The stored charge in the capacitor in steady state of the following circuit is ______ μC.
Answer: 200
Solution
In the steady state no current passes through the capacitor, so the branch holding the final 10Ω and the capacitor carries none. In the conducting network the 5Ω in series with the middle section (the 10Ω vertical in parallel with the 4+4+2Ω path, which is 5Ω) in series with the lower 2Ω totals 5+5+2=12Ω, so the 12V source drives a branch current of 1A. The potentials across the middle section are then 7V at the top and 2V at the bottom. The 0.5A flowing through the 4Ω-4Ω-2Ω path makes the potential at the capacitor's top plate 5V and at its bottom plate 3V, a difference of 2V. The stored charge is Q=CV=100μF×2V=200μC.