question_answer

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

Answer:

                Electric Generator or Dynamo It is a device which converts mechanical energy into electrical energy. Principle It works on the principle of the electromagnetic induction, i.e., when there is a relative change in magnetic field linked with a coil, there is an induced current in the coil.                          Electric generators are of two types DC generators and AC generators  (Alternators). The diagram of electric generator is shown below Working                          As the coil rotates, the two rings also rotate with the coil. The brushes P and Q always keep contact with the rotating ring. When the coil starts rotating with the arm AB moving up and CD moving down (clockwise) cutting the magnetic lines, then according to Fleming's right-hand rule, a current is induced in these arms in the direction ABCD. After a half rotation, arm CD moves down and AD moves up, hence the direction of current in each segment changes, giving rise to net induced current in the direction DCBA. Thus, after every rotation polarity of the current in the respective arm changes, thereby generating an alternating current.              (2)