18WuD2x

234 electric conduction • electric generator
electric conduction The flow of current carriers
through a conductor.
electric constant Also called permitivity of vacuum.
The fixed electrical permitivity of free space,
the value of which is 8.8542 × 10 –12 farad per
meter.
electric contact See CONTACT, 1, 2.
electric controller An adjustable device for modifying
the operating voltage or power of a component
or system. Compare ELECTRONIC
CONTROLLER.
electric cooling 1. Cooling via PELTIER EFFECT.
2. See ELECTROSTATIC COOLING. 3. Forced-air
cooling (of equipment) by electric blowers or fans.
electric current The phenomenon wherein charge
carriers move in a directed manner through a
material or vacuum. In most electrical conductors,
current results from movement of electrons.
In a semiconductor material, electric current can
result from the movement of holes, as well as
electrons; the proportion of holes to electrons depends
on the nature of the semiconductor. In a
gas or electrolyte, current consists of a flow of
ions. In certain situations, electric currents can
result from the movement of positrons, protons,
anti-protons, alpha particles, and various atomic
nuclei.
electric current density See CURRENT DENSITY.
electric delay line See DELAY LINE.
electric density See ELECTRIC SPACE DENSITY
and ELECTRIC SURFACE DENSITY.
electric dipole A pair of equal charges having opposite
polarity and separated by a fixed distance.
electric discharge See ELECTRICAL DISCHARGE.
electric-discharge lamp See DISCHARGE LAMP.
electric disintegration See ELECTRIC DISPER-
SION.
electric dispersion In a colloidal suspension, dispersion
accomplished by passing an electric current
through the material.
electric displacement The movement of a body or
particle in response to an electric current or field.
electric double refraction See KERR ELECTRO-
OPTICAL EFFECT.
electric dust precipitator See DUST PRECIPITA-
TOR.
electric eel An eel (fish) capable of delivering a disabling
shock on contact.
electric elasticity See ELASTIVITY, 1, 2.
electric endosmosis See ELECTRO-OSMOSIS.
electric eye A sensing device that uses a radiant
energy beam to detect objects. It generally uses a
laser diode as the beam source, and a photoelectric
cell, phototransistor, or photovoltaic cell as
the beam detector. The output is used to control
some external machine or system.
electric fence A wire fence through which an electric
current is passed. Anyone touching the fence
will receive a shock. It is used in some prisons,
and also by cattle ranchers to keep people or animals
contained.
electric fidelity The frequency response of a circuit
or device.
electric field The space surrounding an electric
charge or charged body, in which electric energy
acts (electric lines of flux fill the space).
electric field intensity See ELECTROSTATIC
FIELD INTENSITY.
electric field strength 1. Symbol, E. In an electromagnetic
wave, the amplitude of the electric component
of the field, expressed in volts per meter.
2. Dielectric strength.
electric-field vector See ELECTRIC-FIELD
STRENGTH, 1.
electric filter See ELECTRIC WAVE FILTER.
electric fish Fish capable of generating intense electric
shocks (e.g., electric catfish and electric eel).
electric flux See ELECTROSTATIC FLUX.
electric flux density Symbol, D. In an electric
field, the number of lines of flux per unit area,
usually expressed in coulombs per square meter.
electric flux lines The direction of the electric field
in the vicinity of a charged object. The field is denoted
by means of “lines of flux” or “lines of
force,” with each line representing a designated
electric field intensity. The closer together the
lines, the more intense the field in a given region.
electric focusing See ELECTROSTATIC FOCUS-
ING.
electric force The force exerted by an electrically
charged particle or an electric field.
electric forces The forces exerted by electric
charges or electric fields. Also see UNIT ELEC-
TROSTATIC CHARGE.
electric furnace An electrically heated chamber
(sometimes heated by an electric arc) used in ore
reduction, carbide manufacture, and other hightemperature
processes.
electric generator A device for producing electricity.
Thus, many different devices, such as bat-