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Electrical potential of charged sphere

  1. May 22, 2008 #1
    1. The problem statement, all variables and given/known data

    Two charged metal spheres are connected by a wire. Sphere A is larger than sphere B. The magnitude of the electrical potential of A...

    a) is greater than at the surface of sphere B
    b) is less than at the surface of sphere B
    c) is the same as that at the surface of sphere B

    3. The attempt at a solution

    Electric potential: V = q/(4*pi*e0*r)

    Since the spheres are connected by a wire, their charge will be equal. We regard the charges at the spheres as point charges in the centers of the spheres. Then the magnitude of the electrical potential of A is less than at the surface of B since rA > rB

    Why am I wrong?
     
  2. jcsd
  3. May 22, 2008 #2

    Dick

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    Science Advisor
    Homework Helper

    I don't know how to say this without giving the whole thing away, but do you really think that if I connect a huge sphere with a lot of charge (like the earth) to a small sphere (like a steel marble) that they will they will split the charge equally? Something will be equal between the two spheres, but it won't be charge.
     
  4. May 23, 2008 #3
    So c) is the correct answer. How can this be explained?
     
  5. May 23, 2008 #4
    The potential on the surface must be constant, otherwise there would exist tangential field E that moves the charges until equipotential is reached.
     
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