DELTA --A three-phase connection in which
COMPOUND-WOUND MOTORS AND
windings are connected end to end, forming a
GENERATORS --Machines that have a series
closed loop that resembles the Greek letter delta.
field in addition to a shunt field. Such machines
A separate phase wire is then connected to each
have characteristics of both series- and shunt-
of the three junctions.
wound machines.
CONDUCTANCE --The ability of a material
DEMODULATOR --A circuit used in servo
to conduct or carry an electric current. It is the
systems to convert an ac signal to a dc signal, The
reciprocal of the resistance of the material, and
magnitude of the dc output is determined by the
is expressed in mhos.
magnitude of the ac input signal, and its polarity
is determined by whether the ac input signal is in
CONDUCTIVITY --The ease with which a
or out of phase with the ac reference voltage.
substance transmits electricity.
DIELECTRIC --An insulator; a term that
CONDUCTOR --Any material suitable for
refers to the insulating material between the plates
carrying electric current.
of a capacitor.
CORE --A magnetic material that affords an
DIFFERENTIAL --A mechanical computing
easy path for magnetic flux lines in a coil.
device used to add or subtract two quantities.
COUNTER EMF --Counter electromotive
force; an EMF induced in a coil or armature that
DIGITAL COMPUTER --A type of com-
opposes the applied voltage.
puter in which quantities are represented in
numerical form. It is generally made to solve
COUNTING CIRCUIT --A circuit that
complex mathematical problems by use of the
receives uniform pulses representing units to be
fundamental processes of addition, subtraction,
counted and produces a voltage in proportion to
multiplication, and division. Its accuracy is
their frequency.
limited only by the number of significant figures
provided.
COVALENT BOND --A type of linkage
between atoms in which the atoms share valence
DIODE --A material of either germanium or
electrons.
silicon that is manufactured to allow current to
flow in only one direction. Diodes are used as
CPR --See CARDIOPULMONARY RESUS-
rectifiers and detectors.
CITATION.
DIRECT CURRENT --An electric current
CURRENT --The movement of electrons past
that flows in one direction only.
a reference point. The passage of electrons
through a conductor. Measured in amperes.
DISCRIMINATOR --A dual-input circuit in
CURRENT LIMITER --A protective device
which the output is dependent on the variation
similar to a fuse, usually used in high amperage
of one input from the other input or from an
circuits.
applied standard.
CYCLE --One complete positive and one
DOPPLER EFFECT --An apparent change in
complete negative alternation of a current or
the frequency of a sound wave or electromagnetic
voltage.
wave reaching a receiver when there is relative
motion between the source and the receiver.
D'ARSONVAL METER MOVEMENT --
The permanent-magnet moving-coil movement
EDDY CURRENT --Induced circulating
used in most meters.
currents in a conducting material that are caused
by a varying magnetic field.
DEGREES OF FREEDOM (GYRO) --A term
applied to gyros to describe the number of
EFFICIENCY --The ratio of output power to
variable angles required to specify the position of
input power, generally expressed as a percentage.
the rotor spin axis relative to the case.
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