JEE Physics 2023 Question with Solution

Given: A bar magnet is dropped through a metallic cylindrical pipe and compared with a non-magnetic bar of the same geometry and mass.

Find: Which assertion-reason option is correct.

When the magnet falls through the metallic pipe, the magnetic flux linked with the pipe changes. This induces eddy currents in the pipe.

According to Lenz's law, the induced eddy currents produce a magnetic field that opposes the change causing them. Therefore, the induced magnetic effect opposes the motion of the falling magnet.

Because of this opposing force, the magnet descends more slowly than a non-magnetic bar of the same mass and geometry.

So, Assertion $A$ is true.

Also, the statement in Reason $R$ correctly states that eddy currents are produced in the metallic pipe and they oppose the motion of the magnetic bar. Hence, Reason $R$ is true.

Since the reason directly explains why the magnet takes more time to come down, Reason $R$ is the correct explanation of Assertion $A$.

Therefore, the correct option is D.

The solution shows "The Correct Option is A", but the accompanying explanation and final answer clearly conclude that both $A$ and $R$ are true and $R$ correctly explains $A$. Hence the defensible correct option from the listed choices is D.