant the word ampere should be

included.

551   STANDARD ELECTRICAL DICTIONARY.

Turns, Dead, of a Dynamo.

The rotations of a dynamo armature while it is building itself up or

exciting itself. The expression is a bad one, as it is likely to be

confounded with the dead turns of armature wire.

Turns, Primary Ampere-.

The ampere-turns in a primary circuit of an induction coil or

transformer. In an electric welding transformer, or in the transformer

used in the alternating current system, where efficiency is an important

element, the ampere-turns in primary and secondary for an efficiency of

100 per cent. should be equal. In the case of an experimental induction

coil other considerations outweigh that of mere efficiency. Insulation,

including security from piercing, and the production of as long a spark

as possible, are, in these cases, the controlling consideration.

[Transcriber's note: A 100 per cent efficient transformer is impossible,

but over 99 per cent is common. At room temperature there is always some

lost flux, eddy currents and resistive losses.]

Turns, Secondary Ampere-.

The ampere-turns on the secondary circuit of an induction coil or

transformer. These depend on the path provided for the current. If of

negligible inductance, such as a number of incandescent lamps would

provide, the ampere-turns should be equal to those of the primary coil.

(See Turns, Primary Ampere.)

Typewriter, Electric.

A typewriter in which the work of printing or of pressing the type faces

against the paper, or printing ribbon, is done by electro-magnetic

attraction. The keys close electric circuits, throwing the

electro-magnetic action into play. This involves the use of electricity

for what is ordinarily only a mechanical process. The strength of the

impression, however, is independent of the touch of the operator. It has

not come into very extensive use.

[Transcriber's note: IBM introduced widely used electric typewriters in

1935.]

551   STANDARD ELECTRICAL DICTIONARY.

Ultra-gaseous Matter.

Gas so rarefied that its molecules do not collide or very rarely do so.

Experiments of very striking nature have been devised by Crookes and

others to illustrate the peculiar phenomena that this matter presents.

The general lines of this work are similar to the methods used in

Geissler tube experiments, except that the vacua used are very much

higher.

When the vacuum is increased so that but one-millionth of the original

gas is left the radiant state is reached. The molecules in their kinetic

movements beat back and forth in straight lines without colliding, or

with very rare collisions. Their motions can be guided and rendered

visible by electrification. A tube or small glass bulb with platinum

electrodes sealed in it, is exhausted to the requisite degree and is

hermetically sealed by melting the glass. The electrodes are connected

to the terminals of an induction coil or other source of high tension

electrification. The molecules which come in contact with a negatively

electrified pole are repelled from it in directions normal to its

surface. They produce different phosphorescent or luminous effects in

their mutual collisions.

Thus if they are made to impinge upon glass, diamond or ruby, intense

phosphorescence is produced. A piece of platinum subjected to molecular

bombardment is brought to white heat. A movable body can be made to move

under their effects. Two streams proceeding from one negative pole repel

each other. The stream of molecules can be drawn out of their course by

a magnet.

The experiments are all done on a small scale in tubes and bulbs,

resembling to a certain extent Geissler tubes.

[Transcriber's note: These effects are caused by plasma--ionized gas and

electrons.]

552   STANDARD ELECTRICAL DICTIONARY.

Unbuilding.

The loss of its charge or excitation by a self-exciting dynamo. It is

the reverse of building-up. The latter indicates the exciting of the

field by the action of the machine itself; the former the spontaneous

loss of charge on open circuit or from other cause.

Underground Conductor.

An electric conductor insulated and placed under the surface of the

earth, as distinguished from aerial conductors.

Underground Electric Subway.

A subway for the enclosing of electric telegraph and other conductors

under the surface, generally in the line of streets, to do away with

telegraph poles and aerial lines of wire. Many systems have been

devised. The general type includes tubes called ducts in sets, called

conduits, bedded in concrete or otherwise protected. Every two or three

hundred feet the sets lead into a cistern-like cavity called a manhole.

The insulated wires or cables, generally sheathed with a lead alloy are

introduced into the tubes through the man-holes. A rope is first fed

through the tube. To do this short rods which screw together are

generally employed. One by one they are introduced, and each end one is

screwed to the series of rods already in the duct. When the end of the

duct is reached the rope is fastened to the last rod, and the rods are

then drawn through, unscrewed one by one and removed, the rope following

them. By means of the rope a windlass or capstan may be applied to draw

the cable into the duct. At least at every second man-hole the cables

have to be spliced.

Each cable may contain a large number of conductors of small size for

telephoning, or a smaller number for electric light and power. The

tendency is now to separate the different classes of wires in important

lines, placing the heavier wires on one side of the street and the

telephone and telegraph wires on the other. This of course necessitates

two separate conduits.

The advantage of underground distribution affects not only the

appearance of streets in doing away with unsightly telegraph poles, but

it also removes an element of danger at fires. Aerial wires interfere

greatly with the handling of ladders at fires, and expose the firemen

who attempt to cut them to danger to their lives from shock.

533   STANDARD ELECTRICAL DICTIONARY.

Unidirectional. adj.

Having one direction as a "unidirectional current" or "unidirectional

leak." The term is descriptive, and applicable to many cases.

Uniform. adj.

Unvarying; as a uniform potential difference, uniform current or

conductor of uniform resistance per unit of length. The term is

descriptive, and its application and meaning are obvious.

Uniform Field of Force.

A field of evenly distributed force; one in which the number of lines of

force per unit of area of any equipotential surface is the same.

Unipolar. adj.

Strictly speaking this term means having only one pole, and is applied

to magnets, armatures and the like. In its use a solecism is involved,

for there is no such condition possible as unipolar magnetism or

distribution of magnetism. An example of its use is shown in unipolar

magnets. (See Magnet, Unipolar.)

Unipolar Armature.

An armature of a unipolar dynamo; an armature whose windings

continuously cut the lines of force about the one pole, and hence whose

polarity is unchanged in its rotation.

Unipolar Current Induction.

Current induction produced by moving a conductor through a magnetic

field of force so that it always cuts the lines in similar relation to

itself. Thus it produces a constant current through its own circuit, if

a closed one, and no commutator is required. As this case always in

practice amounts to the cutting of lines of force in the neighborhood of

a single pole the term unipolar is employed to designate the action.

The simplest representation of unipolar induction is the rotating of a

conductor around the end of a bar magnet, its axis of rotation

corresponding with the axis of the magnet.

Unipolar Dynamo.

A dynamo in which one part of the conductor slides on or around the

magnet, so as always to cut lines of force near the same pole of the

magnet.

Unit.

A directly or indirectly conventional and arbitrary quantity, in terms

of which measurements of things with dimensions expressible in the

chosen units are executed.

Thus for length the c. g. s. unit is the centimeter; the B. E. unit is

the foot.

554   STANDARD ELECTRICAL DICTIONARY.

Unit, Absolute.

A unit based on the three fundamental units of length, mass and time.

These units are the centimeter, gram and second. Each one in itself may

be termed a fundamental absolute unit. The system of such units is

termed the centimeter-gram-second system.

Unit, Angle.

A factor or datum in angular velocity, q. v. It is the angle subtended

by a portion of the circumference equal in length to the radius of the

circle. It is equal very nearly to 57.29578° or 57° 17' 44.8".

Unit, B. A.

This term, while logically applicable to any of the British Association

units, is often restricted to the ohm as formerly defined by the British

Association, the B. A. Unit of Resistance, q. v.

Unit, Fundamental.

The three units of length, mass and time, the centimeter, gram and

second, are termed fundamental units. On them is based the absolute

system of units, and on multiples of them the practical system of units.

Unit Jar.

A Leyden jar which is used as a unit of measure of charge.

It consists of a Leyden jar about 4 inches long and 3/4 inch diameter,

with about 6 square inches of its outer and the same of its inner

surface coated with tinfoil. It is placed between a source of

electricity and a larger jar or battery of jars which is to be charged.

The inner coating connects with the machine; the outer coating with the

jars to be charged. Short conductors terminating in knobs connect with

inner and outer coatings, and the knobs are adjusted at any desired

distance apart.

By the charging operation the large jar or battery of jars receives a

charge by induction, and the charge of the small jar is at first equal

to this quantity. After a while a spark passes from knob to knob,

discharging the small jar. This indicates the reception by the large

jars of the quantity of electricity represented by the charge of the

small jar. The charging goes on, and for every spark approximately the

same quantity of electricity is received by the larger jars.

The sparking distance m is directly proportional to the quantity of

electricity, and inversely proportional to the area of coated surface,

or is proportional to the potential difference of the two coats. This is

only true for short sparking distance, hence for accuracy the knobs

should be adjusted not too far from each other.

555   STANDARD ELECTRICAL DICTIONARY.

Unit of Supply.

A commercial unit for the sale of electric energy, as defined

provisionally by the English Board of Trade; 1,000 amperes flowing for

one hour under an E. M. F. of 1 volt; 3,600,000 volt-coulombs, or 1,000

watt-hours, are its equivalent. It is equal to 1000/746 = 1.34 electric

horse power.

Synonym--Board of Trade Unit.

[Transcriber's note: Now called a kilowatt-hour.]

Units, Circular.

A system of units of cross-sectional area, designed especially for use

in describing wire conductors. The cross-sectional area of such is

universally a circle, and the areas of two wires of different sizes vary

with the square of their radii or diameters. Hence if the area of a

circle of known diameter is determined it may be used as a unit for the

dimensions of other circles. Any other circle will have an area

proportioned to the area of the unit circle, as the squares of the

diameters are to each other.

In practise the commonest circular unit is the circular mil. This is the

area of a circle one mil, 1/1000 inch, in diameter and is equal to

.0000007854 square inch. A wire two mils in diameter has an area of four

circular mils; one ten mils in diameter has an area of one hundred

circular mils.

Thus if the resistance of a given length of wire 1 mil in diameter is

stated, the corresponding resistance of the same length of wire of the

same material, but of other diameter, is given by dividing the first

wire's resistance by the square of the diameter in mils of the wire in

question.

As it is a basic unit, most conveniently applied by multiplication, the

smaller units are used; these are the circular mil, and circular

millimeter.

Units, Derived.

Units derived by compounding or other processes, from the three

fundamental units. Such are the units of area, volume, energy and work,

momentum and electric units generally. In some cases the dimensions of

the derived unit may reduce to those of a simple unit as inductance

reduces to length, but the unit, as deduced from the fundamental ones,

is still a derived unit.

Units, Practical.

A system of units employed in practical computation. The absolute units,

especially in electricity, have been found too large or too small, and

the attempt to make them more convenient has resulted in this system. It

is based on exactly the same considerations as the absolute system of

units, except that multiples of the original fundamental units of

length, mass, and time have been taken as the base of the new system.

These basic units are multiples of the fundamental units. They are the

following: The unit of length is 1E9 centimeters; the unit of mass is

1E-11 gram; the unit of time remains 1 second.

While this has conduced to convenience in giving better sized units,

micro- and mega-units and other multiples or fractions have to be used.

The following are the principal practical electric units:

Electrostatic     Electromagnetic

C. G. S Units.    C. G. S. Units.

Intensity-Ampere   equal to     3E9               1E-1

Quantity-Coulomb     "          3E9               1E-1

Potential-Volt       "         (1/3)* E-2         1E8

Resistance-Ohm       "         (1/9)* E-11        1E9

Capacity-Farad       "         9E11               1E-9

556   STANDARD ELECTRICAL DICTIONARY.

Universal Battery System.

A term in telegraphy. If several equal and high resistance telegraphic

circuits are connected in parallel with each other from terminal to

terminal of a battery of comparatively low resistance each circuit will

receive the same current, and of practically the same strength as if

only one circuit was connected. This is termed the universal battery

system. It is a practical corollary of Ohm's law. The battery being of

very low resistance compared to the lines the joining of several lines

in parallel practically diminishes the total resistance of the circuit

in proportion to their own number. Thus suppose a battery of ten ohms

resistance and ten volts E. M. F. is working a single line of one

hundred ohms resistance. The total resistance of the circuit is then one

hundred and ten ohms. The total current of the circuit, all of which is

received by the one line is 10/110 = .09 ampere, or 90 milliamperes. Now

suppose that a second line of identical resistance is connected to the

battery in parallel with the first. This reduces the external resistance

to fifty ohms, giving a total resistance of the circuit of sixty ohms.

The total current of the circuit, all of which is received by the two

lines in equal parts, is 10/60 = .166 amperes. But this is equally

divided between two lines, so that each one receives .083 ampere or 83

milliamperes; practically the same current as that given by the same

battery to the single line. It will be seen that high line resistance

and low battery resistance, relatively speaking, are required for the

system. For this reason the storage battery is particularly available.

The rule is that the resistance of the battery shall be less than the

combined resistance of all the circuits worked by it.

Unmarked End.

The south-seeking pole of a magnet, so called because the other end,

called the marked end, is usually marked with a scratch or notch by the

maker, while the south pole is unmarked.

556   STANDARD ELECTRICAL DICTIONARY.

V.

(a) Symbol for velocity.

(b) Symbol or abbreviation for volume.

(c) Symbol or abbreviation for volt.

557   STANDARD ELECTRICAL DICTIONARY.

V. A.

Symbol or abbreviation for voltaic alternatives, q. v.

Vacuum.

A space destitute of any substance. The great pervading substance is in

general sense the atmosphere. It is the gaseous mixture which surrounds

and envelopes the earth and its inhabitants. It consists of a simple

mixture of oxygen, 1 part, nitrogen, 4 parts, with 4 to 6 volumes of

carbonic acid gas in 10,000 volumes of air, or about one cubic inch to

one cubic foot. It presses with a force of about 14.7 lbs. per square

inch under the influence of the force of gravity. The term vacuum in

practise refers to any space from which air has been removed. It may be

produced chemically. Air may be displaced by carbonic acid gas and the

latter may be absorbed by caustic alkali or other chemical. The air may

be expelled and the space may be filled with steam which is condensed to

produce the vacuum. Of course in all cases the space must be included in

an hermetically sealed vessel, such as the bulb of an incandescent lamp.

But the universal method of producing a vacuum is by air pumps. An

absolute vacuum means the entire absence of gas or air, something almost

impossible to produce. A high vacuum is sometimes understood to mean one

in which the path of the molecules is equal in length to the diameter of

the containing vessels, as in Crookes' Radiometer and other apparatus

for illustrating the radiant condition of matter. The air left after

exhaustion is termed residual air or residual atmosphere.

[Transcriber's note: Dry air is about .78 nitrogen, .21 oxygen, .01

argon, .00038 carbon dioxide, and trace amounts of other gases. Argon

was suspected by Henry Cavendish in 1785. It was discovered in 1894 by

Lord Rayleigh and Sir William Ramsay.]

Vacuum, Absolute.

A space free of all material substance. It is doubtful whether an

absolute vacuum has ever been produced.

Vacuum, High.

An approximate vacuum, so nearly perfect that the molecules of the

residual gas in their kinetic motions rarely collide, and beat back and

forth between the walls of the containing vessel, or between any solid

object contained in the vessel and the walls of the vessel. The gas in

such a vacuum is in the radiant or ultra-gaseous state. (See

Ultra-gaseous Matter.)

Vacuum, Low.

A vacuum inferior to a high vacuum; a vacuum in which the molecules

collide with each other and do not move directly from side to side of

the containing vessel.

Vacuum, Partial.

A space partially exhausted of air so as to contain less than an equal

volume of the surrounding atmosphere. It really should come below a low

vacuum, but is often treated as synonymous therewith.

Vacuum, Torricellian.

The vacuum existing above the mercurial column in a barometer tube. The

principle of this vacuum is applied in the Geissler and other air pumps.

(See Pump, Geissler--Pump, Sprengel--Pump, Swinburne.)

558   STANDARD ELECTRICAL DICTIONARY.

Valency.

The relative power of replacing hydrogen or combining therewith

possessed by different elements; the number of atomic bonds belonging to

any element. Thus oxygen has a twofold valency, is bivalent or is a

dyad, and combines with two atoms of hydrogen because the latter has a

unitary atomicity, is monovalent or is a monad.

Valve, Electrically Controlled.

A valve which is moved by or whose movements are regulated by

electricity.

In the block system of railroad signaling the semaphores are worked by

weights and pneumatic cylinders and pistons. The valves for admitting or

releasing the compressed air are operated by coil and plunger mechanism.

There are many other instances of the control of valves by the electric

current.

Vapor Globe.

A protecting glass globe surrounding an incandescent lamp, when the lamp

is to be used in an atmosphere of explosive vapor, as in mines or

similar places; or when in a place where it is exposed to dripping water

which would break the hot lamp bulb if it fell upon it.

Variable Period.

The period of adjustment when a current is started through a conductor

of some capacity. It is the period of duration of the variable state, q.

v., in a conductor. As indicated in the next definition in a cable of

high electrostatic capacity a variable period of nearly two minutes may

exist. This indicates the retardation in signaling to be anticipated in

cables and other lines of high capacity.

Variable State.

When an electric circuit is closed the current starts through the

conductor with its full strength from the point of closure, and advances

with a species of wave front so that some time elapses before it attains

its full strength in the most distant parts of the conductor, owing to

its having to charge the conductor to its full capacity at the given

potential. The state of the line while the current thus varies is called

the variable state.

A long telegraph line when a message is being transmitted may be always

in the variable state. The current at the receiving end may never attain

its full strength.

In the case of such a conductor as the Atlantic cable, 108 seconds would

be required for a current to attain 9/10 of its full strength at the

distant end, and but 1/5 second to attain 1/100 of its final value.

During the period of increase of current the variable state exists.

Variation of the Compass.

The declination of the magnetic needle. (See Elements, Magnetic.) As the

declination is subject to daily, annual and secular variations, it is

unfortunate that this term is synonymous with declination. Thus the

variation of the compass means its declination, while there is also the

variation of the declination and of other elements. The term variation

of the compass is more colloquial than the more definite expression

"declination," or "magnetic declination."

559   STANDARD ELECTRICAL DICTIONARY.

Variometer.

An apparatus used in determining the relative values of the horizontal

component of the earth's magnetic field in different places.

Varley's Condenser.

A static condenser whose conducting surfaces are platinum electrodes

immersed in dilute sulphuric acid. When the potential difference is

1/50th that of a Daniell's cell, two square inches of platinum have a

capacity equal to that of an air condenser whose plates have an area of

80,000,000 square inches, and separated 1/8th of an inch from each

other. As the E. M. F. increases the capacity also increases.

Varley's Resistances.

Variable resistances formed of discs of carbonized cloth, q. v., piled

up, and pressed together more or less firmly to vary the resistance as

desired.

Varnish.

A glossy transparent coating of the nature of paint, applied as a

protective, or ornamental coating to objects.

Varnish, Electric.

Alcoholic or etherial varnishes are the best for electrical apparatus.

They dry quickly and perfectly, and tend to form surfaces unfavorable to

the hygroscopic collection of water. Sealing wax dissolved in alcohol,

or shellac dissolved in the same solvent are used for electrical

apparatus, although the first is rather a lacquer than a varnish.

Etherial solution of gum-copal is used to agglomerate coils of wire. It

is well to bake varnished objects to harden the coating.

Varnish, Red.

A solution of sealing wax in 90 per cent. alcohol. It is best made thin

and applied in several coats, each coat being allowed to dry perfectly

before the next is applied. It is often seen on Leyden jars. It is a

protector from surface leakage.

Vat.

A vessel for chemical or other solutions. A depositing vat is one in

which a plating solution is worked, for the deposition of electroplate

upon articles immersed in the liquid, and electrolyzed by an electric

current.

Velocity.

The rate of motion of a body. It is usually expressed in distance

traversed per second of time. The absolute unit is one centimeter per

second or kine. The foot per second is very largely used also.

The dimensions of velocity are length (L) divided by time (T) or L/T.

Velocity, Angular.

Velocity in a circle defined by the unit angle, or the angle which

subtends a circular arc equal in length to itself. The radius of the

circle traversed by the moving body does not enter into this definition,

as the real velocity of the object is not stated. If its angular

velocity and the radius of the path it travels are given its actual

velocity can be deduced.

560   STANDARD ELECTRICAL DICTIONARY.

Velocity of Signaling.

The speed of transmission of electric signals is affected by the nature

of the line, as regards its static capacity, and by the delicacy of the

receiving instruments, which may need a more or less strong current to

be affected. Thus of an original current one per cent. may suffice to

operate a sensitive instrument. This might give almost the velocity of

light, while if the instrument would only respond to the full current

nearly two minutes (see Variable State) might be required for the

production of a signal.

Velocity Ratio.

A term applied to the ratios existing between the electrostatic and

electro-magnetic units. If we take as numerators the dimensions of the

different qualities in the electrostatic system, and their dimensions in

the electro-magnetic system as denominators, the fractions thus obtained

reduce to expressions containing only velocity or V in some form. Thus

if we divide the dimensions of the electrostatic quantity by the

dimensions of electro-magnetic quantity the quotient is simply V or

velocity. A like division for potential, electrostatic and

electro-magnetic gives (1/V), and so on.

The value of the velocity ratio is very nearly 3E10 (sometimes given as

2.98E10) centimeters per second. This is almost exactly that of light

(2.9992E10 centimeters per second.) This is one of the proofs of Clerk

Maxwell's magnetic theory of light. (See Maxwell's Theory of Light.)

[Transcriber's note: The SI metre was defined in 1983 such that the

speed of light in a vacuum is exactly 299,792,458 metres per second or

about 186,282.397 miles per second.]

Ventilation of Armature.

In a dynamo or motor ventilation of the armature is often provided for

by apertures through it in order to prevent heating. This heating is

caused by Foucault currents. By proper disposition of the interior of

the armature with properly disposed vanes and orifices an action like

that of a fan blower can be produced, which by creating a current of air

cools the machine very efficiently.

Verticity, Poles of.

Points upon the earth's surface where the horizontal component of

magnetic force disappears, leaving only the vertical component active.

The term is derived from the verticity of the dipping needle when over

either of them.

561   STANDARD ELECTRICAL DICTIONARY.

Vibration Period.

In electrical resonance the period of a vibration in an electrical

resonator. The length of this period indicates the quality of the

resonator in responding to electrical oscillations by sympathetic

vibration. For conductors of small resistance the period is thus

calculated. Let T be the period of one-half a full vibration; L the

absolute coefficient of self-induction expressed in centimeters or in

henries X 10-9; C the electrostatic capacity of the terminals, also

expressed in the same unit; v the velocity of light in centimeters per

second. Then we have the formula

T = PI * SquareRoot( L * C ) / v

[Transcriber's note: If the inductance is in henries and the capacitance

in farads, frequency in hertz = 1/(2 * PI * squareRoot( L * C ) )]

Vibration, Sympathetic.

A vibration in a cord or other body susceptible of elastic vibration

produced by the vibrations of exactly the same period in a neighboring

vibrating body. Thus if two tuning forks are tuned to precisely the same

pitch, and are placed near each other, if one is sounded it will start

the other into vibration by sympathy.

In electricity its application is found in electric resonance

experiments. The resonator has a definite period of electric resonance,

and is made to give a spark by the exciter of identical period. This is

by what may be called electric sympathetic vibration, and is exactly

analogous to the action of the tuning forks upon each other.

Vibrator, Electro-magnetic.

The make and break mechanism used on induction coils, or other similar

apparatus in which by alternate attractions by and releases from an

electro-magnet an arm or spring is kept in motion. In most cases the

work is done by a single magnet, whose armature is attracted to the

magnet, when the latter is excited, but against the action of a spring

which tends to pull it away from the magnet. In its motions a make and

break action is produced, to give the requisite alternations of

attraction and release. Two electro-magnets may be connected so as

alternately to be excited and keep an arm carrying a mutual armature in

vibration, or the same result may be attained by a polarized relay. The

make and break is illustrated under Bell, Electric--Coil, Induction--

Anvil.

Villari's Critical Value.

Magnetization induced or residual in a wire is diminished on stretching,

provided that the magnetization corresponds to an inducing force above a

certain critical value, known as above; this being (Sir Wm. Thomson)

about 24 times the terrestrial intensity. Below that critical value

tension increases the magnetization of a magnetized wire. The effects of

transverse expansive stress are opposed to those of longitudinal

stretching. (Daniell.)

Viole's Standard of Illuminating Power.

A standard authorized by the International Congress of 1881. It is the

light given by one square centimeter of platinum, melted, but just at

the point of solidification. It is equal to 20 English standard candles

almost exactly.

It has not been very widely accepted, the tendency among photometrists

being to adhere to the old standards, carcel or candle. It is obvious

that actual use of the Viole would be very inconvenient and would

involve expensive apparatus, difficult to work with.

Synonym--Viole.

562   STANDARD ELECTRICAL DICTIONARY.

Vis Viva.

The kinetic energy of a body in motion; "mechanical energy."

Vitreous Electricity.

Positive electricity; the electricity produced on the surface of glass

by rubbing it with silk and other substances. (See Electrostatic

Series.)

The term "positive electricity" should be allowed to supplant it. It is

the analogue and opposite of resinous electricity.

Vitriol, Blue.

A colloquial or trade name for copper sulphate (Cu SO4).

Vitriol, Green.

A colloquial or trade name for ferrous sulphate (Fe SO4).

