PRIMARY WINDING --The winding of a
PICKOFF --In gyros, a sensing device that
measures the angle of the spin axis with respect
to its reference and provides an error signal that
PRIME MOVER --The source of the turning
indicates the direction and (in most cases) the
force applied to the rotor of a generator, This may
be an electric motor, a gasoline engine, a steam
POLARITY --The character of having mag-
turbine, and so forth.
netic poles, or electric charges.
PROTON --A positively charged particle in
POLYPHASE --A circuit that uses more than
the nucleus of an atom.
one phase of alternating current.
RADAR --An acronym for radio detecting
POSITIVE CHARGE --The electrical charge
carried by a body that has become deficient in
RADAR ALTIMETER --Airborne radar that
measures the distance of the aircraft above the
POSITIVE FEEDBACK --Feedback in which
the feedback signal is in phase with the input
RADIAN --In a circle, the angle included
within an arc equal to the radius of the circle. A
POSITIVE TEMPERATURE COEFFI-
complete circle contains 2 radians. One radian
CIENT --The characteristic of a conductor in
equals 57.3 degrees, and 1 degree equals 0.01745
RATE GYRO --A gyro with one degree of
POTENTIAL --The amount of charge held by
freedom that has an elastic restraint, with or
a body as compared to another point or body.
without a damper, and whose output will be
Usually measured in volts.
proportional to the rate of the applied torque.
POTENTIOMETER --A variable voltage
RATIO --The value obtained by dividing one
divider; a resistor that has a variable contact arm
number by another, indicating their relative
so that any portion of the potential applied
between its ends may be selected.
REACTANCE --The opposition offered to
POWER --The rate of doing work or the rate
the flow of an alternating current by the
of expending energy. The unit of electrical power
is the watt.
RECTIFIERS --Devices used to change
POWER FACTOR --The ratio of the actual
alternating current to unidirectional current.
power of an alternating or pulsating current, as
These may be vacuum tubes, semiconductors,
measured by a wattmeter, to the apparent power,
such as germanium and silicon, and dry-disk
rectifiers, such as selenium and copper oxide.
The power factor of an inductor, capacitor, or
tion that a material offers to magnetic lines of
POWER SUPPLY --A unit that supplies
electrical power to another unit. It changes ac to
dc and maintains a constant voltage output within
of current caused by the nature and physical
dimensions of a conductor.
applied torque, which causes the gyro to tilt itself
RETENTIVITY --The measure of the ability
at right angles to the direction of the applied
of a material to hold its magnetism.
torque in such a manner that the direction of spin
of the gyro rotor will be in the same direction as
RHEOSTAT --A variable resistor.
the applied torque.