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Additionl field proportional to magnetisation?

  1. Feb 23, 2012 #1
    Magnetisation of a sample is net dipole moment per unit volume i.e. M = m(net) / V

    It turns out that magnetic field due to the material is proportional to magnetisation
    i.e. B(magnetic field due to material) = μM
    Any explanation to this? It should be proportional but any proof for this or is it just experimental
  2. jcsd
  3. Feb 23, 2012 #2


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    hi jd12345! :smile:
    isn't it B = µo(M + H) = µH ?

    M and H are measured in electric units, as electric current/distance (Am-1),

    (magnetic dipole moment is charge times distance/time, = distance times charge/time = distance times electric current, in A.m)

    but B is measured in magnetic units, as magnetic flux/area (Wb.m-2)

    there's no fundamental reason for this … they're all the same thing! :rolleyes: … it's just more convenient in practice! :biggrin:

    so to convert between these different species of units, we must have a universal conversion factor, and that's µo (in Wb.A-1m-1 or T.m.A-1) :wink:

    µ (as opposed to µo) is just a trick to make it look as if B is proportional to H on its own
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