Magnet, Axial.
A straight-solenoid with axial core.
Magnet, Bar.
A bar magnet is one in the shape of a bar, i. c., straight with parallel
sides and considerably longer than wide or deep.
Magnet, Bell-shaped.
A form of permanent magnet used in some galvanometers. In shape it is a
thick-sided cylindrical box with two slots cut out of opposite sides, so
as to make it represent a horseshoe magnet. Its shape enables it to be
surrounded closely by a mass of copper, for damping its motion, to
render the instrument dead-beat. Such a magnet is used in Siemens &
Halske's galvanometer.
Magnet Coil.
A coil to be thrust over an iron core, to make an electro-magnet. They
are often wound upon paper or wooden bobbins or spools, so as to be
removable from the core if desired.
Magnet, Compensating.
(a) A magnet fastened near a compass on an iron or steel ship to
compensate the action of the metal of the ship upon the magnetic needle.
The ship itself always has some polarity and this is neutralized by one
or more compensating magnets.
(b) See below.
Magnet, Controlling.
A magnet attached to a galvanometer by which the directive tendency of
its magnetic needle is adjusted. In the reflecting galvanometer it often
is a slightly curved magnet carried by a vertical brass spindle rising
from the center of the instrument, and which magnet may be slid up and
down on the spindle to regulate or adjust its action.
Synonym--Compensating Magnet.
Magnet, Compound.
A permanent magnet, built up of a number of magnets. Small bars can be
more strongly magnetized than large. Hence a compound magnet may be made
more powerful than a simple one.
Magnet Core.
The iron bar or other mass of iron around which insulated wire is wound
for the production of an electro-magnet. The shapes vary greatly,
especially for field magnets of dynamos and motors. For these they are
usually made of cast iron, although wrought iron is preferable from the
point of view of permeability.
Magnet, Damping.
A damping magnet is one used for bringing an oscillating body to rest.
The body may be a metallic disc or needle, and the action of the magnet
depends on its lines of force which it establishes, so that the body has
to cut them, and hence has its motion resisted.