Magnetic Self-induction.
The cause of a magnet weakening is on account of this quality, which is
due to the direction of the lines of force within a magnet from the
positive towards the negative pole. "A magnet thus tends to repel its
own magnetism and to weaken itself by self-induction." (Daniell.)
Magnetic Separator.
An apparatus for separating magnetic substances from mixtures. Such
separators depend on the action of electro-magnets. In one form the
material falls upon an iron drum, magnetized by coils. Any magnetic
substance adheres to the drum and is thereby separated. They are used by
porcelain makers for withdrawing iron particles from clay, by machinists
to separate iron filings and chips from brass, and for similar purposes.
Fig. 224. MAGNETIC SEPARATOR.
Magnetic Shell.
A theoretical conception of a cause of a magnetic field or of a
distribution of magnetism. If we imagine a quantity of very short
magnets arranged in contact with their like poles all pointing in the
same direction so as to make a metal sheet, we have a magnetic shell.
Its magnetic moment is equal to the sum of the magnetic moment of all
its parts. If the shell is of uniform strength the magnetic moment of a
unit area gives the strength of the shell; it is equal to the magnetic
quantity per unit of area, multiplied by the thickness of the shell.
If its strength is uniform throughout a magnetic shell is called simple;
if its strength varies it is termed complex.
Emtage thus defines it: A magnetic shell is an indefinitely thin sheet
magnetized everywhere in the direction normal to itself.
Magnetic Shell, Strength of.
The magnetic quantity per unit of area of the shell multiplied by the
thickness of the shell.