18WuD2x

indoor antenna • induction modulator 361
indoor antenna An antenna erected and operated
in a building, but kept away from other objects as
much as possible.
indoor radiation Electromagnetic radiation from
the part of an antenna feeder or lead-in that is inside
the transmitter building.
indoor transformer A power service transformer
that, for protection against the elements, is installed
inside the building it serves.
induced Brought about by the influence of a magnetic
or electric field.
induced charge An electric charge produced in a
body by the electric field surrounding another
charge.
induced current An alternating current established
in one circuit by the alternating magnetic
field of another circuit. Also see INDUCTION.
induced EMF See INDUCED VOLTAGE.
induced failure A form of component failure that
occurs because of operation beyond the normal
specifications.
induced voltage An alternating voltage set up
across one circuit (especially a coil) by the alternating
magnetic field of another circuit. Also see
INDUCTION.
inductance Symbol, L. Unit, henry. In a conductor,
device, or circuit, the inertial property
(caused by an induced reverse voltage) that opposes
the flow of current when a voltage is applied;
it opposes a change in current that has
been established. Also see HENRY, INDUCTION,
and MUTUAL INDUCTANCE.
inductance bridge An alternating-current bridge
for measuring inductance in terms of a standard
inductance or a standard capacitance. See, for
example, HAY BRIDGE, MAXWELL BRIDGE, and
OWEN BRIDGE.
inductance-capacitance Abbreviation, LC. 1. A
combination of inductance and capacitance in a
circuit, such as a filter, a parallel-resonant circuit,
or a series-resonant circuit. 2. Pertaining to
a device for measuring inductance and capacitance
(e.g., LC bridge and LC meter).
inductance-capacitance bridge An alternatingcurrent
bridge for measuring inductance and capacitance
only.
inductance-capacitance filter A filter composed
of inductors and capacitors. Also called LC filter.
inductance-capacitance meter A direct-reading
meter for measuring inductance and capacitance.
inductance-capacitance-resistance Abbreviation,
LCR. 1. A combination of inductance, capacitance,
and resistance in a circuit, such as a basic
tuned circuit. The resistive component represents
loss in the inductor and capacitor. 2. Pertaining
to a device for measuring inductance, capacitance,
and resistance (e.g., LCR bridge and LCR
meter).
inductance-capacitance-resistance bridge See
IMPEDANCE BRIDGE.
inductance coil See INDUCTOR.
inductance filter A filter using only an inductor,
usually a coil of wire.
inductance-resistance time constant The time
constant t (see ELECTRICAL TIME CONSTANT) of
a circuit containing, ideally, only inductance and
resistance. Mathematically, t = LR, where t is in
seconds, L is the inductance in henrys, and R is
the resistance in ohms. Also called LR time constant.
inductance standard A highly accurate, stable inductor
used in precision measurements. Also see
PRIMARY STANDARD and SECONDARY STAN-
DARD.
induction 1. The ability of an alternating, pulsating,
or otherwise changing current flowing in one
circuit to set up a current in a nearby circuit. The
circuits need not be physically connected, but
need only be linked by magnetic lines of flux. Also
see SELF-INDUCTION. 2. The phenomenon
whereby a body becomes electrically charged by
the field surrounding a nearby charged body.
Also see ELECTRIC CHARGE.
induction coil A special high-voltage step-up
transformer having an open core and a vibratorinterrupter
in series with the primary winding,
which carries direct current from a battery. The
current is broken up into short pulses by the interrupter,
and a high alternating-current voltage
is generated in the secondary winding.
induction compass A compass whose indications
depend on current induced in a coil revolving in
the earth’s magnetic field. Compare GYROCOM-
PASS and MAGNETIC COMPASS.
induction factor The ratio of total current to nonproductive
current in an alternating-current circuit.
induction field The portion of an electromagnetic
field that returns to a radiator, such as a coil, as
opposed to the RADIATION FIELD.
induction frequency converter A mechanical device
used for converting a signal at a fixed frequency
to a signal at another fixed frequency.
induction furnace A furnace in which highfrequency
magnetic fields induce currents in
metal ores, causing the ore to become hot enough
to melt.
induction heater A high-power, radio-frequency
generator designed especially for induction heating.
induction heating The heating of metallic work
samples by placing them in (but insulated from) a
WORK COIL carrying current from a high-power
radio-frequency generator. The workpiece is heated
by radio-frequency currents induced in it as a result
of the intense alternating magnetic field within
the coil. Compare DIELECTRIC HEATING.
induction loss Loss of energy from a currentcarrying
conductor because of inductive coupling
to a nearby conductor.
induction modulator See ELECTROMECHANI-
CAL MODULATOR.