and then in the other, thus producing electromotive forces therein,
first in one direction and then in the other.

Referring now to Fig. 68, and supposing that the loop _4_ is revolving
in the direction of the curved arrow shown between the upper edges of
the pole pieces, it will be evident that just as the loop stands in
the vertical position, its horizontal members will be moving in a
horizontal direction, parallel with the lines of force and, therefore,
not cutting them at all. The electromotive force and the current will,
therefore, be zero at this time.

As the loop advances toward the position shown in dotted lines, the
upper portion of the loop that is parallel with the axis will begin to
cut downwardly through the lines of force, and likewise the lower
portion of the loop that is parallel with the axis will begin to cut
upwardly through the lines of force. This will cause electromotive
forces in opposite directions to be generated in these portions of the
loop, and these will tend to aid each other in causing a current to
circulate in the loop in the direction shown by the arrows associated
with the dotted representation of the loop. It is evident that as the
motion of the loop progresses, the rate of cutting the lines of force
will increase and will be a maximum when the loop reaches a horizontal
position, or at that time the two portions of the loop that are
parallel with the axis will be traveling at right angles to the lines
of force. At this point, therefore, the electromotive force and the
current will be a maximum.

From this point until the loop again assumes a vertical position, the
cutting of the lines of force will still be in the same direction, but
at a constantly decreasing rate, until, finally, when the loop is