Under these conditions, so long as heat is applied at two
points equidistant from N and S, we might, if we so pleased, cause the
armature to be rotated by an external source of power, and we should
then have an E.M.F. generated in the armature coils--that is to say, the
machine would work as an ordinary dynamo, and the power expended in
driving the armature would be proportionate to the output.
Suppose next that the points of heating, and with them the alternate
points of cooling 90 deg. apart, are shifted round about 45 deg., so
that the two hot regions are no longer symmetrically situated in respect
to each pole of the field. The distribution of the magnetization has
therefore become unsymmetrical, and the iron core is no longer in
equilibrium in the magnetic field. We have, in fact, the conditions of
Schwedoff's experiment upon a larger scale, and if the forces are
sufficient to overcome the frictional resistance, a rotation of the ring
ensues in the endeavor to restore equilibrium. The regions of heating
and cooling being fixed in space, this rotation is continuous so long as
the difference of temperature is maintained. The ring in rotating
carries with it the armature coils, and of course an E.M.F. is generated
in the same way as if the motive power came from an external source.
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