Induction, Mutual, Electrostatic.
A charged body always induces a charge upon any other body near it; and
the same charge in the second body will induce the other charge in the
first body if the latter is unexcited. In other words the second body's
induction from the first is the measure of the charge the second would
require to induce in the first its own (the second's) induced charge.
This is the law of mutual electrostatic induction.
Induction, Open Circuit.
Inductive effects produced in open circuits. By oscillatory discharges a
discharge can be produced across a break in a circuit otherwise
complete. The requirements for its production involve a correspondence
or relation of its dimensions to the inducing discharge. The whole is
analogous to the phenomena of sound resonators and sympathetic
vibrations. Synonym--Oscillatory induction.
Induction, Self-.
(a) A phenomenon of electric currents analogous to the inertia of
matter. Just as water which fills a pipe would resist a sudden change in
its rate of motion, whether to start from rest, to cease or decrease its
motion, so an electric current requires an appreciable time to start and
stop. It is produced most strongly in a coiled conductor, especially if
a core of iron is contained within it.
As in the case of two parallel wires, one bearing currents which vary,
momentary currents are induced in the other wire, so in a single
conductor a species of inertia is found which retards and prolongs the
current. If a single conductor is twisted into a helix or corresponding
shape, its separate turns react one on the other in accordance with the
general principles of electromagnetic induction. (See Induction,
Electro-magnetic.) Thus when a current is suddenly formed the coils
acting upon each other retard for an instant its passage, producing the
effect of a reverse induced current or extra current opposing the
principal current. Of course no extra current is perceptible, but only
the diminution. When the current is passing regularly and the current is
broken, the corresponding action prolongs the current or rather
intensifies it for an instant, producing the true extra current. This is
current self-induction.
[Transcriber's note: See inductance.]
Synonyms--Electric Inertia--Electro-dynamic Capacity.
(b) A permanent magnet is said to tend to repel its own magnetism, and
thus to weaken itself; the tendency is due to magnetic self-induction.
Induction Sheath.
In the brush dynamo a thin sheet of copper surrounding the magnet cores
with edges soldered together. The winding is outside of it. Its object
is to absorb extra currents set up by variations in magnetic intensity
in the cores. These currents otherwise would circulate in the cores.