18WuD2x

thin-film semiconductor • three-phase rectifier 683
thin-film semiconductor A very shallow layer of
semiconductor material, such as single-crystal
silicon, electrodeposited on a substrate. Also see
THIN FILM.
thin-film transistor A transistor fabricated by
thin-film techniques. Also see THIN FILM and
THIN-FILM COMPONENT.
thin magnetic film See MAGNETIC THIN FILM.
third-generation computer A computer in which
the active discrete components are integrated circuits.
Third Law of Thermodynamics As the temperature
of absolute zero is approached in an isothermal
process involving a solid or liquid, the change
in entropy approaches zero; and the entropy of a
substance is zero at absolute zero.
third-octave band See ONE-THIRD-OCTAVE
BAND.
thirty-channel multiplex A form of pulse-codemodulated
(PCM) multiplex using eight digits and
the A-law. There are 30 speech channels and two
utility channels.
Thomson bridge See KELVIN BRIDGE.
Thomson effect The liberation or absorption of
heat (depending on the material of interest) when
an electric current flows from a warmer to a
cooler part of a conductor.
Thomson heat The amount of thermal energy
transferred because of Thomson effect.
Thomson voltage The voltage drop between two
points on a conductor that are at different temperatures.
thoriated-tungsten filament In a vacuum tube, a
filament made of tungsten to which thorium oxide
has been added to increase the emission
of electrons. Also see THERMION and THER-
MIONIC EMISSION.
thorium Symbol, Th. A radioactive metallic element.
Atomic number, 90. Atomic weight,
232.04. Thorium, when heated, is a copious emitter
of electrons, so the filaments or cathode cylinders
of some electron tubes are coated with one of
its compounds.
thoron Symbol, Tn. A radioactive isotope of RADON.
three-address instruction A computer program
instruction having three addresses, two for
operands and one for the result (of the operation
called for).
three-channel stereo A form of stereophonic
sound recording and reproduction in which three
distinct channels are used; these are usually designated
the left, right, and center channels.
three-coil meter See ELECTRODYNAMOMETER.
three-conductor jack A female connector in which
two separate conductors are provided, in addition
to the ground conductor.
three-conductor plug A male connector in which
two separate conductors are provided, in addition
to the ground conductor.
three-dimensional television See STEREO-
SCOPIC TELEVISION.
Sleeve
contact
Tip contact
Ring contact
three-conductor jack
Sleeve
Ring
three-conductor plug
Tip
three-electrode tube See TRIODE.
three-element tube See TRIODE.
three-gun picture tube A color-television picture
tube having a separate gun for each primary color
(red, green, and blue).
three-halves-power law See CHILD’S LAW.
three-junction transistor A pnpn or npnp transistor.
Also see NPNP DEVICE.
three-phase bridge rectifier A bridge-rectifier circuit
for three-phase alternating current. Two
diodes are provided for each phase. The ripple
frequency is six times the line frequency. Also see
BRIDGE RECTIFIER, POLYPHASE RECTIFIER,
and THREE-PHASE CIRCUIT.
three-phase circuit The circuit of a three-phase
system. See THREE-PHASE SYSTEM and, specifically,
DELTA CONNECTION and WYE CONNEC-
TION.
three-phase current Current in a three-phase circuit.
The currents in the three legs differ in phase
by 120°.
three-phase four-wire system See FOUR-WIRE
WYE SYSTEM.
three-phase generator A (usually dynamo-type)
generator of three-phase current or voltage. See
THREE-PHASE SYSTEM.
three-phase half-wave rectifier A half-wave rectifier
circuit for three-phase alternating current.
One diode is provided for each phase. The ripple
frequency is three times the line frequency. Also
see HALF-WAVE RECTIFIER, POLYPHASE REC-
TIFIER, and THREE-PHASE CIRCUIT. Compare
THREE-PHASE BRIDGE RECTIFIER.
three-phase motor An alternating-current motor
operating on three-phase power. Above fractional-horsepower
size, the three-phase motor is
smoother running and more simply structured
than the single-phase counterpart.
three-phase power The total power dissipated or
delivered in a three-phase alternating-current
circuit.
three-phase rectifier A rectifier for three-phase alternating
current. At least one diode is included