18WuD2x

apogee • arc cosecant 37
apogee 1. The point at which an earth-orbiting
satellite attains its highest altitude. It occurs
once for every complete orbit. At this point, the
satellite travels slower than at any other point in
the orbit. 2. The altitude, measured from the
earth’s surface or the earth’s center, of an earthorbiting
satellite at its most distant point.
A power supply A term sometimes used to denote
the unit that supplies energy to a vacuum-tube
filament. Compare B POWER SUPPLY.
apparent bearing In radio-direction finding, the
uncorrected direction from which a signal appears
to arrive.
apparent power In an ac circuit, the power value
obtained by multiplying the current by voltage (P
equals IE), with no consideration of the effects of
phase angle. Compare TRUE POWER.
apparent power loss The loss in an ammeter or
voltmeter, caused by the imperfection of the instrument.
At full scale, the ammeter has a certain
voltage across its terminals; the apparent power
loss is the current multiplied by this voltage. A
voltmeter carries a small current; the apparent
power loss is the product of the current and the
indicated voltage.
appearance potential The potential through
which an electron must move to produce a certain
ion from the atom with which it is associated.
applause meter An instrument consisting essentially
of a microphone, audio amplifier, and indicating
meter (reading directly in sound level). It is
so called because of its familiar use in measuring
audience response, as indicated by loudness of
applause.
Applegate diagram For a velocity-modulated tube,
a plot of the positions of electron bunches in the
drift space versus time.
Appleton layer Collectively, the F1 and F2 layers
of the ionosphere, at a height between 150 and
400 kilometers above the surface of the earth.
apple tube A color picture tube, used in television,
with the red, blue, and green phosphor in vertical
strips.
appliance Electrical equipment in general. This
might include any home-operated device.
application A task or job for which an electronic
device or system is used. It especially pertains to
personal-computer software that has practical
usefulness.
application factor A factor involved in determining
the failure rate of a circuit or system affected
by unusual operating conditions.
application schematic diagram A diagram of pictorial
symbols and lines that illustrate the interrelationship
of functional circuit blocks in a
specific program mode.
applicators 1. In dielectric heating, the electrodes
between which the dielectric body is placed and
the electrostatic field developed. 2. In medical
electronics, the electrodes applied to a patient
undergoing diathermy or ultrasonic therapy.
applied voltage The voltage presented to a circuit
point or system input, as opposed to the voltage
drop resulting from current flow through an element.
applique circuit A circuit for adapting equipment
to a specialized job.
approach-control radar A radar installation serving
a ground-controlled approach (GCA) system.
approximate data 1. Data obtained through physical
measurements. Such data can never be exact;
all measurements are subject to error. 2.
Loosely estimated data or imprecise calculations.
AQL Abbreviation of ACCEPTABLE QUALITY
LEVEL. A statistically defined quality level, defined
in terms of percent defective, accepted on
an average of 95 percent of the time.
Aquadag A tradename for a material that consists
of a slurry of fine particles of graphite. Aquadag
forms a conductive coating on the inside and outside
walls of some cathode-ray tubes.
aqua pura Pure water; in most instances, distilled
water. Formula, H 2 O. Pure water is a nonconductor
with a dielectric constant of about 81.
Ar Symbol for ARGON.
arbitrary function fitter A circuit or device, such
as a potentiometer, curve changer, or analog
computer element, providing an output current
or voltage that is some preselected function of the
input current or voltage.
arc 1. A luminous sustained discharge between
two electrodes. Because it is sustained, rather
than intermittent, an arc is distinguished from a
spark discharge, the latter being a series of discharges
(sparks)—even when it appears continuous.
2. In graphical presentations, a section of
curved line, as of a circle.
arc angle The angle in degrees traced out by a circular
arc if the center point of the circle is considered
to be the vertex of an angle formed by
two rays intersecting the arc at designated
points.
arc cosecant Abbreviated arc csc or csc –1 . 1. The
inverse of the cosecant function. 2. The angle, in