In the circuit, all elements are ideal. For time t<0, S1 remained closed and S2 open. At t=0, S1 is opened and S2 is closed. If the voltage Vc2 across the capacitor C2 at t=0 is zero, the voltage across the capacitor combination at t=0+ ?? I tried this problem. Obviously, Vc1(0) = 3V ; Given that Vc2(0) = 0V. Then C1 = 1μF and C2 = 2μF are connected at t=0. So, Q1(0) = 3 C. Q2(0) = 0 C. At t=0+ how charges are distributed and hence the voltage ?? I was thought (according to charge conservation) that, charges are distributed to two cap. such that voltage across them is equal. So, Q1 = 1 C , Q2 = 2 C. Hence Vc1 = Vc2 = 1 V. All these things happen at steady state. How about at t=0+ ?????