Magnetic Circuit.
A magnetic field of force is characterized by the presence of lines of
force, which, while approximately parallel, curve around and tend to
form closed curves. The polarity of a field of force is referred to an
imaginary direction of the lines of force from the north pole through
space to the south pole, and in the part of the field corresponding to
the body of the magnet, from the south to the north pole. The cut
indicates these features. Hence the magnetic field of force is termed
the magnetic circuit, and to it are attributed a species of resistance
termed reluctance, q. v., and the producing cause of the field or lines
of force is termed sometimes magneto-motive force, q. v.) corresponding
to the electro-motive force. The modern treatment of the magnetic
circuit is similar to the application of Ohm's law and the laws of
resistance and conductivity to the electric circuit.
Magnetic Circuit, Double.
A magnetic circuit which virtually represents two horseshoe magnets
placed with their like poles in contact. It is used for field magnets,
the armatures occupying a place between the consequent poles.
Fig. 221. ONE-HALF PORTION OF A DOUBLE MAGNETIC CIRCUIT.
Magnetic Concentration of Ores.
The concentration of ores or the freeing them from their gangue by
magnetic attraction. It is only applicable to those cases in which
either the ore itself or the gangue is attracted by the magnet. Its
principal application is to the concentration of magnetic iron sands.
(See Magnetic Concentration.)
Magnetic Concentrator.
An apparatus similar to a magnetic separator, q. v., but used to
concentrate magnetic iron sands. By the action of electro-magnets the
magnetic iron sand (magnetite) is separated from the sand with which it
is mixed.
Magnetic Conductivity and Conductance.
The first notion of permeance and of the magnetic circuit included the
idea of magnetic conductivity, which conducted lines of force urged by
magneto-motive force through a magnetic circuit. The terms are displaced
by permeability and permeance.