In 1831, Micheal Faraday formulated two laws on the bases of experiments. These laws are called Faraday's laws of electromagnetic induction.
First Law of Faraday's Electromagnetic Induction state that whenever a conductor are placed in a varying magnetic field emf are induced which is called induced emf, if the conductor circuit are closed current are also induced which is called induced current.
Whenever a conductor is rotated in magnetic field emf is induced which are induced emf.
Second Law of Faraday's Electromagnetic Induction state that the induced emf is equal to the rate of change of flux linkages (flux linkages is the product of turns, n of the coil and the flux associated with it).
Initial flux linkages = Nφ1
Final flux linkages = Nφ2
Change in flux linkages= Nφ2 – Nφ1
If (φ2-φ1)= φ
Then change in flux linkages=Nφ
Rate of change of flux linkages= Nφ/t wb/sec
Taking derivative of right hand side we get
Rate of change of flux linkages= Ndφ/dt wb/sec
Rut according to Faraday's laws of electromagnetic induction, the rate of change of flux linkages equal to the induced emf, hence we can write
= Ndφ/dt volt
Generally Faraday's laws is written as
e = -Ndφ/dt volt
Where negative sign represents the direction of the induced current in the conductor will be such that the magnetic field produced by it will oppose the verb cause produce it.