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⚛️ Physics  ·  Electromagnetic Induction  ·  NEET & JEE

The EMF induced in a rod of length L moving at speed v perpendicular to a field B is:

Answer: BLv.

  • A BLv
  • B B divided by Lv
  • C BLv²
  • D L divided by Bv

Correct answer: A. BLv

Explanation: The motional EMF is ε = BLv.

EMF is Induced Only While Flux is ChangingΦmagnet approachingmagnet stationary inside coilEMFEMF ≠ 0 (flux changing)EMF = 0 (flux constant)t

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.

Read the full Electromagnetic Induction notes →