Vitriol, White.

A colloquial or trade name for zinc sulphate (Zn SO4).

Volt.

The practical unit of electro-motive force or potential difference. It

may be referred to various data.

An electro-motive force of one volt will cause a current of one ampere

to flow through a resistance of one ohm.

A condenser of one farad capacity charged with one coulomb will have a

rise of potential of one volt.

The cutting of 100,000,000 lines of force per second by a conductor

induces one volt E. M. F.

A Daniell's battery gives an E. M. F. of 1.07 volts; about the most

familiar approximate standard that can be cited.

It is equal to 1/300 absolute electrostatic unit.

It is equal to 1E8 absolute electro-magnetic units.

[Transcriber's note: The SI definition of a volt: The potential

difference across a conductor when a current of one ampere dissipates

one watt of power.]

Voltage.

Potential difference or electro-motive force expressed in volts; as a

voltage of 100 volts. Thus voltage may express the electro-motive force

absorbed in a conductor, while electro-motive force is a term generally

applied where it is produced, evolved or present in the object. The term

voltage of a lamp expresses simply the volts required, but does not

suggest the possession of electromotive force.

563   STANDARD ELECTRICAL DICTIONARY.

Voltage, Terminal.

The voltage or potential difference at the terminals of an electric

current generator, such as a dynamo, as distinguished from the total

electro-motive force of the dynamo or generator.

In batteries the distinction is not generally made in practice; the

total electro-motive force of the battery is made the basis of

calculations.

Voltaic. adj.

This adjective is used to qualify a great many things appertaining to or

connected with current electricity. It is derived from Volta, the

inventor of the voltaic battery, and now tends to displace the term

"galvanic," formerly in general use.

Voltaic Alternatives.

A term used in electro-therapeutics or medical electricity to indicate

an alternating battery current.

Synonym--Alternative current.

Voltaic Effect.

The potential difference developed by contact of different conductors.

It is the basis of the contact theory, q. v., of electricity, although

it may be accepted as the expression for a condition of things by those

who reject the above theory. This potential difference is slight when

the conductors are separated, but it is calculated that it would be

enormous could the metals be so quickly separated as to hold each its

own charge.

Thus if a copper and a zinc plate are assumed to be in contact, really

1/20000000 centimeter or 1/50000000 inch apart, they may be treated as a

pair of condenser plates. Being so near, their density of charge, which

is a strongly bound charge, is enormous. If it were possible to separate

them without permitting any discharge, their potential would rise by the

separation, on the principle of Epinus' condenser, q. v., to such an

extent that they would spark through twenty feet of air. (See Volta's

Fundamental Experiment.)

Voltaic Electricity.

Electricity of low potential difference and large current intensity;

electricity such as produced by a voltaic battery; current or dynamic

electricity as opposed to static electricity.

Voltameter.

In general an apparatus for determining the quantity of electricity

passing through a conductor by measuring the electrolytic action it can

perform.

Voltameter, Copper.

An apparatus which may be of similar construction with the silver

voltameter (see Voltameter, Silver), but in which a copper anode and a

solution of copper sulphate are substituted for the silver anode and

silver nitrate solution. One coulomb corresponds to .329 milligram or

.005084 grain of copper deposited. It is not accepted as of as high a

standard as the silver voltameter.

The electrodes should be placed half an inch from each other. Two square

plate electrodes may conveniently be used, and not less than two square

inches on each plate should be the area per ampere of current.

564   STANDARD ELECTRICAL DICTIONARY.

Voltameter, Differential, Siemens'.

A volume or gas voltameter with duplicate eudiometers and pairs of

electrodes. It is used for determining the resistance of the platinum

conductor used in his pyrometer. A current divides between the two

voltameters; in one branch of the circuit the platinum conductor is

placed, in the other a known resistance. The current strength varying

inversely with the resistance, the resistances of the two conductors are

inversely proportional to the gas evolved.

Voltameter, Gas.

A voltameter whose indications are based on the electrolysis of water,

made an electrolyte by the addition of sulphuric acid. The gases evolved

are measured. It may take several forms.

In one form it is an apparatus consisting of a single eudiometer or

graduated glass tube with upper end closed and its lower end or mouth

open, collecting the mixture of hydrogen and oxygen.

In the form shown in the cut three tubes are connected, the side tubes

representing eudiometers. For each side tube there is a platinum

electrode. In this apparatus the oxygen and hydrogen are connected in

opposite tubes. A is an open tube filled with dilute sulphuric acid. By

opening the cocks on B and C they can both be completely filled with

acid. As shown in the cut, this operation is not yet completed. The

hydrogen alone may in this case be measured.

The mixed gas voltameter has only one eudiometer.

The exact equivalents are only approximately known. The volume of mixed

gases per coulomb is given as .1738 cubic centimeters (Ayrton); .172

cubic centimeters (Hospitalier); and other values by other authorities.

The hydrogen is equal to 1/3 of the mixed gases almost exactly.

Synonyms--Volume Voltameter--Sulphuric Acid Voltameter.

The gas is measured at 0º (32º F.) and 76 centimeters, or 30 inches

barometer.

Fig. 341. GAS VOLTAMETER.

565   STANDARD ELECTRICAL DICTIONARY.

If the gas is measured in cubic inches, the temperature in degrees F.,

and the barometric height in inches, the following formula may be used

for reduction to standard pressure and temperature. It is the volume

corresponding to one coulomb.

( .01058 * 30 * (491 + Fº - 32) ) / (h* 491)

For the metric measurements and degrees C.

(.1738 * 76 * (273 + Cº)) / (h X 273)

Voltameter, Silver.

An apparatus consisting of a platinum vessel containing a solution of

silver nitrate into which solution a silver anode dips, whose end is

wrapped in muslin to prevent the detachment of any particles. When a

current is passed by connecting one terminal to the dish and the other

to the rod, securing a proper direction of current, silver will be

deposited on the dish and the same amount will be dissolved from the

rod. The dish is weighed before and after the test. Its increase in

weight gives the silver deposited.

FIG. 342. SILVER VOLTAMETER.

In the cut Ag is the silver anode, Pt is the platinum dish, r is the

conducting rod, p is a wooden standard, Cu is a copper plate on which

the dish rests and which also serves as a conductor and contact surface,

b is a muslin cloth to place over the silver plate to prevent detached

particles falling in the dish; s s' are the binding screws.

The weight of silver corresponding to a coulomb is given variously by

different authorities. Ayrton and Daniell take 1.11815 milligrams or

.017253 grain of metallic silver. Other determinations are as follows:

1.1183 milligrams   (Kohlrausch).

1.124   "           (Merscart).

The solution of silver nitrate should be from 15 to 30 per cent. of

strength. The current should not exceed one ampere per six square

inches; or in other words not more than about 3/1000 grain of silver

should be deposited per second on a square inch area of the dish. The

edge of the silver disc or anode should be about equidistant from the

side and bottom of the dish. The latter notes are due to Lord Rayleigh.

566   STANDARD ELECTRICAL DICTIONARY.

Voltameter, Weight.

A voltameter in which the amount of decomposition is determined by

weighing the products, or one of the products of the electrolysis. The

titles Voltameter, Copper, and Voltameter, Silver, may be cited.

Fig. 343. WEIGHT VOLTAMETERS.

In the cuts are shown examples of weight gas voltameters. These are

tubes light enough to be weighed when charged. Each contains a

decomposition cell T, with its platinum electrodes, and charged with

dilute sulphuric acid, while t is calcium chloride or other drying agent

to collect any water carried off as vapor or as spray by the escaping

gases; c are corks placed in position when the weighing is being

executed, so as to prevent the calcium chloride from absorbing moisture

from the air.

In use the tubes are weighed. They are then connected to the circuit,

after removal of the corks, and the decomposition proceeds. After a

sufficient time they are removed, the corks put in place, and they are

weighed again. The loss gives the water decomposed.

The water corresponding to one coulomb is

.09326 milligram   .001430 grain,   Ayrton,

.092      "                         Hospitalier,

.0935     "                         Daniell.

567   STANDARD ELECTRICAL DICTIONARY.

Voltametric Law.

The law on which voltameters are based. The amount of chemical

decomposition produced by an electric current in a given electrolyte is

proportional to the quantity of electricity passed through the solution.

Fig. 344. VOLTA'S FUNDAMENTAL EXPERIMENT.

Volta's Fundamental Experiment.

The moistened finger is placed on the upper plate of a condensing or

electrophorous electroscope. The other hand holds a plate of zinc z,

soldered to a plate of copper c. The lower plate is touched with the

copper. On removing the cover the gold leaves l diverge and with

negative electricity. Hence zinc is supposed to be positively

electrified when in contact with copper. The experiment is used to

demonstrate the contact theory of electricity.

568   STANDARD ELECTRICAL DICTIONARY.

Volta's Law of Galvanic Action.

The electro-motive force between any two metals in an electro-chemical

series (see Electro-Chemical Series) is equal to the sum of the

electro-motive forces between all the intervening metals.

Volta's Law of Thermo-electricity.

In a compound circuit, consisting of a number of different metals, all

points of which are at the same temperature, there is no current.

Volt, B. A.

The volt based on the B. A. ohm. It is equal to .9889 legal volt.

Volt, Congress.

The volt based upon the congress or legal ohm; the legal volt.

Volt-coulomb.

The unit of electric work; the watt-second; it is equivalent to

1.0E7     ergs.

.24068   gram degree C. (calorie)

.737337  foot lbs.,

.00134   horse power seconds.

Volt Indicator.

A form of easily read voltameter for use in electric light stations and

for similar work.

Volt, Legal.

The legal volt based upon the legal ohm. It is equal to 1.00112 B. A.

volt.

Voltmeter.

An instrument for determining the potential difference of any two

points.

In many cases it is a calibrated galvanometer wound with a coil of high

resistance. The object to be attained is that it shall receive only an

insignificant portion of current and that such portion shall suffice to

actuate it. If connected in parallel with any portion of a circuit, it

should not noticeably diminish its resistance.

The divisions into which ammeters range themselves answer for

voltmeters. In practice the same construction is adopted for both. The

different definitions of ammeters in disclosing the general lines of

these instruments are in general applicable to voltmeters, except that

the wire winding of the coils must be of thin wire of great length. The

definitions of ammeters may be consulted with the above understanding

for voltmeters.

In the use made of voltmeters there is a distinction from ammeters. An

ammeter is a current measurer and all the current measured must be

passed through it. But while a voltmeter is in fact a current measurer,

it is so graduated and so used that it gives in its readings the

difference of potential existing between two places on a circuit, and

while measuring the current passing through its own coils, it is by

calibration made to give not the current intensity, but the

electro-motive force producing such current.

In use it may be connected to two terminals of an open circuit, when as

it only permits an inconsiderable current to pass, it indicates the

potential difference existing between such points on open circuit. Or it

may be connected to any two parts of a closed circuit. Owing to its high

resistance, although it is in parallel with the intervening portion of

the circuit, as it is often connected in practice, it is without any

appreciable effect upon the current. It will then indicate the potential

difference existing between the two points.

569    STANDARD ELECTRICAL DICTIONARY.

Voltmeter, Battery.

A voltmeter for use in running batteries. In one form (Wirt's) it is

constructed for a low range of voltage, reading up to two and a half

volts and having exactly one ohm resistance, thus giving the battery

some work to do.

Voltmeter, Cardew.

A voltmeter in which the current passing through its conductor heats

such conductor, causing it to expand. Its expansion is caused to move an

index needle. By calibration the movements of the needle are made to

correspond to the potential differences producing the actuating currents

through it. The magnetic action of the current plays no part in its

operation. It is the invention of Capt. Cardew, R. E.

The construction of the instrument in one of its most recent forms is

shown in the cut. On each side of the drum-like case of the instrument

are the binding screws. These connect with the blocks m and n. To these

the fine wire conductor is connected and is carried down and up over the

two pulleys seen at the lowest extremity, its centre being attached to

c. From c a wire is carried to the drum p, shown on an enlarged scale on

the left of the cut. A second wire from the same drum or pulley connects

to the spring S. The winding of the two wires is shown in the separate

figure of c, where it is seen that they are screwed fast to the

periphery of the little drum, and are virtually continuations of each

other. By the screw A the tension of the spring S is adjusted.

On the shaft of the little drum p is a pinion, which works into the

teeth of the cog-wheel r. The shaft of r is extended through the dial

of the instrument, and carries an index. The dial is marked off for

volts; g g and h h are standards for carrying the pulleys.

570   STANDARD ELECTRICAL DICTIONARY.

The action of the instrument is as follows. The current passing through

the wire heats it. This current by Ohm's law is proportional to the

electro-motive force between the terminals. As it is heated it expands

and as it cools contracts, definite expanding and contracting

corresponding to definite potential differences. As the wire expands and

contracts the block or pin c moves back and forth, thus turning the drum

p and cogwheel r one way or permitting it to turn the other way under

the pull of the spring S.

Fig. 345. CARDEW VOLTMETER.

In this construction for a given expansion of the wire the piece c only

moves one half as much. The advantage of using a wire twice as long as

would be required for the same degree of movement were the full

expansion utilized is that a very thin wire can be employed. Such a wire

heats and cools more readily, and hence the instrument reaches its

reading more quickly or is more deadbeat, if we borrow a phraseology

properly applicable only to instruments with oscillating indexes.

In the most recent instruments about thirteen feet of wire .0025 inch in

diameter, and made of platinum-silver alloy is used.

571   STANDARD ELECTRICAL DICTIONARY.

If the potential difference to be measured lies between 30 and 120 volts

the wire as described suffices. But to extend the range of the

instrument a resistance in series is required. If such resistance is

double that of the instrument wire, and remains double whether the

latter is hot or cold the readings on the scale will correspond to

exactly twice the number of volts. This is brought about in some

instruments by the introduction in series of a duplicate wire, precisely

similar to the other wire, and like it, carried around pulleys and kept

stretched by a spring.

[Transcriber's note: If the series resistance is twice that of the

voltmeter, the indicated voltage will be ONE THIRD of the total

voltage.]

Thus whatever ratio of resistance exists between the two wires cold, it

is always the same at any temperature, as they both increase in

temperature at exactly the same rate. Tubes are provided to enclose the

stretched wires and pulleys, which tubes are blackened.

The voltmeter is unaffected by magnetic fields, and, as its

self-induction is very slight, it is much used for alternating currents.

The tubes containing the wire may be three feet long.

Its disadvantages are thus summarized by Ayrton. It absorbs a good deal

of energy; it cannot be constructed for small potential differences, as

the wire cannot be made thicker, as it would make it more sluggish;

there is vagueness in the readings near the zero point and sometimes

inaccuracy in the upper part of the scale.

Volts, Lost.

The volts at the terminals of a dynamo at full load fall short of their

value on open circuit. The difference of the two values are termed lost

volts.

Voltmeter, Electrostatic.

A voltmeter based on the lines of the quadrant electrometer. It includes

two sets of quadrants, each oppositely excited by one of the two parts,

whose potential difference is to be determined. They attract each other

against a controlling force as of gravity.

One form has the two sets poised on horizontal axes, bringing the parts

so that the flat quadrants move in vertical planes.

In another form a number of quadrants are used in each set, the members

of the two sets alternating with each other. One set is fixed, the

others move and carry the index.

Vulcanite.

Vulcanized india rubber which by high proportion of sulphur and proper

vulcanization has been made hard. It is sometimes distinguished from

ebonite as being comparatively light in color, often a dull red, while

ebonite is black. For its electrical properties see Ebonite.

Both substances have their defects, in producing surface leakage.

Washing with weak ammonia, or with dilute soda solution, followed by

distilled water, is recommended for the surface, if there is any trouble

with surface leakage. It may also be rubbed over with melted paraffine

wax.

572   STANDARD ELECTRICAL DICTIONARY.

W.

(a) A symbol or abbreviation for watt.

(b) A symbol or abbreviation for work.

(c) A symbol or abbreviation for weight.

Wall Bracket.

A telegraph bracket to be attached to the external walls of buildings to

which wires are attached as they come from the poles to reach

converters, or for direct introduction into a building.

Wall Sockets.

Sockets for incandescent lamps constructed to be attached to a wall.

Ward.

Direction in a straight line; a term proposed by Prof. James Thompson.

The words "backward" and "forward" indicate its scope.

Water.

A compound whose molecule consists of two atoms of hydrogen and one atom

of oxygen; formula, H2 O.

Its specific gravity is 1, it being the base of the system of specific

gravities of solids and liquids.

If pure, it is almost a non-conductor of electricity. If any impurity is

present it still presents an exceedingly high, almost immeasurable true

resistance, but becomes by the presence of any impurity an electrolyte.

Water Equivalent.

In a calorimeter of any kind the weight of water which would be raised

as much as is the calorimeter with its contents by the addition of any

given amount of heat received by the calorimeter.

Waterproof Lamp Globe.

An outer globe for incandescent lamps, to protect them from water.

Watt.

(a) The practical unit of electric activity, rate of work, or rate of

energy. It is the rate of energy or of work represented by a current of

one ampere urged by one volt electro-motive force; the volt-ampere.

It is the analogue in electricity of the horse power in mechanics;

approximately, 746 watts represent one electric horse power.

Ohm's law, taken as C = E/R, gives as values for current, C and E/R, and

for electro- motive force C R. In these formulas, C represents current

strength, R represents resistance and E represents electro-motive force.

Then a watt being the product of electro-motive force by current

strength, we get the following values for rate of electric energy, of

which the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R.

The equivalents of the watt vary a little according to different

authorities. Ayrton gives the following equivalents: 44.25 foot pounds

per minute--.7375 foot pounds per second--1/746 horse power. These

values are practically accurate. Hospitalier gives .7377 foot pounds per

second. Hering gives .737324 foot pounds per second, and 1000/745941

horse power.

573   STANDARD ELECTRICAL DICTIONARY.

It is equal to 1E7 ergs per second.

Synonym--Volt-ampere.

(c) It has been proposed to use the term as the unit of energy, instead

of activity or rate of energy (Sir C. W. Siemens, British Association,

1882); this use has not been adopted and may be regarded as abandoned.

[Transcriber's note; Watt is a unit of POWER--energy per unit of time.]

Watt-hour.

A unit of electric energy or work; one watt exerted or expended for one

hour.

It is equivalent to :

866.448  gram-degrees C. (calories)

2654.4    foot lbs.

3600      watt-seconds or volt-coulombs.

60      watt-minutes.

Watt-minute.

A unit of electric energy or work; one watt exerted or expended for one

minute.

It is equivalent to

14.4408  gram-degrees C. (calories),

44.240   foot pounds,

60       watt seconds or volt-coulombs,

1/60     watt hour.

Watts, Apparent.

The product in an alternating current dynamo of the virtual amperes by

the virtual volts. To give the true watts this product must be

multiplied by the cosine of the angle of lead or lag. (See Current,

Wattless.)

[Transcriber's note: This is now called a volt-amp. The usual usage is

KVA, or kilovolt-ampere.]

Watt-second.

A unit of electric energy or work. One watt exerted or expended for one

second.

It is equivalent to

.24068     gram degree C. (calorie),

.000955    lb. degree F.,

.737337    foot lbs.,

.0013406   horse power second (English),

.0013592   horse power second (metric).

Synonym--Volt-coulomb.

Waves, Electro-magnetic.

Ether waves caused by electromagnetic disturbances affecting the

luminiferous ether. (See Discharge, Oscillatory--Maxwell's Theory of

Light--Resonance. Electric.)

[Transcriber's note: The Michaelson-Morley experiment (1887) had already

called ether into question, but quantum theory and photons are decades

in the future.]

574   STANDARD ELECTRICAL DICTIONARY.

Weber.

(a.) A name suggested by Clausius and Siemens to denote a magnet pole of

unit strength. This use is abandoned.

(b.) It has been used to designate the unit of quantity--the coulomb.

This use is abandoned.

(c.) It has been used to designate the unit of current strength the

ampere. This use is abandoned.

[Transcriber's note: Definition (a) is now used. One weber of magnetic

flux linked to a circuit of one turn produces an electromotive force of

1 volt if it is reduced to zero at a uniform rate in 1 second.]

Weber-meter.

An ampere-meter or ammeter. The term is not used since the term "weber,"

indicating the ampere or coulomb, has been abandoned.

Welding, Electric.

Welding metals by heat produced by electricity. The heat may be produced

by a current passing through the point of junction (Elihu Thomson) or by

the voltaic arc. (Benardos & Olzewski.)

Fig. 346. ELECTRIC WELDING INDUCTION COIL.

The current process is carried out by pressing together the objects to

be united, while holding them in conducting clamps. A heavy current is

turned on by way of the clamps and rapidly heats the metals at the

junction, which is of course the point of highest resistance. As the

metal softens, it is pressed together, one of the clamps being mounted

with feed motion, flux is dropped on if necessary, and the metal pieces

unite.

The most remarkable results are thus attained; almost all common metals

can be welded, and different metals can be welded together. Tubes and

other shapes can also be united. In many cases the weld is the strongest

part.

575   STANDARD ELECTRICAL DICTIONARY.

The alternating current is employed. A special dynamo is sometimes used

to produce it. This dynamo has two windings on the armature. One is of

fine wire and is in series with the field magnets and excites them. The

other is of copper bars, and connects with the welding apparatus, giving

a current of high intensity but actuated by low potential.

Where the special dynamo is not used, an induction coil or transformer

is used. The primary includes a large number of convolutions of

relatively fine wire; the secondary may only be one turn of a large

copper bar.

The cut shows in diagram an electric welding coil. P is the primary coil

of a number of turns of wire; S S is the secondary, a single copper bar

bent into an almost complete circle. It terminates in clamps D D for

holding the bars to be welded. B C, B' C are the bars to be welded. They

are pressed together by the screw J. The large coil I of iron wire

surrounding the coils represents the iron core.

The real apparatus as at present constructed involves many

modifications. The diagram only illustrates the principle of the

apparatus.

In welding by the voltaic arc the place to be heated is made an

electrode of an arc by connection with one terminal of an electric

circuit. A carbon is connected to the other terminal. An arc is started

by touching and withdrawal of the carbon. The heat may be used for

welding, soldering, brazing, or even for perforating or dividing metal

sheets.

Welding Transformer.

The induction coil or transformer used in electric welding. For its

general principles of construction, see Welding, Electric.

Wheatstone's Bridge.

A system of connections applied to parallel circuits, including

resistance coils for the purpose of measuring an unknown resistance. A

single current is made to pass from A through two parallel connected

branches, joining together again at C. A cross connection B D has a

galvanometer or other current indicator in circuit. In any conductor

through which a current is passing, the fall of potential at given

points is proportional to the resistance between such points. Referring

to the diagram a given fall of potential exists between A and C. The

fall between A and B is to the fall between A and C as the resistance r

between A and B is to the resistance r + r' between A and C. The same

applies to the other branch, with the substitution of the resistances s

and S' and the point D for r r' and B. Therefore, if this proportion

holds, r : r' : : s : S'. No current will go through B D , and the

galvanometer will be unaffected. Assume s' to be of unknown resistance,

the above proportion will give it, if r, r' and s are known, or if the

ratio of r to r' and the absolute value of s is known.

576   STANDARD ELECTRICAL DICTIONARY.

In use the resistances r, r', and s are made to vary as desired. To

measure an unknown resistance it is introduced at S', and one of the

other resistances is varied until the galvanometer is unaffected. Then

the resistance of S' is determined by calculation as just explained. The

artificial resistances may be resistance coils, q. v., or it is enough

to have one unknown resistance at s. Then if the length of wire ABC is

accurately known, the point B can be shifted along it until the balance

is attained. The relative lengths A B, and B C, will then give the ratio

r : r' needed for the calculation. This assumes the wire ABC to be of

absolutely uniform resistance. This is the principle of the meter-bridge

described below. The use of coils is the more common method and is

carried out by special resistance boxes, with the connections arranged

to carry out the exact principle as explained. The principle of

construction and use of a resistance box of the Wheatstone bridge type,

as shown in the cut, is described under Box Bridge, q. v.

FIG. 347. WHEATSTONE BRIDGE CONNECTIONS.

FIG. 348. TOP OF BOX BRIDGE.

577   STANDARD ELECTRICAL DICTIONARY.

The next cut shows the sliding form of bridge called the meter bridge,

if the slide wire is a meter long or a half- or a quarter-meter bridge,

etc., according to the length of this wire. It is described under Meter

Bridge, q. v. Many refinements in construction and in proper proportion

of resistances for given work apply to these constructions.

Synonyms--Electric Balance--Resistance Bridge--Wheatstone's Balance.

Fig. 349. METER BRIDGE.

Whirl, Electric.

(a) A conductor carrying an electric current is surrounded by circular

lines of force, which are sometimes termed an electric whirl.

(b) The Electric Flyer. (See Flyer, Electric.)

Wimshurst Electric Machine.

An influence machine for producing high potential or static electricity.

Two circular discs of thin glass are mounted on perforated hubs or

bosses of wood or ebonite. Each hub has a groove turned upon it to

receive a cord. Each disc is shellacked. They are mounted on a

horizontal steel spindle so as to face and to be within one-eighth of an

inch of each other. On the outside of each disc sixteen or eighteen

sectors of tinfoil or thin metal are cemented.

