Fig. 296. ELECTRICAL RESONATOR.
Resonator, Electric.
A small open electric circuit, with ends nearly touching. When exposed
to electric resonance, or to a sympathetic electric oscillatory
discharge, a spark passes from across the gap. The production of this
spark is altogether a matter of the inductance of the resonator. The
simplest form is a circle of copper wire with its ends nearly touching.
The length of the gap is adjustable by bending. A screw adjustment may
also be provided. Another form is shown in the cut, Fig. 296. Here
sheets of tinfoil are used to regulate the electrostatic capacity, while
at m is shown the finger piece for regulating the size of the spark gap
a.
Synonym--Spark Micrometer.
Resultant.
The line indicating the result of the application of two or more forces
to a point. Its direction and length give the elements of direction and
intensity. (See Forces, Resolution of Forces, Composition of
Components.)
Resultant Polarity.
The magnetic polarity imparted to a mass of iron acted on by two or more
separate inducing forces or currents. It appears in dynamos and motors.
The final polarity is the resultant of the inducing effect of the field
magnet poles and of the windings.
Retardation.
In telegraphy a retardation of the rate of transmission of signals. It
is due to several causes.
(a) The self-induction of the circuit, especially if it includes many
electro-magnets, produces extra currents (see Currents, Extra.) These
are opposed to the main current on closing it and hence retard the
action. They are in the same direction on opening it and hence again
retard the action.
(b) Every line has a certain static capacity. This is affected by the
proximity of the lines to the earth. For each signal electricity has to
be charged upon the line until the line is charged to its end with a
certain proportion of the initial density. This charging takes time and
hence introduces retardation.
(c) The cores of the electro-magnets of the relays or sounders are not
instantly magnetized and demagnetized. This magnetic lag, q. v.,
introduces retardation.