1. The problem statement, all variables and given/known data Two capacitors are connected parallel to each other and connected to the battery with voltage 30 V. Let C1 = 9.8 micro F,C2 = 4.0 micro F be their capacitances. Suppose the charged capacitors are disconnected from the source and from each other, and then reconnected to each other with plates of opposite sign together. By how much does the energy of the system decrease? 2. Relevant equations U = (1/2)QV For PPC connected in parallel, Q1 = C1V and Q2 = C2V Ceq = C1 + C2 + C3....... 3. The attempt at a solution I found the charge stored on the plates initially, and was trying to find the charge stored on them after they were reconnect, but failed. I really don't know what to do. Do I have to find the new voltage too?