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Homework Help: Simple Electric Charge Problem

  1. Jan 26, 2009 #1
    1. The problem statement, all variables and given/known data
    Consider three identical metal spheres, A, B, and C. Sphere A carries a charge of +5q. Sphere B carries a charge of -q. Sphere C carries no net charge. Spheres A and B are touched together and then separated. Sphere C is then touched to Sphere A and then separated from it. Lastly, Sphere C is touched to sphere B and then separated from it. (a) How much charge ends up on sphere C? What is the total charge on the three spheres (b) before they are allowed to touched each other and (c) after they have touched.

    2. Relevant equations

    3. The attempt at a solution
    I understand most concepts related to this but my teacher hasn't really explained everything about charge transfer to us yet. I just don't know how the charge cleanly transfers.

    Thanks for any effort! =D
  2. jcsd
  3. Jan 26, 2009 #2


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    Homework Helper

    Just approach the problem with the idea that when they contact, the charges equalize on the 2 spheres, ie if a -8q sphere touches a -4q then they should both end up at -6q, if they were identical spheres as the charge densities of the -8 and -4 would be identical and spread out between the two equal spheres.
  4. Jan 26, 2009 #3
    Ahhh... that's what I did at first, but I just had to go wrong somewhere.... Thanks for leading me back to that!
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