they press the slip rings to obtain current from the coil. When these brushes are connected to external devices like TV, radio, we can make them work with current supplied from ends of carbon brushes.

The current obtained by this process changes its direction alternatively for each half cycle as shown in fig.-17(b).

This current is called alternating current (AC) in which, the direction of charge flow reverses periodically. So AC possesses certain frequency. The generator that we discussed here is called AC generator.

• How can we get DC current using a generator? • What changes do we need to make in an AC generator to be converted into a DC generator?

Let us find out.

If two half slip rings are connected to ends of the coil as shown in fig.-17(c), the AC generator works as DC generator to produce DC current.

Let us see how it works.

When the coil is in the vertical position the induced current generated during the first half rotation, rises from zero to maximum and then falls to zero again. As the coil moves further from this position, the ends of the coil go to other slip rings. Hence during the second half rotation, the current is reversed in the coil itself, the current generated in the second half rotation of the coil is identical with that during the first half of direct current (DC) as shown in fig.-17(d) for one revolution.



In generators, mechanical energy is converted ibbye nto the electrical energy.