Answer: 9 J.
- A 3 J
- B 6 J
- C 9 J
- D 18 J
Correct answer: C. 9 J
Explanation: U = (1/2)LI² = 0.5·2·9 = 9 J.
As a magnet approaches a coil, flux rises steadily and a constant non-zero EMF is induced (Faraday's law). Once the magnet stops moving, flux stays constant and the induced EMF drops to zero - EMF only exists while flux is actively changing.
Concept context
Faraday's and Lenz's laws, motional EMF, self/mutual inductance, eddy currents, and the AC generator - how a changing magnetic flux creates an electric current.