578   STANDARD ELECTRICAL DICTIONARY.

Two curved brass rods terminating in wire brushes curved into a

semi-ellipse just graze the outer surfaces of the plates with their

brushes. They lie in imaginary planes, passing through the axis of the

spindle and at right angles from each other.

Four collecting combs are arranged horizontally on insulating supports

to collect electricity from the horizontal diameters of the discs. These

lie at an angle of about 45° with the other equalizing rods. Discharging

rods connect with the collecting combs.

The principle of the machine is that one set of sector plates act as

inductors for the other set. Its action is not perfectly understood.

It works well in damp weather, far surpassing other influence machines

in this respect. On turning the handle a constant succession or stream

of sparks is produced between the terminals of the discharging rods.

Windage.

In a dynamo the real air gap between the armature windings and pole

pieces is sometimes thus termed.

Wind, Electric.

The rush of air particles from a point connected to a statically charged

condenser.

Winding, Compound.

A method of winding a generator or motor in which a shunt winding is

used for the field magnets and in which also a second winding of the

magnet is placed in series with the outer circuit. (See Winding,

Series--Winding, Shunt.)

Fig. 350. CHARACTERISTIC CURVES OF SHUNT AND SERIES WINDING.

The object of compound winding is to make a self-regulating dynamo and

this object is partly attained for a constant speed.

The characteristic curves of shunt and series winding are of opposite

natures. The first increases in electro-motive force for resistance in

the outer circuit, the latter decreases under the same conditions. If

the windings are so proportioned that these conditions for each one of

the two windings are equal and opposite, it is evident that the

characteristic may be a straight line. This, however, it will only be at

a single speed of rotation.

579   STANDARD ELECTRICAL DICTIONARY.

Winding, Disc.

A winding which (S. P. Thompson) may be treated as a drum winding

extended radially, the periphery corresponding to the back end of the

drum. The magnet poles are generally placed so as to face the side or

sides of the disc.

Winding, Lap.

A method of winding disc and drum armatures. It consists in lapping back

each lead of wire towards the preceding lead upon the commutator end of

the armature. Thus taking the letter U as the diagrammatical

representation of a turn of wire in connecting its ends to the

commutator bars they are brought towards each other so as to connect

with contiguous commutator bars. This carries out the principle of

keeping the two members of the U moving in regions of opposite polarity

of field, so that the currents induced in them shall have opposite

directions, thus producing a total current in one sense through the bent

wire.

Winding, Long Shunt.

A system of compound winding for dynamos and motors. The field is wound

in series and, in addition thereto, there is a shunt winding connected

across from terminal to terminal of the machine, and which may be

regarded either as a shunt to the outer circuit, or as a shunt to the

series-field and armature winding. (See Winding, Short Shunt.)

Synonyms--Series and Long Shunt Winding.

Winding, Multiple.

A winding of an electro-magnet, in which separate coils are wound on the

core, so that one or any number may be used as desired in parallel or in

series. For each coil a separate binding post should be provided.

Winding, Multipolar.

Winding adapted for armatures of multi-polar dynamos or motors.

Winding, Series.

A method of winding a generator or motor, in which one of the

commutator-brush connections is connected to the field-magnet winding;

the other end of the magnet winding connects with the outer circuit. The

other armature-brush connects with the other terminal of the outer

circuit.

Winding, Series and Separate Coil.

A method of automatic regulation applied to alternating current dynamos.

Winding, Short Shunt.

A method of compound winding for dynamos and motors. The field is wound

in series, and in addition thereto there is a shunt winding connected

from brush to brush only, thus paralleling the armature. (See Winding,

Long Shunt.)

Synonyms--Series and Short Shunt Winding.

580   STANDARD ELECTRICAL DICTIONARY.

Winding, Shunt.

A method of winding a generator or motor. Each commutator-brush has two

connections. One set are the terminals of the outer circuit, the other

set are the terminals of the field-magnet windings. In other words, the

field-magnet windings are in shunt or in parallel with the outer

circuit.

Winding, Shuttle.

A method of dynamo or motor-armature winding. A single groove passes

longitudinally around the core and in this the wire is continuously

wound. The system is not now used. The old Siemens' H armature

illustrates the principle.

Winding, Wave.

A method of winding disc and drum armatures. It consists in advancing

the commutator ends of the U shaped turns progressively, so that as many

commutator bars intervene between any two consecutive commutator

connections of the wire as there are leads of wire on the drum between

consecutive leads of the wire. This is carried out with due regard to

the principle that taking the letter U as the diagrammatical

representation of a turn of wire, its two members must move through

regions of the field of opposite polarity.

Wire Finder.

A galvanometer or other instrument used for identifying the ends of a

given wire in a cable containing several.

Work.

When a force acts upon a body and the body moves in the direction of the

force, the force does work. Hence, work is the action of a force through

space against resistance.

It is generally expressed in compound units of length and weight, as

foot-pounds, meaning a pound raised one foot.

Work, Electric, Unit of.

The volt-coulomb, q. v., or watt-second, as it is often termed.

Working, Diode.

In multiplex telegraphy the transmission of two messages,

simultaneously, over one wire. (See Telegraphy, Multiple.)

Working, Contraplex.

A variety of duplex telegraphy in which the messages are sent from

opposite ends of the line, simultaneously, so as to be transmitted in

opposite directions. (See Working, Diplex.)

Working, Diplex.

In duplex telegraphy the sending of two independent messages from the

same end of the line in the same direction.

581   STANDARD ELECTRICAL DICTIONARY.

Working, Double Curb.

A method of working telegraph lines. When a signal is sent the line is

charged. This has to be got rid of, and is an element of retardation. In

double curb working it is disposed of by sending a momentary current

first in the reverse, and then in the same, and finally in the reverse

direction. This is found to reduce the charge to a very low point.

Working, Hexode.

In multiplex telegraphy the transmission of six messages simultaneously

over one wire. (See Telegraphy, Multiplex.)

Working, Pentode.

In multiplex telegraphy the transmission of five messages simultaneously

over one wire. (See Telegraphy, Multiplex.)

Working, Reverse Current.

A method of telegraphy, in which the currents are reversed or alternated

in direction.

Working, Single Curb.

A simpler form of telegraph signaling than double curb working. It

consists in sending a reverse current through the line for each signal

by reversing the battery connection.

Working, Tetrode.

In multiplex telegraphy the transmission of four messages simultaneously

over the same line. (See Telegraphy, Multiplex.)

Working, Triode.

In multiplex telegraphy the transmission of three messages

simultaneously over the same wire. (See Telegraphy, Multiplex.)

Work, Unit of.

The erg, q. v. It is the same as the unit of energy, of which work is

the corelative, being equal and opposite to the energy expended in doing

it. There are many other engineering units of work, as the foot-pound

and foot-ton.

Yoke.

In an electro-magnet, the piece of iron which connects the ends furthest

from the poles of the two portions of the core on which the wire is

wound.

Zamboni's Dry Pile.

A voltaic pile or battery. It is made of discs of paper, silvered or

tinned on one side and sprinkled on the other with binoxide of

manganese. Sometimes as many as 2,000 of such couples are piled up in a

glass tube and pressed together with two rods which form the terminals.

They maintain a high potential difference, but having very high

resistance and slight polarization capacity, give exceedingly small

quantities.

Zero.

(a) The origin of any scale of measurement.

(b) An infinitely small quantity or measurement.

582   STANDARD ELECTRICAL DICTIONARY.

Zero, Absolute.

From several considerations it is believed that at a certain temperature

the molecules of all bodies would touch each other, their kinetic motion

would cease, and there would be no heat. This temperature is the

absolute zero. It is put at -273° C. (-459° F.)

[Transcriber's note; The modern value is 0° Kelvin,  -273.15° C, or

-459.67° F. The lowest reported temperature observed is 1E-10° K.]

Zero, Potential.

Conventionally, the potential of the earth. True zero potential could

only exist in the surface of a body infinitely distant from other

electrified bodies.

Zero, Thermometric.

There are three thermometric zeros. In the Réaumur and centigrade

scales, it is at the temperature of melting ice; in the Fahrenheit

scale, it is 32° F. below that temperature, or corresponds to -17.78° C.

The third is the absolute zero. (See Zero, Absolute.)

Zinc.

A metal; one of the elements; atomic weight, 65.1;

specific gravity, 6.8 to 7.2.

microhms.

Resistance at 0° C. (32° F.), per centimeter cube,   5.626

Resistance at 0° C. (32° F.), per inch cube,         2.215

Relative resistance (silver = 1),                    3.741

ohms.

Resistance of a wire, 1 foot long, weighing 1 grain,   .5766

(a) 1 foot long, 1 millimeter diameter,            33.85

(b) 1 meter long, weighing 1 gram,                   .4023

(c) 1 meter long, 1 millimeter diameter,             .07163

Zinc is principally used in electrical work as the positive plate in

voltaic batteries.

Zincode.

The terminal connecting with the zinc plate, or its equivalent in an

electric circuit; the negative electrode; the kathode. A term now little

used.

Zinc Sender.

An apparatus used in telegraphy for sending a momentary reverse current

into the line after each signal, thus counteracting retardation.

Zone, Peripolar.

In medical electricity, the region surrounding the polar zone, q. v.

Zone, Polar.

In medical electricity, the region surrounding the electrode applied to

the human body.

583-624  INDEX.

