(a) When there is a relative motion between the coil and magnet, magnetic flux linked with the coil changes. As shown in figure b, the coil is moved towards the north pole of magnet, so the magnetic flux through the coil increases. Similarly, if the coil is moved away from the north pole of magnet, the magnetic flux through the coil decreases. Due to change in the magnetic flux linked with the coil, an e.m.f. is induced in the coil. The induced e.m.f. causes a current to flow in the coil if the circuit of coil is closed.
(b) The magnitude of induced e.m.f. depends on the rate of change of magnetic flux linked with each turn.
(c) The direction of induced e.m.f. depends on whether there is an increase or decrease in the magnetic flux. It can be determined by any of the following two rules (i) Fleming's right hand rule, (ii) Lenz's law.