Answer: Rate of change of magnetic flux.
- A Rate of change of current
- B Rate of change of magnetic flux
- C Magnetic field strength
- D Conductor length only
Correct answer: B. Rate of change of magnetic flux
Explanation: Faraday's law: EMF = -d(phi)/dt. Induced EMF equals the negative rate of change of magnetic flux.
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.