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Finding the Net charge

  1. Jan 28, 2008 #1
    1. The problem statement, all variables and given/known data

    A metal sphere has a charge of +8.0 µC. What is the net charge after 9.00 *10^13 electrons have been placed on it?


    2. Relevant equations

    q=Ne where q is the charge, N is the number of electrons, and e is given as 1.6*10^-19

    3. The attempt at a solution

    Well the problem gives us a charge, q, and the N, number of electrons, so I figure somehow I need to use this equation. I am not sure where to start though, could someone get me started? Thanks!
     
  2. jcsd
  3. Jan 28, 2008 #2

    Kurdt

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    The electrons have a negative charge. That charge will be given by the product of the number of electrons and the charge of the electrons. Since the sphere starts with a positive charge the net charge will be the initial positive charge plus whatever charge all the electrons have. Be careful with signs here.
     
  4. Jan 28, 2008 #3
    I'm still having trouble...what number needs to be negative?
     
  5. Jan 28, 2008 #4

    Kurdt

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    Electrons have a negative charge.
     
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