18WuD2x

vector power factor • velocity modulation 721
active power to vector power) produces a figure
identical to the conventional power factor.
vector quantity A quantity having both magnitude
and direction, and that can, therefore, be
represented by a vector.
vectorscope A special oscilloscope for visual adjustment
of a color-television receiver by means
of a color-phase diagram.
vector sum The resultant of two nonparallel vectors;
therefore, the resultant of the forces or
quantities represented by them. For example, reactance
and resistance can be represented by two
perpendicular vectors.
vector voltmeter A voltmeter that indicates the
phase as well as the amplitude of an alternatingcurrent
voltage.
V EE Symbol for emitter-voltage supply of a bipolar
transistor.
vee antenna A center-fed antenna in which the
two halves of the radiator form an angle considerably
less than 180 degrees.
vee-beam system An elevation-measuring radar
system in which fan-shaped vertical and inclined
beams, intersecting at ground and rotating continuously
around the vertical axis, are radiated
by one antenna. Target elevation is determined
from the interval between successive echoes from
the target.
vee connection of transformers In a three-phase
system, a method of connecting two transformers
so that the line current and voltage equal the
phase current and voltage. Also called open-delta
connection.
vee-cut crystal A piezoelectric plate cut from a
quartz crystal so that its faces are not parallel to
the x, y, or z axis of the crystal. Also see CRYSTAL
AXES and CRYSTAL CUTS.
vee particle A short-lived elementary particle that
results when high-energy neutrons or protons
collide with nuclei. The particle can be positive,
negative, or neutral, and gets its name from its
cloud-chamber track.
vee signal In radiotelegraphy, the letter V (di-di-didah)
transmitted as a test signal, usually three
times in rapid succession. It is used during onthe-air
transmitter tests, followed by the station’s
call letters.
vehicle An inert substance, usually a liquid, that
acts as a solvent, carrier, or binder for some
other, more active substance. Thus, shellac can
be the vehicle for the metallic powder in a silver
paint used in silk-screening electronic circuits.
vehicle smog-control device See COMPUTER-
CONTROLLED CATALYTIC CONVERTER and
EXHAUST ANALYZER.
vel Abbreviation of VELOCITY.
velocimeter 1. An instrument for measuring the
velocity of sound in various materials. 2. An
electronic velocity meter—especially a radialvelocity
meter using Doppler radar. 3. An electronic
flow meter.
velocity Symbol, v. Abbreviation, vel. Unit, distance
per unit time [e.g., meters per second
(m/s)]. 1. The change in the position of a body
over a specified period of time. 2. The derivative of
displacement with respect to time. Compare AC-
CELERATION.
velocity constant See VELOCITY FACTOR.
velocity error For a servomechanism in which the
input and output shafts rotate at the same speed,
the angular displacement between them.
velocity factor Abbreviation, v. For a transmission
line, the ratio of the speed of electromagnetic
wave propagation in the line to the speed of electromagnetic
waves in a vacuum (299,792 kilometers
per second). It can be expressed as a number
between 0 and 1, or as a percentage between 0
and 100. In practical feed lines, v ranges from
about 0.66 (for coaxial line with a solid polyethylene
dielectric) to about 0.95 (for open-wire line
with widely separated spacers).
velocity hydrophone A hydrophone whose output,
like that of the velocity microphone, is proportional
to the instantaneous particle velocity in
the sound wave impinging on the device.
velocity-lag error A lag (proportional to the inputvariation
rate) between the input and output of a
device, such as a servomechanism.
velocity level For a sound, the ratio v 0 , expressed
in decibels:
v 0 = 20 log 10 (v s /v r )
where v s is the particle velocity of the sound, and
v r is a reference particle velocity.
velocity microphone A microphone in which the
vibratory element is a thin, aluminum or Duralumin
ribbon suspended loosely between the poles
of a strong permanent magnet. Vibration of the
corrugated ribbon in the magnetic field causes an
audio-frequency voltage to be induced across the
ribbon. The microphone is so called because its
output is proportional to the instantaneous particle
velocity in the sound wave impinging on the
ribbon. Also called ribbon microphone.
velocity-modulated amplifier A circuit in which
radio-frequency amplification is obtained by velocity
modulation.
velocity-modulated oscillator A vacuum-tube
device in which an electron stream is velocitymodulated
(see VELOCITY MODULATION) as it
passes through a resonant cavity (the buncher);
the subsequent energy, of a higher intensity, is
extracted from the bunched stream as it passes
through another resonant cavity (the catcher).
Feedback from catcher to buncher sustains oscillations.
See, for example, KLYSTRON OSCILLATOR.
velocity-modulated tube A vacuum tube utilizing
velocity modulation. See, for example, KLYSTRON.
velocity modulation The process in which the input
signal of a vacuum tube varies the velocity of
the electrons in a constant-current electron beam
in sympathy with the input signal.