Physics-
General
Easy

Question

A metal disc rotates freely, between the poles of a magnet in the direction indicated. Brushes P and Q make contact with the edge of the disc and the metal axle What current, if any, flows through R?

  1. a current from P to Q    
  2. a current from Q to P    
  3. no current, because the emf in the disc is opposed by the back emf    
  4. no current, because the emf induced in one side of the disc is opposed by the emf induced in the other side.    

The correct answer is: a current from P to Q

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