Question

A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,

• A. the induced current will flow in the anticlockwise direction.
• B. the induced current will flow in the clockwise direction.
• C. no induced current will flow in the solenoid.
• D. the magnet will fall with a constant velocity.

Hint:

Lenz’s law always opposes change in magnetic flux, not the flux itself.

Answer 1

The Correct Option is A

Concept: Use Faraday’s law and Lenz’s law: induced current opposes change in magnetic flux.

Step 1: Direction of magnetic field - North pole of magnet is facing downward. - Field lines emerge from north pole. - So flux through solenoid is directed downward and increases as magnet approaches.

Step 2: Apply Lenz’s law Since downward flux is increasing, solenoid must oppose it by creating upward magnetic field.

Step 3: Right-hand rule To produce upward magnetic field: - Thumb upward - Fingers curl anticlockwise (viewed from top) Final Answer: \[ \boxed{(A)\ \text{anticlockwise}} \]