# How to calculate voltage across capacitor C1?

If the voltage

$$\v_I = \frac{jωC1R3}{1 + jωC1R3}*Vs \$$

does that mean the voltage across the capacitor would be equal to $$\v_S - v_I\$$ ?

• Welcome to EE.SE! Please pay attention that current is though. Voltage is across. – winny Apr 8 '20 at 6:46
• The problem with though, through, thought, tough is that they all pass the spelling test. – Oldfart Apr 8 '20 at 6:51
• Remember that in steady-state the average current through an ideal capacitor is always zero. And you can use a superposition to find the DC component and AC component separately. electronics.stackexchange.com/questions/301921/… – G36 Apr 8 '20 at 7:30

The voltage across the cap (not through it) is, by definition vS - vI. So yes.

• Because the capacitor is DC blocking does that mean its voltage value will be the real part of the complex voltage? – Simba N Apr 8 '20 at 7:04
• The direct voltage across the capacitor will be the direct voltage present in $\small v_s$. The real part of $\small v_s$ is not the direct voltage, it's the in-phase component. – Chu Apr 8 '20 at 8:43