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.