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) Thanks.