Magnetism, Free.
The magnetism or magnetic field outside of a magnetic circuit. It is due
to escape of lines of force and to the magnetic leakage through the air.
The lines of force are never, under the most favorable circumstances,
confined to the metallic circuit of the magnet and armature. In a simple
magnet without armature all the lines of force have to follow an air
path, and the field is at its strongest. As the magnetism is strongest
at the surface near the poles, the term is sometimes understood as
applying to the surface attraction. In such case it is defined as the
distribution, on a magnetized bar or mass, of magnetic lines of force as
they emerge from its surface.
Synonym--Surface Magnetization.
Magnetism, Hughes' Theory of.
A theory accounting for magnetic phenomena by assuming that each
molecule is a magnet, and that in a polarized or magnetized body they
are all arranged with their poles in the same direction, while in an
unmagnetized body their poles, alternating in direction, neutralize each
other.
Magnetization consists in a partial rotation of the molecules so as to
make them agree in position, thus, as a resultant developing north and
south poles at the ends of the bar.
The theory is in a certain sense simpler than Ampere's theory, but is
not so generally adopted.
Magnetism, Lamellar Distribution of.
The distribution of magnetism in thin and uniform or "simple magnetic
shells," q. v. A given distribution is termed lamellar if the substance
in which it exists can be divided into simple magnetic shells, which
either form closed surfaces, or have their edges in the surface of the
substance. In lamellar distribution the polar area is very large
compared with the distance between opposite poles.
Magnetism of Gases.
Faraday experimented on this point by coloring gases with a little vapor
of iodine or other colored gas, and letting them flow between the two
poles of a powerful electromagnet. In this way he found some are
repelled, some attracted, and in the case of oxygen, it is attracted at
one temperature and repelled at another. At ordinary temperatures a
cubic yard of oxygen possesses the magnetism of 5.5 grains of iron and
when liquefied it is strongly attracted.
Magnetism or Magnetization, Temporary.
When a mass of iron is magnetized by a current, when the current ceases
the portion of its magnetism which disappears is the temporary
magnetism; the portion retained is the residual or permanent magnetism.
Magnetism, Red.
A term arising from the two fluid theory of magnetism; the magnetism of
the north pole of a magnet. (See Magnetic Fluids.) The magnetism of the
south pole is termed blue magnetism. Both terms originated in the
painting of magnets. They are but little used.
Synonym--North Magnetic Fluid.