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Homework Help: Maximum current a superconductor can carry

  1. Nov 2, 2012 #1
    1. The problem statement, all variables and given/known data
    Niobium metal becomes a superconductor when cooled below 9 K. Its superconductivity is destroyed when the magnetic field inside the superconductor exceeds 0.100 T. Determine the maximum current a 3.00-mm-diameter niobium wire can carry and remain fully superconducting, in the absence of any external magnetic field.

    2. Relevant equations
    So we know if B > 0.1 T, the superconductor is destroyed, thus we have to find an I that will not make it exceed such figure. The formula I was thinking of using is:

    B = (μ0I)/(2∏r)

    r = 1.5 mm, or 0.00015m
    B = 0.100 T
    Solve for I

    3. The attempt at a solution

    Solving for I: (B2∏r)/(μ0) = I

    Does that make sense? I can't find much info in my book about superconductors to guide me
  2. jcsd
  3. Nov 4, 2012 #2
    Anyone? I'm trying to do as good as possible in these assignments, but this one has got me stumped :/
  4. Nov 4, 2012 #3
    That's the way I would do it. You'll have to assume a DC current is flowing so that the current is spread evenly across the wire cross section. Keep in mind you will be calculating B inside the wire.. how much of the current is enclosed when applying Ampere's Law?
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