Answer: Conservation of energy.
- A Faraday's law only
- B Conservation of energy
- C Newton's second law
- D Ampere's law
Correct answer: B. Conservation of energy
Explanation: Lenz's law: induced current opposes the change causing it: this is energy conservation (opposing change requires work).
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.