Faraday’s Laws of Electromagnetic Induction

Faraday’s Laws of Electromagnetic Induction:

Faraday summed up the above facts into two laws known as Faraday’s Laws of Electromagnetic Induction.

First Law: It states : Whenever the magnetic flux linked with a circuit changes, an e.m.f. is always induced in it.

or

Whenever a conductor cuts magnetic flux, an e.m.f. is induced in that conductor.

Second Law: It states : The magnitude of the induced e.m.f. is equal to the rate of change of flux-linkages.

Explanation. Suppose a coil has N turns and flux through it changes from an initial value of Φ1 webers to the final value of Φ2 webers in time t seconds. Then, remembering that by flux-linkages mean the product of number of turns and the flux linked with the coil, we have

Initial flux linkages = NΦ1, add Final flux linkages = NΦ2

∴ induced e.m.f. e = (NΦ2 – NΦ1/t ) Wb/s or volt or e = N (Φ2 – Φ1/t ) volt

Putting the above expression in its differential form, we get

e = d/dt (N Φ) = N d/dt volt

Usually, a minus sign is given to the right-hand side expression to signify the fact that the induced

e.m.f. sets up current in such a direction that magnetic effect produced by it opposes the very cause

producing it.

e = -N dΦ/dt volt