Page

A  7

Absolute  7

Absolute Calibration  97

Absolute Electric Potential  429

Absolute Electrometer  222

Absolute Galvanometer  266

Absolute Measurement  8

Absolute Potential  428

Absolute Temperature  8

Absolute Unit  554

Absolute Unit Resistance, Weber's   468

Absolute Vacuum  557

Absolute Zero  581

Abscissa  7

Abscissas, Axis of   54

Absorption, Electric   8

A. C. C.  8

Acceleration  8

Accumulator  8

Accumulator, Electrostatic  8

Accumulator, Water Dropping   9

Acetic Acid Battery   58

Acheson Effect   208

Acid, Carbonic  108

Acid, Chromic, Battery  61

Acid, Hydrochloric, Battery   66

Acid, Spent  491

Acid, Sulphuric    497

Acidometer  10

Acierage  494

Aclinic Line  10

Acoustic Telegraphy   10

Acoutemeter  10, 53

Action, Electrophoric   230

Action, Local  331

Action, Magne-crystallic   335

Action, Refreshing  454

Action, Secondary  477

Actinic Photometer  411

Actinic Rays.   11

Actinism  11

Actinometer, Electric   11

Active Electric Circuit,   123

Activity  11

Actual Horse Power  290

Adapter  11

A. D. C.,   11

Adherence, Electro-magnetic   11

Adherence, Magnetic  338

Adjuster, Cord   152

Adjustment of Brushes  90

Admiralty Rules of Heating  12

AEolotropic  34

Aerial Cable  95

Aerial Conductor  12

Affinity  12

Affinity, Molecular   380

After Current,.   159

Agglomerate Leclanché Battery  66

Agir Motor   13

Agone  13

Agonic Line,   13

Air  13

Air Blast  13

Air Condenser  14

Air Field  252

Air Gaps  15

Air Line Wire  15

Air Pump, Heated   15

Air Pump, Mercurial   16

Air Pumps, Short Fall   16

Alarm, Burglar   16

Alarm, Electric  17

Alarm, Fire, Electric Automatic   257

Alarm, Fire and Heat  17

Alarm, Overflow   18

Alarm, Water Level   18

Alcohol, Electric Rectification of   18

Alignment,   18

Allotropy  18

Alloy  18

Alloy, Platinum  419

Alloy, Platinum-Silver  419

Alloys, Paillard  400

Alphabet, Telegraphic   19

Alternating  23

Alternating Current  159

Alternating Current Arc  23

Alternating Current Dynamo  193

Alternating Current Generator or Dynamo  24

Alternating Current Meter  373

Alternating Current System  23

Alternating Field  252

Alternative Current  563

Alternative Path  24

Alternatives, Voltaic   563

Alternator  24

Alternator, Constant Current   24

Alternator, Dead Point of an   177

Alternation  23

Alternation, Complete   23

Alternation, Cycle of   175

Alum Battery  58

Aluminum  24

Aluminum Battery  58

Amalgam  24

Amalgamation  25

Amber  25

American Twist Joint   309

Ammeter  26

Ammeter, Ayrton   26

Ammeter, Commutator   26

Ammeter, Cunynghame's   26

Ammeter, Eccentric Iron Disc  27

Ammeter, Electro-magnetic  27

Ammeter, Gravity  27

Ammeter, Magnetic Vane  27

Ammeter, Magnifying Spring   28

Ammeter, Permanent Magnet   28

Ammeter, Reducteur for   453

Ammeter, Solenoid   28

Ammeter, Spring   28

Ammeter, Steel Yard  28

Ammunition Hoist, Electric   29

Amperage  29

Ampere  29

Ampere- and Volt-meter Galvanometer  274

Ampere Arc   30

Ampere Balance  56

Ampere Currents  30

Ampere Feet  30

Ampere-hour  30

Amperes, Lost   30

Ampêre's Memoria Technica   30

Ampere Meters  26, 30

Ampere Meter, Balance  391

Ampere Meter, Neutral Wire   391

Ampere-minute  30

Ampere Ring  30

Ampere-second  30

Ampere's Theory of Magnetism  354

Ampere-turns  31

Ampere-turns, Primary   31

Ampere-turns, Secondary   31, 551

Ampere Windings  31

Ampérian Currents  165

Amplitude of Waves  31

Analogous Pole  31, 425

Analysis  31

Analysis, Electric  32

Analysis, Electrolytic  214

Analyzer, Electric   32

Anelectrics  32

Anelectrotonus  32

Angle of Declination  32, 177

Angle of the Polar Span  32

Angle of Inclination or Dip  33

Angle of Lag  33-318

Angle of Lead  33

Angle of Maximum Sensitiveness  479

Angle of Polar Span  423

Angle, Polar   423

Angle, Unit  554

Angular Currents  165

Angular Currents, Laws of   165

Angular Force  544

Angular Velocity  32, 559

Animal Electricity  33

Animal System, Electric Excitability of   247

Anion  33

Anisotropic  34

Annealing, Electric  34

Annular Electro-magnet  216

Annunciator  34

Annunciator Clock  35

Annunciator Clock, Electric   127

Annunciator Drop  35

Annunciator, Gravity Drop   35

Annunciator, Needle  35

Annunciator, Swinging or Pendulum  35

Anodal Diffusion  35

Anode  36

Anodic Closure Contraction  36

Anodic Duration Contraction  36

Anodic Opening Contraction  36

Anodic Reactions  36

Anomalous Magnet  335

Anti-induction Conductor   36, 145

Anti-magnetic Shield  37

Antilogous Pole,   425

Antimony  37

Anvil  37

A. O. C.  38

Aperiodic  38

Aperiodic Galvanometer  266

Apparent Coefficient of Magnetic Induction  346

Apparent Resistance  297, 462

Apparent Watts  573

Arago's Disc  88

Arc  39

Arc, Ampere   30

Arc, Compound.   39

Arc, Electric Blow-pipe   84

Arc, Metallic  39

Arc, Micrometer   39, 376

Arc, Multiple   387

Arc, Simple  39

Arc, Voltaic   39

Arc Box, Multiple   387

Arc Lamp  319

Arc Lamp, Differential   320

Arc Lamp, Double Carbon   191

Areometer  41

Areometer, Bead   41

Argyrometry  41

Arm   41

Armature  41

Armature, Bar   42

Armature, Bipolar   42

Armature Bore  42

Armature Chamber  42

Armature, Closed Coil   43

Armature Coil, or Coils   43

Armature Conductors, Lamination of   319

Armature Core  43

Armature, Cylinder   43

Armature, Cylindrical   45

Armature, Disc   43

Armature, Drum  45

Armature Factor  45

Armature, Flat Ring   45

Armature, Girder   49

Armature, H  49

Armature, Hinged   45

Armature, Hole  45

Armature, Intensity   45

Armature Interference  45

Armature, Load of   46

Armature, Multipolar   46

Armature, Neutral   46

Armature, Neutral Relay  46, 390

Armature, Non-polarized   46

Armature of Influence Machine  46

Armature of Leyden Jar or Static Condenser  46

Armature, Open Coil   46

Armature, Perforated   45

Armature, Pivoted   47

Armature Pockets  47

Armature, Polarized   47

Armature, Pole   47

Armature, Quantity   47

Armature, Radial   47

Armature Reactions  41

Armature, Revolving, Page's   47

Armature, Ring   48

Armature, Rolling  49

Armatures, Gyrostatic Action of   288

Armature, Shuttle  49

Armature, Siemens' Old  49

Armature, Spherical  49

Armature, Stranded Conductor   49

Armature, Unipolar  50, 553

Armature, Ventilation of   560

Armor of Cable  50

Arm, Rheostat   472

Arms, Proportionate   436

Arms, Ratio  437

Arms, Rocker  50-474

Arrester, Lightning   328

Arrester, Lightning, Counter-electro-motive Force   329

Arrester, Lightning, Plates   329

Arrester, Lightning, Vacuum.   329

Arrester Plate  417

Arrester, Spark   489

Arrival Curve  168

Articulate Speech  50

Artificial Carbon  106

Artificial Magnet  335

Ascending Lightning  330

Assymmetrical Resistance  462

Astatic  50

Astatic Circuit  12

Astatic Couple  157

Astatic Galvanometer  266

Astatic Needle  50

Astronomical Meridian,   372

Asymptote  51

Atmosphere  51

Atmosphere, Residual  51, 460

Atmospheric Electricity  51

Atom  52

Atomic Attraction   52

Atomic Current  160

Atomic Energy  238

Atomic Heat  52-285

Atomic Weight  53

Atomicity   52

Attracted Disc Electrometer  223

Attraction  53

Attraction, Atomic  52

Attraction, Magnetic   338

Attraction, Molar   380

Attraction, Molecular  380

Attraction and Repulsion, Electro-dynamic  211

Attraction and Repulsion, Electro-magnetic  217

Attraction and Repulsion, Electro-static   234

Attraction and Repulsion, Electro-static, Coulomb's Law of   155

Audiometer  53

Aura, Electrical   53

Aurora  53

Austral Pole  54

Autographic Telegraph  510

Automatic Circuit Breaker  121

Automatic Cut Out  175, 475

Automatic Drop  192

Automatic Electric Bell  78

Automatic Electric Fire Alarm  257

Automatic Switch   500

Automatic Telegraph  504

A. W. G.,    54

Axial Couple  514

Axial Force  544

Axial Magnet  336

Axis, Electric   54

Axis, Magnetic   338

Axis of Abscissas   54

Axis of Ordinates  54, 397

Axis of X  54

Axis of Y  54, 397

Ayrton's Ammeter  26

Azimuth    54

Azimuth Circle  54

Azimuth Compass  141

Azimuth, Magnetic   338

B   55

B. A.   55

Back Electro-motive Force of Polarization  156

Back Induction  55

Back Shock or Stroke of Lightning  55

Back Stroke  55

Bagration Battery  59

Balance  55

Balance, Ampere  56

Balance Ampere Meter  391

Balance, Electric  577

Balance, Inductance   293

Balance, Plating  417

Balance, Slide  374

Balance, Thermic   85

Balance, Torsion, Coulomb's   544

Balance, Wheatstone's  577

Balata  56

Ballistic Galvanometer  567

Balloon Battery  59

B. and S. W. G.   56

Banked Battery  59

Bank of Lamps  323

B. A. Ohm  394

Barad  56

Bar, Armature   42

Bar, Bus  94

Bar Electro-magnet  217

Bar Magnet  336

Barometer  56

Bar, Omnibus   94

Bar Photometer  411

Bars, Commutator   56, 140

Bath  57

Bath, Bipolar Electric   57

Bath, Copper  152

Bath, Copper Stripping   152

Bath, Electric Head   284

Bath, Electric Shower   57

Bath, Gold  279

Bath, Gold Stripping  279

Bath, Multipolar Electric   57

Bath, Nickel  391

Bath, Plating  418

Baths, Electro-medical   222

Bath, Silver  484

Bath, Silver Stripping   484

Bath, Stripping  57

Bath, Unipolar Electric   57

Batten  57-58

Battery, Acetic Acid   58

Battery, Alum  58

Battery, Aluminum  58

Battery, Bagration  59

Battery, Balloon   59

Battery, Banked  59

Battery, Bichromate   59

Battery, Bunsen   59

Battery, Cadmium   60

Battery, Callan  60

Battery, Camacho's   60

Battery, Carré's   60

Battery, Cautery   61

Battery Cell, Element of a   237

Battery, Chloric Acid  61

Battery, Chloride of Lime   61

Battery, Chromic Acid   61

Battery, Closed Circuit   61

Battery, Column   61

Battery, d'Arsonval's   62

Battery, de la Rue  .62

Battery, de la Rive's Floating   179

Battery, Dry  63

Battery, Elements of   63

Battery, Faradic  63

Battery, Ferric Chloride   63

Battery, Fuller's  63

Battery, Gas  63

Battery, Gas, Grove's   281

Battery Gauge  64

Battery, Gravity   64

Battery, Grenet   65

Battery, Grove's  65

Battery, Hydrochloric Acid   66

Battery, Lalande & Chaperon   69

Battery, Lalande-Edison   69

Battery, Lead Chloride   66

Battery, Lead Sulphate  66

Battery, Leclanché   66

Battery, Leclanché Agglomerate  66

Battery, Local   66, 831

Battery, Magnetic   338

Battery, Main  66

Battery, Marié Davy's   67

Battery, Maynooth's   67

Battery, Medical  67

Battery, Meidinger's  68

Battery, Mercury Bichromate   63

Battery Mud  68

Battery, Multiple Connected   68

Battery, Niaudet's  61

Battery, Nitric Acid   68

Battery of Dynamos  6S

Battery of Leyden Jars,   68

Battery, Open Circuit  68

Battery or Pile, Thermo-electric   530

Battery, Oxide of Copper   68

Battery, Peroxide of Lead   69

Battery, Platinized Carbon   69

Battery, Plunge   69

Battery, Pneumatic   69

Battery, Primary   69, 434

Battery, Pulvermacher's Electro-medical   69

Battery, Sal Ammoniac   69

Battery, Salt, or Sea Salt  69

Battery, Sand  70

Battery, Secondary  70

Battery, Secondary, Planté's   72

Battery, Secondary, Real Efficiency of   205

Battery, Sir William Thomson's   72

Battery, Siemens and Halske's  72

Battery, Skrivanow   72

Battery, Smee's   73

Battery Solutions, Chromic Acid   73

119, 178, 192, 232, 318, 421, 542, 549

Battery, Spiral  73

Battery, Split   73

Battery, Sulphate of Mercury   67

Battery System, Universal  556

Battery, Thermo-chemical   530

Battery, Trough  73

Battery, Trouvé's Blotting Paper   73

Battery, Tyer's  74

Battery, Upward's  75

Battery, Varley's  76

Battery, Volta's   76

Battery, Voltaic or Galvanic   76

Battery Voltmeter  569

Battery, Water  77

Battery, Wollaston  78

B. A. Unit,  554

B. A. Unit of Resistance  78, 462

B. A. Volt  568

B. E.   78

Bead Areometer  41

Becquerel's Laws of Thermo-electricity   78

Beaumé Hydrometer  78

Bed-piece  78

Bell, Automatic Electric    78

Bell, Call   78, 98

Bell Call  79

Bell Call, Extension   248

Bell, Circular  79

Bell, Differentially Wound   79

Bell, Electric  79

Bell, Electro-mechanical    80

Bell, Indicating   80, 297

Bell, Magneto  80

Bell, Magneto Call   361

Bell, Night  392

Bell-shaped Magnet,   336

Bells, Relay  80, 457

Bell, Trembling   78

Bell, Vibrating.    78

Belts, Joints in  311

Bennett's Electroscope  233

Bias  80

Bias of Tongue of Polarized Relay  542

Bichromate Battery  59

Bichromate Mercury Battery  63

Bifilar Suspension  498

Bifilar Winding  81

Binary Compound  81

Binding   81

Binding Posts or Screws  81

Binnacle  81

Biology, Electro-  208

Bioscopy, Electric   82

Bipolar Armature  42

Bipolar Electric Bath  57

Bisected Coils  132

Bismuth  82

Bi-telephone  82, 524

Black, Platinum   419

Blasting, Electric  83

Bleaching, Electric   83

Block, Branch   87

Block, Cross-over   158

Block System  83

Block Wire  83

Blotting Paper Battery, Trouvé's   73

Blow-pipe  83

Blow-pipe, Electric Arc   84

Blue Magnetism  355

Bluestone  84

Blue Vitriol   562

Board, Cross-connecting   157

Board, Fuse   263

Board, Hanger   284

Board, Key   313

Board, Multiple Switch   387

Board of Trade Ohm  394

Board of Trade Unit  555

Board, Switch  500

Boat, Electric   84

Bobbins  84

Body Protector  84

Bohenberger's Electroscope  233

Boiler Feed, Electric  84

Boiling   84

Boll  85

Bolometer   85

Bombardment, Molecular   380

Bore, Armature   42

Boreal Pole  85

Bot  85

Bound Charge  115

Box Bridge  85

Box, Cable  95

Box, Cooling  151

Box, Distributing   190

Boxes, Flush  258

Box, Fishing  311

Box, Fuse  263

Boxing the Compass  86

Box, Junction  311

Box, Multiple Arc   387

Box, Resistance  462

Box, Resistance, Sliding   463

Box Sounding Relay  457

Box, Splice   492

Bracket, Saddle   475

Bracket, Wall   572

Braid, Tubular  550

Brake, Electro-magnetic   86

Brake, Magneto-electric   362

Brake, Prony  435

Branch   87

Branch Block  87

Branch Circuit  121

Branch Conductor  87

Branding, Electric   87

Brassing  87

Brazing, Electric   87

Break  88

Break, Circuit Loop   125

Break-down Switch  88

Breaker, Automatic Circuit   121

Breaker, Circuit  121

Breaker, Circuit, File   121

Breaker, Contact  121, 146

Break Induced Current  162

Breaking Weight  89

Break, Loop    332

Break Shock  482

Breath Figures, Electric   89

Breeze, Electric   89

Breeze, Static  493

Breguet Unit of Resistance  463

Bridge   89

Bridge, Box  89

Bridge, Inductance   293

Bridge, Induction   293

Bridge Key   313

Bridge, Magnetic  338

Bridge, Meter  373

Bridge, Resistance   577

Bridge, Reversible    472

Bridge, Slide  374

Bridge, Wheatstone .   575

Bridge, Wheatstone, Commercial   36

British Association Bridge  89

Britannia Joint  309

Broadside Method  89

Broken Circuit  125

Bronzing  89

Brush  90

Brush, Carbon  90

Brush, Collecting  90

Brush, Discharge   187

Brushes, Adjustment of   90

Brushes, Lead of   90

Brushes, Negative Lead of   324

Brushes, Scratch   476

Brush, Faradic   251

Brush Holders  91

Brush, Pilot  91

Brush, Rotating    91

Brush, Third  91

Brush Trimmer  549

Brush, Wire Gauge   92

Buckling  92

Bug  92

Bug Trap  92

Bunched Cable  95

Bunsen Battery  59

Bunsen Disc  92

Bunsen's Photometer   412

Buoy, Electric  93

Burglar Alarm  16

Burner, Electric Gas   93

Burning  94

Bus Bar  94

Bus Rod  94

Bus Wire  94

Butt Joint  310

Button, Call   98

Button, Press   94

Button, Push   93, 98

Buzzer  94

B. W. G.  94

C  95

C. C.  109

Cable  95

Cable, Aerial  95

Cable, Armature of   50

Cable, Armor of   50

Cable Box  95

Cable, Bunched  95

Cable, Capacity of   95

Cable Clip  97

Cable Core  96

Cable, Duplex   96

Cable, Flat   96

Cablegram  96

Cable Grip  96

Cable Hanger  96

Cable Hanger Tongs  97

Cable, Suspension Wire of   97

Cable Tank  97

Cadmium Battery  60

Calamine  97

Cal Electricity  208

Calibration  97

Calibration, Absolute   97

Calibration, Invariable   97

Calibration, Relative  98

Call Bell  78, 79, 98

Call Bell, Extension   248

Call Bell, Magneto   361

Call Button  98

Call, Thermo  530

Call, Thermo-electric   531

Callan Battery   60

Calling Drop  98

Calorie or Calory  98

Calorimeter  98

Calorimetric Photometer  412

Calory or Calorie  98

Cam, Listening   330

Camacho's Battery  60

Candle  99

Candle, Concentric   99

Candle, Debrun   99

Candle, Decimal  99

Candle, Electric   99

Candle-foot  259

Candle, German Standard   99

Candle Holder  99

Candle, Jablochkoff   100

Candle, Jamin   100

Candle, Meter    374

Candle Power  100

Candle Power, Nominal   101

Candle Power, Rated  101

Candle Power, Spherical   101

Candle, Standard   101

Candle, Wilde   101

Caoutchouc  101

Cap, Insulator  306

Capacity, Carrying   108

Capacity, Dielectric   102

Capacity, Electric or Electrostatic   102

Capacity, Instantaneous  102

Capacity, Magnetic Inductive   346, 349

Capillarity, Electro-  209

Capillary Electrometer  224

Capacity of a Telegraph Conductor  103

Capacity of Cable  95

Capacity of Polarization of a Voltaic Cell  103

Capacity, Polarization  424

Capacity, Residual  103

Capacity, Specific Inductive   103

Capacity, Storage  105, 495

Capacity, Unit of   105

Capillarity  105

Capillary Telephone  525

Carbon  106

Carbon, Artificial  106

Carbon Brush  90

Carbon, Concentric  107

Carbon, Cored   107

Carbon Dioxide  107

Carbon Holders  107

Carbonic Acid,   108

Carbonic Acid Gas  108

Carbonization  107

Carbonized Cloth  107

Carbon, Platinized, Battery   69

Carbon Resistance   463

Carbon, Retort    471

Carbons, Lamp, Flashing of Incandescent   257

Carbon, Telephone  525

Carbon Transmitter  549

Carbon, Volatilization of   108

Carburetted Hydrogen, Heavy   397

Carcel  108

Carcel Gas Jet  108

Carcel Lamp  108

Card, Compass   142

Cardew Voltmeter  569

Carré's Battery  60

Carrying Capacity  108

Cascade  108

Cascade, Charging and Discharging Leyden Jars in   108

Cascade, Gassiot's   275

Case-hardening, Electric   109

Cataphoresis  109

Catch, Safety  175

Cathode, etc. See Kathode   312

Caustry, Galvano  109

Cautery Battery   61

Cautery, Electric  109

Cautery, Galvano  109

Cautery, Galvano-electric  109

Cautery, Galvano-thermal   109

Cell, Battery, Element of a   237

Cell, Constant  109

Cell, Electrolytic   109

Cell, Porous    427

Cell, Selenium   478

Cell, Standard Voltaic  109

Cell, Standard Voltaic, Daniells'  109

Cell, Standard Voltaic, Latimer Clark's  110

Central Station  493

Central Station Distribution or Supply  112

Centre of Gravity  112

Centre of Gyration  112

Centre of Oscillation  112

Centre of Percussion  112

Centrifugal Force  112

Centrifugal Governor  113

C. G. S.  113

Chain, Molecular  380

Chamber, Armature  42

Chamber of Incandescent Lamp  113

Change, Chemical  116

Changer, Pole  425

Changing Over Switch  500

Changing Switch  500

Chaperon, Lalande &, Battery   69

Characteristic  169

Characteristic Curve  113, 168

Characteristic Curve, External  171

Characteristic Curve of Converter  169

Characteristic, Drooping   114

Characteristic, External   114

Characteristic, Internal   114

Characteristics of Sound  114

Charge  114

Charge and Discharge Key    313

Charge, Bound   115

Charge Current  160

Charge, Density of   115, 180

Charge, Dissipation of   115

Charge, Distribution of   115

Charge, Free  115

Charge, Negative  389

Charge, Residual   116

Charging Curve  170

Chatterton's Compound  116

Chemical Change  116

Chemical Electric Meter   375

Chemical, Electro-, Equivalents   244

Chemical Element  236

Chemical Energy  239

Chemical Equivalent  244

Chemical, Cautery Galvano   265

Chemical Recorder  117

Chemical Telephone  526

Chemical Equivalent, Thermo-   245

Chemistry  118

Chemistry, Electro-   209

Cheval, Force de  260

Chicle  56

Chimes, Electric   118

Chloric Acid Battery  61

Chloride, Ferric, Battery   63

Chloride, Lead, Battery  66

Chloride of Lime Battery  61

Chlorimeter   73

Choking Coil  132

Chronograph, Electric   118

Chromic Acid Battery   61

Chromic Acid Battery Solutions  73

Chromoscope  119

Chutaux's Solution  119

Cipher Code  130

Circle, Azimuth   54

Circle, Delezenne's  133

Circle, Galvanic or Voltaic   119

Circle, Magic  119

Circuit  120

Circuit, Astatic   120

Circuit, Branch  121

Circuit Breaker  121

Circuit Breaker, Automatic   121

Circuit Breaker, File  121

Circuit Breaker, Mercury  121

Circuit Breaker, Pendulum  121

Circuit Breaker, Tuning-fork  121

Circuit, Broken  125

Circuit Changing Switch  500

Circuit, Closed, Battery   61

Circuit, Derivative  123

Circuit, Derived   123

Circuit, Electrostatic   123

Circuit, Electric, Active   123

Circuit, External   123

Circuit, Grounded   123

Circuit, Incomplete  125

Circuit Indicator  298

Circuit Induction, Open   303

Circuit, Leg of   325

Circuit, Local   331

Circuit, Loop  125

Circuit, Loop Break  125

Circuit, Magnetic  340

Circuit, Magnetic Double   340

Circuit, Main  125

Circuit, Main Battery   125

Circuit, Metallic  125

Circuit, Negative Side of   125

Circuit, Open  125

Circuit, Positive Side of   125

Circuit, Recoil   125

Circuit, Return  125

Circuits, Forked   126

Circuit, Short   482

Circuit, Shunt   123, 126

Circuit, Simple  126

Circuits, Parallel   123, 126

Circuit, Voltaic  126

Circuit Working, Short   482

Circular Bell,  79

Circular Current,   160

Circular, Mil   379

Circular Units  126, 555

Circumflux  126

Clamp  126

Clark's Compound  126

Cleansing, Fire   257

Clearance Space,   489

Cleat, Crossing   127

Cleats  127

Cleavage, Electrification by   127

Clip, Cable  97

Clock, Annunciator   35

Clock, Controlled   127

Clock, Controlling   127

Clock, Electric Annunciator   127

Clock, Electrolytic   128

Clock, Master  127

Clock, Secondary  127

Clock, Self-winding, Electric  128

Clockwork Feed  128

Cloisons  128

Closed Circuit Battery  61

Closed Coil Armature  43

Closure  128

Closure Contraction, Kathodic   312

Cloth, Carbonized  107

Club-foot Electro-magnet  217

Clutch  128

Clutch, Electro-magnetic  128

Coatings of a Condenser, or Prime Conductor  129

Cockburn Fuse   263

Code, Cipher  130

Code, S. N.   486

Code, Telegraphic   130, 511

Coefficient  130

Coefficient, Apparent, of Magnetic Induction   346

Coefficient, Economic   130, 204, 205

Coefficient of Electrical Energy  205

Coefficient of Expansion  247

Coefficient of Induced Magnetization  359, 354

Coefficient of Magnetic Induction  346, 349

Coefficient of Mutual Induction  301

Coefficient of Self-induction  298

Coercitive Force  471

Coercive Force   471

Coercive or Coercitive Force  131

Coil and Plunger  131

Coil and Coil Plunger  131

Coil and Plunger, Differential    132

Coil, Armature   43

Coil, Choking   132

Coil, Earth   133

Coil, Electric    133

Coil, Exploring   350

Coil, Flat   133

Coil, Induction   133

Coil, Induction, Inverted    136

Coil, Induction, Telephone   137

Coil. Kicking  132

Coil, Magnet  336

Coil, Magnetizing   137

Coil, Reaction   132

Coil, Resistance    137

Coil, Resistance, Standard   464

Coil, Rhumkorff   138

Coil, Ribbon   138

Coils, Bisected  132

Coils, Compensating   138

Coils, Sectioned   138

Coils, Henry's   138

Coils, Idle  295

Coil, Single, Dynamo   202

Coil, Spark   489

Coil, Sucking  132

Collecting Brush  90

Collecting Ring  139

Collector  139

Colombin,  139

Colophony  460

Colors of Secondary Plates  478

Column Battery  61

Column, Electric    139

Comb  140

Combined Resistance  464

Comb Protector  437

Commercial Efficiency   204

Commercial Efficiency of Dynamo  195

Commercial Wheatstone Bridge  86

Common Reservoir  460

Communicator  140

Commutation, Diameter of   182

Commutator  140

Commutator Ammeter  26

Commutator Bars  140, 56

Commutator, Flats in   140

Commutator, High Bars of   289

Commutator, Neutral Line of   390

Commutator, Neutral Point of   390

Commutator of Current Generators and Motors  140

Commutators, Bars of   56

Commutator Segments  56

Commutator, Split Ring   141

Commuted Current  160

Commuter  140

Commuting Transformer  547

Compass  141

Compass, Azimuth  141

Compass, Boxing the   86

Compass Card,  142

Compass, Declination   142

Compass, Inclination   142

Compass, Mariners'  142

Compass, Points of the   143

Compass, Spirit  143

Compass, Surveyors   143

Compass, Variation of the   32, 558

Compensating Coils  138

Compensating Magnet  336

Compensating Poles  426

Compensating Resistance  144

Complementary Distribution  144

Complete Alternation  23

Component  144

Components of Earth's Magnetism  356

Composition of Forces  260

Compound Arc  39

Compound, Binary  81

Compound, Chatterton's   116

Compound, Clark's   126

Compound Dynamo  195

Compounding, Over-   399

Compound Magnet  336

Compound or Compound Wound Motor  382

Compound Winding   578

Concentration of Ores, Magnetic   340

Concentrator, Magnetic    340

Concentric Candle  99

Concentric Carbon  107

Condenser  144

Condenser, Coatings of a, or Prime Conductor   129

