18WuD2x

308 gain-level linearity • gamma rays
ing the output to the input level over a range of
input signal levels.
gain reduction The drop in gain of an amplifier at
high- and low-frequency extremes.
gain sensitivity control See DIFFERENTIAL GAIN
CONTROL.
gain stability The degree to which the gain of a
system remains constant during changes in related
factors, such as temperature, supply power,
and loading.
gain temperature coefficient The extent to which
the full-scale current varies over a certain temperature
range, expressed in parts per million per
degree Celsius (ppm/°C).
galactic noise Radio noise propagated from the
plane of our galaxy, and especially from the center,
located in the direction of the constellation
Sagittarius. It is of significance in space communications
and radio astronomy.
galena Formula, PbS. Natural lead sulfide, which
in nature takes the form of bluish-gray, cubical
crystals.
gallium Symbol, Ga. Atomic number, 31. Atomic
weight, 69.72. One of the constituents of the
semiconductor compound GALLIUM ARSENIDE.
gallium arsenide Formula, GaAs. A compound of
gallium and arsenic, used as a semiconductor
material. It is noted for its low-noise characteristics.
gallium-arsenide diode A diode in which the semiconductor
material is processed gallium arsenide.
gallium-arsenide varactor A low-noise, microwave
varactor in which the semiconductor material
is gallium arsenide.
gallium-phosphide diode A light-emitting diode in
which the semiconductor material is processed
gallium phosphide.
galloping ghost A form of radio-control system in
which the elevation and rudder can be moved to
the desired extent.
Galton whistle A device for producing highfrequency
acoustic waves (ultrasound), similar to
a common dog whistle.
galvanic cell Generic term for any electrochemical
primary voltaic cell.
galvanic corrosion Corrosion that occurs on one
of two dissimilar metals when they are immersed
in an electrolyte. Caused by battery action between
them. Compare ELECTROLYTIC CORRO-
SION.
galvanic couple See VOLTAIC COUPLE.
galvanic current A very small direct current such
as that produced by dissimilar metals in acid or
by nervous reaction in living tissue.
galvanic pile See VOLTAIC PILE.
galvanic series A list of metals and alloys arranged
in order of the most to least likely to oxidize in a
given environment.
galvanic skin response Abbreviation, GSR. The
variations in electrical resistance of the (usually
human) skin. This phenomenon is a useful indicator
in physiology, psychology, and criminology.
galvanic taste A sharp, metallic taste experienced
when a small electric current is passed through
the tip of the tongue.
galvanism (After Luigi Galvani, 1737–1798) The
production of an electric current by chemical action,
as in a battery.
galvanize To coat steel with zinc to forestall corrosion.
galvanometer A sensitive, bi-directional current
meter. Used in various electrical tests—especially
as a null indicator in bridge operation. Also see
MICROAMMETER.
galvanometer constant The number by which a
galvanometer reading must be multiplied in order
to obtain the current in microamperes, milliamperes,
or amperes.
galvanometer recorder A graphic recorder in
which a mirror in a movable-coil galvanometer reflects
a beam of light to a passing strip of photographic
film.
galvanometer shunt A resistor placed in parallel
with a galvanometer to decrease its sensitivity.
Also see SHUNT RESISTOR.
galvanometry The use of galvanometers to determine
the intensity and direction of electric currents.
galvanoplastics The science of ELECTROPHO-
RESIS and ELECTROPLATING.
galvanoscope An instrument for detecting and
showing the direction of very weak electric currents.
galvanotherapy The use of electric currents to
produce heat in the body of a human or animal.
gamma ferric oxide A form of coating used in formulation
of magnetic recording tape.
gamma match A linear transformer for matching
an unbalanced (usually coaxial) feed line to a balanced
(usually half-wave) antenna. The outer
conductor of the cable is connected to the center
of the radiator, and an extension of the center
conductor runs for a short distance parallel to the
radiator, making a right-angle bend before connecting
to the radiator.
Coaxial
feed line
gamma match
Radiator
Matching
section
gamma rays High-energy, ionizing radiation emitted
by radioactive substances; similar to X rays,
but of a shorter wavelength.