Question:
A magnet with north pole down is dropped along the axis of a closed solenoid. Observed from top, the induced current is
A magnet with north pole down is dropped along the axis of a closed solenoid. Observed from top, the induced current is
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Lenz’s law always opposes change in magnetic flux, not the flux itself.
Updated On: Jul 2, 2026
- anticlockwise
- clockwise
- no current
- constant velocity
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The Correct Option is A
Solution and Explanation
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: \[ \boxed{(A)\ \text{anticlockwise}} \]
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: \[ \boxed{(A)\ \text{anticlockwise}} \]
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