A coil is held in a magnetic field perpendcular to its plane. When will the average e.m.f. induced in the coil be maximum ? (i) magnetic field is strong but it does not change (ii) magnetic field is small, but its rate of change is large (iii) magnetic field is large, but its rate of change is small.

Explanation

As `e = (d phi)/(dt) = - (d B)/(dt)`, therefore, induced e.m.f. will be maximum, when rate of change of magnetic field is large, even through the field is small. Choice (ii) is correct.