In co-axial concentric coils of radius `r_(1)` and `r_(2)` such that `r_(1) lt lt r_(2)` Fig. find direction of induced current when K is (i) pressed (ii) released.

Explanation

(i) When key K is pressed, current in outer coil increases from 0 to maximum. Current induced in inner coil opposes the growth of current in outer coil, by flowing in the opposite direction, i.e. in anticlock wise direciton, as shown in Fig. (ii) When key K is released, current in outer coil decreases from maximum to zero. Current induced in inner coil opposes the decay of current in outer coil, by flowing in the same direction, i.e. in clockwise direction as shown in Fig.