Two concentric loops with different radii lie in the same plane. The current in the outer loop is clockwise and increases with time. The induced current in the inner loop is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → anticlockwise
By Lenz’s law, the induced current flows so as to oppose the change in magnetic flux that produces it.
A clockwise current in the outer loop produces, inside it, a magnetic field directed into the plane of the loops (right-hand rule, viewing the loops from the side where the current looks clockwise). As the current increases, this inward flux through the inner loop increases.
To oppose the increase, the inner loop must produce a field out of the plane inside it, which needs an anticlockwise current.
Why the other options are incorrect
Option (1) clockwise — Incorrect. A clockwise current would add to the inward flux and so assist the change, which contradicts Lenz’s law.
Option (2) Zero — Incorrect. The induced current is zero only when the flux is steady; here the outer current is increasing.
Option (4) alternating current. — Incorrect. The outer current increases steadily in one direction, so the induced current keeps one direction; it would alternate only if the outer current alternated.