Rankers Physics
Topic: Electromagnetic Induction

20. A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is: (2013)

Six times per revolution
Once per revolution
Twice per revolution
Four times per revolution

Solution:

The induced emf in a rotating loop varies sinusoidally as $e = e_0 \sin(\omega t)$.
In one complete revolution ($2\pi$ radians), the sine function alternates between positive and negative half-cycles.
Thus, the direction of the induced e.m.f. reverses twice per revolution.

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