# Capacitors in parallel and in series question

#### Tonyr1084

Joined Sep 24, 2015
5,494
I know that if I put two capacitors in parallel their total capacitance is the sum of both caps added together. But here's where I get a little foggy, if they're in series - assume two identical caps (say for the sake of example 220 µF) the capacitance is going to be 110 µF. I believe that's right. But I was wondering about voltages: If these two example caps are 10 volts each, in parallel, are they still 10 volts? In series, are they going to be 20 volts ? ? ?

Been reading the AAC education stuff and didn't find anything on the voltage side of the equation. Your guidance is needed.

Thanks all.

#### LesJones

Joined Jan 8, 2017
2,836
It should be 20 volts but as the capacitors are probably electrolytic they would have leakage current. As the leakage current would probably be different for each capacitor the voltage across each capacitor would not be the same so you could not assume they wold share the voltage equaly. It is normal practice to put the same value resistor in parallel with each capacitor. The value is chosen to mask the variation in leakage currents.

Les.

Joined Jan 15, 2015
5,714
Capacitors in parallel are treated the same way as resistors in series and capacitors in series are treated the same as resistors in parallel. Now as to the voltages? Generally when capacitors are placed in series to achieve a higher working voltage resistors are placed across each capacitor for the reason LesJones just mentioned above. The idea being if a capacitor is going to have leakage we may as well create a greater leakage path. The only time I have seen this done is in the case of a few high voltage power supplies and really rather than capacitors in series to increase the working voltage it is best to find a capacitor which has the desired working voltage.

Ron

• cmartinez