Electromagnetic induction is the phenomenon in which whenever the magnetic flux linked with a closed circuit changes with time, an electric current is induced in the circuit.
When the magnetic flux linked with the circuit changes with time a current is induced in the circuit.
The direction of the induced current is reversed if the magnetic field begins to decay instead of growing with time.
The magnitude of induced emf is proportional to the rate of change of the magnetic field.
If be the magnetic flux linked with a circuit at any time then the laws of electromagnetic induction can be expressed mathematically as
Here, the negative sign indicates that the induced emf opposes the cause of the production of emf (change in the magnetic flux).