18WuD2x

428 magnetic memory • magnetic shielding
magnetic memory 1. See RETENTIVITY. 2. A digital
memory circuit using magnetic fields to store
data bits. Example: BUBBLE MEMORY.
magnetic meridian The circle of the celestial
sphere that passes through the zenith and
earth’s magnetic poles.
magnetic mine A naval mine detonated by a magnetic
switch that is closed by the proximity of the
steel hull of a ship.
magnetic modulator A core-type device that is
somewhat similar to a magnetic amplifier used
for amplitude modulation. Modulating current
passes through the control winding, and the carrier
current through the output winding.
magnetic moment Unit, joule per tesla. For a
magnet, the product of pole strength and the distance
between poles.
magnetic needle The pivoted magnetic pointer in
a magnetic compass.
magnetic north See NORTH MAGNETIC POLE.
magnetic oxide Iron oxide used as the sensitive
coating of magnetic recording tape.
magnetic pickup 1. A phonograph pickup of the
variable-reluctance type (see VARIABLE-RELUC-
TANCE PICKUP). 2. A magnetic transducer (such
as a phono cartridge, tape recording head, or
similar input element).
magnetic-pickup head In a tape recorder, the
transducer that receives up magnetic impulses
from the passing tape and converts them into alternating
currents. These currents are amplified
to obtain the original sound. Compare MAG-
NETIC RECORDING HEAD.
magnetic-plate wire Wire in which a magnetic
metal has been plated on top of a nonmagnetic
metal.
magnetic poles 1. The points in a MAGNET at
which the magnetic lines of flux converge. 2. The
points on the earth at which the geomagnetic
lines of flux converge. See NORTH MAGNETIC
POLE and SOUTH MAGNETIC POLE.
magnetic pressure See MAGNETOMOTIVE
FORCE.
magnetic printing 1. Also called magnetic printthrough.
In a recording material, such as magnetic
tape, the transfer of information from one
part of the material to another part (or from one
medium to another) by the magnetic field of the
recorded material. This phenomenon, which is
also called PRINT-THROUGH, sometimes occurs
in recording tape on a reel. 2. Conventional
lithography, letterpress, or other reproduction
process in which MAGNETIC INK is used.
magnetic print-through See MAGNETIC PRINT-
ING, 1.
magnetic probe A loop or coil inserted in an electromagnetic
field to sample the magnetic component.
See, for example, WAVEGUIDE PROBE.
Compare ELECTRIC PROBE.
magnetic recording 1. The recording of sounds or
data by varying the magnetization of a medium,
Tape
Motion of tape
magnetic recording
Modulating
waveform
such as a magnetic disk or tape. 2. A magnetic
medium on which data has been recorded.
magnetic recording head In a tape recorder, the
transducer that receives current impulses
(analogs of the original sound vibrations) from an
amplifier and converts them into magnetic impulses
that magnetize spaces on the passing
tape. Compare MAGNETIC PICKUP HEAD.
magnetic recording medium 1. A magnetic cylinder,
disk, drum, tape, or wire used in the recording
of sound or data. 2. The sensitive material
with which any of these is coated.
magnetic relay A relay having a permanent magnet
in whose field a coil, bar, or reed moves to
open or close a pair of contacts.
magnetic remanence See RESIDUAL MAG-
NETISM.
magnetic repulsion The force that causes a magnetic
pole to push away a similar magnetic pole,
although they are not in mutual contact. Thus,
two north poles repel each other, and so do two
south poles. Compare MAGNETIC ATTRACTION.
magnetic-resonance accelerator See CYCLO-
TRON.
magnetics 1. Collectively, magnetic components
and equipment. 2. Collectively, magnetic materials.
3. A branch of physics dealing with magnets
and magnetism.
magnetic saturation The condition in which a
magnetic material passes all of the magnetic lines
of flux that its permeability allows. Increasing the
intensity of the magnetizing force will produce no
increase in magnetization.
magnetic scan See ELECTROMAGNETIC DE-
FLECTION.
magnetic screen See ELECTROMAGNETIC
SHIELD.
magnetic shield See ELECTROMAGNETIC
SHIELD and MAGNETIC SHIELDING.
magnetic shielding 1. Enclosing a magnetic field
to confine its flux, thus preventing interaction