Parallel Capacitors: C1+C2 or C1-C2?

[flyers]

I know that the equivalent capacitance for two capacitors in parallel is C1+C2=Ceq. But consider I charge 2 plate capacitors so that each capacitor has a positive and negative plate and then I connect the positive plate of one cap. to the negative plate of the other capacitor in a parallel connection. My question is should the equivalent capacitance be c1+c2 OR c1-c2?

 

[gneill]

c1 + c2

It's like adding two containers of volumes v1 and v2. The net size of the resulting container does not depend upon the contents.