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A bar magnet is dropped through a vertical conducting ring. The magnet:
AFalls faster than free fall
BFalls at exactly g
CFalls slower than free fall
DAccelerates indefinitely
Answer & Solution
Correct answer: C. Falls slower than free fall
1. As the magnet approaches the ring, flux through the ring increases.
2. Lenz's law: induced current opposes the increase — equivalent to the ring repelling the magnet (or attracting it back).
3. So a magnetic drag force acts UPWARD on the falling magnet — it falls slower than g.
4. Energy 'missing' from KE shows up as ohmic heating in the ring.
_Source: NCERT Class 12 Physics Ch 6 §6.5 Lenz's Law (qualitative)_
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