As shown in figure two identical conducting rings of radius r are placed in magnetic field. In figure (a) magnetic field increasing at the rate of 0.3 T/s and in figure(b) magnetic field decreasing at the rate of 0.2 T/s. The direction of current in ring (a) and ring(b), when observe from top are .

Question

Accepted Answer

(2) Anticlockwise, Anticlockwise. Idea: Lenz's law - the induced current's own field opposes the change in flux, not the flux itself. Seen from the top, an anticlockwise current makes a field out of the page inside the ring, a clockwise current one into the page. Read the figure first: panel (a) is drawn with crosses, so its field is into the page; panel (b) is drawn with dots, so its field is out of the page. Ring (a): the inward field is growing at 0.3 T/s. To oppose the growing inward flux the induced field must point out of the page, so the current is anticlockwise. Ring (b): the outward field is dying away at 0.2 T/s. To oppose the falling outward flux the induced field must also point out of the page, so this current is anticlockwise too. The two rates fix how big the currents are, not which way they go. So the currents are anticlockwise in (a) and anticlockwise in (b).

Step-by-step solution

Why the other options are wrong