Answer: mu0 n1 n2 Al.
- A mu0 n1 n2 Al
- B mu0 n1 n2 A
- C mu0 n1 A/n2
- D mu0 n12 Al
Correct answer: A. mu0 n1 n2 Al
Explanation: M = mu0 n1 n2 A l (for closely wound coaxial solenoids). Flux linkage from inner to outer = n2 l x mu0 n1 I x A.
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.