1. The problem statement, all variables and given/known data When the switch is closed, Potential drops to 40v across C1 & C2(Parallel series). Find the Capacitance of C2 2. Relevant equations Before switch is closed C1=300uF and holds a charge of Q1=3e4 uC V=100v After switch is closed V'=40v 3. The attempt at a solution V1=V2 So Q1/C1=Q2/C2 Q=Q1+Q2 How could I find the charge on C2?