B. W. G.
Abbreviation for Birmingham Wire Gauge. (See Wire Gauge, Birmingham.)
C.
(a) Abbreviation for Centigrade, as 100 C., meaning 100 Centigrade. (See
Centigrade Scale.)
(b) A symbol of current or of current strength. Thus in the expression
of Ohm's law C = E/R. C indicates current strength or intensity, not in
any fixed unit, but only in a unit of the same order in which E and R
are expressed; E Indicating electro-motive force and R resistance.
Cable.
(a) Abbreviation for Cablegram, q. v.
(b) v. It is also used as a verb, meaning to transmit a message by
submarine cable.
(c). An insulated electric conductor, of large diameter. It often is
protected by armor or metallic sheathing and may be designed for use as
an aerial, submarine, subterranean or conduit cable. A cable often
contains a large number of separately insulated conductors, so as to
supply a large number of circuits.
Cable, Aerial.
A cable usually containing a large number of separately insulated wires,
and itself insulated. It is suspended in the air. As its weight is
sometimes so great that it could not well sustain it, a suspending wire
is in such cases carried along with it, to which it is suspended by
cable hangers, q. v.
Cable Box.
A box for receiving underground cable ends and connecting the separate
wires of the cable to air-line wires. It is often mounted on a pole,
which forms the starting point of the air-line portion of the system.
Cable, Bunched.
A cable containing a number of separate and individual conductors. In
some forms it consists virtually of two or more small cables laid
tangent to each other and there secured. Thus each in section represents
two or more tangent circles with the interstice solidly filled with the
metal sheathing.
Cable, Capacity of.
The electrostatic capacity of a cable. A cable represents a Leyden jar
or static condenser. The outer sheathing or armor, or even the more or
less moist coating, if it is unarmored, represents one coating. The wire
conductors represent the other coating, and the insulator is the
dielectric.
The capacity of a cable interferes with its efficiency as a conductor of
broken or interrupted currents, such as are used in telegraphy or
telephoning. As each impulse or momentary current is sent into the line,
it has to charge the cable to at least a certain extent before the
effects of the current are perceptible at the other end. Then the cable
has to discharge itself. All this creates a drag or retardation.
The capacity of a cable is used to determine the locality of breaks in
the continuity of the conductors. The capacity per unit of length being
accurately known, it is obvious that, if the conductor breaks without
disturbance of the insulator, the distance of the break from the end can
be ascertained by determining the capacity of the cable from one end.
This capacity will be in proportion to the capacity of a mile, a knot or
any fixed unit, as the distance to the break is to the length used as
standard.