Question

Two parallel-plate condensers of capacitance of $20\mu F$ and $30\mu F$ are charged to the potential of $30V$ and $20V$ respectively. If likely-charged plates are connected together then the common potential difference will be :

• A. $10V$
• B. $24V$
• C. $50V$
• D. $100V$

Answer 1

Answer: (B)

$24V$

The common potential difference is:
$V_c=\frac{C_1{V}_1+C_2{V}_2}{C_1+C_2}$
$V_c=\frac{(20\times 30)+(30\times 20)}{20+30}=\frac{1200}{50}=24V$