A metal ring is placed on the core of a coil carrying alternating current. The ring
Correct answer: B. is thrown upwards, because the induced current opposes the changing flux
- A. is attracted into the coil
- B. is thrown upwards, because the induced current opposes the changing flux
- C. remains unaffected
- D. melts instantly
Explanation
The changing flux induces a current in the closed ring, and by Lenz's law the ring's field opposes the coil's, so the two repel and the ring jumps. Cutting a slit in the ring stops the induced current from circulating and the effect disappears, which is the standard control. The ring also warms up because of the current flowing in its own resistance.
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About Lenz's Law
Lenz's law states that the induced current flows in a direction that opposes the change in magnetic flux producing it. Questions connect this rule with Faraday's law, magnetic flux, induced emf and the direction of motion or current, while distinguishing opposition to flux change from opposition to the magnetic field itself.
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