1. The problem statement, all variables and given/known data This is not homework but it's kind of similar so may be I will post it here. I want to find the force between two charge sphere given radius, permittivity,distance, and voltage by diverge other equation to coulomb's law. 2. Relevant equations Coulomb law F=k Q1 Q2 /r2 F = force k = electric constant Q = electrostatic quality r= distance Voltage-dependent capacitors Q=CV Q = electrostatic quality C = capacitance V = voltage Capacitance of sphere C=4πεa C = capacitance ε = permittivity a = radius 3. The attempt at a solution 1. F=k Q1 Q2 /r2 start with Coulomb's law 2. F=k (CV)1 (CV)2/r2 replace Q with CV since Q=CV 3. F=k (4πεaV)1 (4πεaV)2/r2 replace C with 4πεa since C=4πεa So F=k (4πεaV)1 (4πεaV)2/r2 Is this correct, I replace voltage-dependent capacitors and capacitance of sphere equation into coulomb law to find how much force is acting on it. So when I evaluate radius, permittivity,distance, and voltage it should gives me amount of force.