Faraday’s law of electromagnetic induction
Electromagnetic induction – As we know when electric current passes through a conductor then magnetic field developed across the conductor , first discovered by Oersted . But Michael Faraday found its converse is also possible i.e. Whenever magnetic field changes around a coil ( and hence magnetic flux linked across the coil changes ) electric current induced in the coil , such phenomena is called electromagnetic induction (E.M.I.) . And the current induced in the coil is known as induced current and emf developed is known as induced emf .
Faraday’s laws of electromagnetic induction – On the basis of experiments Faraday’s gave the two laws –
(i) Whenever electric flux linked with the coil changes then emf induced in the coil . The emf lasts only for the time for which flux is changing .
(ii) The magnitude of induced emf is directly proportional to rate of change of magnetic flux linked with the coil. I.e. emf e α ɸ2 – ɸ1 / t (time taken).
Or e = – k dɸ/ dt . ( Here negative sign shows the induced emf oppose any change in the magnetic flux through the coil.
After combining these two equations Faraday’s law states “ An induced emf is produced in any closed circuit if there is a varying magnetic flux . the magnitude of induced emf is equal to the negative of the time rate change of magnetic flux through the circuit .”