Alternator output on a graph
The output of a generator can be represented on an induced current–time graph which is shown below.
It shows four different positions of the coil of the generator, and the corresponding induced current.
A - The coil is at 0°. The coil is moving parallel to the direction of the magnetic field, so no current is induced.
B - The coil is at 90°. The coil is moving at 90° to the direction of the magnetic field, so the induced current is at its maximum.
C - The coil is at 180°. The coil is moving parallel to the direction of the magnetic field, so no current is induced.
D - The coil is at 270°. The coil is moving at 90° to the direction of the magnetic field, so the induced potential difference is at its maximum. Here, the induced current is in the opposite direction to what it was at B.
E - The coil is at 360°, ie it is back at its starting point, having done a full rotation. The coil is moving parallel to the direction of the magnetic field, so no current is induced.