Question

Explain the construction and working of an electric generator (AC) with the help of a neat diagram.

Answer 1

A generator which converts mechanical energy into electrical energy in the form of alternating current is called A.C. generator.

Construction: The main components of A.C. generator are:

1. Rectangular coil: A large number of turns of insulated copper wire wound on iron core in rectangular shape form a coil ABCD as shown in the figure.
2. Strong magnets: The coil is placed in between two pole pieces (N and S) of a strong magnet. This provides a strong magnetic field.
3. Rings: The two ends of the coil are connected to two rings R₁ and R₂. These rings rotate along with the coil.
4. Brushes: Two carbon brushes B₁ and B₂ are used to press the rings.
5. Axle: The two rings have resistive coating in their inner surfaces and are tightly fitted on the axle and the function of the axle is to rotate with the coil.

Working:

1. When the axle is rotated with the help of a machine from outside, the coil ABCD starts rotating.
2. On rotating the axle, the branch AB move upwards and branch CD move downwards hence coil ABCD rotates clockwise.
3. According to Fleming’s right-hand rule, electric current flows in the direction A→B→C→D. Therefore, current flows from B₂ to B₁ in the external circuit through a galvanometer.
4. After half rotation, the branch AB and CD exchange their position and the induced current flows as D→B→A.
5. Since, branch BA is in contact with brush B₁ and branch DC is in contact with B₂, current flow from B₁ to B₂ in the external circuit i.e., in the direction opposite to the previous half rotation.
6. This repeats after every half rotation and in this way, an alternate current is produced using an AC generator.