In which of the loops shown in the figure is the direction of the induced current a → c → b? In each loop the magnetic field is uniform and perpendicular to the plane of the loop (×: into the page, : out of the page), and it is changing as stated below the loop.

Question

Accepted Answer

(4) (4). Idea: Lenz's law says the induced current sets up a field that opposes the change in flux through the loop. As drawn, going a → c → b (top, lower right, lower left) is clockwise, and a clockwise current makes a field into the page inside the loop. So the induced field must point into the page. That happens when the flux out of the page is increasing, or the flux into the page is decreasing. (1) Into the page, increasing: induced field out of the page, anticlockwise (a → b → c). (2) Out of the page, decreasing: induced field out of the page, anticlockwise (a → b → c). (3) Steady field: no change in flux, no induced current. (4) Out of the page, increasing: induced field into the page, clockwise, that is a → c → b. So the answer is loop (4).

In which of the loops shown in the figure is the direction of the induced current a → c → b? In each loop the magnetic field is uniform and perpendicular to the plane of the loop (×: into the page, : out of the page), and it is changing as stated below the loop.

Step-by-step solution

Why the other options are wrong