Magnet, Unipolar.
No such thing as a unipolar magnet is possible. The name is given to
poised or suspended magnets, one of whose poles lies in the axis of
suspension. It is obvious that such a magnet will act, as far as its
directive tendency and rotatory movements are concerned, as if it had
only one pole. As shown in the cut, the pole s in both magnets lies in
the axis of suspension or directly under the filament by which they are
suspended, while the other pole n is the active pole in causing rotation
or directive tendency; c c are counterweights or counterpoises.
Fig. 236. UNIPOLAR MAGNETS.
Magnetophone.
An apparatus for producing a loud sound, involving the principles of the
telephone. A rapidly alternating or make and break current being
produced by any means and being transmitted through the telephone gives
a loud note of pitch dependent on the current producing it. Sometimes a
perforated metallic disc is rotated in a magnetic field, and produces
the requisite type of current.
Magnus' Law.
A law of thermo-electricity. In a homogeneous circuit, however, the
temperature varies from point to point; there is no current.
Whatever potential differences may be established by the variations in
temperature it is evident that they must counteract each other and
reduce to zero.
Mains, Electric.
The larger conductors in a system of electric light or power
distribution.
Make. v.
To complete a circuit, as by closing a switch.
Make and Break Current.
A current which is continually broken or interrupted and started again.
It is applied only where the "makes" and "breaks" succeed each other
with great rapidity, as in the action of an induction coil or pole
changer, etc. It has had considerable importance in litigation affecting
the Bell telephone patents, the courts holding that the original Bell
patent (No. 174,465, of 1876,) covered the undulating current, for the
transmission of speech. Many efforts have been made by litigants to
prove that specific telephones have transmitted articulate speech by the
make and break current, but without success. If this could have been
proved the assumption is that the courts would have sustained the use of
such device as not infringing upon the claims of the Bell patent.
Malapterurus.
A fish, sometimes called the thunder fish, an inhabitant of African
rivers, occurring in the Nile and Senegal. It possesses considerable
electric power, similar to that of the gymnotus and torpedo, although
inferior in amount.