Condenser, Epinus'   242

Condenser, Plate  417

Condenser, Sliding  144

Condenser, Varley's   559

Condensing Electroscope  233

Conductance  144

Conductance, Magnetic  340

Conduction  144

Conduction, Electrolytic    215

Conductive Discharge  187

Conductivity  144

Conductivity, Magnetic   340

Conductivity, Specific  145

Conductivity, Unit of   145

Conductivity, Variable   145

Conductor  145

Conductor, Anti-induction   145

Conductor, Branch  87

Conductor, Capacity of a Telegraph  103

Conductor, Conical  145

Conductor, Imbricated   146

Conductor, Interpolar  307

Conductor, Leakage   325

Conductor, Prime  146, 434

Conductors, Equivalent  146

Conductors, Lamination of Armature  319

Conductors, Service  481

Conductor, Underground   552

Congress Ohm  395

Congress Volt   568

Conical Conductor  145

Conjugate  146

Connect  146

Connection, Cross   158

Connection, Relay   457

Connector   146

Consequent Points  422

Consequent Poles  146, 478

Conservation of Electricity  146

Conservation of Energy  239

Constant Current  160

Constant Current Alternator  24

Constant Current Regulation  454

Constant, Dielectric  183

Constant, Galvanometer   268

Constant Potential  429

Constant Potential Regulation  455

Constant, Time    54l

Contact Breaker  121, 146

Contact, Electric   147

Contact Electricity  147

Contact Faults  147

Contact Key, Double   314

Contact Key, Sliding    316

Contact Lamp  320

Contact, Line of   330

Contact Point  147

Contact Potential Difference  147

Contact Ring  473

Contact Spring  148

Contact Series  147

Contact Theory  148

Continuity, Magnetic   340

Continuous Alternating Transformer  547

Continuous Current  161

Continuous Current Transformer  384, 547

Contraction, Anodic Closure  36

Contraction, Anodic Duration   36

Contraction, Anodic Opening  36

Contraction, Kathodic Closure   312

Contraction, Kathodic Duration  312

Contractures  148

Contraplex Working  580

Control, Electro-magnetic   218

Control, Gravity   281

Controlled Clock,  127

Controlling Clock  127

Controlling Field  148

Controlling Force  148

Controlling Magnet  185, 336

Control, Magnetic   341

Control, Spring  492

Convection, Electric   149

Convection, Electrolytic   149, 214

Convection of Heat, Electric   149

Convective Discharge  187

Conversion, Efficiency of   205

Converter  149

Cooling Box  151

Co-ordinates, Origin of   391

Co-ordinates, System of   150

Copper  151

Copper Bath  152

Copper Stripping Bath  152

Copper Voltameter  563

Cord Adjuster  152

Cord, Flexible   152

Cord, Pendant   405

Core  152

Core, Armature   43

Core, Cable    96

Cored Carbon  107

Core-discs  152

Core-discs, Perforated   154

Core-discs, Pierced   152

Core-discs, Toothed   154

Core, Laminated   154

Core, Magnet   336

Core Ratio  154

Core, Ribbon   154

Core, Ring  155

Cores, Krizik's   318

Core, Stranded   155

Core, Tangentially Laminated   155

Core Transformer  155

Core, Tubular  155

Corpusants  155

Corresponding Points  422

Coulomb  155

Coulomb's Law of Electrostatic Attraction and Repulsion  155

Coulomb's Law of Magnetic Attraction and Repulsion  338

Coulomb's Torsion Balance  544

Coulomb, Volt-   568

Counter, Electric   156

Counter Electro-motive Force  156, 228

Counter-electro-motive Force Lightning Arrester  329

Counter Inductive Effect  204

Couple  156

Couple, Astatic  157

Couple, Axial  544

Couple, Magnetic    341

Couple, Moment of  544

Couple, Thermo-electric   532

Couple, Voltaic or Galvanic   156

Coupling  259

Coupling of Dynamo  201

C. P.  157

Crater  157

Creep, Diffusion   184

Creeping  157

Creeping, Magnetic  341

Creeping of Magnetism  356

Crith  157

Critical Current  161

Critical Distance of Alternative Path  190

Critical Resistance  464

Critical Speed  157

Critical Value, Villari's   561

Crookes' Dark Space  489

Cross  157

Cross-connecting Board  157

Cross Connection  158

Cross Induction  298

Crossing Cleat  127

Crossing Wires  158

Cross-magnetizing Effect  158, 298

Cross-over Block  158

Cross, Peltier's  405

Cross Talk  158

Crucible, Electric    158

Crystallization, Electric   158

Cube, Faraday's   249

Culture. Electro-  209

Cunynghame's Ammeter  26

Cup, Mercury   371

Cup, Porous   159, 426

Current  159

Current, After  159

Current, Alternating  159

Current, Alternating System   23

Current, Alternative  563

Current Arc, Alternating   23

Current, Atomic  160

Current, Break Induced   162

Current, Charge  160

Current, Circular   160

Current, Commuted   160

Current, Constant   160

Current, Continuous  161

Current, Continuous, Transformer   384

Current, Critical   161

Current, Daniel  161

Current, U. S. or Siemens' Unit   161

Current, Demarcation   161

Current Density  161

Current, Derived   164

Current, Diacritical   161

Current, Diaphragm   161

Current, Direct  162

Current, Direct Induced   162

Current, Direction of  162

Current, Displacement   162

Current, Extra   162

Current, Faradic   162

Current, Field of Force of a   255

Current, Foucault   163

Current, Franklinic   163

Current Generator  277

Current, Induced  163

Current Induction  163

Current Induction, Unipolar   553

Current Intensity  163

Current, Inverse Induced   163

Current, Jacobi's Unit of   163

Current, Joint   163

Current, Linear   164

Current, Make and Break   164, 367

Current, Make Induced   163

Current Meter  164, 375

Current Meter, Alternating   373

Current, Negative  164

Current, Nerve and Muscle   164

Current, Opposed   164

Current, Partial   164

Current, Polarizing   164

Current, Positive   164

Current, Power of Periodic   433

Current, Pulsatory  164

Current, Rectified   164

Current, Rectilinear   165

Current, Redressed   165

Current Regulation, Constant    454

Current, Reverse Induced   163

Current Reverser  165

Currents, Ampere  30

Currents, Ampérian   165

Currents, Angular.   165

Currents, Angular, Laws of   165

Currents, Earth   166

Current, Secondary  166

Current, Secretion   166

Currents, Eddy   163

Currents, Eddy Displacement  162

Currents in Parallel Circuits, Independence of   297

Current, Sinuous   166

Current, Sheet   166

Current, Shuttle   483

Currents, Local   163

Currents, Local  331

Currents, Multiphase   166

Currents, Natural   166, 389

Currents, Nerve   390

Currents of Motion  167

Currents of Rest  167

Currents, Orders of   167

Currents, Parasitical   163

Currents, Polyphase   167

Currents, Rotatory  167

Currents, Thermo-electric   167

Current Streamlets  495

Current, Swelling   167

Current, Tailing  501

Current, Undulatory   167

Current, Unit  167

Current, Wattless   168

Curve, Arrival  168

Curve, Characteristic   113, 168

Curve, Characteristic, of Converter   169

Curve, Charging   170

Curve, Discharging   170

Curve, Elastic  206

Curve, Electro-motive Force   170

Curve, External Characteristic   . 171

Curve, Harmonic  174, 485

Curve, Horse Power   171

Curve, Isochasmen   171

Curve, Life    171

Curve, Load  172

Curve, Magnetization   172

Curve of Distribution of Potential in Armature  172

Curve of Dynamo  173

Curve of Saturation of Magnetic Circuit  174

Curve of Sines  173, 485

Curve of Torque  174

Curve, Permeability Temperature   174

Curve, Sine   174, 485

Curve, Sinusoidal  174, 485

Curves, Magnetic   341

Cut In  174

Cut Out  174

Cut Out, Automatic   175, 475

Cut Out, Magnetic  175

Cut Out, Plug   175

Cut Out, Safety  175

Cut Out, Spring Jack   493

Cut Outs, Time  541

Cut Out, Wedge  175

Cutting of Lines of Force  175

Cycle of Alternation  175

Cycle of Magnetization  360

Cylinder, Armature  43

Cylinder, Electric Machine   333

Cylindrical Armature  45

Cystoscopy  175

Damper  176

Damping  176

Damping Magnet  336

Daniell's Standard Voltaic Cell  109

Dark Space, Faraday's   249

D'Arsonval's Battery  62

Dash-pot  176

Dead Beat  38, 176

Dead Beat Discharge  187

Dead Earth  176, 203

Dead Point of an Alternator  177

Dead Turns  177

Dead Turns of a Dynamo  551

Dead Wire  177

Death, Electrical   177

Debrun Candle  99

Decalescence  177

Decay of Magnetism  356

Deci  177

Decimal Candle  99

Declination, Angle of   32-177

Declination Compass  142

Declination, Magnetic   342

Declination Map  309

Declination of the Magnetic Needle  178

Decomposition  178

Decomposition, Electrolytic   178

Decrement  178

De-energize  178

Deflagration  178

Deflagrator, Hare's   73

Deflecting Field  178

Deflection  178

Deflection Method  178

Deflection of Magnet  337

Degeneration, Reaction of   179

Degradation of Energy  239

Deka  179

De la Rive's Floating Battery  179

De la Rue Battery  62

Delaurier's Solution  179

Delezenne's Circle  133

Demarcation Current  161

Demagnetization  179

Density, Current   161

Density, Electrical  115

Density, Electric Superficial   180

Density, Field   252

Density, Magnetic   342

Density of Charge  115, 180

Dental Mallet, Electric   180

Deposit, Electrolytic   180

Deposit, Nodular   392

Depolarization  180

Depolarizing Fluid  258

Derivation, Points of   180, 423

Derivative Circuit  123

Derived Circuit  123

Derived Current  164

Derived Units  555

Desk Push  180

Detector  180

Detector, Lineman's  180

Deviation of Discharge  188

Deviation, Quadrantal   180

Deviation, Semi-circular   181

Device, Safety  475

Dextrotorsal  181

Diacritical  181

Diacritical Current  161

Diagometer  181

Diagnosis, Electro-  181, 210

Diagram, Thermo-electric   532

Dial Telegraph  505

Diamagnetic  181

Diamagnetic Polarity  181, 423

Diamagnetism  182

Diameter of Commutation  182

Diapason, Electric  182

Diaphragm  182

Diaphragm Current  161

Dielectric,  182

Dielectric Capacity   102

Dielectric Constant  183

Dielectric, Energy of   183

Dielectric Polarization  183

Dielectric Resistance  183, 464

Dielectric Strain  183

Dielectric Strength  183

Dielectric Stress  496

Differential Arc Lamp  320

Differential Coil and Plunger  132

Differential Galvanometer  268

Differentially Wound Bell,   79

Differential Magnetometer  365

Differential Motor  382

Differential Relay  457

Differential Thermo-electric Pile  533

Differential Winding Working  183

Diffusion  184

Diffusion, Anodal .   35

Diffusion Creep  184

Digney Unit of Resistance  464

Dimensions and Theory of Dimensions  184

Dimmer  185

Diode Working  580

Dioxide, Carbon   107

Dioxide, Sulphur  497

Dip, Magnetic  342, 346

Dip of Magnetic Needle  185

Dipping  185

Dipping Needle  185

Direct Current  162

Direct Current Dynamo  197

Direct Induced Current,  .  162

Direct Reading Galvanometer  269

Directing Magnet  185

Direction  185

Direction of Current  162

Direction, Positive   428

Directive Power  187

Disc, Arago's   38

Disc, Armature  43

Disc, Bunsen   92

Disc, Dynamo  197

Disc, Faraday's  249

Discharge and Charge Key  313

Discharge, Brush  187

Discharge, Conductive  187

Discharge, Convective  187

Discharge, Dead Beat   187

Discharge, Disruptive   187

Discharge, Duration of   188

Discharge, Glow  187

Discharge, Impulsive   188

Discharge Key, Kempe's   315

Discharge, Lateral  188

Discharge of Magnetism  356

Discharge, Oscillatory  188

Discharger  188

Discharger, Henley's Universal   189

Discharger, Universal  189

Discharger, Universal, Henley's  189

Discharge, Silent  187, 189, 206

Discharge, Spark   189

Discharge, Surging   188

Discharging Curve  170

Discharging Rod  189

Discharging Tongs  189

Disconnection  189

Discontinuity, Magnetic  342

Discovery, Oerstedt's  394

Disc Winding  579

Dispersion Photometer  412

Displacement Current  162

Displacement, Electric   188

Displacement, Oscillatory   398

Disruptive Discharge  187

Disruptive Tension  189

Dissimulated Electricity  189

Dissipation of Charge  115

Dissociation  189, 535

Distance, Critical, of Alternative Path   190

Distance, Explosive   190

Distance, Sparking   190

Distance, Striking    496

Distant Station  493

Distillation  190

Distortion of Field  252

Distributing Box  190

Distributing Switches  190

Distribution, Complementary   144

Distribution, Isolated   309

Distribution of Charge  115

Distribution of Electric Energy, Systems of   190

Distribution of Magnetism, Lamellar,   357

Distribution of Magnetism, Solenoidal  358

Distribution of Supply, Central Station   112

Door Opener, Electric   190

Dosage, Galvanic  190

Double Break Switch  500

Double Carbon Arc Lamp  191

Double Contact Key  314

Double Curb Working  581

Double Fluid Theory  191

Double Fluid Voltaic Cell  191

Double Magnetic Circuit  340

Double Needle Telegraph  506

Double Plug  191

Double Pole Switch  500

Double Tapper Key  314

Double Touch, Magnetization by  358

Double Trolley  549

Double Wedge  191

Doubler  191

D. P.  191

Drag  191

Drag of Field  254

Dreh-Strom  191

Drill, Electric   191

Drip Loop  192

Driving Horns  192

Dronier's Salt  192

Drooping Characteristic  114

Drop, Annunciator   35

Drop, Automatic   192

Drop, Calling   98

Drum Armature  45

Drum, Electric   193

Dry Battery  63

Dry Pile, Zamboni's   581

Dub's Laws  193

Duct  193

Duplex Bridge Telegraph  506

Duplex Cable  96

Duplex Differential Telegraph  507

Duplex Telegraph,  506

Duration Contraction, Kathodic  312

Duration of Electric Spark  490

Dyad  193

Dyeing, Electric  193

Dynamic Electricity  193

Dynamic, Electro-   211

Dynamic Induction, Magnetic   347

Dynamo, Alternating Current   193

Dynamo, Alternating Current Regulation of   195

Dynamos, Battery of    68

Dynamo, Commercial Efficiency of   195

Dynamo, Compound   195

Dynamo, Coupling of   201

Dynamo, Curve of  173

Dynamo, Dead Turns of a   551

Dynamo, Direct Current   197

Dynamo, Disc  197

Dynamo-electric Machine  197

Dynamo, Electroplating  198

Dynamo, Equalizing  198

Dynamo, Field and Armature Reaction of  450

Dynamo, Far Leading  198

Dynamo or Magneto-electric Generator, Flashing in a   257

Dynamo, Inductor   199

Dynamo, Interior Pole  199

Dynamo, Iron Clad  200

Dynamo, Ironwork Fault of a   308

Dynamo, Motor  200

Dynamo, Multipolar   200

Dynamo, Non-polar   200

Dynamo, Open Coil  200

Dynamo, Overtype  399

Dynamos, Regulation of   455

Dynamo, Ring  200

Dynamo, Self Exciting  201

Dynamo, Separate Circuit  201

Dynamo, Separately Excited   201, 479

Dynamo, Series   201

Dynamo, Shunt   202

Dynamo, Single Coil  202

Dynamo, Tuning Fork   202

Dynamo, Unipolar  202, 553

Dynamograph  199

Dynamometer  200

Dyne  203

Earth  203

Earth Coil  133

Earth Currents  166

Earth, Dead  176, 203

Earth, Magnetization by   359

Earth, Partial  203, 404

Earth Plate  203

Earth Return  203

Earth's Magnetism, Components of   356

Earth, Solid  203

Earth, Swinging    203

Earth, Total   203

Ebonite  203

Eccentric Iron Disc Ammeter  27

Economic Coefficient  130, 204, 205

Eddy Currents  163

Eddy Displacement Currents  162

Ediswan  204

Edison Effect  204

Edison-Lalande Battery  69

Eel, Electric  204

Effect, Acheson  208

Effect, Counter-inductive   204

Effect, Cross-magnetizing   158, 298

Effect, Edison  204

Effect, Faraday   249

Effect, Ferranti   251

Effect, Hall   284

Effect, Joule   311

Effect, Kerr  235, 312

Effect, Mordey   381

Effect, Page   401

Effect, Peltier  404

Effect, Photo-voltaic   415

Effect, Seebeck  478

Effect, Skin  486

Effect, Thomson   538

Effect, Voltaic   563

Efficiency  204

Efficiency, Commercial   204

Efficiency, Electrical   205

Efficiency, Gross  205

Efficiency, Intrinsic  205

Efficiency, Net  205

Efficiency of Conversion  205

Efficiency of Secondary Battery Quantity   205

Efficiency of Secondary Battery, Real   205

Efflorescence  206

Effluvium, Electric   206

Egg, Philosopher's   409

Elastic Curve  206

Elasticity, Electric   206

Electrepeter   206

Electric, Absolute, Potential   429

Electric Absorption  8

Electric Actinometer  11

Electric Alarm  17

Electrical Classification of Elements   237

Electrically Controlled Valve  558

Electric Ammunition Hoist  29

Electric Analysis  32

Electric Analyzer  32

Electric Annealing  34

Electric Annunciator Clock  127

Electric Arc Blow-pipe  84

Electric Aura  53

Electric Automatic Fire Extinguisher  257

Electric Axis  54

Electric Balance  577

Electric Bath, Bipolar  57

Electric Bath, Multipolar   57

Electric Bath, Unipolar   57

Electric Bell  79

Electric Bell, Automatic   78

Electric Bioscopy  82

Electric Blasting  83

Electric Bleaching  83

Electric Boat  84

Electric Boiler Feed  84

Electric Branding  87

Electric Brazing  87

Electric Breath Figures  89

Electric Breeze  89

Electric Buoy  93

Electric Candle  99

Electric Case Hardening  109

Electric Cautery  109

Electric Chimes  118

Electric Chronograph  118

Electric Circuit, Active  123

Electric Clock, Self-winding    128

Electric Coil  133

Electric Column  139

Electric Contact  147

Electric Convection  149

Electric Convection of Heat  149, 286

Electric Counter  156

Electric Crucible  158

Electric Crystallization  158

Electric Death  177

Electric Density  115

Electric Dental Mallet  180

Electric Diapason  182

Electric Displacement  189

Electric Door Opener  190

Electric Double Refraction  454

Electric Drill   191

Electric Drum  193

Electric Dyeing  193

Electric Eel  204

Electric Efficiency   205

Electric Effluvium  206

Electric Elasticity  206

Electric Endosmose  238

Electric Energy  239

Electric Energy, Coefficient of  205

Electric Energy, Systems of Distribution of   190

Electric Engraving  245

Electric Entropy  242

Electric Etching  245

Electric Evaporation  246

Electric Excitability of Animal Systems  247

Electric Exosmose  247

Electric Expansion  247

Electric Fire Alarm, Automatic  257

Electric Floor Matting  369

Electric Fluid  258

Electric Fly or Flyer  259

Electric Fog  259

Electric Furnace  263

Electric Fuse  264

Electric Gas Burners  93

Electric Headlight  285

Electric Head Bath  284

Electric Heat  285

Electric Heater  286

Electric Horse Power  290

Electric Image  296

Electric Incandescence  297

Electric Influence  305

Electric Insulation  305

Electricities, Separation of   479

Electricity  206

Electricity, Animal   33

Electricity, Atmospheric    51

Electricity, Cal  208

Electricity, Conservation of   146

Electricity, Contact  147

Electricity, Dissimulated   189

Electricity, Dynamic   193

Electricity, Frictional   262

Electricity, Latent   323

Electricity, Negative   389

Electricity, Plant   317

Electricity, Positive  428

Electricity, Specific Heat of   491

Electricity, Static  493

Electricity, Storage of   495

Electricity, Voltaic   563

Electricity, Vitreous   562

Electric Machine, Plate  417

Electric Machine, Wimshurst   577

Electric Mains  367

Electric Mass  368

Electric Matter  368

Electric Meter, Chemical   375

Electric Meter, Thermal   375

Electric Meter, Time   375

Electric Mortar  382

Electric Motor  382

Electric or Electrostatic Capacity  102

Electric Organ  397

Electric Oscillations  398

Electric Osmose  398

Electric Pen  405

Electric Pendulum  405

Electric Piano  415

Electric Picture   415

Electric Pistol  416

Electric Popgun  282

Electric Portrait  415

Electric Potential Difference   429

Electric Potential, Unit of   432

Electric Power   433

Electric Pressure  434

Electric Probe  435

Electric Prostration  437

Electric Protector   437

Electric Radiometer  447

Electric Ray  450

Electric Rectification of Alcohol  18

Electric Reduction of Ores  453

Electric Reduction of Phosphorous   410

Electric Register  454

Electric Residue  116, 460

Electricity, Resinous   461

Electric Resonance   468

Electric Resonator  470

Electric Rings  392

Electrics  208

Electric Saw  476

Electric Screen,   476

Electric Shadow   480

Electric Shock  482

Electric Shower Bath   57

Electric Soldering  487

Electric Spark, Duration of   490

Electric Sphygmophone  491

Electric Storms  495

Electric Striae  496

Electric Subway   496

Electric Subway, Underground   552

Electric Sunstroke   497

Electric Superficial Density  180

Electric Swaging  499

Electric Tele-barometer  504

Electric Telemanometer   521

Electric Telemeter  521

Electric Tempering  527

Electric Tension  529

Electric Thermometer  535

Electric Thermostat  537

Electric Torpedo  543

Electric Tower  545

Electric Transmission of Energy  240

Electric Trumpet  550

Electric Tube  550

Electric Typewriter  551

Electric Unit of Work  580

Electric Varnish  559

Electric Welding   574

Electric Whirl  577

Electric Wind  578

Electrification  208

Electrification by Cleavage  127

Electrification by Pressure  434

Electrified Body, Energy of an   . 241

Electrization  208

Electro-biology  208

Electro-capillarity  209

Electro-chemical Equivalents  209, 244

Electro-chemical Series  209

Electro-chemistry   209

Electro-culture  209

Electrode  210

Electrode, Indifferent   210

Electrodes, Erb's Standard of   210

Electrodes, Non-polarizable  210

Electrodes, Shovel   483

Electrode, Therapeutic   210

Electro-diagnosis  181, 210

Electro-dynamic  211

Electro-dynamic Attraction and Repulsion,   211

Electro-dynamic Rotation of Liquids  474

Electro-dynamometer, Siemens'  212

Electro-gilding  277

Electro-kinetic  211

Electrolier  212

Electrolysis  212

Electrolysis, Laws of   213

Electrolyte  214

Electrolytic Analysis  214

Electrolytic Cell  109

Electrolytic Clock  128

Electrolytic Conduction  215

Electrolytic Convection  149, 214

Electrolytic Deposit  180

Electrolytic Iron  308

Electrolytic Resistance  464

Electro-magnet  215, 337

Electro-magnet, Annular   216

Electro-magnet, Bar  217

Electro-magnet, Club-foot   217

Electro-magnet, Hinged  217

Electro-magnet, Hughes'    291

Electro-magnetic Ammeter  27

Electro-magnetic and Magnetic Equipotential Surface  244

Electro-magnetic Attraction and Repulsion  217

Electro-magnetic Brake  86

Electro-magnetic Clutch  128

Electro-magnetic Control  218

Electro-magnetic Eye  248

Electro-magnetic Field of Force  218

Electro-magnetic Force  260

Electro-magnetic Gun  282

Electro-magnetic Induction  218, 299

Electro-magnetic Inertia  305

Electro-magnetic Induction, Mutual  302

Electro-magnetic Interrupter for Tuning Fork  307

Electro-magnetic Leakage  219

Electro-magnetic Lines of Force  219

Electro-magnetic Liquids, Rotation of   475

Electro-magnetic Meter  375

Electro-magnetic Quantity  445

Electro-magnetic Quantity, Practical Unit of   445

Electro-magnetic Shunt  .483

Electro-magnetic Stress  219, 496

Electro-magnetic Theory of Light  219

Electro-magnetic Unit of Energy  220

Electro-magnetic Vibrator  561

Electro-magnetic Waves,   573

Electro-magnet, Ironclad   219

Electro-magnetism  220

Electro-magnet, Joule's  337

Electro-magnet, Long Range  220

Electro-magnet, One Coil  219

Electro-magnet, Plunger  220

Electro-magnet, Polarized  220

Electro-magnets, Interlocking   221

Electro-magnets, Multiple Wire Method of Working   388

Electro-magnet, Stopped Coil  221

Electro-magnets, Surgical   222

Electro-mechanical Bell  80

Electro-mechanical Equivalent  244

Electro-medical Baths  222

Electro-medical Battery, Pulvermacher's  69

Electro-metallurgy  222

Electrometer  222

Electrometer, Absolute  222

Electrometer. Attracted Disc   223

Electrometer, Capillary  224

Electrometer Gauge  226

Electrometer, Lane's   226

Electrometer, Quadrant   226

Electrometer, Thermo-   536

Electrometer, Weight  223

Electro-motive Force  227

Electro-motive Force, Counter-   228

Electro-motive Force Curve  170

Electro-motive Force, Impressed   297

Electro-motive Force, Motor  384

Electro-motive Force. Oscillatory  398

Electro-motive Force, Transverse  549

Electro-motive Force, Unit   228

Electro-motive Intensity  228

Electro-motive Potential Difference  429

Electro-motive Series  228

Electro-motograph  229

Electro-motor  229

Electro-muscular Excitation  229

Electro-negative   229

Electro-optics  229

Electrophoric Action  230

Electrophorus  230

Electro-physiology  231

Electroplating  231, 418

Electroplating Dynamo  198

Electro-pneumatic Signals  231

Electropoion Fluid  232

Electro-positive  232

Electro-puncture  232

Electro-receptive  232

Electroscope  232

Electroscope, Bennett's   233

Electroscope, Bohenberger's   233

Electroscope, Condensing  233

Electroscope, Gold Leaf   233

Electroscope, Pith Ball  234

Electrostatic Attraction and Repulsion  234

Electrostatic Attraction and Repulsion. Coulomb's Law of   155

Electrostatic Circuit  123

Electrostatic Equipotential Surface  244

Electrostatic Field of Force  254

Electrostatic Force  260

Electrostatic Induction  302

Electrostatic Induction, Coefficient of   234

Electrostatic Induction, Mutual   303

Electrostatic Lines of Force  234

Electrostatic Quantity  445

Electrostatic Refraction  235

Electrostatics  235

Electrostatic Series  235

Electrostatic Stress  236, 496

Electrostatic Telephone  526

Electrostatic Voltmeter  571

Electro-thermal Equivalent  245

