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Enclosed superconducting loop

  1. May 1, 2012 #1

    If I take an enclosed superconducting wire loop, and apply a time dependent magnetic field in the space enclosed by the wire ( and therefore a time dependent magnetic flux) , this should induce electromotive force ( according to faraday's law). However any potential difference should not be possible due to the vanishing electrical resistance. I understand that a superconductor acts to cancel any magetic field within the superconductor, but here the magnetic field can be in the middle of the space enclosed by the loop, distanced from the superconductor itself.

    Any help would be appreciated
  2. jcsd
  3. May 1, 2012 #2
    The current in the loop generates a mag field opposite to the external mag per law of Lenz. Equilibrium is reached when cancellation occurs not only inside the conductor, but in the interior of the loop as well. The plane formed by the loop receives an incident mag field, time varying. A Lorentz force moves the electrons in the conductor around the loop. A mag field surrounds this conductor. Law of Lenz describes this field as having a polarity opposite to the external mag field. Use the right hand rule, and the internal mag field extends into the interior of the loop.

    Eventually the fields will cancel. Since J = sigma*E, per Ohm's law, sigma is infinite for a superconductor, so E has to be zero, likewise potential is zero. Does this help?

    Last edited: May 1, 2012
  4. May 1, 2012 #3

    Thanks allot.
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