Answer: (1/2)LI 2.
- A LI
- B LI<sup>2</sup>
- C (1/2)LI<sup>2</sup>
- D L/I
Correct answer: C. (1/2)LI<sup>2</sup>
Explanation: Magnetic energy in inductor U = (1/2)LI<sup>2.</sup> Analogous to (1/2)mv<sup>2</sup> 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.