Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

Explanation

Electric generator labelled diagram is as follows :

Principle: An electric generator works on the principle of electromagnetic induction.
Working: Let the in the beginnings brushes
`B_1` and `B_2`
are kept pressed separately on rings
`R_1` and `R_2` respectively. Let the axle attached to the rings is rotated such that arm AB of the coil moves up and arm CD moves down in the magnetic field. Due to rotation of arms AB and CD induced current are set up in them. As per Fleming.s right hand rule, induced current in these arms along the directions AB and CD respectively and current flows into
`B_1` and `B_2`
After half rotation, arm AB moves downward and arms CD upward to change the direction opposite to first case. Thus, after every half rotation current changes its direction and an alternate current is obtained in the generator.
Brushes are kept pressed on the two slip rings separately. Outer ends of the brushes are connected to the galvanometer. Thus, brushes help in transferring current from the coil ABCD to external circuit.