Question

what is electromagnetic induction?

Answer 1

The phenomenon of electromagnetic induction is the existence of an induced current in a circuit (such as a coil) placed in a region where the magnetic field motion changes with the time. The magnetic field may change due to relative motion between coil and magnet placed near the coil as shown in the Fig. 1. We know that a current-carrying conductor also produces magnetic field that changes with a change in the current flowing through it. Thus if a coil is placed near to a current-carring conductor, an induced current in the coil may setup  due to a change in the current through the current-carrying conductor.

Answer 2

When the magnetic flux passing through a closed loop changes with time..
then an emf is induced in the loop in a direction in which it opposes the cause that produces it..
That's the definition of electromagnetic induction..
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