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Homework Help: Electric Forces and Fields

  1. Feb 14, 2010 #1
    1. The problem statement, all variables and given/known data
    A 3.0mm-diameter copper ball is charged to 50nC.What fraction of its electrons have been removed? The density of copper is 8900kgm^3.

    2. Relevant equations

    d=m/v; v=4/3* pi r^3

    3. The attempt at a solution

    I worked through it and got 5.682 E -16, but that answer was wrong. I first found the number of electrons were in it (3.125 E 11). I then found the volume (1.414 E -8), and I think that's where I got stuck after that.
  2. jcsd
  3. Feb 14, 2010 #2
    So what did you try to do after that?
  4. Feb 14, 2010 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Welcome to Physics Forums.
    Can you show the work you did to get those numbers? It would be easier to help you if you do that.
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