Magnetic Remanence.
The residual magnetism left in a bar of steel or other paramagnetic
material after the application of a powerful magnet. It is distinguished
from coercive force, as the latter is the amount of negative magnetizing
or of demagnetizing force required to reduce the remanent magnetism to
zero.
Synonym--Remanence--Residual Magnetism.
Magnetism, Solenoidal Distribution of.
The distribution of magnetism in such a way that the poles are very far
apart in proportion to their area. The magnetization of a long thin bar
of steel illustrates solenoidal distribution.
Magnetism Sub-permanent.
The magnetism of a paramagnetic substance which presents a considerable
degree of permanency, but which gradually disappears, leaving the
permanent magnetism present. It is noticeable in iron or steel ships
whose magnetism gradually reduced in quantity, eventually becomes fully
permanent.
Magnetism, Weber's Theory of.
The molecules of a magnetizable material by this theory are supposed to
be magnets with their poles lying in every direction, and hence
neutralizing each other. By magnetization these are supposed to be
turned with their similar poles in the same direction, and their axis
parallel, hence acting like a group of magnets. It is practically
identical with Hughes' theory.
Magnetism, Terrestrial.
The magnetism of the earth. (See Magnetic Elements.)
Fig. 228. MAGNETIZATION BY DOUBLE TOUCH.
Magnetization by Double Touch.
The process of magnetizing a steel bar by simultaneously stroking it
with two poles of a horseshoe magnet or with two opposite poles of two
bar magnets. The poles must be close but not touching. A block of wood
may be placed between the ends if single magnets are used. The poles are
placed on the middle of the bar and carried back and forth to one end,
then to the other, and so on, ending at the middle of the bar in such
direction as to give each end the same number of strokes. The poles must
be close together or consequent poles will be produced. If bar magnets
are used they may be held inclined at an angle of 15º to 20º with the
horizontal bar to be magnetized. The ends of the latter may rest on
poles of two other magnets, each end on a pole of the same name as that
of the magnetizing magnet on its side. (See Magnetization, Hoffer's
Method.)