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Homework Help: AP Physics C Question

  1. Aug 23, 2007 #1
    1. The problem statement, all variables and given/known data
    This was on the 1982 AP Physics C E&M Free Response
    1982 Physics C Problem.JPG
    2. Relevant equations
    Electric flux through a closed surface = (Charge enclosed)/epsilon_0
    3. The attempt at a solution
    This is the official solution given:
    1982 Physics C Solution.JPG
    I believe, however, that the electric flux must be undefined. The electric flux is the integral of E.dA. But since there are charges *on* (as opposed to inside) two of the points on the sphere, E at those points would be infinite. Thus, integral E.dA would be undefined.

    Any help would be greatly appreciated.
    Thank You in Advance.
  2. jcsd
  3. Aug 23, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I think you have misread the question. The radius of the sphere is 2a, not a.
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