Question

Two capacitors of $10pF$ and $20pF$ are connected to $200V$ and $100V$ sources respectively. If they are connected in parallel by the wire, what is the common potential of the capacitors?

• A. $133.3Volt$
• B. $150Volt$
• C. $300Volt$
• D. $400Volt$

Answer 1

The correct option is A $133.3Volt$

Total charge on the two capacitors is:

$Q=Q_1+Q_2=C_1{V}_1+C_2{V}_2$

$Q=10\times {10}^{-9}\times 200+20\times {10}^{-9}\times 100$

$Q=4\mu C$

Net capacitance of two capacitors in parallel is:

$C=C_1+C_2$

$C=30pF$

Common potential of the parallel combination of capacitors is:

$V=\frac{Q}{C}$

$V=\frac{4\times {10}^{-6}}{30\times {10}^{-9}}=133.3V$