The Standard Electrical Dictionary / A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering

by T. O'Conor Sloane

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.