Answer: ½LI².
- A ½LI²
- B the value LI
- C the value ½LI
- D the value LI²
Correct answer: A. ½LI²
Explanation: The magnetic energy stored is U = ½LI².
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.