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554 primary colors • print
primary colors See COLOR PRIMARY.
primary current The current flowing in the primary
winding of a transformer. Also called
TRANSFORMER INPUT CURRENT. Compare
SECONDARY CURRENT.
primary electron The electron possessing the
greater energy after a collision between two electrons.
Compare SECONDARY ELECTRON.
primary emission Emission arising directly from a
source, such as the cathode of an electron tube.
Compare SECONDARY EMISSION.
primary frequency standard A device that generates
unmodulated signals at precise frequencies.
It generally uses a highly stable crystal oscillator
that can be referred to a time standard and periodically
corrected. A string of multivibrators, together
with harmonic amplifiers and buffers,
divide, and multiply the fundamental crystal frequency.
The resulting signals provide markers for
calibrating receivers and test equipment. Compare
SECONDARY FREQUENCY STANDARD.
Also see PRIMARY STANDARD.
primary impedance 1. The impedance of the primary
winding of a transformer whose secondary
winding is unloaded. Compare SECONDARY
IMPEDANCE, 1. 2. An external impedance presented
to the primary winding of a transformer.
Compare SECONDARY IMPEDANCE, 2.
primary inductance The inductance of the primary
winding of a transformer whose secondary
winding is unloaded. Compare SECONDARY IN-
DUCTANCE.
primary kVA The kilovolt-amperes in the primary
circuit of a transformer. Compare SECONDARY
KVA.
primary measuring element A detector, sensor,
or transducer that performs the initial conversion
in a measurement or control system. Such an element
converts a phenomenon into a signal that
can be transmitted to appropriate instruments
for translation and evaluation.
primary power Power in the primary circuit of a
transformer. Also see PRIMARY KVA and PRI-
MARY VA. Compare SECONDARY POWER.
primary radiator 1. The driven element of a directive
antenna system that incorporates parasitic
elements. 2. The driven element of a directive antenna
that uses a reflector, such as a screen or
dish.
primary resistance The direct-current resistance
of the primary winding of a transformer. Compare
SECONDARY RESISTANCE.
primary standard A usually stationary source of a
quantity (e.g., capacitance, frequency, time, inductance,
resistance, etc.). This source is so precise,
and is maintained with such care, that it
can be used as a universal reference. Compare
SECONDARY STANDARD.
primary turns Symbol, N p . The number of turns in
the primary winding of a transformer. Compare
SECONDARY TURNS.
primary utilization factor Abbreviation, UF p . For
a transformer in a rectifier circuit, the ratio of
direct-current power output to primary voltamperes.
Numerically, the primary utilization
factor is higher than the secondary utilization
factor, but is less than 1. Also see SECONDARY
UTILIZATION FACTOR and UTILITY FACTOR.
primary VA The volt-amperes in the input circuit
of a transformer. Compare SECONDARY VA.
primary voltage The voltage across the primary
winding of a transformer. Also called transformer
input voltage. Compare SECONDARY VOLTAGE.
primary winding The normal or usual input winding
of a transformer. Also called primary coil.
Compare SECONDARY WINDING.
prime meridian See ZERO MERIDIAN.
prime mover A machine, such as a gas engine,
steam engine, or water turbine, that converts a
natural force or material into mechanical power.
primitive oscillation period In a complex oscillation
waveform, the shortest period for which a
definite repetition occurs; the highest fundamental
frequency.
principal axis The line passing through the center
of the spherical part of a lens, mirror, or dish reflector.
principal focus The focal point of rays arriving
parallel to the principal axis of a lens, mirror, or
dish reflector.
Principal focus
principal focus
Principal axis
principal mode See DOMINANT MODE.
principal ray The path described by an electron entering
an electron lens parallel to the lens’ axis, or
by an electron leaving this lens parallel to the axis.
print 1. The material transferred from a typewriter
onto paper. 2. The command, in a computer sys-