Principle: Electric generator works on the principle of
electromagnetic induction. It converts mechanical energy into electrical
energy.
Construction: A loop ABCD is rotated in a
permanent magnetic field. Its ends are connected with two semi-circular rings
as shown in the figure below. These rings are insulated from each other and can
slide while remaining in contact with brushes X and Y. A
galvanometer is connected between the two ends of the brush.
Working: On rotating the loop in a magnetic field, the side AB moves upward and
the side CD moves downwards. Thus magnetic flux linked with the loop changes
and a current is induced in it whose direction can be determined by Flemings
right hand rule.In the figure, the current is flowing through the path
B-A-G-D-C.
After half rotation, the ring P comes in contact with brush Y and the ring Q,
comes in contact with brush X. Thus, the brush X is always in contact with the
side moving upwards and brush Y is always in contact with side moving downwards
as a result of which the current flows in one direction. This current is called
direct current. This type of generator is called D.C. generator. Similarly,
instead of a half ring, if a full ring is used then, A.C. current can be
generated and such a generator is called an A.C. generator.