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

by T. O'Conor Sloane

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.