Question

A capacitor of $20\mu F$ charged to $500\text{V}$, is connected in parallel to another capacitor of $10\mu F$ charged to $200\text{V}$, Find the common potential?

• A. $200\text{V}$
• B. $400\text{V}$
• C. $600\text{V}$
• D. $800\text{V}$

Answer 1

The correct option is B $400\text{V}$

The common potential
$V_{\text{common}}=\frac{C_1{V}_1+C_2{V}_2}{C_1+C_2}$
Here $C_1=20\mu F=20\times {10}^{-6}\text{F},V_1=500\text{V}$
$C_2=10\mu F=10\times {10}^{-6}\text{F},V_2=200\text{V}$
$\Rightarrow V_{\text{common}}=\frac{20\times {10}^{-6}\times 500+10\times {10}^{-6}\times 200}{20\times {10}^{-6}+10\times {10}^{-6}}$
$\Rightarrow V_{\text{common}}=400\text{V}$