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⚛️ Physics  ·  Electromagnetic Induction  ·  NEET & JEE

A square coil (N=100, side 10 cm, R=10 ohm) rotates at 600 rpm in B=0.1 T. Peak induced EMF:

Answer: 6.28 V.

  • A pi V
  • B 2pi V
  • C 6.28 V
  • D 62.8 V

Correct answer: C. 6.28 V

Explanation: omega = 600/60 x 2pi = 20pi rad/s. E<sub>0</sub> = NBAomega = 100 x 0.1 x 0.01 x 20pi = 2pi = 6.28 V.

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 →