Question

Assertion (A): It is difficult to move a magnet into a coil of large number of turns when the circuit of the coil is closed.
Reason (R): The direction of induced current in a coil with its circuit closed, due to motion of a magnet, is such that it opposes the cause.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false and Reason (R) is also false.

Hint:

Lenz's Law states that the direction of the induced current is always such that it opposes the change causing it.

Answer 1

The Correct Option is A

This problem presents an assertion and a reason concerning electromagnetic induction. We will now analyze them:

Assertion (A): Moving a magnet into a coil with a large number of turns is difficult when the coil's circuit is closed.

Reason (R): The direction of induced current in a closed-circuit coil, generated by a magnet's motion, opposes the motion that caused it.

The phenomenon described in both the assertion and the reason is governed by Lenz's Law. This law states that the induced current's direction opposes the change that produced it, which is a manifestation of the conservation of energy.

When a magnet is inserted into a coil (particularly one with many turns) and the circuit is complete, a change in magnetic flux induces a current. This induced current generates its own magnetic field, which opposes the magnet's movement. Consequently, greater force is required to move the magnet into the coil compared to when the coil's circuit is open. This validates the assertion.

The reason accurately reflects that the induced current's direction opposes the event that initiated it (the magnet's movement). Therefore, both the assertion and the reason are valid, and the reason correctly explains the assertion.

Consequently, the appropriate option is:
Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).