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Magnetic pole

  1. Mar 12, 2006 #1
    I started reading Lectures on Electrical Engineering Vol I, Steinmetz. I thought I should be able to understand most of it, but I don't get the first page! It says that: 'The total number of lines of force issuing from a magnet pole is called its magnetic flux. The magnetic flux, phi, of a magnet pole of strength m is, phi = 4*pi*m '.

    What does this mean, and what are the units of m? I thought that because the magnetic lines always formed closed circuits that the flux through a closed surface around a magnetic pole should be zero. I'd really appreciate it if someone could explain this to me.
  2. jcsd
  3. Mar 13, 2006 #2

    Meir Achuz

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    If a magnetic pole existed, the equations for a pole of strength m would by much like those for a charge q.
    1. "Magnetic flux" here means [tex]\oint{\bf B\cdot dS}[/tex].
    2. Just like Gauss's law, [tex]\oint{\bf B\cdot dS}=4\pi m[/tex],
    in Gaussian units.
    3. In Gaussian units, the units of m would be gauss-cm^2.
    In SI units, I think it would be Webers (Whoever he was).
    3. "I thought that because the magnetic lines always formed closed circuits...". That is only in the absence of a magnetic monopole.
    With magpoles, magnetostatics becomes just like electrostatics.
    I suspect your text is using one end of a long bar magnet as an abstraction for a magnetic pole, and not including the B inside the magnet
    in finding the flux of 4\pi m.
  4. Mar 13, 2006 #3


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    Yes, it seems that this book starts off really badly...
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