Magnetic Adherence.
The tendency of a mass of iron to adhere to the poles of a magnet. It is
best figured as due to the virtual shortening of lines of force, as the
more permeable iron gives a better path for them than the air can
afford, and consequently a virtually shorter one.
Magnetic Attraction and Repulsion.
The attraction of a magnet for iron, steel, nickel and cobalt and of
unlike poles of magnets for each other. It is identical with
electro-magnetic attraction, q.v. (Also see Electro-magnetism.)
Magnetic Attraction and Repulsion, Coulomb's Law of.
Magnetic attraction and repulsion are inversely as the square of the
distance. (Ganot.)
While theoretically true in the case of isolated poles, in practise it
does not generally apply on account of the large diameter and relative
shortness of magnets.
Magnetic Axis.
The line connecting the poles of a magnet. It does not generally
coincide exactly with any symmetrical axis of figure. In such cases an
error is introduced into the indications of the needle which must be
determined and allowed for in compasses. To determine it with a magnetic
needle the suspension cup is made removable, so that the needle can be
reversed. Readings are taken with one side of the needle and then with
the other side of the needle up, and the average corresponds with the
position of the magnetic axis in both positions of the needle.
Magnetic Azimuth.
The angle, measured on a horizontal circle, between the magnetic
meridian and a great circle of the earth passing through the observer
and any observed body. It is the astronomical azimuth of a body referred
to the magnetic meridian and therefore subject to the variation of the
compass. The angle is the magnetic azimuth of the observed body.
Magnetic Battery.
A name for a compound permanent magnet; one made up by bolting or
clamping together, or to single soft iron pole pieces, a number of
single permanent magnets. There are a number of forms of compound
magnets. In making them care has to be taken to have them of even
strength. It is also well to have them slightly separated. The object of
both these precautions is to prevent a stronger element or magnet from
depolarizing its neighbor.
Synonym--Compound Magnet.
Magnetic Bridge.
An apparatus for testing the relative permeability of iron. It consists
of a rectangular system of iron cores. Three of the sides are wound with
wire as shown. The other side is built up of double bars, and from the
centre two curved arms rise, as shown in the cut. The arms do not touch.
Between them a short magnet is suspended by a filament, which also
carries a mirror and an index.