Magnetic Strain.
The strain produced by magnetic lines of force in substances exposed to
their action. It is observed in substances placed between the poles of a
strong electro-magnet, and evinces itself in the alteration of the
optical properties of transparent substances.
Magnetic Stress.
The stress produced by magnetic lines of force on substances through
which they pass, evidenced in alteration of the optical properties of
transparent bodies thus treated.
Magnetic Susceptibility.
The specific intrinsic susceptibility of any material for magnetic
induction. It refers to the particle of matter, and not to the mass, as
in the latter its own particles react on each other and bring about what
is termed permeability, q. v. (See also Magnetization, Coefficient of
Induced, and Magnetic Induction, Coefficient of.)
Synonym--Coefficient of Induced Magnetization.
Magnetic Tick.
When a bar of iron is suddenly magnetized or demagnetized it emits a
slight sound, called the Page sound, or the magnetic tick. This has been
utilized in a telephone by Reiss. The telephone will receive sound, but
is very weak. It consists of a bar surrounded with a coil of insulated
wire. Variations in current produce sounds, which may be articulate if
the currents are produced by a telephonic transmitter.
Magnetic Twist.
A bar of iron held in the magnetic meridian and pointing to the pole and
twisted becomes to some extent permanently magnetized. Conversely a bar
when magnetized seems to have a twist set up in it. The latter is
magnetic twist.
Magnetic Variations.
Changes in the value of magnetic declination or inclination. (See
Magnetic Elements.)
Magnetism, Ampére's Theory of.
A theory accounting for magnetic phenomena by assuming the existence of
currents circulating around the molecules of permanent magnets. If such
currents so circulate and all in the same direction, the result is the
same as if the body of the magnet was enveloped in currents representing
those of an electro-magnet or solenoid. This is because in the interior
the current around one molecule would counteract the current around its
neighboring ones in part, so that the only virtual currents left would
be represented by those on the outer surfaces of the outer shell of
molecules, and these virtually resolve themselves into one general
current sheet, surrounding the magnet and coinciding with its surface.
The theory assumes that such currents permanently circulate around the
molecules of paramagnetic substances. Under ordinary conditions there is
no coincidence in their direction and no resultant current is produced.
When magnetized or polarized the molecules are brought into order, so
that the direction of their current coincides and the body becomes a
magnet.