plz...i can't undrstd working of a.c generator??

An AC generator works on the principle of electromagnetic induction and is used to convert mechanical energy to electrical energy. Here we shall discuss a simple working model of an AC generator.

As shown in the figure we have a rectangular loop in between two poles of a magnet. The ends of the wire are connected to two circular metal rings, which is connected to the external circuit by two graphite brushes. The axle of the rectangular coil is connected to a small water turbine. Water from tape is used to give a controlled rotation to the turbine.

When the faucet of the tap is opened, the flow of water rotates the turbine. As a result the magnetic flux through the rectangular coil changes. This change in magnetic flux induces a current in the rectangular loop.


A is the area of the rectangular loop. B is the strength of the uniform magnetic field.

Initially, the plane of the coil is perpendicular to the magnetic field. The magnetic flux through the coil in this position is,

Ø = B.A = BA cos0 = BA

After time t the coil rotates through an angle θ = ωt. The flux now is,

Ø = BA cos ωt

Using Faraday’s Law, the emf induced in the loop is given by,

The emf varies sinusoidally with time with an angular frequency ω, hence with a time period T = 2π/ω.

For N turns of the coil, the induced emf is,


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