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Homework Help: Electrostatic exercise, Electrical charge calculation

  1. Jan 11, 2012 #1
    Hello, i have to solve the following problem, i have the result, but i can get the way to arrive to it.
    This is the problem:
    There are 2 spheres of copper, separated at 1 meter, each sphere have a weight of 1 Kg initially.

    The problem want's to know how many electrons i need to transfer from one sphere to the other one, to get a attractive force between the both spheres of 1x10^4 Newtons.

    The result it's 6.59x10^15 electrons

    I planted the Coulomb equation, but it's don't work. (B it's the number of electrons to transfer)
    [itex]Q_{1} = 2.7502*10^{26}electrons - B [/itex]
    [itex]Q_{2} = 2.7502*10^{26}electrons + B [/itex]

    [itex]1*10^{4}= \frac{Q_{1}*(-1.6)*10^19*Q_{2}*(-1.6)*10^19}{1^{2}}[/itex]

    Greets from Argentina!
  2. jcsd
  3. Jan 11, 2012 #2


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    First things first.

    Use Coulomb's law to find how much charge needs to be transferred. Of course, Q1 = -Q2 , so I suggest letting Q = Q1 and Q2 = - Q.

    After finding Q, then find out how many electrons need to be transferred.
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