Question

Figure shows planar loops of different shapes moving out of or into a region of magnetic field which is directed normal to the plane of loops downwards. Determine the direction of induced current in each loop using Lenz’s law.

Answer 1

(a) In Fig. (i) the rectangular loop abcd and in Fig. (iii) circular loop are entering the magnetic field, so the flux linked with them increases; The direction of induced currents in these coils, will be such as to oppose the increase of magnetic flux; hence the magnetic field due to current induced will be upward, i.e., currents induced will flow anticlockwise. 

(b) In Fig. (ii), the triangular loop abc and infig. (iv) The zig-zag shaped loop are emerging from the magnetic field, therefore magnetic flux linked with these loops decreases. The currents induced in them will tend to increase the magnetic field in downward direction, so the currents will flow clockwise. 

Thus in fig. (i) Current flows anticlockwise, 

In fig. (ii) Current flows clockwise, 

In fig. (iii) Current flows anticlockwise, 

In fig. (iv) Current flows clockwise.