Lamp, Pilot.
A lamp connected to a dynamo, and used by its degree of illumination to
show when the dynamo on starting becomes excited, or builds itself up.
Lamp, Polyphote.
An arc lamp adapted to be used, a number in series, upon the same
circuit. The electric regulating mechanism is placed in shunt or in
parallel with the carbons and arc. (See Lamp, Arc.)
Lamps, Bank of.
A number of lamps mounted on a board or other base, and connected to
serve as voltage indicator or to show the existence of grounds, or for
other purposes.
Lamp, Semi-incandescent.
A lamp partaking of the characteristics of both arc and incandescence; a
lamp in which the imperfect contact of two carbon electrodes produces a
part of or all of the resistance to the current which causes
incandescence.
The usual type of these lamps includes a thin carbon rod which rests
against a block of carbon. The species of arc formed at the junction of
the two heats the carbons. Sometimes the upper carbon or at least its
end is heated also by true incandescence, the current being conveyed
near to its end before entering it.
Semi-incandescent lamps are not used to any extent now.
Lamp Socket.
A receptacle for an incandescent lamp; the lamp being inserted the
necessary connections with the two leads are automatically made in most
sockets. The lamps may be screwed or simply thrust into the socket and
different ones are constructed for different types of lamps. A key for
turning the current on and off is often a part of the socket.
Latent Electricity.
The bound charge of static electricity. (See Charge, Bound.)
Law of Intermediate Metals.
A law of thermo-electricity. The electro-motive force between any two
metals is equal to the sum of electro-motive forces between each of the
two metals and any intermediate metal in the thermo-electric series, or
the electro-motive force between any two metals is equal to the sum of
the electromotive forces between all the intermediate ones and the
original two metals; it is the analogue of Volta's Law, q. v.
Law of Inverse Squares.
When force is exercised through space from a point, its intensity varies
inversely with the square of the distance. Thus the intensity of light
radiated by a luminous point at twice a given distance therefrom is of
one-fourth the intensity it had at the distance in question.
Gravitation, electric and magnetic attraction and repulsion and other
radiant forces are subject to the same law.