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Field due to Magnetic Materials

  1. Sep 4, 2014 #1
    Say you have a paramagnetic (or diamagnetic) sphere (or some other shape) and you apply a field of H = 10 Oe. Now, we have [itex]H=(1/\mu)B-M[/itex].

    That would indicate that outside of the material, B and H are essentially the same, right? B = 10 Gauss, outside of the material.

    But shouldn't the magnetization of the material affect the field outside, as well?

    Certainly if these were permanent magnets it would. I would expect that in all cases we would want to integrate M over the volume of our shape, then calculate the field from that dipole moment. But these equations seem to suggest that would be zero. Or am I misunderstanding their terms?

    Thanks!
     
  2. jcsd
  3. Sep 4, 2014 #2

    clem

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    The magnetization of the material affects both fields outside, but B and H are still equal.
     
  4. Sep 4, 2014 #3
    So let's say that I have a sphere (radius R) of permeability [itex]\mu[/itex] and I apply a field H = 10 Oe. Would it be correct to say that the field around the sphere is not uniformly 10 Oe, because the sphere changes its value? (And also correct that B = H?)

    If so, what good is [itex]H=(1/\mu_0)B-M[/itex]?
     
  5. Sep 5, 2014 #4
    Perhaps my question is not totally clear.

    In H=(1/u)B-M, is H the applied field, or the total field, after the contributions of the magnetic material? And if it is the total field, how does this do us any good? I have always heard that H is what you "set on the dial."
     
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