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.
