Physics Question help

I have to calculate the voltage across a 50 uF (micro Farad) capacitor. The circuit voltage supply is 20V the capacitor is in series. There's an 100uF capacitor and 70uF capacitor parallel in the same circuit. I know that V=Charge/Capacitance however I don't know how to work out the charge to find the voltage. The capacitance of the circuit is 38.6uF

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Original post by ToonLegend_

I have to calculate the voltage across a 50 uF (micro Farad) capacitor. The circuit voltage supply is 20V the capacitor is in series. There's an 100uF capacitor and 70uF capacitor parallel in the same circuit. I know that V=Charge/Capacitance however I don't know how to work out the charge to find the voltage. The capacitance of the circuit is 38.6uF

Let C₁ =50 μF, C₂ = 100 μF and C₃ = 70 μF.

Knowing that C₂ and C₃ are in parallel, so let's call the effective capacitance to be C₂₃.

The p.d. across C₁ and C₂₃ is V₁ and V₂₃, respectively.
Since the power supply is in series with C₁ and C₂₃, we have
20 = V₁ + V₂₃ ---- Eqn(1)
Knowing that V = Q/C, rewrite eqn(1)

\dfrac{Q_{\text{tot}}}{C_{\text{tot}}} = \dfrac{Q_1}{C_1} + \dfrac{Q_{23}}{C_{23}}

C_tot = 38.6 μF
Do you know how are Q_tot, Q₁ and Q₂₃ related?
Once you know their relationship, you can work out the p.d. across C₁.

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