Answer: 20 V.
- A 10 V
- B 40 V
- C 5 V
- D 20 V
Correct answer: D. 20 V
Explanation: Self-induced emf = L(dI/dt) = 0.5 × (6 - 2)/0.1 = 0.5 × 40 = 20 V.
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.