Why AC must be induced in a conductor rotating in a bipolar magnetic field

Let us investigate the voltage obtain from coil as it rotates in a magnetic field.

The voltage induced in the coil at position (1) zero. Because the conductor, at this instant is moving parallel to the lines of flux and therefore is not cutting any lines.

At position 2 the voltage induced in the coil is maximum because the conductors are moving at right angle to the lines of flux. The direction of the current in accordance with Fleming right-handle rule, is shown in the diagram.

The voltage is again zero in position 3. Just as it was at position (1). coil side A is now at the bottom instead of at the top.

Why The wave form of the induced voltage is sinusoidal:

Let us investigate the voltage obtain from coil as it rotates in a magnetic field.

The voltage induced in the coil at position (1) zero. Because the conductor, at this instant is moving parallel to the lines of flux and therefore is not cutting

any lines.

The voltage is again zero in position 3. Just as it was at position (1).coil side A is now at the bottom instead of at the top.

At position 4, the voltage is again at a maximum as at position. Applying Fleming’s right-hand rules the current in side-A of the coil at opposite 4 , is possible to the direction of current when the coil was in the position-2. The changed of current was produced by change in the direction of motion with respect to the flux. In position 2 side-A was moving in a down-ward direction, while in position 4 it is moving upward.

At position 5 is same as position 1. Where the induced voltage is again zero and if the coil continues to rotate it will repeat the above sequence of induced voltage. Figure 2 is a plot of the voltage induced in the coil which is sinusoidal.