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Homework Help: ELECTROSTATICS numerical

  1. Jun 28, 2012 #1
    1. The problem statement, all variables and given/known data:
    the excess(equal in number) of electrons that must be placed on each of two small spheres spaced 3 cm apart, with force of repulsion between the spheres to be 10^-19N, is...?


    3. The attempt at a solution:
    since,
    f=kq^2/r^2.
    ive calculated q from here which is 1x10^-16N..
    then used,
    q=ne..
    from here n becomes 625 electrons. but answer in my book is 25 electrons.can someone point out my mistake?
     
  2. jcsd
  3. Jun 28, 2012 #2
    Your answer is correct, 25 electrons does not give 10^-19 N.
     
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