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Question 20190
JEE Physics · Hard

Electromagnetic Induction and Alternating Current: Faraday's Disk — Homopolar Generator MCQ

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Faraday's Disk — Homopolar GeneratorHardQuestion 20190

Question

In Faraday's disk (homopolar generator), when the disk rotates, EMF is induced because:
  1. A
    The flux through the circuit changes
  2. B
    Charge carriers in the rotating disk experience a Lorentz force along the radius
    Correct
  3. C
    The magnetic field changes with time
  4. D
    The resistance changes with speed

Correct answer

Charge carriers in the rotating disk experience a Lorentz force along the radius

Explanation

Even though flux through the circuit is constant, the Lorentz force on each radial element of the rotating disk pushes charge from centre to rim (or vice versa), building up an EMF. This is a case where Faraday's law using flux gives the wrong answer without careful treatment — only the motional EMF approach works.

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