1. The problem statement, all variables and given/known data Q: Two conducting balls of radius 0.1 m are situated 3m apart in free space. Electrons are transferred from one ball to another at a rate of 10^13 per second. How long does it take for a p.d of 100 kv to develop? 2. Relevant equations where ε0 is the electric constant (permittivity of vacuum) 3. The attempt at a solution First I calculated the charge needed for the particular voltage using the potential equation. Then I found C/s by multiplying the number of electrons by charge per electron. Finally I divided the charge needed by the charge per second to get the time to reach the charge. This answer does not match the book. I think I need to take the increase in potential of one ball and the fall in potential of the other in account. But I have no idea how to do that? Any help would be appreciated!