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Magnetizing force

  1. Feb 19, 2010 #1

    How does magnetizing force of a permanent magnet relate to magnetizing of steal rods of different sizes?

    i.e. if I bring a permanent magnet and a piece of steal of the same sizes, put them together, the steal piece becomes magnetized.
    what if I bring a much much larger piece of steal for the same size permanent magnet. how much magnetizing force will be in the tip of that big one?

    is there a formula which takes size in account?

  2. jcsd
  3. Feb 20, 2010 #2
    It is complicated and all formulas take size into account. The attractive effect of magnets is not straight forward. At least I don't know any better way to calculate forces than to calculate the whole magnetic field. Maybe you will find some rule of thumb in an engineering book.
  4. Feb 20, 2010 #3
    For steel, you probably will need H = ~1000 amp-turns per meter. See


    For permanent magnet materials (e.g., neodymium), see Fig. 2 on page 7 of


    You will probably need over 800,000 to 3 million amp-turns per meter. The can be done using current pulses.

    Bob S

    added attachment for magnetizing neodymium magnets. Looks like 3 MA/m (3 million amps per meter) are required.

    Attached Files:

    Last edited: Feb 20, 2010
  5. Feb 23, 2010 #4
    A magnet works by adding electrons to the atom to create an unstable molecular structure in a iron molecule witch creates action at a distance. The process of energising the atom in the iron molecule to give an uneven amount of electron, creates fields and poles to keep a stable balance between protons and electron. The magnet attracts more protons to even out the instability.

    Saying this, it depends on the excitement of the electrons in the iron molecule witch will affect the energy transferred. but you can only energize a molecule so much until it explodes.
  6. Feb 23, 2010 #5
    If I build a magnet that can pull all the protons out of water, will I have only oxygen left?

    Bob S
  7. Feb 24, 2010 #6
    In an inductance curve of a core where the Magnetizing Force in ampere-turns in the horizontal axis and [tex]A_L{}[/tex]-value = [tex]\mu[/tex] * H/N[tex]^{2}[/tex] in the vertical axis.
    What exactly does the value of vertical axis mean?
    and what does [tex]A_L{}[/tex]-value stand for?

    Many thanks
  8. Feb 24, 2010 #7
    If a magnet powerful enough to pull the protons from water, then it would also pull the proton from oxygen not just the hydrogen. Maybe this would cause a breaqkdown of the basic atomic structure of the owygen also?
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