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Magnetic Dipole Moment does not include the permeability of free space?

  1. Jun 7, 2005 #1
    Magnetic Dipole Moment does not include the permeability of free space???


    The formula for a magnetic field in a current loop involves the permeability of free space.

    But the formula for the magnetic dipole moment which seems to represent the flux through a current loop does not incorporate the permeability of free space.

    Whats happening here?

  2. jcsd
  3. Jun 7, 2005 #2

    Meir Achuz

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    It's just a question of where you put the constant mu0.
    It's not usually put in the mag mom. Then mu0/4pi is put into the Eq. for B, just as it is for B due to currents.
    The mag mom is NOT the flux through a current loop.
  4. Jun 7, 2005 #3
    Anything that you measure involving the magnetic moment also involves a magnetics field, and the permeability is included in that magnetic fielc.
  5. Jun 7, 2005 #4
    Thanks for that, though its still not entirely clear.

    What exactly is the Magnetic Dipole Moment a measure of then?

    I ask this as I know in the Stern Gerlach exp. the Ag atoms experience a torque due to the dipole moments of the electrons being acted upon by the magnetic field into which it enters. And I originally assumed that the dipole moment was a way of stating the magentic field strength of the current loop....

  6. Jun 7, 2005 #5
    It is a measure of how strong the interaction between that dipole and an external magnetic field would be.
  7. Jun 7, 2005 #6


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    Use the analogue of the electric dipole moment. This is simply the charge times a separation. You do not see [itex]\epsilon_0[/itex] anywhere, do you ?

    Likewise, there is no reason for the magnetic dipole moment to have [itex]\mu_0[/itex] in it. This is by definition.
    Last edited: Jun 7, 2005
  8. Jun 8, 2005 #7
    Thanks guys, its all much clearer now.

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