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Homework Help: Gauss's Law for Magnetism

  1. Nov 20, 2007 #1


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    http://web.ics.purdue.edu/~yeo/phys1.jpg [Broken]

    Formula: (Gauss's Law for Magnetism)
    Line integral of[B dot nhat(perpendicular unit vector) * deltaA] = 0

    3. The attempt at a solution
    So, if there is a bar magnet inside, the side arrows are pointing in the wrong direction, so I ruled that out.

    A magnetic monopole will have all arrows emanating from the center or all pointing towards the center, so I ruled that out.

    The total flux is not 0, so there has to be something in it?

    ->That left me with only 2 other choices, but I've tried all combinations of them and none of them are correct. Any help guys? I only have 2 more tries left and its due tomorrow....

    Thanks alot!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 21, 2007 #2


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    The fourth choice is correct, because if you keep a current carrying coil inside it will also have the lines of magnetic fields entering and leaving.
    Last edited: Nov 21, 2007
  4. Nov 21, 2007 #3


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    The flux through the box is nonzero. You are right, there is 'something' inside it. If you believe the flux. But we know of no magnetic sources (i.e. monopoles). And a current carrying wire is NOT A SOURCE. It has div(B)=0. Conclusion?
    Last edited: Nov 21, 2007
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