# The induced current in an electric generator is alternating. After half a rotation does it alternate? 10p?

Or a quarter? Why?

Update:

So it alternates every half or quarter turn of the coil?

Update 2:

Relevance

One cycle of AC current looks like a sine wave. It rises in the positive direction from 0 to a maximum at 1/4 rotation, goes back through 0 at 1/2 rotation and then goes negative to a maximum negative at 3/4 turn and then returns to 0 to begin another cycle.

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Lv 6

If it is just a single loop of wire rotating between a pair of magnetic poles, the current is at maximum when the two sides of the loop cross a line between the north and south poles of the magnet. As the sides of the loop rotate away from that position, the current decreases. When the loop has rotated 1/4 turn, the line between the two poles passes through the center of the loop and the current is zero. When the coil has rotated another 1/4 turn, the side of the coil that previously passed the north pole is passing the south pole and the current is at its maximum in the opposite direction. In another 1/4 turn, the current is zero and a full turn completes one cycle of alternation.

That describes the function of a 2-pole, single-phase alternator. The frequency is related to the number of poles and the rotational speed by f = p X RPM / 60 where p is the number of pairs of poles.