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Emf induced in a ring rolling in non-uniform magnetic field

  1. Aug 9, 2011 #1
    I have got a doubt regarding the situation when a ring rolls in a non-uniform magnetic field. We can see that the flux linkage is increasing (considering dB/dt to be positive). So EMF should be induced in the loop.
    But if we join any two points, say the instantaneous axis of rotation and the diametrically opposite point, we will get two rods completing a loop with EMFs being induced in opposite direction and equal in magnitude, which should cancel out (I am not talking about the potential difference between these points, I am just talking about the EMF of the loop).

    This contradiction is confusing me. Please help.
  2. jcsd
  3. Aug 9, 2011 #2


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    Are you sure they are equal in magnitude? Why should they be?
  4. Aug 9, 2011 #3
    If the ring is spinning in a non-uniform B field. The free electrons in the ring would each experience a different Lorentz force at opposite sides of the ring because B would be different.
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