Page 26 - The Illustrated Dictionary of Electronics

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ac plate voltage • active chord mechanism 11

ac plate voltage Symbol, E P(ac). The ac component ac source voltage Symbol, V S(ac). The ac compo-
of plate voltage in an electron tube. The ac out- nent of source voltage in a field-effect transistor.
put-signal voltage in a common-cathode ampli- The ac output-signal voltage in a source-follower
fier. (grounded-drain) FET amplifier.
ac power Symbol, P ac. Unit, watt (W). The power acss Abbreviation of analog computer subsystem.
acting in an ac circuit, P ac equals EI cos q, where ac time overcurrent relay A device with a certain
E is in volts, I in amperes, and q is the phase an- time characteristic, which breaks a circuit when
gle. Compare DC POWER. Also see POWER. the current exceeds a certain level.
ac power supply A power unit that supplies ac actinic rays Short-wavelength light rays in the vi-
only (e.g., ac generator, vibrator-transformer, os- olet and ultraviolet portion of the spectrum that
cillator, or inverter). Compare DC POWER give conspicuous photochemical action.
SUPPLY. actinism The property whereby radiant energy
acquisition 1. The gathering of data from trans- (such as visible and ultraviolet light, X-rays, etc.)
ducers or a computer. 2. Locating the path of an causes chemical reactions.
orbiting body for purposes of collecting teleme- actinium Symbol, Ac. A radioactive metallic ele-
tered data. 3. Orienting an antenna for optimum ment. Atomic number, 89. Atomic weight, 227.
pickup of telemetered data. actinodielectric Exhibiting a temporary rise in
acquisition and tracking radar An airborne or electrical conductivity during exposure to light.
ground radar, which locks in on a strong signal actinoelectric effect The property whereby cer-
and tracks the body that reflects (or transmits) tain materials (such as selenium, cadmium sul-
the signal. fide, germanium, and silicon) change their
acquisition radar A radar that spots an oncoming electrical resistance or generate a voltage on ex-
target and supplies position data regarding the posure to light. Also see ACTINODIELECTRIC.
target to a fire-control or missile-guidance radar, actinometer An instrument for measuring the di-
which then tracks the target. rect heating power of the sun’s rays or the actinic
acr 1. Abbreviation of AUDIO CASSETTE RE- power of a light source.
CORDER. 2. Abbreviation of AUDIO CASSETTE action current A small transient current that
RECORDING SYSTEM. flows in a nerve in the human body as a result of
ac reclosing relay The controlling component in stimulation.
an alternating-current circuit breaker. It causes activate To start an operation, usually by applying
the breaker to reset after a specified period of an appropriate enabling signal.
time. activation 1. Supplying electrolyte to a battery cell
ac relay A relay designed to operate on alternating to prepare the cell for operation. 2. Causing the
current without chattering or vibrating. acceleration of a chemical reaction.
ac resistance Pure resistance in an ac circuit. Un- activation time In the activation of a battery cell
like reactance and impedance, which are also (see ACTIVATION, 1), the interval between addi-
forms of opposition to the flow of current, ac re- tion of the electrolyte and attainment of full cell
sistance introduces no phase shift. voltage.
acronym A word formed from letters or syllables activator A substance added to an accelerator (see
taken from other applicable words of a multiword ACCELERATOR, 3) to speed the action of the ac-
term. Acronyms are convenient for naming new celerator.
devices and processes in electronics. Usually, a active Pertaining to a circuit or device that re-
term is considered an acronym only when it is quires a power supply for its operation. This dif-
spelled in all-capital letters; once the term is ac- fers from a passive circuit or device, which
cepted and popularized, it is written as a conven- operates with no external source of power.
tional word and is no longer thought of as an active antenna An antenna that uses a small
acronym. For example, LASER was once an whip, loop, or ferrite loopstick with a high-gain
acronym for light amplification by the stimulated amplifier for receiving at very-low, low, medium,
emission of radiation. By the popularization pro- and high radio frequencies (approximately 9 kHz
cess, the acronym became a conventional word to 30 MHz).
from which other terms (such as the verb “lase”) active area The forward-current-carrying portion
were derived. of the rectifying junction of a metallic rectifier.
acrylic resin A synthetic resin used as a dielectric active arm See ACTIVE LEG.
and in electronic encapsulations. It is made from active balance In telephone repeater operation, the
acrylic acid or one of its derivatives. sum of return currents at a terminal network bal-
ACS Abbreviation of automatic control system. anced against the local circuit or drop resistance.
ac source current Symbol, I S(ac). The ac component active chord mechanism Abbreviation, ACM. In
of source current in a field-effect transistor. robots, an electromechanical gripper capable of
ac source resistance Symbol, R S(ac). The dynamic conforming to irregular objects. It has a structure
source resistance in a field-effect transistor; R S(ac) similar to the human spine, with numerous
equals dV S/dI S for a constant value of V G. small, rigid links connected by hinges.