Question

A part of a circuit in steady state along with current flowing in the branches with value of each resistance is shown in figure. Calculate the energy stored in the capacitor $C_0$.

Answer 1

Your objective is to find out potential difference across the capacitor first. Applying Kirchoff's junction law at A and B
At $A:2+1-I_1;I_1=3A$
At $B:I_2+1-2=0;I_2=1A$
Now applying KVL in the mesh ADCBA (mesh means smallest loop or closed path)
$=(-3)\times 5-3\times 1-1\times 2+V_{AB}=0$
$V_{AB}=20V$
So, energy stored in the capacitor
$U=\frac{1}{2}C{V}^2=\frac{1}{2}\times (4\times {10}^{-6})\times {20}^2=8\times {10}^{-4}J$