Electro-therapeutics or Therapy  236

Electrotonic State  493

Electrotonus  236

Electrotype  236

Element, Chemical   236

Element, Galvanic  264

Element, Mathematical   237

Element, Negative  390

Element of a Battery Cell  237

Element, Positive  277

Elements, Electrical Classification of   237

Elements, Magnetic   342

Elements of Battery  63

Elements, Thermo-electric   237

Element, Voltaic  237

Elias' Method of Magnetization  360

Elongation  237, 540

Elongation, Magnetic   344

Embosser, Telegraph   237

E. M. D. P.  238

E. M. F.  238

Energy  238

Energy, Atomic  238

Energy, Chemical  239

Energy, Conservation of    239

Energy, Degradation of   239

Energy, Electric  239

Energy, Electrical, Coefficient of   205

Energy, Electric Transmission of   240

Energy, Electro-magnetic, Unit of   220

Energy, Kinetic  241

Energy, Mechanical   241

Energy Meter  375

Energy, Molar  241

Energy, Molecular   241

Energy of an Electrified Body  241

Energy of Dielectric  183

Energy of Position  211

Energy of Stress  241

Energy, Physical   241

Energy, Potential, or Static   241

Energy, Radiant    446

Energy, Thermal   242

End-on Method  238

End or Pole, Marked  368

Endosmose, Electric   238

End Play  238

End, Unmarked   556

English Absolute or Foot Second Unit of Resistance  465

Engraving, Electric   245

Entropy  242

Entropy, Electric  242

Epinus Condenser  242

E. P. S.  243

Equator, Magnetic   344

Equator of Magnet   337

Equipotential  244

Equipotential Surface  498

Equipotential Surface, Electrostatic  244

Equipotential Surface, Magnetic and Electro-magnetic   244

Equalizer  243

Equalizer, Feeder  251

Equalizing Dynamo  198

Equivalent, Chemical   116, 244

Equivalent Conductors  146

Equivalent, Electro-thermal   245

Equivalent, Joule's  311

Equivalent Resistance  465

Equivalents, Electro-chemical  209, 244

Equivalent, Thermo-chemical   245

Equivalent, Water   572

Equivolt  245

Erb's Standard of Electrodes  210

Erg   245

Erg-ten  245

Error, Heating  286

Escape  245

Essential Resistance  465, 466

Etching, Electric   245

Ethene  397

Ether  246

Eudiometer   246

Evaporation, Electric  246

Ewing's Theory of Magnetism  356

Exchange, Telephone  246

Excitation, Electro-muscular   229

Excitability, Faradic   246

Excitability, Galvanic   247

Excitability of Animal System, Electric   247

Exciter  247

Exosmose, Electric  247

Expansion, Coefficient of   247

Expansion, Electric  247

Experiment, Franklin's   261

Experiment, Hall's   284

Experiment, Kerr's  312

Experiment, Matteueci's   369

Experiments, Hertz's  470

Experiment, Volta's Fundamental  567

Experiment with Frog, Galvani's   262

Exploder  247

Explorer  247

Exploring Coil  350

Explosive Distance  190

Extension Bell Call  248

Extension, Polar  423

External Characteristic  114

External Characteristic Curve  171

External Circuit  123

External Resistance  465, 467

Extinguisher, Automatic Electric Fire    257

Extra Current  162

Extra-polar Region  454

Eye, Electro-magnetic  248

Eye, Selenium  478

Facsimile Telegraph  510

Factor, Armature   45

Fahrenheit Scale  248

Fall of Potential  430

False Poles, Magnetic   350

Farad  248

Faraday, Effect   249

Faraday's Cube  249

Faraday's Dark Space  249, 489

Faraday's Disc  249

Faraday's Net  250

Faraday's Ring  473

Faraday's Transformer  250

Faraday's Voltameter  250

Faradic  250

Faradic Battery  63

Faradic Brush  251

Faradic Current  162

Faradic Excitability  246

Faradization   251

Faradization, Galvano-  265

Far Leading Dynamo  198

Fault of a Dynamo, Ironwork   308

Faults  251

Faults, Contact   147

Feed Clockwork  128

Feeder  251

Feeder, Equalizer   251

Feeder, Main or Standard   251

Feeder, Negative   251

Feeder, Neutral   251

Feeder, Positive   251

Feeder, Switch   500

Feet, Ampere   30

Ferranti Effect  251

Ferric Chloride Battery  63

Ferro-magnetic  252

Fibre and Spring Suspension   252

Fibre Suspension  252

Field, Air  252

Field, Alternating   252

Field and Armature Reaction of Dynamo,  450

Field, Controlling    148

Field, Deflecting   178

Field Density  252

Field, Distortion of   252

Field, Drag of  254

Field, Intensity of a Magnetic   306

Field Magnet  337

Field of Force  .  254

Field of Force, Electro-magnetic  218

Field of Force, Electrostatic   254

Field of Force, Magnetic   344

Field of Force of a Current  255

Field of Force, Uniform   553

Field, Pulsatory   256

Field, Rotating   256

Field, Stray  256, 495

Field, Uniform  256

Field, Uniform Magnetic   345

Field, Waste   256

Figure of Merit  256

Figures, Haldat's   284

Figures, Lichtenberg's   327

Figures, Magnetic   345

Filament  256

Filament, Magnetic   345

Filaments, Paper   402

File, Circuit Breaker   121

Finder, Position   427

Finder, Range   447

Finder, Wire  580

Fire Alarm, Electric Automatic  257

Fire and Heat Alarm  17

Fire Extinguisher, Electric Automatic  257

Fire Cleansing  257

Fire, St. Elmo's   494

Fishing Box  311

Flashing in a Dynamo or Magneto-Electric Generator  257

Flashing of Incandescent Lamp Carbons  257

Flashing Over  258

Flash, Side   484

Flat Cable  96

Flat Coil  133

Flat Ring Armature  45

Flats  258

Flats in Commutator  140

Flexible Cord  152

Floating Battery, De la Rive's   179

Floating Magnets, Meyer's  370

Floor Matting, Electric  369

Floor Push  258

Fluid, Depolarizing   258

Fluid, Electric  258

Fluid, Electropoion   232

Fluid, Insulator.   306

Fluid, North Magnetic   357

Fluids, Magnetic  345

Fluid, South Magnetic  356

Fluid Theory, Single   486

Fluorescence  258

Flush Boxes  258

Fluviograph  259

Flux, Magnetic  345

Fly or Flyer, Electric   259

Foci Magnetic  259

Fog, Electric  259

Following Horns  259

Foot-candle  259

Foot, Mil-  379

Foot-pound  259

Foot-step  259

Force  259

Force, Annular  544

Force, Axial  544

Force, Centrifugal   112

Force, Coercive or Coercitive   131-471

Force, Controlling  148

Force, Counter-electro-motive   156

Force de Cheval  260

Force, Electro-magnetic  260

Force, Electro-motive   227

Force, Electro-motive, Transverse   549

Force, Electrostatic   260

Force, Field of  254

Force, Field of, of a Current   255

Force, Field of, Electrostatic  254

Force, Kapp Line of   312

Force, Lines of  330

Force, Magnetic  346

Force, Magnetic Field of   344

Force, Magnetic Lines of   348

Force, Magneto-motive  365

Force, Motor Electro-motive   384

Force of Polarization, Back Electro-motive  156

Force, Oscillatory, Electro-motive   398

Force, Photo-electro-motive   410

Forces, Composition of   260

Forces, Parallelogram of   260

Forces, Resolution of  261

Force, True Contact   549

Force, Tubes of   261

Force, Unit of  261

Forked Circuits  126

Fork, Tuning, Dynamo   202

Forming  261

Formula of Merit  256

Foucault Current  163

Foundation Ring  261

Fourth State of Matter  261

Frame  261

Frame, Resistance   465

Franklinic Current  163

Franklin's Experiment  261

Franklin's Plate  262

Franklin's Theory  262-486

Free Charge  115

Free Magnetism  356

Frequency  262

Frequency, High  289

Frictional Electricity  262

Frictional Electric Machine  333

Frictional Heating  262

Friction Gear, Magnetic   276

Friction, Magnetic  295-346

Fringe  262

Frog, Galvani's Experiment with   262

Frog, Rheoscopic   262

Frying  263

Fulgurite  263

Fuller's Battery  63

Fulminating Pane  262

Fundamental Unit  554

Furnace, Electric   263

Fuse Block  175

Fuse Board  263

Fuse Box  263

Fuse, Cockburn   263

Fuse, Electric   264

Fuse Links  330

Fuse, Safety   175-475

Galvanic  264

Galvanic Action, Volta's Law of  568

Galvanic Dosage  190

Galvanic Element  264

Galvanic Excitability  247

Galvanic or Voltaic Battery  76

Galvanic or Voltaic Circle  119

Galvanic or Voltaic Couple  156

Galvanic Polarization  265

Galvani's Experiment with Frog  262

Galvanism  265

Galvanization  265

Galvanization, Labile   265

Galvanized Iron  265

Galvano-cautery  109

Galvano-cautery, Chemical   265

Galvano-electric Cautery  109

Galvano-faradization  265

Galvanometer  265

Galvanometer, Absolute   266

Galvanometer, Aperiodic   266

Galvanometer, Astatic   266

Galvanometer, Ballistic   267

Galvanometer Constant  268

Galvanometer, Differential   268

Galvanometer, Direct Reading   269

Galvanometer, Marine   269

Galvanometer, Mirror   271

Galvanometer, Potential  269

Galvanometer, Proportional   269

Galvanometer, Quantity   269

Galvanometer, Reflecting   270

Galvanometer, Shunt   271-483

Galvanometer, Sine  271

Galvanometer, Tangent    272

Galvanometer, Torsion   273-544

Galvanometer, Upright   274

Galvanometer, Vertical  274

Galvanometer, Volt and Ampere Meter  274

Galvano-plastics   275

Galvano-puncture  232-275

Galvanoscope  275

Galvano-thermal Cautery  100

Gap, Spark   490

Gas Battery  63

Gas Battery, Grove's   281

Gas Burner, Electric   93

Gas, Carbonic Acid   108

Gas, Electrolytic  275

Gases, Magnetism of   357

Gases, Mixed  275

Gas Jet, Carcel   108

Gas, Olefiant  397

Gassing   275

Gassiot s Cascade  275

Gastroscope  275

Gas Voltameter  564

Gauge, Battery  64

Gauge, Electrometer   226

Gauss  275

Gauss' Principle  276

Gauss, Tangent Positions of   276

Gauze Brush, Wire  92

Gear, Magnetic  346

Gear, Magnetic Friction    276

Geissler Pump  437

Geissler Tubes  276

Generating Plate  277

Generator, Current   277

Generator Inductor  199

Generator, Magneto-electric  362

Generator, Magneto-electric, Flashing in a Dynamo or   257

Generator, Motor  384

Generator, Pyromagnetic.   442

Generators and Motors, Commutator of Current  140

Generator, Secondary   277-477

Geographic Meridian  372

German Mile Unit of Resistance  466

German Silver  277

German Standard Candle  99

Gilding, Electro-  277

Gilding Metal   277

Gimbals  278

Girder Armature  49

Glass  278

Globe or Globular Lightning  330

Glow Discharge  187

Gold  278

Gold Bath  279

Gold Leaf Electroscope  233

Gold Stripping Bath  279

Governor, Centrifugal   113

Governor, Rate   449

Graduator  279

Gram  280

Gram-atom  280

Gram-molecule  280

Graphite  280

Gravitation  280

Gravity, Acceleration of   280

Gravity Ammeter  27

Gravity Battery  64

Gravity, Centre of   112

Gravity Control  281

Gravity Drop Annunciator  35

Grease Spot  92

Green Vitriol  562

Grenet Battery  65

Grid  281

Grid Plug   420

Grip, Cable   96

Gross Efficiency  205

Ground  281

Grounded Circuit  123

Ground Plate  417

Ground Wire  281

Grove's Battery  65

Grove's Gas Battery  281

Guard Ring  282

Guard Tube  282

Gun, Electro-magnetic   282

Gutta Percha  282

Gyration, Centre of   112

Gyrostatic Action of Armatures  283

H   283

H Armature  49

Haarlem Magnet  337

Hair, Removal of, by Electrolysis   283

Haldat's Figures  284

Hall Effect  284

Hall Effect, Real  284

Hall Effect, Spurious   284

Halleyan Lines  308

Hall's Experiment  284

Halske's and Siemens' Battery  72

Hand Hole  190

Hanger Board  284

Hanger, Cable   96

Hanger, Cable, Tongs  97

Harcourt's Pentane Standard  406

Hare's Deflagrator  73

Harmonic   23

Harmonic Curve  174, 485

Harmonic Motion, Simple   486

Harmonic Receiver  284, 451

Head Bath, Electric   284

Head-light, Electric  285

Head, Torsion   544

Heat  285

Heat and Fire Alarm  17

Heat, Atomic   52, 285

Heat, Electric   285

Heat, Electric, Convection of   149, 286

Heat, Irreversible.  286

Heat, Mechanical Equivalent of  286

Heat, Molecular  286

Heat, Specific  286

Heat, Specific, of Electricity   288

Heat Units  288

Heater, Electric  286

Heating, Admiralty Rules of  12

Heating Error  286

Heating, Frictional   262

Heating Magnet  286

Heavy Carburetted Hydrogen,   397

Hecto  288

Hedgehog Transformer  548

Heliograph  288

Helix  288

Henley's Universal Discharger  189

Henry  288

Henry's Coils  138

Hermetically Sealed   289

Hertz's Experiments  470

Heterostatic Method  280

Hexode Working  581

High Bars of Commutator  289

High Frequency  289

High Vacuum  557

Hinged Armature  45

Hinged Electro-magnet  217

Hissing  289

Hittorf's Resistance  466

Hittorf's Solution  289

Hoffer's Method of Magnetization  360

Hole Armature  45

Hole, Hand   190

Holders  289

Holder, Brush   91

Holder, Candle   99

Holders, Carbon   107

Holophote Lamp  321

Holtz's Influence Machine  334

Home Station  493

Hood  290

Horizontal Induction  302

Horns  290

Horns, Driving   132

Horns, Following   259

Horns, Leading   324

Horns, Trailing   259

Horse Power  290

Horse Power, Actual   290

Horse Power Curve  171

Horse Power, Electric   290

Horse Power Hour  290

Horse Power, Indicated   290

Horseshoe Magnet  337

Hour, Ampere-  30

Hour, Horse Power   290

H. P.  290

Hughes' Electro-magnet  291

Hughes' Induction Balance  291

Hughes' Sonometer  488

Hughes' Telegraph   511

Hughes' Theory of Magnetism  357

Hughes' Type Printer  511

Human Body, Resistance of   467

Hydrochloric Acid Battery  66

Hydro-electric  293

Hydro-electric Machine  293

Hydrogen  294

Hydrogen, Carburetted, Heavy  397

Hydrometer, Beaumé   78

Hygrometer  294

Hyperbolic Logarithms  389

Hysteresis  295

Hysteresis, Magnetic   294

Hysteresis, Static  295

Hysteresis, Viscous   295, 356

Idioelectrics  295

Idiostatic Method  295

Idle Coils  295

Idle Poles  296

Idle Wire  291

Igniter  296

I. H P.  296

Illuminating Power  296

Illuminating Power, Spherical  296

Illuminating Power, Standard of, Viole's   561

Illumination, Unit of   296

Image, Electric  296

Imbricated Conductor  146

Immersion, Simple  185

Impedance  297, 462

Impedance, Impulsive   297

Impedance, Oscillatory   297

Impressed Electro-motive Force  297

Impulse  297

Impulsive Discharge  188

Impulsive Impedance  297

In-and-out, Soaking  486

Incandescence, Electric   297

Incandescent Lamp  321

Incandescent Lamp Carbons, Flashing of   257

Incandescent Lamp, Chamber of   113

Incandescent Lamp, Life of   327

Incandescent Lamp, Three Filament   322

Inclination Compass  142

Inclination, Magnetic   346

Inclination Map  297

Inclination or Dip, Angle of   33

Incomplete Circuit  125

Increment Key  314

Independence of Currents in Parallel Circuits  297

India Rubber  102

Indicated Horse Power  290

Indicating Bell   80, 297

Indicator  298

Indicator, Circuit  298

Indicator, Throw-back   540

Indicator, Volt  568

Indifferent Electrode  210

Indifferent Point  421

Induced Current  163

Induced Magnetization, Coefficient of  354, 359

Inductance  298

Inductance Balance  293

Inductance Bridge  293

Induction, Anti-, Conductor   36

Induction, Back  55

Induction Balance, Hughes  291

Induction, Coefficient of Magnetic  349

Induction, Coefficient of Mutual   301

Induction, Coefficient of Self-   298

Induction Coil  133

Induction Coil, Inverted   136

Induction Coil, Telephone   137, 526

Induction, Cross   298

Induction Current  163

Induction, Electro-magnetic   218, 299

Induction, Electrostatic  302

Induction, Electrostatic, Coefficient of  234

Induction, Horizontal   302

Induction, Lateral   302

Induction, Lines of   330

Induction, Magnetic   302, 346

Induction, Magnetic, Apparent Coefficient of  346

Induction, Magnetic, Coefficient of  346

Induction, Magnetic Dynamic   347

Induction, Magnetic, Self-  352

Induction, Magnetic Static   347

Induction, Magnetic, Tube of   347

Induction, Mutual, Electro-magnetic   302

Induction, Mutual, Electrostatic  303

Induction, Open Circuit   303

Induction, Oscillatory  398

Induction Protector, Mutual   481

Induction, Self-   303

Induction Sheath  303

Induction. Unipolar   304

Induction, Unit of Self-   304

Induction, Vertical  304

Inductive Capacity, Magnetic   346, 349

Inductive Effect, Counter-   204

Inductive Resistance  466

Inductophone  304

Inductor  305

Inductor Dynamo  199

Inductor Generator  199

Inductor, Magneto-  363

Inductor, Pacinotti's   400

Inductorium  138

Inertia  305

Inertia, Electro-magnetic   305

Inertia, Magnetic  347

Infinity Plug  305, 420

Influence, Electric   305

Influence Machine  334

Influence Machine, Armature of   46

Influence Machine, Holtz   334

Influence, Magnetic  346

Installation  305

Instantaneous Capacity  102

Insulating Stool  305

Insulating Tape  305

Insulating Varnish  306

Insulation, Electric   305

Insulation, Magnetic   347

Insulation, Oil  396

Insulation Resistance  466

Insulator  306

Insulator Caps  306

Insulator, Fluid   306

Insulator, Line or Telegraph   306

Intensity  306

Intensity Armature  45

Intensity Current  163

Intensity, Electro-motive   228

Intensity, Magnetic  348

Intensity of a Magnetic Field  306

Intensity of Magnetization  360

Intensity, Poles of  426

Inter-air Space  489

Intercrossing  307

Interference, Armature   45

Interferric Space  489

Interior Pole Dynamo  191

Interlocking- Electro-magnets.   229

Intermediate Metals, Law of   323

Intermittent,  307

Internal Characteristic  114

Internal Resistance  466

lnterpolar Conductor  307

Interpolar Region  307

Interpolation  307

Interrupter, Electro-magnetic, for Tuning Fork   307

Intrinsic Efficiency  205

Invariable Calibration   97

Inverse Induced Current  163

Inverse Squares, Law of   323

Inversion, Thermo-electric   533

Ions  307

Iron  308

Ironclad Dynamo  200

Ironclad Electro-magnet,   219

Ironclad Magnet  356

Iron Disc Ammeter, Eccentric   27

Iron, Electrolytic   308

Iron, Galvanized   265

Ironwork Fault of a Dynamo  308

Irreversible Heat  286

Isochasmen Curve  171

Isochronism  308

Isoclinic Lines  308

Isoclinic Map  308

Isodynamic Lines  308

Isodynamic Map  308

Isoelectric Points  422

Isogonal Lines  308

Isogonic Map  309

Isolated Distribution  309

Isolated Plant  309

Isolated Supply  309

Isotropic  309

Isthmus Method of Magnetization  360

I. W. G.,   309

J  309

Jablochkoff Candle  160

Jack. Spring-  492

Jacketed Magnet  356

Jacobi's Law  309

Jacobi's Method of Magnetization  360

Jacobi's Unit of Current  163

Jacobi's Unit of Resistance   466

Jamin Candle  100

Jar, Leyden   325

Jar, Lightning   330

Jar, Luminous  332

Jars, Leyden, Charging and Discharging   108

Jar, Unit   554

Jewelry  309

Joulad  311

Joule  311

Joule Effect  311

Joule's Electro-magnet  337

Joule's Equivalent,   311

Joint, American Twist  309

Joint, Britannia   309

Joint, Butt   310

Joint Current  160

Joint, Lap  310

Joint, Marriage   310

Joint, Resistance   464

Joints in Belts  311

Joint, Sleeve   310

Joint, Splayed   311

Junction Box  311

Junction, Thermo-electric   533

K.   311

Kaolin  311

Kapp. Line of Force   312

Kathelectrotonus  312

Kathode  312

Kathodic Closure Contraction  312

Kathodic Duration Contraction  312

K. C. C.  312

K. D. C.  312

Kempe's Discharge Key  315

Keeper  312

Kerr Effect  235, 312

Kerr's Experiment  312

Key  313

Key Board  313

Key, Bridge   313

Key, Double Contact  314

Key, Double Tapper  314

Key, Charge and Discharge   313

Key, Increment  314

Key, Kempe's Discharge   315

Key, Magneto-electric   315

Key, Make and Break   316

Key, Plug   316

Key, Reversing  316

Key, Sliding-contact   316

Key, Telegraph   316

Kicking Coil  132

Kilo  316

Kilodyne  316

Kilogram  317

Kilojoule  317

Kilometer  317

Kilowatt  317

Kine  317

Kinnersley's Thermometer  536

Kinetics, Electro-   211

Kinetic Energy  241

Kirchoff's Laws  317

Knife Break Switch  501

Knife Edge Suspension  317

Knife Edge Switch  501

Knife Switch  501

Knot  317

Kohlrausch's Law  317

Kookogey's Solution   318

Krizik's Cores  318

L  318

Lag, Angle of   33, 318

Lag, Electric   332

Lag, Magnetic   348

Lalande & Chaperon Battery  69

Lalande-Edison Battery  69

Lamellar Distribution of Magnetism  357

Laminated  318

Laminated Core  154

Laminated Core, Tangentially   155

Lamination  318

Lamination of Armature Conductors  319

Lamination of Magnet  361

Lamp, Arc  319

Lamp, Arc, Double Carbon   191

Lamp Carbons, Flashing of Incandescent   257

Lamp, Carcel   108

Lamp, Contact  320

Lamp, Differential Arc   320

Lamp Globe, Waterproof   572

Lamp, Holophote  321

Lamp-hour  321

Lamp, Incandescent   321

Lamp, Incandescent, Chamber of   113

Lamp, Incandescent, Three Filament  322

Lamp, Life of Incandescent   327

Lamp, Lighthouse   322

Lamp, Monophote   321

Lamp, Pilot  323

Lamp, Polyphote  323

Lamp, Semi-Incandescent   323

Lamp-socket  323

Lamps, Bank of  323

Lane's Electrometer  226

Langdon Davies' Rate Governor or Phonophone  450

Lenz's Law  325

Lap Joint  310

Lap Winding  570

Latent Electricity  323

Lateral Discharge  188

Lateral Induction  302

Latitude, Magnetic   348

Law, Jacobi's  309

Law, Kohlrausch's   317

Law, Lenz's  325

Law of Angular Currents  165

Law of Electrolysis  213

Law of Intermediate Metals  323

Law of Inverse Squares  323

Law of Magnetic Attraction and Repulsion. Coulomb's   338

Law of Successive Temperatures  324

Law, Magnus'   367

Law, Ohm's  396

Law, Pflüger's.   409

Law, Right Handed Screw  324

Law, Sine  486

Laws, Kirchoff's  317

Laws of Thermo-electricity, Becquerel's   78

Law, Tangent   502

Law, Voltametric   567

Lead  324

Lead, Angle of   33

Lead Chloride Battery  66

Lead of Brushes  90

Lead of Brushes, Negative  324

Lead, Peroxide of, Battery   69

Lead Sulphate Battery  66

Lead Tee  504

Leading Horns  324

Leading-in Wires  324

Leak  324

Leakage  324

Leakage Conductor  325

Leakage, Electro-magnetic   219

Leakage, Magnetic.   348

Leakage, Surface  498

Leclanché Agglomerate Battery  66

Leclanché Battery  66

Leg of Circuit  325

Legal Ohm  395

Legal Quadrant  444

Legal Volt  568

Length of Spark  490

Letter Boxes, Electric   325

Leyden Jar  325

Leyden Jar, Armature of   46

Leyden Jars, Battery of   68

Leyden Jars, Charging and Discharging  108

Leyden Jars, Sir William Thomson's   326

Lichtenberg's Figures  327

Life Curve  171

Life of Incandescent Lamp  327

Light, Electro-magnetic, Theory of   219

Light, Maxwell's Theory of  369

Lighthouse Lamp  322

Lightning  327

Lightning Arrester  328

Lightning Arrester, Counter-electro-motive Force  329

Lightning Arrester Plates  329

Lightning Arrester, Vacuum   329

Lightning, Ascending  330

Lightning, Globe or Globular   330

Lightning Jar  330

Lightning, Back Stroke or Shock of  55

Lime, Chloride of, Battery   61

Limit, Magnetic  348

Limit of Magnetization  361

Linear Current  164

Lineman's Detector  180

Line of Commutator, Neutral   300

Line of Contact  330

Line of Force, Kapp  312

Line of Magnet, Neutral  361

Line or Telegraph Insulator  306

Lines, Halleyan   308

Lines, Isoclinic  308

Lines, Isodynamic  308

Lines, Isogonal   308

Lines, Isogonic   308

Lines of Force  330

Lines of Force, Cutting of  175

Lines of Force, Electro-magnetic  219

Lines of Force, Electrostatic   234

Lines of Force, Magnetic   348

Lines of Induction  330

Lines of Slope  330

Lines or Points of Least Sparking  490

Lines, Trunk   550

Links, Fuse  330

Liquids, Electro-dynamic Rotation of   474

Liquids, Electro-magnetic Rotation of    475

Liquor, Spent   491

Listening Cam  330

Lithanode  331

Load  331

Load Curve  172

Load of Armature  46

Local Action  331

Local Battery  331

Local Circuit  331

Local Currents  163, 331

Localization  331

Locus  331

Lodestone  332

Logarithm  332

Logarithms, Hyperbolic   389

Logarithms, Napierian  389

Local Battery  66

Long Coil Magnet   361

Long Range Electro-magnet  220

Long Shunt and Series Winding  579

Long Shunt Winding  579

Loop  332

Loop Break  332

Loop, Circuit   125

Loop, Drip   192

Lost Amperes  30

Lost Volts  571

Low Vacuum  557

Luces  332

Luminous Jar  332

Luminous Pane  401

Luminous Tube  550

Lux  332

M  332

Machine, Cylinder Electric  333

Machine, Electric, Wimshurst   577

Machine, Frictional Electric   333

Machine, Holtz Influence   334

Machine, Hydro-electric   293

Machine, Influence  334

Machine, Nairne's Electrical   389

Machine, Plate Electrical   417

Machine, Rheostatic  472

Machine, Toeppler-Holtz   334

Machine, Wimshurst  335

Mack  335

Magic Circle  119

Magne-crystallic Action  335

Magnet  335

Magnet, Anomalous   335

Magnet, Artificial  335

Magnet, Axial   336

Magnet, Bar  336

Magnet, Bell Shaped   336

Magnet Coils, Sheath for   481

Magnet, Compensating   336

Magnet, Compound   336

Magnet, Controlling   185, 336

Magnet, Damping   336

Magnet, Deflection of   337

Magnet, Directing   185

Magnet, Electro-   215, 337

Magnet, Equator of   337

Magnet, Field   337

Magnet, Haarlem   337

Magnet, Heating   286

Magnet, Horseshoe   337

Magnet, Ironclad   356

Magnet, Joule's Electro-   337

Magnet-keeper  361

Magnet, Lamination of   361

Magnet, Long Coil  361

Magnet, Natural  361

Magnet, Neutral Line of   361

Magnet, Normal   361

Magnet Operation  365

Magnet, Permanent  365

Magnet Pole  365

Magnet, Portative Power of   366

Magnet, Projecting Power of a   435

Magnet, Relay   457

Magnet, Simple   366

Magnet, Solenoidal   366

Magnet, Sucking   366

