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Homework Help: Electrostatics - Charges

  1. Jan 31, 2014 #1
    1. The problem statement, all variables and given/known data
    The ball 1 can be charged to a certain charge Q by a generator. After that, through contact with the ball 2, the first ball can transfer to second ball part of its charge. After the first contact, the ball 2 has a charge q. Before the contact, the ball 2 was neutral. What charge the ball 2 can acquire repeating the process repeatedly.

    http://www.luiseduardo.com.br/electricity/electrostatics/electrostaticsproblems_arquivos/image002.jpg [Broken]

    2. Relevant equations
    Q = Q'+q --> Conservation of Charges
    Q = C.V ---> Capacitor charge
    C = r/K ----> Capacitance of a sphere

    3. The attempt at a solution

    Well, first, I tried to use the conservation of charges equation several times replacing Q' (charge of the sphere that will be recharged) by C.V, where C is the capacitance and V the potential. After that, I didn't find a way to find the answer of the problem. Could anyone help me? Please give me your complete explanation or solution.

    PS: The answer of the problem is qQ/(Q-q)

    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jan 31, 2014 #2
    The charge from one ball to another ball will flow till they are at the same potential.
    Now, to give you a start, let me tell you the first step:

    Assume C1 and C2 as the capacitances of ball 1 and ball2 respectively, equate the potential and find the ratio of [itex]\frac{C1}{C2}[/itex]. Now equate the potential for the 2nd step till you find a relation between the charges transferred.

    P.S: 1) The charges will be a part of a series. it is for you to guess which one.
    2) It is against the rule of this forum to give a detailed solution. Moreover, I think you should try
    your fullest before you look for the solution.

    Best of luck!

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