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Homework Help: Ampere's Law

  1. Dec 14, 2012 #1
    1. The problem statement, all variables and given/known data

    Consider two infinitely long cylinders with radius a and b and currents:

    J =

    (Jo r)/a for r less than a

    -Jo for a less than r less than b

    Find the magnetic field in

    1) r less than a

    2) a less than r less than b

    3) r greater than b

    2. Relevant equations

    3. The attempt at a solution

    I think I was able to compute the magnetic field for r less than a

    using Ampere's law

    H 2 pi r = (the integral from 0 to a of) (Jo r) /a 2 pi r dr

    the result that I found for H was H = (Jo r squared )/3a

    In the other cases Im confused about the integration limits and the addition of magnetic fields.
    How can I find the magnetic field for a less than r less than b, and for r greater than b ?

    I would appreciate some help, thanks a lot.
  2. jcsd
  3. Dec 15, 2012 #2
    Can anyone give me an idea how to solve this please? I ll truly appreciate it.
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