1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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?

  2. jcsd
  3. Sep 4, 2014 #2


    User Avatar
    Science Advisor

    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."
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook