Question

Draw a neat diagram of an AC generator and explain its working.

Answer 1

An alternating current (AC) generator, consists of a rotating rectangular coil ABCD called armature placed between the two poles of a permanent magnet. The two ends of this coil are connected to the two slip rings S₁ and S₂. The inner sides of these rings are insulated. Two conducting stationary brushes B₁ and B₂ are kept separately on the rings S₁ and S₂ respectively. The two rings S₁ and S₂ are internally attached to an axle. The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field. Outer ends of the two brushes are connected to the external circuit.

When the coil is rotated, the magnetic flux linked with the coil changes. This change in magnetic flux will lead to generation of induced current. The direction of the induced current, as given by Fleming’s Right Fland Rule, is along ABCD in the coil and in the outer circuit it flows from B₂ to B₁. During the second half of rotation, the direction of current is along DCBA in the coil and in the outer circuit it flows from B₁ to B₇. As the rotation of the coil continues, the induced current in the external circuit is changing its direction for every half a rotation of the coil.