The cut, Fig. 231, shows an alternating current machine. In it a pair of
bobbins, wound in series, and both either right-handed or left-handed,
are rotated between permanent magnet poles. The current may be taken off
by two brushes bearing on two collecting rings on the axis of the
bobbins, the ends of the wire being connected thereto. Or if a shocking
current is desired, one of the brushes or springs may strike a series of
pins forming virtually a broken or interrupted collecting ring. This
gives a current for medical purposes.
Synonyms--Magneto-dynamo--Magneto-electric Machine.
Magnetograph.
An apparatus for recording variations in magnetic elements. One type
includes a magnetic needle to which a concave mirror is attached. The
light ray from the mirror is reflected upon sensitized paper where its
movements are photographically reproduced. The movements of the spot are
due to the movements of the needle and act as the record of the same.
Magneto-Inductor.
An instrument for use with a ballistic galvanometer to reproduce a
definite current impulse. Two magnets are fastened together in one
straight line, the north poles almost touching. This is mounted at the
end of a rod like a pendulum, the axis of the magnets transverse to the
rod. The magnets are carried by a frame and oscillate at the end of the
rod, back and forth within a fixed coil, which is one-half the length
of the double magnet. A bob is attached to the bottom of the frame by
which the whole can be swung. As the magnets are of fixed value, their
time of oscillation constant, and the coil fixed in size, the apparatus
provides a means of getting a definite instantaneous current of
identical value whenever needed.
Fig. 232. MAGNETO-INDUCTOR.