18WuD2x

250 electron stream • electrophorus
2. The electrons moving between the cathode and
plate in an electron tube.
electron-stream instrument See ELECTRON-
BEAM INSTRUMENT.
electron-stream meter An oscilloscope (or cathode-ray
tube alone) used as a device for making
measurements.
electron-stream transmission efficiency The ratio
of the current through a positive electrode to
the current impinging on it. In a tube, for example,
some electrons are absorbed by the plate,
and others are reflected.
electron telescope A telescope using a combination
of a glass lens, photocathode, and electrostatic
focusing. Light from the object is focused
on the photocathode by the lens, the electrons
emitted being focused electrostatically on a phosphorescent
viewing screen.
electron transit time The time required for an electron
to travel a given distance. For a vacuum tube,
the upper frequency limit of operation is governed
by the time required for an electron to reach the
plate after leaving the cathode. Transit time is
usually stated in fractions of a microsecond.
electron tube An evacuated or gas-filled chamber
in which electrons are emitted (usually by a hot
cathode) and controlled (usually by a voltage applied
to a grid electrode).
electron unit See ELEMENTARY CHARGE.
electron velocity The velocity acquired by an electron
that moves between two points having a
given potential difference. Also see ELECTRON
MOTION, 2.
electronvolt Abbreviation, eV. The energy acquired
by a unit charge moving through a potential
difference of one volt; it is equal to
approximately 1.6022 × 10 –19 joule.
electron-wave tube A tube, such as a klystron or
traveling-wave tube, in which electrons traveling
at different velocities interact with each other,
modulating the electron stream.
electro-oculogram A recording of the voltage that
is found between the anterior and posterior parts
of the eyeball.
electro-optical transistor A phototransistor or
pair of phototransistors in a single package. Used
in electronic circuits to sense changes in light
levels.
electro-optical valve See KERR CELL.
electro-optic radar A form of radar that makes
use of visual apparatus for locating a target.
electro-optics The branch of electronics dealing
with related electrical and optical phenomena:
photoelectricity, light generation, laser technology,
light amplification, etc. It is also concerned
with electronic phenomena that are analogous to
optical phenomena, such as electronic focusing,
reflection, refraction, diffraction, etc. Also called
electron optics and optoelectronics.
electro-osmosis Causing liquids to flow by applying
an electric field across the walls of a porous
plug. The force exerted by the field on ions in the
liquid causes it to flow.
electropad The skin-contacting electrode of an
electrocardiograph.
electropathy See ELECTROTHERAPY.
electrophilic Pertaining to the tendency to seek
electrons.
electrophobia An irrational fear of electricity, a
psychological condition sometimes exhibited by
victims of serious electric shock.
electrophonic effect Sound heard by a person
when an alternating current is passed through
some part of the body.
electrophoresis The movement of dielectric particles
through a liquid in which they are suspended,
produced by the electric field between
electrodes immersed in the suspension.
electrophoresis equipment 1. Any device intended
for the purpose of depositing a dielectric
material onto a metal by means of electrophoresis.
2. Any equipment in which electrophoresis
occurs.
electrophoresis scanner A device that senses the
movement of charged particles caused by electrophoresis
effects.
electrophoretic deposition A type of deposition in
which a low-voltage direct current passing
through a colloidal suspension of dielectric polymer
particles deposits them as a coating on a
metallic body (the anode in the process). It can
provide a better coating than one obtained with
spray painting or dipping.
Anode part
to be coated
Suspended particles
+ −
electrophoretic deposition
Cathode
electrophorus A simple device used to demonstrate
electrostatic generation and induction. It
consists of a smooth metal plate at the end of an
insulating handle and an accompanying cake of
resin or hard rubber. The cake is rubbed with
cat’s fur, making it negatively charged. The metal
plate is touched to the charged cake; by induction,
it acquires a bound positive charge on the
face that touched the cake and a free negative
charge on the opposite face. When the plate is
lifted and its top face touched momentarily with
the finger or grounded, the negative charge leaks