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Homework Help: Magnetic fields and conduction

  1. Mar 23, 2008 #1
    1. The problem statement, all variables and given/known data

    12.5A, 3.1x10^-5

    2. Relevant equations

    How far from a long conductor passing a current of 12.5A is the magentic field of strength 3.1x10^-5T?

    3. The attempt at a solution

    B= uI/2(pi)r

    r=uI/2(pi)B
    =(4pi)(12.5A)/ 2(pi)(3.1x10^-5T)
    = 8.1x10^5m
     
  2. jcsd
  3. Mar 23, 2008 #2
    u_0 isn't 4 pi.
     
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