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P

POWER FACTOR

The ratio of the actual power of an alternating or pulsating current, as measured by a wattmeter, to the apparent power, as indicated by ammeter and voltmeter readings. The power factor of an inductor, capacitor, or insulator is an expression of their losses [2] [16].


POWER GAIN

In an antenna, the ratio of its radiated power to that of a reference [11] [18].

POWER LOSS

(1) The electrical power, supplied to a circuit, that does no work and is usually dissipated as heat [2] [4]. (2) The heat loss in a conductor as current flows through it [10].


POWER PENTODE

A special purpose tube used to provide high-current gain or power mplification.
Each grid wire is directly in line with the one before and after it, a fact which allows more electrons to reach the plate [6].


POWER RATIO

See POWER GAIN [11].

POWER STANDING-WAVE RATIO

The ratio of the square of the maximum and minimum voltages of a transmission line [10].


POWER SUPPLY

A unit that supplies electrical power to another unit. It changes ac to dc and maintains a constant voltage output within limits [6] [7].


POWER-AMPLIFIER TRANSMITTER

Transmitter that uses a series of power amplifiers to create a high level of power [18].


PREAMPLIFIER

An amplifier that raises the output of a low-level source for further processing without appreciable degradation of the signal-to-noise ratio [18].


PRECESSION

The rotation of the spin axis of a gyro in response to an applied force. The direction of precession is always perpendicular to the direction of applied force [15].



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