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

by T. O'Conor Sloane

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.