piece. As a result there will still be a good path for the lines of
force through the iron of the core and comparatively little change in
the number of lines passing through the armature winding. As the
corners of the armature flange pass away from the corners of the pole
pieces, however, there is a sudden change in condition which may be
best understood by reference to the right-hand portion of Fig. 71. The
lines of force now no longer find path through the center portion of
the armature core--that lying at right angles to their direction of
flow. Two other paths are at this time provided through the now
horizontal armature flanges which serve almost to connect the two pole
pieces. The lines of force are thus shunted out of the path through
the armature coils and there is a sudden decrease from a large number
of lines through the turns of the winding to almost none. As the
armature continues in its rotation the two paths through the flanges
are broken, and the path through the center of the armature core and,
therefore, through the coils themselves, is reëstablished.

As a result of this consideration it will be seen that in actual
practice the change in the number of lines passing through the
armature winding is not of the gradual nature that would be indicated
by a consideration of Fig. 68 alone, but rather, is abrupt, as the
corners of the armature flanges leave the corners of the pole pieces.
This abrupt change produces a sudden rise in electromotive force just
at these points in the rotation, and, therefore, the electromotive
force and the current curves of these magneto generators is not
usually of the smooth sine-wave type but rather of a form resembling
the sine wave with distinct humps added to each half cycle.

[Illustration: Fig. 72. Generator with Magnets Removed]