According to Fleming’s right hand rule, when the thumb and the central finger of right hand are kept perpendicular to each other, the thumb shows the direction of motion of the conductor, the first finger the direction of magnetic field when the current induced is in the direction of central finger.

AC generator

Principle: It works on the principle of electromagnetic induction. Induced current is produced, whenever current is produced.

Construction: A generator consists of mainly four parts, namely coil, magnets, slip rings and brushes just like an electric motor.

Coil: A large number of insulated copper wires wound on a rectangular frame.

Magnets: A large permanent magnet to provide a strong a magnetic field.

Slip rings: Two solid rings connected the two ends of the coil used to convey the current produced to outside circuit.

Brushes: Two carbon brushes remain in sliding contact with slip rings.

Working: The coil of the generator is rotated with the help of an axel. When coil rotates, it cuts through the magnetic filed of the magnet. So a current is induced in the coil by electromagnetic induction. The direction of this current is given by Fleming’s right hand rule.

As the coil turns clockwise, arm AB moves up and arm CD goes down. The direction of the current is from A to B and C to D. When after half rotation CD starts going up and AB starts coming down, the direction of the current in the coil also reverses. Now it is from D to C and from B to A. This alternating current with the help of slip rings which are in sliding contact with brushes B₁ and B₂ is given out to the circuit. Hence the current produced by the generator is alternating and such a generator is called AC generator.

To get direct current in place of slip rings, split rings are used so that one brush is always in contact with the arm that goes downward. Then the current given out to the outer circuit is in the same direction. This type of generator is called DC generator.