INDUCTIVE REACTANCE --The opposi-
GROUND POTENTIAL --Zero potential
tion to the flow of alternating or pulsating current
with respect to the ground or earth.
caused by the inductance of a circuit. It is
GYROSCOPE --A wheel or disk so mounted
measured in ohms.
as to spin rapidly about one axis and be free to
move about one or both of the two axes mutually
INERTIA --The physical tendency of a body
perpendicular to the axis of spin.
in motion to remain in motion and a body at rest
to remain at rest unless acted upon by an outside
HALF-WAVE RECTIFIER --A rectifier
force (Newton's first law of motion).
using only one-half of each cycle to change ac to
pulsating dc.
lNFINITE --(1) Extending indefinitely,
endless. (2) Boundless, having no limits, (3) An
HEAT SHUNT --A device (preferably a
incalculable number.
clip-on type) used to absorb heat and protect
heat-sensitive components during soldering.
IN PHASE --This term is applied to the
condition that exists when two waves of the same
HERO --Hazardous electromagnetic radiation
frequency pass through their maximum and
to ordnance.
minimum values of like polarity at the same
instant.
HERTZ --A unit of frequency equal to one
cycle per second.
lNSULATION --A material used to prevent
the leakage of electricity from a conductor and
HMI --Handbook Maintenance Instructions.
to provide mechanical spacing or support as
protection against accidental contact with the
HORSEPOWER --The English unit of power,
conductor.
equal to work done at the rate of 550 foot-pounds
per second. Equal to 746 watts of electrical power.
INTEGRATING CIRCUIT --A circuit whose
output voltage is proportional to the product of
HYSTERESIS --A lagging of the magnetic
the instantaneous applied input voltages and their
flux in a magnetic material behind the magnetizing
durations.
force that is producing it.
INTEGRATOR --A computing device used
Hz --See HERTZ.
for summing up an infinite number of minute
quantities.
IMPEDANCE --The total opposition offered
to the flow of an alternating current. It may
I N V E R S E L Y --Inverted or reversed in
consist of any combination of resistance, inductive
position or relationship.
reactance, and capacitive reactance.
ISOGONIC LINE --An imaginary line drawn
INDUCED CURRENT --Current caused by
through points on the earth's surface where the
the relative motion between a conductor and a
magnetic variation is equal.
magnetic field.
JOULE. --A unit of energy or work. A joule
INDUCTANCE --The property of a circuit
of energy is liberated by 1 ampere flowing for 1
that tends to oppose a change in the existing
second through a resistance of 1 ohm.
current.
JUNCTION --(1) The connection between
I N D U C T I O N --The act or process of
producing voltage by the relative motion of a
two or more conductors, (2) The contact between
two dissimilar metals or materials, as in a
magnetic field across a conductor.
thermocouple.
INDUCTION MOTOR --A simple, rugged,
JUNCTION BOX --A box with a cover that
ac motor with desirable characteristics. The rotor
serves the purpose of joining different runs of wire
is energized by transformer action (induction)
or cable and provides space for the connection
from the stator. Induction motors are used more
and branching of the enclosed conductors.
than any other type.
AI-5