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Homework Help: Magnetic Moment

  1. Oct 1, 2009 #1
    1. A spherical shell of radius R has a constant surface charge density, sigma. It rotates about its diameter with angular speed, w. Find the magnitude of the magnetic moment of the rotating spherical shell.

    2. Magnetic dipole moment u = NIA(normal vector) ; Torque = u X B; Spherical Volume = 4/3 pi R^3

    3. No idea where to start....
  2. jcsd
  3. Oct 1, 2009 #2


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    Consider an element of charge dq = σdA on the surface. As it spins around it becomes a current dI. Find the magnetic moment dm generated by this current then add all such magnetic moments over the surface of the sphere.
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