Magnetic Perturbations.
Irregular disturbances of the terrestrial magnetism, as by the aurora
and in electric storms.
Magnetic Poles.
The points where the equipotential surfaces of the terrestrial field of
force graze the earth's surface; the points toward which the north or
south poles of the magnetic needle is attracted. Over a magnetic pole
the magnetic needle tends to stand in a vertical position. There are two
poles, Arctic or negative, and Antarctic or positive. Magnetic needles
surrounding them do not necessarily point toward them, as they point to
the centres of curvature of their respective magnetic parallels. The
poles constantly change in position. The line joining them does not
coincide with anything which may be termed the magnetic axis of the
earth.
Magnetic Poles, False.
Poles on the earth's surface other than the two regular magnetic poles.
There seem by observation to be several such poles, while analogy would
limit true magnetic poles to two in number.
Magnetic Potential.
The potential at any point of a magnetic field is the work which would
be done by the magnetic forces of the field upon a positive unit of
magnetism as it moves from that point to an infinite distance. (Emtage.)
Magnetic Proof Piece.
A piece of iron used for testing magnets and the distribution of
magnetism in bars, by suspending or supporting above or near the magnet,
by detaching after adherence, and in other ways.
Magnetic Proof Plane.
An exploring coil used for testing the distribution of magnetism. It is
connected in circuit with a galvanometer, and exposed to alternation of
current, or to other disturbing action produced by the magnet or field
under examination. This affects the galvanometer, and from its movements
the current produced in the coil, and thence the magnetic induction to
which it was exposed, are calculated.
Synonym--Exploring Coil.
Magnetic Quantity.
The magnetism possessed by a body; it is proportional to the action of
similar poles upon each other, or to the field produced by the pole in
question. It is also called the strength of a pole.
The force exercised by two similar poles upon each other varies with
their product and inversely with the square of the distance separating
them; or it may be expressed thus (m * m) / (L^2). This is a force, and
the dimensions of a force are ML/(T^2). Therefore, (m^2)/(L^2) =
ML/(T^2) or m = (M^.5)*(L^1.5)/T.