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⚛️ Physics  ·  Electromagnetic Induction  ·  NEET & JEE

Induced EMF in a loop rotating in magnetic field at angular velocity omega (area A, field B):

Answer: BAomega sin(omega t).

  • A BAomega
  • B BAomega cos(omega t)
  • C BAomega sin(omega t)
  • D BA sin(omega t)

Correct answer: C. BAomega sin(omega t)

Explanation: Phi = BA cos(omega t). EMF = -d(phi)/dt = BA omega sin(omega t). Maximum EMF = BAomega.

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 →