Answer: (1/2)LI2.
- A LI
- B LI2
- C (1/2)LI2
- D L/I
Correct answer: C. (1/2)LI2
Explanation: Magnetic energy in inductor U = (1/2)LI2. Analogous to (1/2)mv2 for kinetic energy.
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.