18WuD2x

unidirectional speaker • unilateral field-effect transistor 709
270°
0°
180°
unidirectional pattern
90°
unidirectional speaker See UNIDIRECTIONAL
LOUDSPEAKER.
unidirectional transducer A transducer that operates
in one direction only (i.e., its input and
output cannot be interchanged).
unidirectional voltage A voltage that never changes
polarity, although it might fluctuate in value.
UNIFET Abbreviation of UNIPOLAR FIELD-
EFFECT TRANSISTOR. (Also, UFET.)
unified-field theory A theory, as yet unproved,
that all forces in nature are interrelated and are
controlled by the same causes and factors. Albert
Einstein worked on this theory after he successfully
developed the theories of relativity.
unifilar Having (or wound as) one fiber, wire, filament,
or thread.
unifilar magnetometer A magnetometer in which
a bar is suspended at its center of gravity by a
single thread.
unifilar suspension A method of meter construction
in which the moving part is suspended by a
single filament. The torque might be provided by
this filament or by a spring or other resisting device;
the greater the displacement, the greater the
torque.
uniform circular motion Motion at a uniform rate
and describing a circle (e.g., a motor armature rotating
at a constant speed).
uniform electric field An electric field in which all
the lines of flux are straight and parallel, and in
which the electrostatic force has the same value
at all points (e.g., the field between two oppositely
charged, flat, parallel plates).
uniform field See UNIFORM ELECTRIC FIELD
and UNIFORM MAGNETIC FIELD.
uniform frequency response Frequency response
that is flat throughout a specified range. Such response
is characterized by the transmission of a
signal with no introduced amplitude or phase
distortion.
uniform line A transmission line having identical
electrical properties over its entire length.
uniform magnetic field A magnetic field in which
all the lines of flux are straight and parallel, and
in which the magnetic force has the same value at
all points.
uniform plane wave A free-space plane wave at an
infinite distance from the generator, having constant-amplitude
electric and magnetic field vectors
over the equiphase surfaces.
uniform precession In regions of the uniform
magnetic field of a sample of material, the state in
which the magnetic moments of all atoms are
parallel and precess in phase around the magnetic
field.
uniform waveguide A waveguide having constant
electrical and physical characteristics along its
axis.
uniground 1. The grounding of a circuit at one
point to reduce susceptibility to hum and noise.
2. The point at which such a connection is made.
unijunction transistor A semiconductor device
consisting of a thin silicon bar on which a single
pn junction acting as an emitter is formed near
one end. Two bases are provided—each an ohmic
connection made to one end of the bar. Also
called double-base diode.
Pictorial
Base 1
n
Base 2
p
Base 1
Base 2
Emitter
Symbol
unijunction transistor
Emitter
unilateral area track A film sound track having
modulation on only one edge of the opaque area.
unilateral bearing In radio direction finding, a
bearing obtained with a finder that produces unilateral
response and thereby eliminates 180-
degree error.
unilateral conductivity See UNIDIRECTIONAL
CONDUCTIVITY.
unilateral element See UNIDIRECTIONAL
ELEMENTS.
unilateral field-effect transistor A field-effect
transistor whose source and drain terminals cannot
be interchanged. Also called ASYMMETRICAL
FIELD-EFFECT TRANSISTOR. Compare SYM-
METRICAL FIELD-EFFECT TRANSISTOR.