Magnet, Unipolar  366

Magnet Coil  336

Magnet Core  336

Magnet Poles, Secondary   366

Magnet Pole, Unit  366

Magnetic Adherence  338

Magnetic and Electro-magnetic Equipotential Surface  244

Magnetic Attraction  338

Magnetic Attraction and Repulsion, Coulomb's Law of   338

Magnetic Axis  338

Magnetic Azimuth  338

Magnetic Battery  338

Magnetic Bridge  338

Magnetic Circuit  340

Magnetic Circuit, Curve of Saturation of   174

Magnetic Concentration of Ores  340

Magnetic Concentrator  340

Magnetic Continuity  340

Magnetic Conductance and Conductivity  340

Magnetic Control  341

Magnetic Couple  341

Magnetic Creeping  341

Magnetic Curves  341

Magnetic Cut Out  175

Magnetic Declination  342

Magnetic Density  342

Magnetic Dip  342, 346

Magnetic Discontinuity  342

Magnetic Double Circuit  340

Magnetic Eye, Electro-   248

Magnetic Elements  342

Magnetic Elongation  344

Magnetic Equator  344

Magnetic False Poles  350

Magnetic, Ferro-  252

Magnetic Field, Intensity of a   306

Magnetic Field of Force  344

Magnetic Field, Uniform   345

Magnetic Figures  345

Magnetic Filament  345

Magnetic Fluid, North   357

Magnetic Fluids  345

Magnetic Flux  345

Magnetic Force  346

Magnetic Friction  295, 346

Magnetic Friction Gear   276

Magnetic Fluid, South   356

Magnetic Foci  259

Magnetic Gear  346

Magnetic Hysteresis  294

Magnetic Inclination  346

Magnetic Induction  302

Magnetic Induction, Apparent Coefficient of   346

Magnetic Induction, Coefficient of   346-349

Magnetic Induction, Dynamic   347

Magnetic Induction, Static   347

Magnetic Induction, Tube of   347

Magnetic Inductive Capacity  349

Magnetic Inertia  347

Magnetic Influence  346

Magnetic Insulation  347

Magnetic Intensity   348

Magnetic Lag  348

Magnetic Latitude  348

Magnetic Leakage  348

'Magnetic Limit  348

Magnetic Lines of Force  348

Magnetic Mass  349

Magnetic Matter  349

Magnetic Memory  349

Magnetic Meridian  349

Magnetic Moment  349

Magnetic Needle  349

Magnetic Needle, Declination of the  178

Magnetic Needle, Dip of   185

Magnetic Needle, Oscillation of a   397

Magnetic Output  399

Magnetic Parallels  349

Magnetic Permeability  349

Magnetic Perturbations  350

Magnetic Poles  350

Magnetic Potential  350, 431

Magnetic Proof Piece  350

Magnetic Proof Plane  350

Magnetic Quantity  350

Magnetic Reluctance  351, 458

Magnetic Reluctivity  351

Magnetic Remanence  358

Magnetic Repulsion  338

Magnetic Resistance  458

Magnetic Retentivity  351

Magnetic Rotatory Polarization  351

Magnetic Saturation  251

Magnetic Screen  351

Magnetic Self-induction  352

Magnetic Separator  352

Magnetic Shell  352

Magnetic Shell, Strength of   352

Magnetic Shield  353

Magnetic Shunt  353

Magnetic Storms  353

Magnetic Strain  354

Magnetic Stress  354

Magnetic Susceptibility  254, 359

Magnetic Tick  354

Magnetic Top  542

Magnetic Twist  354

Magnetic Vane Ammeter  27

Magnetic Variations  354

Magnetism, Ampere's Theory of   354

Magnetism, Blue  355

Magnetism, Components of Earth's   356

Magnetism, Creeping of   356

Magnetism, Decay of   356

Magnetism, Discharge of   356

Magnetism, Electro  220

Magnetism, Ewing's Theory of  356

Magnetism, Free   356

Magnetism, Hughes' Theory of  357

Magnetism, Lamellar Distribution of  357

Magnetism of Gases  357

Magnetism, Red  357

Magnetism, Residual  358

Magnetism, Solenoidal Distribution of   358

Magnetism, Sub-permanent   358

Magnetism, Terrestrial  358

Magnetism, Weber's Theory of   358

Magnetization by the Earth  359

Magnetization by Double Touch  358

Magnetization by Separate Touch  359

Magnetization by Single Touch  359

Magnetization, Coefficient of Induced  359

Magnetization Curve  172

Magnetization, Cycle of  360

Magnetization, Elias' Method of   360

Magnetization, Hoffer's Method of   360

Magnetization, Intensity of   360

Magnetization, Isthmus Method of  360

Magnetization, Jacobi's Method  360

Magnetization, Limit of  361

Magnetization, Maximum   361

Magnetization, Specific   361

Magnetization, Surface   356

Magnetizing Coil   127

Magneto  361

Magneto Bell  80

Magneto Call Bell  361

Magneto-electric  361

Magneto-electric Brake  362

Magneto-electric Generator  362

Magneto-electric Generator, or Dynamo, Flashing in a   257

Magneto-electric Key  315

Magneto-electric Telegraph  512

Magnetograph  363

Magneto-inductor  363

Magnetometer  363

Magnetometer, Differential   365

Magnetometry  364

Magneto-motive Force  365

Magnetophone  367

Magnetoscope  365

Magnifying Spring Ammeter  28

Magnus' Law  367

Main Battery  66

Main Battery Circuit  125

Main Circuit  125

Main or Standard Feeder  251

Mains, Electric   367

Make   367

Make and Break Current  164, 367

Make and Break Key  316

Make-induced Current  163

Malapterurus  367

Map, Declination   309

Map, Inclination   297

Map, Isoclinic   308

Map, Isodynamic   308

Map, Isogonic  309

Marié Davy's Battery  67

Marine Galvanometer  269

Mariner's Compass  142

Marked End or Pole  368

Marriage Joint  310

Mass, Electric   368

Mass, Magnetic   349

Master Clock  127

Mathematical Element  237

Matteueci's Experiment  369

Matter, Electric  368

Matter, Fourth State of   261

Matter, Magnetic   349

Matter, Radiant  368

Matter, Ultra Gaseous  551

Matthiessen's Meter-gram Standard Resistance,.   466

Matthiessen's Unit of Resistance   466

Matting, Electric Floor   369

Maximum Magnetization  361

Maxwell's Theory of Light  369

Mayer's Floating Magnet  370

Maynooth's Battery  67

Measurement, Absolute   8

Measurements  370

Mechanical Equivalent of Heat  286

Mechanical Energy  241

Mechanical Equivalent, Electro-   244

Medical Battery  67

Medium, Polarization of the   424

Meg or Mega  370

Meidinger's Battery  68

Memoria Technica, Ampére's   30

Memory, Magnetic   349

Mercury  371

Mercury Bichromate, Battery  63

Mercury Circuit Breaker  121

Mercury Cups  371

Mercury, Sulphate of, Battery   67

Mercurial Air Pump  16

Meridian, Astronomical   372

Meridian, Geographic   372

Meridian, Magnetic.   349

Merit, Figure of   256

Merit, Formula of   256

Metal, Gilding   277

Metallic Arc  39

Metallic Circuit  125

Metallochromes  392

Metallurgy, Electro-  222

Metals, Law of Intermediate  323

Meter. Alternating Current   373

Meter, Ampere and Volt, Galvanometer .   274

Meter, Balance Ampere   391

Meter Bridge  373

Meter Bridge, Slide   486

Meter Candle  374

Meter, Chemical Electric   375

Meter, Current  375

Meter, Electro-magnetic   375

Meter, Energy  375

Meter Gram Standard Resistance, Matthiesen's   466

Meter-millimeter  375

Meter-millimeter Unit of Resistance   466

Meter, Neutral Wire Ampere.   391

Meter, Quantity  445

Meters. Ampere  39

Meter, Thermal-Electric   375

Meter, Time Electric   375

Meter, Watt  375

Method, Broadside   89

Method, Deflection   178

Method, End on   238

Method, Idiostatic   295

Method, Multiple Wire  388

Method, Null  393

Method of Magnetization, Elias'  360

Method of Magnetization, Isthmus   360

Method of Magnetization, Jacobi's   360

Methven Standard or Screen  376

Mho,   376

Mica  376

Mica, Moulded   376

Micro  376

Micrometer  376

Micrometer, Arc   39, 376

Micrometer, Spark   470

Micron  376

Microphone  376

Microphone Relay  377, 457

Microscope. Photo-electric   410

Microtasimeter  377

Mil  379

Mil, Circular   379

Mil-foot  379

Mil-foot Unit of Resistance  467

Milli  379

Milligram  379

Millimeter  379

Milli-oerstedt  380

Mil, Square  379

Minute, Ampere-  30

Mirror Galvanometer.   271

Mixed Gases  275

mm.  380

Molar  380

Molar Energy  241

Molecular Affinity  380

Molecular Attraction  380

Molecular Bombardment  380

Molecular Chain  380

Molecular Energy  241

Molecular Heat  286

Molecular Rigidity  380, 473

Molecular Shadow  480

Molecule  380

Moment  381

Moment, Magnetic   349

Moment of Couple  544

Moment, Turning   544

Monophote Lamp  321

Mordey Effect  381

Morse Receiver  381

Morse Recorder  451

Morse Telegraph  512

Mortar, Electric   382

Motion, Currents of   167

Motograph, Electro-   229

Motor. Compound or Compound Wound,.   382

Motor, Differential   382

Motor, Dynamo   200

Motor, Electric   382

Motor, Electro-   229

Motor, Electro-motive Force   384

Motor-generator  384

Motor, Multiphase  384

Motor, Overtype   399

Motor, Prime  385

Motor, Pulsating  386

Motor, Pyromagnetic   442

Motor, Reciprocating   385

Motor, Series   386

Motor, Shunt   386

Moulded Mica  376

Moulding  58

Movable Secondary  477

Mud, Battery  68

Multiphase Currents  166

Multiphase Motor  384

Multiple  386

Multiple Arc  387

Multiple Arc Box  387

Multiple Connected Battery  68

Multiple-series  387, 480

Multiple Switch  501

Multiple Switch Board  387

Multiple Transformer  548

Multiple Winding  579

Multiple Wire Method  388

Multiplex Harmonic Telegraph  510

Multiplex Telegraph  514

Multiplex Telegraphy  388

Multiplier, Schweigger's  476

Multiplying Power  347, 349

Multiplying Power of a Shunt  388

Multipolar Armature  46

Multipolar Dynamo  200

Multipolar Electric Bath  57

Multipolar Winding  579

Muscular Pile  388

Mutual Electro-magnetic Induction  302

Mutual Electrostatic Induction  303

Mutual Induction, Coefficient of   301

Mutual Induction Protector  481

Myria  388

Nairne's Electrical Machine  389

Napierian Logarithms  389

Nascent State  389

Natural Currents  166, 389

Natural Magnet  361

Needle  389

Needle Annunciator  35

Needle, Astatic   50

Needle, Dipping  185

Needle, Magnetic  349

Needle, Orientation of a Magnetic   397

Needle of Oscillation  389

Needle Telegraph, Single   519

Needle, Telegraphic  389

Negative Charge  389

Negative Current  164

Negative Electricity  389

Negative, Electro-   229

Negative Element  390

Negative Feeder  251

Negative Lead of Brushes  324

Negative Plate  417

Negative Pole  425

Negative Potential  432

Negative Side of Circuit  125

Nerve and Muscle Current  164

Nerve Currents  390

Net Efficiency  205

Net, Faraday's   250

Network  390

Neutral Armature  46

Neutral Feeder  251

Neutral Line of Commutator  390

Neutral Line of Magnet  361

Neutral Point  421

Neutral Point of Commutator  390

Neutral Point, Thermo-electric   390

Neutral Relay Armature  46, 390

Neutral Temperature  390

Neutral Wire  390

Neutral Wire Ampere Meter  391

N. H. P.  391

Niaudet's Battery   61

Nickel  391

Nickel Bath  391

Night Bell  392

Nitric Acid Battery  68

Nobili's Rings  392

Nodal Point  422

Nodular Deposit  392

Nominal Candle Power  101

Non-conductor  392

Non-essential Resistance  465-467

Non-inductive Resistance  467

Non-polar Dynamo   200

Non-polarizable Electrodes  210

Non-Polarized Armature  46

Normal Magnet  361

North Magnetic Fluid  357

North Pole  392

North Seeking Pole  393

Null Method  393

Null Point  422

Occlusion  393

Oerstedt  394

Oerstedt's Discovery  394

Oerstedt, Milli-  380

Ohm  394

Ohmage  394

Ohm, B. A.  394

Ohm, Board of Trade   394

Ohm, Congress   395

Ohmic Resistance  394, 467

Ohm, Legal  395

Ohmmeter  395

Ohm, Rayleigh   396

Ohm's Law  396

Ohm, True  396

Oil Insulation  396

Oil Transformer  548

Old Armature, Siemens'   49

Olefiant Gas  397

Omnibus Bar  94

Omnibus Rod  94

Omnibus Wire  94

One Coil Electro-magnet  219

Open  397

Open Circuit  125

Open Circuit Battery  68

Open Circuit Induction  303

Open Circuit Oscillation  397

Open Coil Armature  46

Open Coil Dynamo  200

Opening Shock  482

Operation, Magnet  365

Opposed Current  164

Optics, Electro-   229

Orders of Currents  167

Ordinate  397

Ordinates, Axis of  54, 397

Ores, Electric Reduction of  453

Ores, Magnetic Concentration of   340

Organ, Electric  397

Orientation of a Magnetic Needle  397

Origin of Co-ordinates  397

Oscillation, Centre of  112

Oscillation, Electric  398

Oscillation, Needle of   389

Oscillation, Open Circuit   397

Oscillatory  23

Oscillatory Discharge  188

Oscillatory Displacement  398

Oscillatory Electro-motive Force  398

Oscillatory Impedance  297

Oscillatory Induction  398

Osmose, Electric  398

Outlet  399

Output  399

Output, Magnetic   399

Output, Unit of   399

Over-compounding  399

Over, Flashing   258

Overflow Alarm  18

Over-house Telegraph  515

Overload  399

Overtype Dynamo or Motor  399

Oxide of Copper Battery  68

Ozone  399

Pacinotti's Inductor   400

Pacinotti's Ring  400

Pacinotti Teeth  400

Page Effect  401

Page's Revolving Armature  47

Paillard Alloys  400

Palladium  401

Pane, Fulminating   262

Pane, Luminous   401

Pantelegraphy  402, 510

Paper Filaments  402

Parabola  402

Parabolic Reflector  402

Paraffine  402

Paraffine Wax  402

Paragrêles  403

Parallax  403

Parallel  403

Parallel Circuits  123-126

Parallelogram of Forces  260

Parallels, Magnetic  349

Paramagnetic  403

Paramagnetism   404

Parasitical Currents  163

Parchmentizing  404

Partial Current  164

Partial Earth  203, 404

Partial Vacuum  557

Passive State  404

Path, Alternative   24

P. D.  404

Peltier's Cross  405

Peltier Effect  404

Pen, Electric   405

Pendant Cord  405

Pendulum Circuit Breaker  121

Pendulum, Electric  405

Pendulum or Swinging Annunciator  35

Pentane Standard, Harcourt's   406

Pentode Working  581

Percussion, Centre of   112

Perforated Armature  45

Perforated Core Discs  154

Perforator  407

Period   407

Period, Vibration   560

Periodic  23

Periodic Current, Power of   433

Periodicity  262, 408

Peripolar Zone  582

Permanency  408

Permanent Magnet  365

Permanent Magnet Ammeter  28

Permanent State  408

Permeability  346-349

Permeability-temperature Curve,   174

Permeameter  408

Permeance  408

Peroxide of Lead Battery  69

Perturbations, Magnetic   350

Pflüger's Law  409

Phantom Wires  409

Phase  409

Phase, Retardation of   471

Phenomenon, Porret's   427

Pherope  409, 527

Philosopher's Egg  409

Phonautograph,   409

Phone   409

Phonic Wheel  409

Phonograph  410

Phonophone or Rate Governor, Langdon Davies'   450

Phonozenograph  410

Phosphorescence  410

Phosphorous, Electrical Reduction of   410

Photo-electric Microscope  410

Photo-electricity  410

Photo-electro-motive Force  410

Photometer  411

Photometer, Actinic   411

Photometer, Bar  411

Photometer, Bunsen's  412

Photometer, Calorimetric   412

Photometer, Dispersion  412

Photometer, Shadow  414

Photometer, Translucent Disc   412

Photophore  415

Photo-voltaic Effect  415

Physical Energy  241

Physiology, Electro-   231

Piano, Electric   415

Pickle  415

Picture, Electric   415

Piece, Bed  78

Piece, Magnetic Proof  350

Piece, Pole   423

Pierced Core-discs,   152

Pile  415

Pile, Differential Thermo-electric   533

Pile, Muscular  388

Pile or Battery, Thermo-electric   530

Pilot Brush  91

Pilot Lamp  323

Pilot Transformer  415

Pilot Wires  415

Pistol, Electric  416

Pith  416

Pith Ball Electroscope  234

Pith-balls  416

Pivoted Armature  47

Pivot Suspension  416

Plane, Magnetic Proof   350

Plant  417

Plant Electricity  417

Plant, Isolated   309

Planté's Secondary Battery,   72

Plate, Arrester   417

Plate Condenser  417

Plate, Earth  203

Plate Electrical Machine  417

Plate, Franklin's  262

Plate, Generating   277

Plate, Ground   417

Plate, Negative   417

Plate, Positive   277, 417

Plating Balance  417

Plating Bath  418

Plating, Electro-   418

Platinized Carbon Battery  69

Platinoid  418

Platinum  419

Platinum Alloy  419

Platinum Black  419

Platinum Silver Alloy  419

Platinum Sponge  419

Play, End  238

Plow  420

Plücker Tubes  420

Plug  420

Plug Cut Out  175

Plug, Double  191

Plug, Grid   420

Plug, Infinity   305, 420

Plug Key  316

Plug Switch  420

Plumbago  421

Plunge Battery  69

Plunge  421

Plunger and Coil  131

Plunger and Coil, Differential   132

Plunger, Coil and  131

Plunger Electro-magnet   220

Pneumatic Battery  69

Pneumatic Signals, Electro-   231

P.O.  421

Pockets, Armature  47

Poggendorf's Solution  421

Point, Contact  147

Point, Indifferent   421

Point, Neutral  421

Point. Nodal  422

Point, Null   422

Point of Commutator, Neutral   390

Point Poles  422

Points, Consequent   422

Points, Corresponding   422

Points, Iso-electric   422

Points of Derivation  180, 423

Point, Thermo-electric Neutral   390

Polar Angle   423

Polar Extension  423

Polarity, Diamagnetic   181, 423

Polarity, Resultant   470

Polarization  423

Polarization, Back Electro-motive force of   156

Polarization Capacity  424

Polarization, Dielectric   183

Polarization, Galvanic  265

Polarization, Magnetic Rotary   351

Polarization of the Medium  424

Polarized Armature  47

Polarized Electro-magnet  220

Polarized Relay  458

Polarized Relay, Tongue of   542

Polarizing Current  164

Polar Region  424

Polar Span  424

Polar Span, Angle of   32, 423

Polar Tips  423

Polar Zone  582

Pole, Analogous   31, 425

Pole, Antilogous   425

Pole, Armature   47

Pole, Austral  54

Pole, Boreal   85

Pole Brackets, Telegraph   515

Pole Changer  425

Pole Changing Switch,   501

Pole Dynamo, Interior   199

Pole, Magnet   366

Pole, Negative   425

Pole, North  392

Pole, North-seeking  393

Pole or End, Marked   368

Pole Piece  423

Pole Pieces  425

Pole, Positive   425

Pole, Salient  426

Pole, Terminal   529

Pole Tips  290, 426

Pole, Traveling  426

Pole, Unit Magnet   366

Poles  425

Poles, Compensating   426

Poles, Consequent   146

Poles, Idle  296

Poles, Magnetic  350

Poles, Magnetic, False   350

Poles of Intensity  426

Poles of Verticity  426, 560

Poles, Point  422

Poles, Secondary  478

Poles, Secondary Magnet   366

Polyphase Currents  167

Polyphote Lamp  323

Popgun, Electric  282

Porous Cell  427

Porous Cup  159, 426

Porret's Phenomenon  427

Portative Power of Magnet  366

Portelectric Railroad  427

Portrait, Electric  415

Position, Energy of   241

Position Finder  427

Position, Sighted   484

Positive Current  164

Positive Direction  428

Positive Electricity  428

Positive Element  277

Positive Feeder  251

Positive Plate  277, 417

Positive Pole  425

Positive Potential  432

Positive Side of Circuit  125

Post Office  428

Posts, Binding, or Screws  81

Potential  428

Potential, Absolute   428

Potential, Constant  429

Potential Difference, Contact   147

Potential Difference, Electric   429

Potential Difference, Electro-motive   429

Potential, Electric Absolute  429

Potential, Fall of  430

Potential Galvanometer  269

Potential in Armature, Curve of Distribution of   172

Potential, Magnetic   350, 431

Potential, Negative  432

Potential or Static Energy  241

Potential, Positive  432

Potential Regulation, Constant   455

Potential, Unit of Electric   432

Potential, Zero   432, 582

Potentiometer   432

Poundal  433

Pound-foot  259

Power  438

Power, Candle   100

Power, Directive   187

Power, Electric   433

Power, Horse  290

Power, Illuminating  296

Power, Multiplying  349

Power of Magnet, Portative   366

Power of Periodic Current  433

Powers of Ten  527

Power, Stray  495

Power, Thermo-electric   533

Press Button  94

Pressel  434

Pressure  434

Pressure, Electric  434

Pressure, Electrification by   434

Primary  434

Primary Ampere-turns  31, 551

Primary Battery  69, 434

Prime  434

Prime Conductor  146, 434

Prime Conductor, Coatings of a  129

Prime Motor   385

Principle, Gauss'   276

Printing Telegraph  515

Probe, Electric  435

Projecting Power of a Magnet  435

Prony Brake  435

Proof Piece, Magnetic  350

Proof-plane  436

Proof Plane, Magnetic   350

Proof-sphere  436

Proportional Galvanometer  269

Proportionate Arms  436

Prostration, Electric  437

Protector, Body   84

Protector, Comb   437

Protector, Electric    437

Pull  437

Pulsatory Current  164

Pulsatory Field  256

Pulsating Motor  386

Pulvermacher's Electro-medical Battery  69

Pump, Geissler   437

Pump, Sprengel   439

Pump, Swinburne   440

Pumping  439

Puncture-electro  232

Puncture-galvano  232

Push Button  93. 98, 440

Push, Desk   180

Push, Floor  258

Pyro-electricity  441

Pyromagnetic Generator  442

Pyromagnetic Motor  441

Pyromagnetism  443

Pyrometer, Siemens' Electric   443

Q  443

Quad  288, 443

Quadrant  288, 443

Quadrantal Deviation  180

Quadrant, Legal  444

Quadrant, Standard   444

Quadrature   444

Quadruplex Telegraph  515

Qualitative  444

Quality of Sound  444

Quantitative  444

Quantity  444

Quantity Armature  47

Quantity, Electric  444

Quantity, Electro-magnetic  445

Quantity, Electro-magnetic, Practical Unit of   445

Quantity, Electrostatic  445

Quantity Galvanometer  269

Quantity, Magnetic  350

Quantity Meter  445

Quartz  445

Quicking  446

R  446

Racing of Motors  446

Radial Armature  47

Radian  446

Radiant Energy  446

Radiant Matter  368

Radiation  446

Radicals  446

Radiometer  447

Radiometer, Electric   447

Radio-micrometer  447

Radiophony  447

Railroad, Portelectric   427

Range Finder  447

Rate Governor  449

Rate Governor or Phonophone, Langdon Davies'   450

Rated Candle Power  101

Ratio Arms  437

Ratio, Core   154

Ratio, Shunt  483

Ratio, Velocity  560

Ray, Electric  450

Rayleigh Ohm  396

Reaction Coil  132

Reaction of a Dynamo Field and Armature  450

Reaction of Degeneration  179

Reactions, Anodic  36

Reactions, Armature   47

Reaction Telephone  527

Reaction Wheel  259

Reading Galvanometer, Direct   269

Reading, Sound   489

Reading Telescope  450

Real Efficiency of Secondary Battery  205

Real Hall Effect  284

Réaumur Scale  450

Recalescence  451

Receiver  451

Receiver, Harmonic   284, 451

Receiver, Morse   381

Receptive, Electro-   232

Recharge  115

Reciprocal  451

Reciprocating Motor  385

Recoil Circuit  125

Recorder, Chemical  117

Recorder, Morse  451

Recorder, Siphon   452

Record, Telephone   451

Rectification of Alcohol, Electric  18

Rectified Current  164

Rectilinear Current  165

Red Varnish  559

Red Magnetism  357

Redressed Current  165

Reduced Resistance  467

Reducteur for Ammeter  453

Reducteur for Voltmeter  453

Reduction of Ores, Electric   453

Reduction of Phosphorous, Electrical  410

Reflecting Galvanometer  270

Reflector, Parabolic  402

Refraction, Electric Double   454

Refraction, Electrostatic   235

Refreshing Action  454

Region, Extra-polar   454

Region, Intrapolar   307

Region, Polar  424

Register, Electric  454

Register, Telegraphic   454

Regulation, Constant Current   454

Regulation, Constant Potential   455

Regulation of Alternating Current Dynamo  195

Regulation of Dynamos  455

Reguline  456

Relative  456

Relative Calibration  98

Relay  456

Relay Bell  80

Relay Bells  457

Relay, Box Sounding  457

Relay Connection  457

Relay, Differential  457

Relay Magnet  457

Relay, Microphone  377, 457

Relay, Neutral, Armature   390

Relay, Polarized   457

Reluctance  458

Reluctance, Magnetic   351, 458

Reluctance, Unit of   438

Reluctivity  459

Reluctivity, Magnetic   351

Remanence  459

Remanence, Magnetic  358

Removal of Hair by Electrolysis  283

Renovate  115

Repeater  459

Repeater, Telegraph   518

Replenisher, Sir Wm. Thomson's  459

Repulsion, Magnetic  338

Repulsion and Attraction, Electrostatic   234

Repulsion and Attraction, Electro-magnetic  217

Reservoir, Common   460

Residual Atmosphere  460

Residual Capacity  103

Residual Charge  116

Residual Magnetism  358

Residue, Electric  116, 460

Resin  460

Resinous Electricity  461

Resistance  461

Resistance, Apparent  297, 462

Resistance, Assymmetrical   462

Resistance Box  462

Resistance, B. A. Unit of   462

Resistance Box, Sliding  463

Resistance, Breguet Unit of   463

Resistance Bridge  577

Resistance Coil  137

Resistance Coil, Standard   464

Resistance, Carbon   463

Resistance, Combined  464

Resistance, Compensating   144

Resistance, Critical  464

Resistance, Dielectric  183, 464

Resistance, Digney Unit of   464

Resistance, Electrolytic  464

Resistance, English Absolute or Foot-second Unit of  465

Resistance, Equivalent   465

Resistance, Essential   465

Resistance, External   465

Resistance Frame  465

Resistance, German Mile Unit of   466

Resistance, Hittorf's   466

Resistance, Inductive  466

Resistance, Insulation   466

Resistance, Internal   466

Resistance, Jacobi's Unit of   466

Resistance, Joint  464

Resistance, Magnetic   351, 458

Resistance, Matthiessen's Meter-gram Standard of    466

Resistance, Matthiessen's Unit of   466

Resistance, Meter-millimeter Unit of   466

Resistance, Mil-foot Unit of   467

Resistance, Non-essential  465, 467

Resistance, Non-inductive   467

Resistance of Human Body  467

Resistance, Ohmic  394, 467

Resistance, Reduced  467

Resistance, Siemens' Unit of  467

Resistance, Specific  467

Resistance. Specific Conduction  467

Resistance, Spurious   467

Resistance, Steadying  468

Resistance, Swiss Unit of   468

Resistance, Thomson's Unit of   468

Resistance to Sparking  490

Resistance, True  467

Resistance, Unit  468

Resistance, Unit of, B. A.   78

