electric generator

 

Electric Generator

 

An electric generator converts the mechanical energy into electrical energy. In an electric generator, mechanical energy is used to rotate the conductor in a magnetic field to produce electricity. It works on the basis of electromagnetic induction.

An electric generator consists of the rotating rectangular coil ABCD which is placed between the poles of a permanent magnet.

There are two rings R1 and R2. The both rings R1 and R2 are connected by the ends of the rectangular coil. the inner side of the rings are made insulated. Brushes B1 and B2 are the electrical contact which produce the electric current between the stationary wires. These brushes B1 and B2 are kept pressed separately on the rings R1 and R2 respectively.

The both two rings R1 and R2 are internally attached to an axle. The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field.

The outer ends of the two brushes are connected to the galvanometer. The galvanometer is used to show the flow of the current in the given external circuit.

When the coil ABCD is rotating in the clockwise direction with the help of the axle attached to the rings R1 and R2. And on rotating the coil in the clockwise direction ,  the arms AB moves up and the arms CD moves down. And the magnetic field in the coils is produced by the permanent magnet.

By applying the fleming’s right hand rule, the induced current are set up in these arms along with direction AB and CD. Thus, an induced current is flowing in the direction of the ABCD. If the number of turns in the coil is larger then the current is also generated in large through the coil. This means that current in the external circuit is flowing from B2 to B1.

When the half rotation is completed, the arms CD moves up and the arms AB moves down. Due to this results, the direction of the induced current in both the arms is changed. Thus, an induced current is flowing in the direction DCBA. The current in the external circuit is flowing from B1 to B2.

Thus after every half rotation , the polarity of the current in the respective arms changes. Such a current which changes the direction after equal intervals of time. That is called an alternating current (or known as AC). And this device as called as AC generator.

 

 

DC generator:--

 

In order to get DC current (direct current) , a split ring type commutator must be used. With this arrangements, one of the brush is in contact with the arm moving up in the field.

While the other brush is in contact with arm moving down. The use of spilt ring in the DC generator is that the direction of the current flowing in the coil is reversed. And the DC current is generated. Thus, a unidirectional current is produced. Thus, this generator is called DC generator.