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Help this problem cost me much time

  1. Aug 14, 2006 #1
    english is my second language,if there are some wrong in the sentence ,don't laugh at me :redface:

    dig a columniform cavity in a infinity uniformity magnetic medium.the

    cavity's radius is r and the high is h,and the axis of the cavity parallels

    the direction of magnetization M in the medium.
    question:1)when h>>r,the magnetic field strength H of the point in the cavity = the magnetic field strength H in the medium.
    2) when r>>h,the magnetic induction strength B of the point in the cavity = magnetic induction strength B in the medium.
    haw to testify ?
  2. jcsd
  3. Aug 16, 2006 #2

    Andrew Mason

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    I'll start by trying to translate the question. Could you tell us what your first language is?

    Make a cylindrical cavity through an infinitely large uniformly magnetic medium. The cylinder's radius is r and its height is h and the axis of the cylinder is parallel to the direction of the magnetic field in the medium.

    1) when h>>r, the magnetic field strength H at any point in the cavity is equal to the magnetic field strength in the medium

    2) where r>>h, the magnetic induction B of the point in the cylinder is equal to the magnetic induction B in the magnetic medium.

    How do you explain this?​

    Perhaps that will get a response for you.

    Last edited: Aug 16, 2006
  4. Aug 16, 2006 #3
    thank you very much,my first language is chinese.i'm not good at english,don't laugh at me . there is no problem in your interpretation.
  5. Aug 16, 2006 #4

    Andrew Mason

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    Ok. I was a little unsure about the difference between magnetic induction and the magnetic field at first, but I think I understand the problem now.

    The magnetic field strength H is the magnetic field that would exist in the absence of the magnetic material (ie in a vacuum), divided by [itex]\mu_0[/itex], the permeability of free space. The magnetic induction B, is the actual measured magnetic field (which depends on the permeability of the magnetic material). H represents a kind of fundamental magnitude of the magnetic field that is independent of the permeability of the material.

    [tex]B = \mu H[/tex]

    Does that help you to answer the question?

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