Explain with a labelled diagram, the principle, construction and working of an electric generator.

Explanation

Electric Generator (AC)
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:
(a.) Rectangular coil: A large number of turns of insulated copper wire wound on iron core in rectangular shape forms a coil ABCD as shown in figure.
(b.) Strong magnets: The coil is placcd in between two pole pieces (N and S) of a strong magnet. This provides a strong magnetic field.
(c.) Rings: The two ends of the coil are connected to two rings `R_(1) and R_(2)`. These rings rotate along with the coil.
(d.) Brushes: Two carbon brushes B1 and B2 are used to press the rings.
(e.) 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:
(a.) When the axle is rotated with the help of a machine from outside, the coil ABCD starts rotating.
(b.) On rotating the axle, the brạnch AB move upwards and branch CD move downwards hence coil ABCD rotates clockwise.
(c.) According to Fleming's right hand rule, electric current flows in the direction `ArarrBrarrCrarrD` . Therefore, current flows from `B_(2) to B_(1)` in the external circuit through galvanometer.
(d.) After half rotation, the branch AB and CD exchange their position and the induced current flows as `DrarrCrarrBrarrA`.
(e.) Since, branch BA is in contact with brush `B_(1)` and branch DC is in contact with `B_(2)`, current flow from `B_(1)` to `B_(2)` in the external circuit i.e., in the direction opposite to the previous half rotation.
(f.) This repeats after every half rotation and in this way, alternate current is produced using AC generator.