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Homework Help: Finding the current given a magnetic dipole, its plug in chug, whats going wrong?

  1. Nov 2, 2005 #1
    Hello everyone, I'm missing this problem and i aksed the professor if i was doing it wrong and he said, nope it looks like you just use that equation and solve for I. Here is the equation:
    M = IA, where M stands for the moment; A stands for Area.
    So you know the Moment is 1022 J/T. You also know the area is 4PIr^2;
    A = 4PI(3200E3)^2;
    A = 1.29E14;
    I = M/A
    I = (8E22)/1.29E14 = 620155038.8 = 6.2E8
    Am i doing this right? It says its wrong!

    The magnetic dipole moment of Earth is 8E22 J/T. Assume that this is produced by charges flowing in Earth's molten outer core. If the radius of their circular path is 3200 km, calculate the current they produce.
    Last edited: Nov 2, 2005
  2. jcsd
  3. Nov 3, 2005 #2


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    The area enclosed by a circle is [itex]\pi r^2[/itex]
  4. Nov 3, 2005 #3
    Ohh my bad, i thought the earth was more of a sphere than a circle, thank you!!
  5. Nov 3, 2005 #4


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    Sure, the earth is a sphere. But we're not talking about the earth here!!! I think you need to take another look at the basic concept.

    We're talking about the area bounded by the circular path of the charges.
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