Answer: 0.32 N.
- A 0.16 N
- B 0.32 N
- C 0.64 N
- D 1.28 N
Correct answer: B. 0.32 N
Explanation: The emf is Blv = 0.8 × 0.5 × 4 = 1.6 V. Current is 1.6/2 = 0.8 A. Hence F = BIl = 0.8 × 0.8 × 0.5 = 0.32 N.
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.