Explain the construction and working of an electric motor. Draw a neat diagram and label it.

Explanation

Figure shows the construction of an AC electric generator. Here, a coil ABCD of copper wire is kept between the pole pieces (N and S) of a strong magnet. The ends of the coil are connected to the conducting rings `R_(1), and R_(2)`, via carbon brushes `B_(1) and B_(2)`. The rings are fixed to the axle and there is a resistive coating in between the rings and the axle. The stationary brushes are connected to a galvanometer used to show the direction of the current in the circuit.
Working : When the axle is rotated with a machine from outside, the coil ABCD starts rotating. Suppose the coil rotates in clockwise direction, as observed from the side AD. Then as the branch AB moves upward, the branch CD moves downward. By Fleming's right hand rule, the induced current flows in the direction `A to B to C to D` and in the external circuit, it flows from `B_(2)` to `B_(1)`, through the galvanometer. The induced current is proportional to the number of turns of the copper wire in the coil. After half a rotation, AB and CD interchange their places. Hence, the induced current flows in the direction `D to C to B to A`. As AB is always in contact with `B_(1)`, and CD is in contact with `B_(2)`, the current in the external circuit flows from `B_(2)`, to `B_(2)`, through the galvanometer. Thus, the direction of the current is the external circuit is opposite to that in the previous half rotation. The process goes on repeating and alternating current is generated.