Resistance, Varley's  559

Resistance, Varley's Unit of  468

Resistance, Virtual   297

Resistance, Weber's Absolute Unit   468

Resolution of Forces  261

Resonator, Electric   468-470

Rest, Currents of   167

Resultant  470

Resultant Polarity  470

Retardation  470

Retardation of Phase  471

Retentivity  471

Retentivity, Magnetic   351

Retort Carbon  471

Return  471

Return Circuit  125

Return, Earth  203

Return Stroke  55

Reversal, Thermo-Electric   533

Reverse Current Working  581

Reverse-induced Current  163

Reverser, Current   165

Reversibility  471

Reversible Bridge  472

Reversing Key  316

Reversing Switch  501

Revivify  115

Revolving Armature, Page's   47

Rheochord  472

Rheometer  472

Rheomotor  472

Rheophore  472

Rheoscope  472

Rheoscopic Frog  262

Rheostat  472

Rheostat Arm  472

Rheostatic Machine  472

Rheostat, Wheatstone's   472

Rheotome  473

Rheotrope  473

Rhigolene  473

Rhumbs  473

Rhumkorff Coil  138, 473

Ribbon Coil  138

Ribbon Core  154

Right-handed Screw Law  324

Rigidity, Molecular  380, 473

Ring, Ampere   30

Ring Armature  48

Ring. Collecting   139

Ring Contact  473

Ring Core  155

Ring, Dynamo  200

Ring, Faraday's   473

Ring, Foundation   261

Ring, Guard  282

Ring, Pacinotti's   400

Rings, Electric   392

Rings, Nobili's  392

Ring, Split, Commutator   141

Roaring  474

Rocker  474

Rocker Arms  50, 474

Rod, Bus  94

Rod, Discharging   189

Rod, Omnibus   94

Roget's Spiral  474

Rolling Armature  49

Rosin  460

Rotary Polarization, Magnetic   351

Rotating Brush   91

Rotating Field  256

Rotation of Liquids, Electro-dynamic   474

Rotation of Liquids, Electro-magnetic   475

Rotatory Currents  167

Rubber  102, 475

Rubber, India   102

Saddle Bracket  475

Safety Catch  175

Safety Cut Out  175

Safety Device  475

Safety Fuse  175, 475

Safety Fuse, Plug, or Strip   475

Sal Ammoniac Battery  69

Salient Pole  426

Salt  475

Salt, Dronier's  192

Salt or Sea-salt Battery  69

Sand Battery  90

Saturated  476

Saturation, Magnetic   351

Saw, Electric   476

Scale, Fahrenheit   248

Scale, Réaumur   450

Scale, Tangent  502

Schweigger's Multiplier  476

Scratch Brushes  476

Screen, Electric   476

Screen, Magnetic   351

Screen, Methven  376

Screws or Posts, Binding   81

Sealed, Hermetically  289

Sea Salt or Salt Battery  69

Secohm  288

Second, Ampere-   30

Secondary Actions  477

Secondary Ampere-turns  31, 551

Secondary Battery  70

Secondary Battery, Efficiency of, Quantity  205

Secondary Battery, Planté's   72

Secondary Clock  127

Secondary Current  166

Secondary Generator  277, 477

Secondary Magnet Poles  366

Secondary, Movable  477

Secondary Plates, Colors of   478

Secondary Poles  478

Secretion Current  166

Section Trolley  549

Sectioned Coils  138

Seebeck Effect  478

Segments  56

Segments, Commutator   56

Selenium  478

Selenium Cell  478

Selenium Eye  478

Self-exciting Dynamo  201

Self-induction  303

Self-induction, Magnetic   352

Self-induction, Unit of   304

Self-repulsion  478

Self-winding Electric Clock  128

Semi-circular Deviation  181

Semi-conductors  478

Semi-incandescent Lamp  323

Sender, Zinc  582

Sensibility  479

Sensitiveness, Angle of Maximum   479

Separate Circuit Dynamo  201

Separate Touch  359, 479

Separate Touch, Magnetization by   359

Separately Excited Dynamo  201, 479

Separation of Electricities  479

Separator  479

Separator, Magnetic   352

Series  479

Series and Long Shunt Winding  579

Series and Separate Coil Winding  579

Series and Short Shunt Winding  580

Series, Contact  147

Series Dynamo  201

Series, Electro-chemical   209

Series, Electro motive   228

Series, Electrostatic   235

Series Motor  386

Series, Multiple-   387

Series-multiple  480

Series, Thermo-electric   534

Series Transformer  548

Series Winding  579

Service Conductors  480

Serving  480

Shackle  480

Shadow, Electric   480

Shadow, Molecular   480

Shadow Photometer  414

Sheath for Magnet Coils  481

Sheath for Transformers  481

Sheath, Induction  303

Sheet Current  166

Shell, Magnetic  352

Shell, Strength of Magnetic  352

Shellac  481

Shellac Varnish  481

Shield, Anti-magnetic   37

Shield, Magnetic   351, 353

Shielded  481

S. H. M.  482

Shock, Back, or Stroke of Lightning   55

Shock, Break   482

Shock, Electric   482

Shock, Opening   482

Shock, Static  482

Short Circuit  482

Short Circuit Working  482

Short Fall Air Pumps  16

Short Shunt Winding   579

Shovel Electrodes  483

Shower Bath, Electric   57

Shunt  483

Shunt Box   483

Shunt Circuit  123, 126

Shunt Dynamo  202

Shunt, Electro-magnetic   483

Shunt, Galvanometer   271, 483

Shunt, Magnetic   353

Shunt Motor  386

Shunt. Multiplying Power of a   388

Shunt Ratio  483

Shunt Winding  580

Shuttle Armature  49

Shuttle Current  483

Shuttle Winding  483, 580

Side Flash  484

Siemens and Halske's Battery  72

Siemens' Differential Voltameter  564

Siemens' Electro-dynamometer  212

Siemens' Old Armature  49

Siemens' Unit of Resistance  467

Sighted Position  484

Signaling, Velocity of  560

Signals, Electro-pneumatic   231

Signal, Telegraph  519

Silent Discharge  187, 189, 206

Silver  484

Silver Bath  484

Silver, German   277

Silver Stripping Bath  484

Silver Voltameter  565

Simple Arc  39

Simple Circuit  126

Simple Harmonic Motion  486

Simple Immersion  185

Simple Magnet  366

Simple Substitution  485

Sims-Edison Torpedo  543

Sine Curve  174, 485

Sine Galvanometer  271

Sine Law  486

Sines, Curve of  173, 485

Single Coil Dynamo  202

Single Curb Working  581

Single Fluid Theory  486

Single Fluid Voltaic Cell  486

Single Needle Telegraph  519

Single Touch, Magnetization by  359

Sinistrotorsal  486

Sinuous Current  166

Sinusoidal Curve  174, 485

Siphon Recorder  452

Sir William Thomson's Battery  72

Skin Effect  486

Skrivanow Battery  72

Sled  486

Sleeve, Joint   310

Slide, Balance   374

Slide Bridge  374

Slide Meter Bridge  486

Sliding Condenser  144

Sliding-contact Key  316

Sliding Resistance Box  463

Slope, Lines of   330

Smee's Battery  73

S. N. Code  486

Snap Switch  501

Soaking-in-and-out  486

Socket, Lamp   323

Socket, Wall  572

Soldering, Electric   487

Solenoid  487

Solenoid Ammeter  28

Solenoidal Distribution of Magnetism  358

Solenoidal Magnet  366

Solid Earth  203

Solutions, Battery, Chromic Acid   73

Solution, Chutaux's  119

Solution, Delaurier's    179

Solution, Hittorf's   289

Solution, Kookogey's   318

Solution, Poggendorf's  421

Solution, Striking  496

Solution, Tissandier's  542

Solution, Trouvé's   549

Sonometer, Hughes'   488

Sonorescence  488

Sound, Characteristics of   114

Sounder  488

Sounders, Tin   542

Sound, Quality of   444

Sound Reading  489

South Magnetic Fluid  356

Space, Clearance  489

Space, Crookes' Dark    489

Space, Dark, Faraday's   249, 489

Space, Faraday's Dark   249, 489

Space, Inter-air   489

Space, Interferric   489

Span, Polar  424

Span, Polar, Angle of the   32

Spark Arrester  489

Spark Coil  489

Spark Discharge  189

Spark, Duration of Electric   490

Spark Gap  490

Spark, Length of   490

Spark Micrometer  470

Spark Tube  491

Sparking  490

Sparking Distance  190

Sparking, Lines or Points of Least   490

Sparking, Resistance to   490

Specific Conduction Resistance  467

Specific Conductivity  145

Specific Heat  286

Specific Heat of Electricity  491

Specific Inductive Capacity  103

Specific Magnetization  361

Specific Resistance  467

Speech, Articulate   50

Speed, Critical   157

Spent Acid  491

Spent Liquor  491

Spherical Armature  49

Spherical Candle Power  101

Spherical Illuminating Power  296

Sphygmophone  491

Sphygmophone, Electric  491

Spiders  491

Spiral   492

Spiral Battery  73

Spiral, Roget's    474

Spiral Winding  492

Spirit Compass  143

Splayed Joint  311

Splice Box  492

Split Battery  73

Split Ring Commutator  141

Spluttering  492

Sponge, Platinum   419

Spot, Grease  92

Sprengel Pump  439

Spring Ammeter  28

Spring and Fibre Suspension  252

Spring-contact  148

Spring Control  492

Spring Jack Cut-out  493

Spurious Hall Effect  284

Spurious Resistance  467

Spurious Voltage  493

Square Mil  379

Square Wire  493

Squares, Law of Inverse   323

St. Elmo's Fire  494

Staggering  493

Standard Candle  101

Standard Candle, German  99

Standard, Harcourt's Pentane   406

Standard, Methven   376

Standard of Illuminating Power, Viole's   561

Standard or Main Feeder  251

Standard Quadrant  444

Standard Resistance Coil  464

Standard Voltaic Cell  109

Standard Voltaic Cell, Daniell's  109

Standard Voltaic Cell, Latimer Clark's.   110

State, Electrotonic   493

State, Nascent  389

State of Matter, Fourth   261

State, Passive  404

State, Permanent   408

Static Breeze  493

Static Condenser, Armature of   46

Static Electricity  493

Static Hysteresis  295

Static Induction, Magnetic   347

Static Shock  482

Station, Central    493

Station, Distant   493

Station, Home  493

Station, Transforming  494

Steadying Resistance  468

Steel  494

Steeling  494

Steel Yard Ammeter  28

Step-by-step Telegraph  506

Step-by-step Telegraphy  494

Step-down  494

Step, Foot-    259

Sticking  494

Stool, Insulating  305

Stopped Coil Electro-magnets  221

Stopping Off  495

Storage Battery  70

Storage Battery Changing Switch  501

Storage Battery, Planté's   72

Storage Capacity  105, 495

Storage of Electricity  495

Storms, Electric   495

Storms. Magnetic   353

Strain  495

Strain, Dielectric   183

Strain, Magnetic  354

Stranded Conductor Armature  49

Stranded Core  155

Stray Field  256, 495

Stray Power  495

Streamlets. Current  495

Strength, Dielectric   183

Strength of Magnetic Shell  352

Stress  495

Stress, Dielectric  496

Stress, Electro-magnetic   219, 496

Stress, Electrostatic  236, 496

Stress, Energy of   241

Stress, Magnetic   354

Striae, Electric   496

Striking Distance  496

Striking Solution  496

Stripping  496

Stripping Bath  57

Stripping Bath, Gold   279

Stripping Bath, Silver   484

Stroke, Back   55

Stroke or Shock of Lightning, Back   55

Stroke, Return  55

Sub-branch  496

Sub-main  496

Sub-permanent Magnetism  358

Substitution, Simple   485

Subway, Electric  496

Successive Temperatures, Law of   324

Sucking Coil  182

Sucking Magnet  366

Sulphate of Lead Battery  66

Sulphate of Mercury Battery  67

Sulphating  497

Sulphur Dioxide  497

Sulphuric Acid  497

Sulphuric Acid Voltameter  564

Sulphurous Acid Gas   497

Sunstroke, Electric  497

Superficial Density, Electric   180

Supersaturated,   497

Supply, Isolated   309

Surface  497

Surface Density  498

Surface, Equipotential   498

Surface Leakage  498

Surface Magnetization  356

Surgical Electro-magnet  222

Surging Discharge  188

Surveyors' Compass  143

Susceptibility, Magnetic  354, 359

Suspension  498

Suspension, Bifilar  498

Suspension, Fibre  252

Suspension, Knife Edge  317

Suspension, Pivot  416

Suspension, Spring and Fibre   252

Suspension, Torsion  545

Suspension Wire of Cable   97

Swaging. Electric  499

Swelling Current  167

S. W. G.  499

Swinburne Pump  440

Swinging Earth  203

Swinging or Pendulum Annunciator  35

Swiss Unit of Resistance   468

Switch  499

Switch, Automatic  500

Switch Board  500

Switch Board, Multiple   387

Switch Board, Trunking   550

Switch, Break-down   88

Switch, Changing  500

Switch, Changing Over   500

Switch, Circuit Changing   500

Switch, Double Break   500

Switch, Double Pole   500

Switch Feeder  500

Switch, Knife   501

Switch, Knife Break   501

Switch, Knife Edge   501

Switch, Multiple  501

Switch, Plug  420

Switch, Pole Changing   501

Switch, Reversing   501

Switch, Snap   501

Switch, Storage Battery Changing   501

Switch, Three Way   501

Switches, Distributing   190

Symmer's Theory  191

Sympathetic Vibration  501, 561

System, Block   83

System of Co-ordinates  150

System, Tower   545

T  501

Tailing Current  501

Tailings  501

Talk, Cross  158

Tamidine  502

Tangent Galvanometer  272

Tangent Law  502

Tangent Positions of, Gauss   276

Tangent Scale  502

Tangentially Laminated Core  155

Tank, Cable  97

Tape, Insulating   305

Tapper Key, Double   314

Teazer  504

Technica, Memoria, Ampére's   30

Tee, Lead  504

Teeth, Pacinotti   400

Tel-autograph  504

Tele-barometer, Electric   504

Telegraph, A. B. C.  504

Telegraph, Autographic   510

Telegraph, Automatic  504

Telegraph, Dial  505

Telegraph, Double Needle   506

Telegraph, Duplex  506

Telegraph, Duplex, Bridge  506

Telegraph, Duplex, Differential   507

Telegraph Embosser  237

Telegraph, Facsimile  510

Telegraph, Harmonic Multiplex   510

Telegraph. Hughes'   511

Telegraph Insulator  306

Telegraph Key  316

Telegraph, Magneto-electric   512

Telegraph, Morse  512

Telegraph, Multiplex  514

Telegraph, Single Needle   519

Telegraph, Overhouse  515

Telegraph Pole Brackets  515

Telegraph, Printing  515

Telegraph, Quadruplex   515

Telegraph Repeater  518

Telegraph Signal  519

Telegraph, Step-by-step  506

Telegraph, Wheatstone's, A. B. C.   521

Telegraph. Writing  521

Telegraphic Alphabet  19

Telegraphic Code  130, 511

Telegraphic Needle  389

Telegraphic Register  454

Telegraphy, Multiplex  388

Telegraphy, Step-by-step   494

Telemanometer, Electric   521

Telemeter, Electric   521

Telepherage  522

Telephone  522

Telephone, Bi-  524

Telephone, Capillary   525

Telephone, Carbon   525

Telephone, Chemical   526

Telephone, Electrostatic   526

Telephone Exchange  246

Telephone Induction Coil  137, 526

Telephone, Reaction   527

Telephone Record  451

Telephone, Thermo-electric   527

Telephone Tinnitus  542

Telephotography  521

Telephote  527

Telescope, Reading  450

Teleseme  527

Tele-thermometer  527

Terminal  529

Terminal Pole  529

Terminal Voltage  562

Temperature, Absolute   8

Temperature, Neutral  390

Temperatures, Laws of Successive   324

Tempering, Electric  527

Temporary Magnetism or Magnetization  357

Ten, Powers of    527

Tension  529

Tension, Disruptive  189

Tension, Electric  529

Terrestrial Magnetism   358

Tetanus, Acoustic   529

Tetrode Working  581

Theatrophone  529

Theory, Contact  148

Theory, Double Fluid   191

Theory, Franklin's  262

Theory of Dimensions  184

Theory of Light, Electro-magnetic  219

Theory of Light, Maxwell's  369

Theory of Magnetism, Ampére's  354

Theory of Magnetism, Ewing's  356

Theory of Magnetism, Hughes'   357

Theory of Magnetism, Weber's   358

Theory, Symmer's  191

Therapeutic Electrode  210

Therapeutics, Electro-   236

Therm  529

Thermaesthesiometer  530

Thermal Electric Meter  375

Thermal Equivalent, Electro-   245

Thermal Energy  242

Thermic Balance  85

Thermo Call  530

Thermo-chemical Battery  530

Thermo-chemical Equivalent  245

Thermo-electric Battery or Pile  530

Thermo-electric Call  531

Thermo-electric Couple  532

Thermo-electric Current  167

Thermo-electric Diagram  532

Thermo-electric Element  237

Thermo-electric Inversion  533

Thermo-electric Junction  533

Thermo-electric Neutral Point   390

Thermo-electric Pile, Differential  533

Thermo-electric Power  533

Thermo-electric Reversal  533

Thermo-electric Series  534

Thermo-electric Telephone  527

Thermo-electric Thermometer  535

Thermo-electricity  533

Thermo-electricity, Laws of, Becquerel's  78

Thermo-electricity, Volta's Law of  568

Thermo-electrometer  536

Thermolysis  535

Thermo-multiplier  536

Thermometer  535

Thermometer, Electric   535

Thermometer, Kinnersley's   536

Thermometer, Tele-   527

Thermometer, Thermo-electric   535

Thermophone  537

Thermostat, Electric   537

Third Brush  91

Thomson Effect  538

Thomson's Replenisher, Sir William   459

Thomson's Battery, Sir William  72

Thomson's Unit of Resistance  468

Three Filament Incandescent Lamp  322

Three Way Switch  501

Three Wire System  539

Throw  237, 540

Throw-back Indicator  540

Thrust Bearings  540

Thunder  540

Ticker   540

Tick, Magnetic   354

Timbre   444

Time Constant  541

Time Cut-outs  541

Time Electric Meter  375

Time-fall   541

Time-reaction  541

Time-rise  541

Tin  541

Tin Sounders  542

Tinnitus, Telephone   542

Tips, Polar   423

Tips, Pole   290, 426

Tissandier's Solution  542

Toeppler-Holtz Machine  334

Tongs, Cable Hanger  97

Tongs, Discharging  189

Tongue of Polarized Relay  542

Tongue of Polarized Relay, Bias of   542

Toothed Core-discs  154

Top, Magnetic   542

Torpedo, Electric  543

Torpedo, Sims-Edison   543

Torque  543

Torque, Curve of   174

Torricellian Vacuum  557

Torsion Balance, Coulomb's   544

Torsion Galvanometer  273, 544

Torsion Head  544

Torsion Suspension  545

Total Earth  203

Touch  545

Touch, Separate   479

Tourmaline   545

Tower, Electric   545

Tower System   545

Trailing Horns  259

Transformer  545

Transformer, Commuting  547

Transformer, Continuous Alternating   547

Transformer, Continuous Current   384, 547

Transformer, Core  547

Transformer, Faraday's   250

Transformer, Hedgehog   548

Transformer, Multiple   548

Transformer, Oil  548

Transformer, Pilot   415

Transformer, Series   548

Transformer. Sheath for  481

Transforming Station  494

Transformer, Welding   548, 575

Translator  519

Translucent Disc Photometer  412

Transmitter  548

Transmitter, Carbon   549

Transmission of Energy, Electric   240

Transposing  549

Transverse Electro-motive Force  549

Trap, Bug  92

Traveling Pole  426

Trembling Bell  78

Trolley  549

Trolley, Double   549

Trolley Section  549

Trough Battery   73

Trouvé's Blotting Paper Battery  73

Trouvé's Solution  549

True Contact Force  549

True Ohm  396

True Resistance  467

Trimmer, Brush   549

Trumpet, Electric   550

Trunk Lines  550

Trunking Switch Board  550

Tube, Electric   550

Tube, Guard  282

Tube, Luminous   550

Tube of Magnetic Induction  347

Tube, Spark  491

Tube, Stratification   495

Tubes, Geissler   276

Tubes of Force   261

Tubes, Plücker  420

Tubular Braid  550

Tubular Core  155

Tubular Magnet  356

Tuning Fork Circuit Breaker  121

Tuning Fork Dynamo  202

Tuning Fork, Interrupter for  307

Turning Moment  544

Turns  550

Turns, Ampere-  31

Turns, Dead, of a Dynamo   551

Turns, Primary Ampere-   551

Turns, Secondary Ampere-   551

Twist Joint, American  309

Twist, Magnetic   354

Tyer's Battery  74

Typewriter, Electric   551

Type Printer, Hughes'   511

Ultra-gaseous Matter  551

Unbuilding  552

Underground Conductor  552

Underground Electric Subway  552

Undulatory  23

Undulatory Current  167

Unidirectional  553

Uniform Field  256

Uniform Field of Force  553

Uniform Magnetic Field  345

Unipolar  553

Unipolar Armature  50, 553

Unipolar Current Induction  553

Unipolar Dynamo  202-553

Unipolar Electric Bath  57

Unipolar Induction   304

Unipolar Magnet  366

Unit  553

Unit, Absolute   554

Unit Angle  554

Unit. B. A.   554

Unit, B. A., of Resistance   462

Unit Current  167

Unit Electro-motive Force  228

Unit, Fundamental   554

Unit Jar  554

Unit Magnet Pole  366

Unit of Capacity  105

Unit of Conductivity  145

Unit of Electric Potential  432

Unit of Energy, Electro-magnetic   220

Unit of Force  261

Unit of Illumination  296

Unit of Output  399

Unit of Reluctance  458

Unit of Resistance, B. A.   78

Unit of Resistance, Breguet   463

Unit of Resistance, Digney  464

U nit of Resistance, English Absolute or Foot-second   465

Unit of Resistance, German Mile  466

Unit of Resistance, Jacobi's  466

Unit of Resistance, Meter-millimeter.   466

Unit of Resistance, Mil-foot   467

Unit of Resistance, Siemens'  467

Unit of Resistance, Swiss  468

Unit of Resistance, Thomson's   468

Unit of Resistance, Varley's   468

Unit of Self-induction  304

Unit of Supply  554

Unit of Work  581

Unit Resistance  468

Units, Circular  126, 555

Units, Derived   555

Units, Heat   288

Units, Practical  555

Universal Battery System  556

Universal Discharger  189

Unmarked End  556

Upright Galvanometer  274

Upward's Battery  75

V  556

V. A.  557

Vacuum  557

Vacuum, Absolute  557

Vacuum, High  557

Vacuum Lightning Arrester  329

Vacuum, Low   557

Vacuum, Partial  557

Vacuum, Torricellian   557

Valency  557

Valve, Electrically Controlled   558

Vapor Globe  558

Variable Conductivity  145

Variable Period  558

Variable State  558

Variation of the Compass  32, 558

Variations, Magnetic   354

Variometer  559

Varley's Battery  76

Varley's Condenser   559

Varley's Resistance  559

Varley's Unit of Resistance   468

Varnish  559

Varnish, Electric    559

Varnish, Insulating   306

Varnish, Red  559

Varnish, Shellac  481

Vat  559

Velocity  559

Velocity, Angular  32, 559

Velocity of Signaling  560

Velocity Ratio  560

Ventilation of Armature  560

Vertical Galvanometer  274

Vertical Induction  304

Verticity, Poles of   426, 560

Vibrating Bell  78

Vibration Period  560

Vibration, Sympathetic   501, 561

Vibrator, Electro-magnetic   561

Villari's Critical Value   561

Viole  562

Viole's Standard of Illuminating Power  561

Virtual Resistance  297

Viscous Hysteresis  295, 356

Vis Viva  562

Vitreous Electricity  562

Vitriol, Blue  562

Vitriol, Green    562

Vitriol, White   562

Volatilization of Carbon  108

Volt  562

Volt-ampere  573

Volt and Ampere Meter Galvanometer  274

Volt, B. A.  568

Volt, Congress   568

Volt, Coulomb   568, 573

Volt Indicator  568

Volt. Legal   568

Voltage  562

Voltage, Spurious  493

Voltage, Terminal   562

Voltaic  563

Voltaic Alternatives  563

Voltaic Arc  39

Voltaic Cell, Daniell's Standard  109

Voltaic Cell, Double Fluid  191

Voltaic Cell, Capacity of Polarization of a   103

Voltaic Cell, Single Fluid   486

Voltaic Cell, Standard   109

Voltaic Cell, Standard, Latimer Clark's   110

Voltaic Circuit  126

Voltaic Effect  563

Voltaic Electricity  563

Voltaic Element  237

Voltaic or Galvanic Battery  76

Voltaic or Galvanic Circle  119

Voltaic or Galvanic Couple  156

Voltameter   563

Voltameter, Copper   563

Voltameter, Differential, Siemens'   564

Voltameter, Faraday's   250

Voltameter, Gas   564

Voltameter, Silver  565

Voltameter, Sulphuric Acid    564

Voltameter, Volume   564

Voltameter, Weight   566

Voltametric Law  567

Volta's Battery  76

Volta's Fundamental Experiments   567

Volta's Law of Galvanic Action  568

Volta's Law of Thermo-electricity  568

Voltmeter  568

Voltmeter, Battery   569

Voltmeter, Cardew  569

Voltmeter, Electrostatic   571

Voltmeter, Reducteur for   453

Volts, Lost  571

Volume Voltameter  564

Vulcanite  571

W  572

Wall Bracket  572

Wall Socket  572

Ward  572

Waste Field  256

Water  572

Water Battery  77

Water Equivalent  572

Water Level Alarm  18

Waterproof Lamp Globe  572

Wattless Current  168

Watt  572

Watt-hour  573

Watt Meter  375

Watt-minute  573

Watt-second  573

Watts, Apparent  573

Wave Winding  580

Waves, Amplitude of   31

Waves. Electro-magnetic   573

Wax, Paraffine   402

Weber   574

Weber s Absolute Unit Resistance  468

Weber-meter  574

Weber's Theory of Magnetism  358

Wedge Cut-out  175

Wedge. Double   191

Weight, Atomic   53

Weight, Breaking   89

Weight Electrometer  223

Weight Voltameter  566

Welding, Electric  574

Welding Transformer  548, 575

Wheatstone's A. B. C. Telegraph  521

Wheatstone's Balance   577

Wheatstone's Bridge   575

Wheatstone's Bridge, Commercial   86

Wheatstone's Rheostat    472

Wheel, Phonic   409

Wheel, Reaction   259

Whirl, Electric   577

White Vitriol   562

Wilde Candle   101

Wimshurst Electric Machine  335, 577

Wimshurst Machine  335, 577

Wind, Electric  578

Windage  578

Windings, Ampere   31

Winding, Bifilar  81

Winding, Compound   578

Winding, Disc  579

Winding, Lap  579

Winding, Long Shunt  579

Winding, Long Shunt and Series  579

Winding, Multiple   579

Winding, Multipolar   579

Winding, Series  579

Winding, Series and Separate Coil   579

Winding, Series and Short Shunt   580

Winding, Short Shunt   579

Winding, Shunt  483, 580

Winding Shuttle  580

Winding, Wave  580

Winding Working, Differential  183

Wire, Block  83

Wire, Bus  94

Wire, Dead   177

Wire Finder   580

Wire Gauze Brush  92

Wire, Idle  296

Wire, Neutral   390

Wire, Omnibus   94

Wire, Square  493

Wire System, Three   539

Wires, Crossing   158

Wires, Leading-in   324

Wires, Phantom   409

Wires, Pilot  415

Wollaston Battery  78

Work  580

Work, Electric, Unit of   580

Work, Unit of  581

Working, Contraplex   580

Working, Diode   580

Working, Diplex   580

Working, Double Curb   581

Working, Hexode   581

Working, Pentode   581

Working, Reverse Current  581

Working, Single Curb   581

Working Tetrode  581

Writing Telegraph  521

X, Axis of   54

Y, Axis of   54, 397

Yoke  581

Zamboni's Dry Pile  581

Zero  581

Zero, Absolute  581

Zero Potential  432, 582

Zero, Thermometric   582

Zinc   582

Zinc Sender  582

Zincode  582

Zone, Peripolar   582

Zone, Polar   582

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