18WuD2x

348 Huygens’ principle • hygrometer
that arise from points in the medium that have
already been passed.
HV Abbreviation of HIGH VOLTAGE.
H vector A vector representing the magnetic field
of an electromagnetic wave. Compare E VECTOR.
hW Abbreviation of HECTOWATT.
H-wave mode In a waveguide, a mode of transmission
in which the electric lines of flux are at right
angles to the direction of the waveguide. Also
called transverse-electric (TE) mode.
hy Occasional abbreviation of HENRY. The SI abbreviation
and symbol, H, is preferred.
hybrid Descriptive of a device that is an offspring
of other devices or a product of dissimilar technologies
(but using elements of each). See,
for example, HYBRID JUNCTION and HYBRID
COIL.
hybrid active circuit An active circuit (such as an
amplifier, oscillator, or switch) using a combination
of two dissimilar active devices (e.g., transistors
and vacuum tubes).
hybrid coil A special type of bridging transformer
used in wire telephony to prevent self-oscillation
in a repeater amplifier that operates in both directions.
hybrid computer A computer system incorporating
more than one major computer technology.
Examples: analog/digital and digital/neuralnetwork.
hybrid electromagnetic wave Abbreviation, HEM
wave. An electromagnetic wave whose electricfield
and magnetic-field vectors are both in the direction
of propagation.
hybrid IC See HYBRID INTEGRATED CIRCUIT.
hybrid integrated circuit Abbreviation, HIC. An
integrated circuit embodying both integrated and
microminiature discrete components (i.e., one
combining both monolithic and thin-film construction).
hybrid junction 1. See MAGIC TEE. 2. A fourterminal
device, such as a resistor circuit, special
transformer, or waveguide assembly, in which a
signal applied to one pair of terminals divides and
appears at only the two adjacent terminals.
hybrid microcircuit A microcircuit containing diffused
or thin-film elements interconnected with
separate chip elements.
hybrid parameters See H PARAMETERS.
hybrid ring A hybrid waveguide junction (see HY-
BRID JUNCTION, 2) consisting essentially of a
reentrant line with four side arms. Used as an
equal power divider.
hybrid-tee See HYBRID JUNCTION, 1.
hybrid thin-film circuit A microcircuit in which
semiconductor devices and discrete components
are attached to passive components and conductors
that have been electrodeposited on a substrate.
hybrid transformer See HYBRID COIL.
hydroacoustic Pertaining to the sound of fluids,
especially water, under pressure.
hydroacoustic transducer A transducer that converts
energy from the high-pressure flow of a fluid
into acoustic energy.
hydrodynamic pressure The pressure of a fluid in
motion. Compare HYDROSTATIC PRESSURE.
hydroelectric Pertaining to the production of electricity
by water power, as by a generator turned
by water turbines.
hydroelectric machine A device for generating
electricity from high-pressure steam escaping
from a series of jets.
hydroelectric power See WATER POWER.
hydrogen Symbol, H. A gaseous element. Atomic
number, 1. Atomic weight, 1.00794. Used in
making semiconductor materials, it is the lightest
and most abundant element in the universe.
Compare DEUTERIUM and TRITIUM.
hydrogen atmosphere The nonoxidizing atmosphere
in which semiconductor materials are
melted and processed, and in which semiconductor
crystals are grown. Occasionally, helium is
used instead of hydrogen.
hydrogen atom A single atom of the element hydrogen,
consisting of one electron and one proton.
hydrogen-ion concentration See pH.
hydrogen lamp A glow-discharge lamp that produces
light by means of the ionization of rarefied
hydrogen gas. Visible light is emitted at discrete
wavelengths.
hydrokinetic Pertaining to fluids in motion or the
forces behind such motion.
hydrolysis The process whereby chemical substances
become ionized in water solution, producing
electrolytes.
hydromagnetics See MAGNETOHYDRODYNAM-
ICS.
hydromagnetic wave In a fluid, a wave in which
the energy is propagated via magnetic and dynamic
modes.
hydrometer An instrument for measuring the specific
gravity of liquids.
hydrophone An underwater sound-to-electricity
transducer (microphone).
hydropower See WATER POWER.
hydrostatic pressure The pressure of a fluid at
rest. Compare HYDRODYNAMIC PRESSURE.
hygristor A resistor, the resistance of which depends
on humidity. A common application is in
the measurement of relative atmospheric humidity.
hygrogram A graphic rendition of atmospheric humidity
versus time, made by a HYGROGRAPH.
hygrograph A device that produces a graphic
recording of atmospheric humidity as a function
of time. Consists essentially of a HYGROMETER
connected to a permanent data-storage device,
such as a computer or pen recorder.
hygrometer An instrument for measuring humidity.
Also see ELECTRIC HYGROMETER, ELECTRONIC
HYGROMETER, and HAIR HYGROMETER.