If a capacitor of capacity $900 \mu \mathrm{F}$ is charged to $100 \mathrm{~V}$ and its total energy is…
If a capacitor of capacity $900 \mu \mathrm{F}$ is charged to $100 \mathrm{~V}$ and its total energy is transferred to a capacitor of capacity $100 \mu \mathrm{F}$, then its potential will be
$30 \mathrm{~V}$
$200 \mathrm{~V}$
$300 \mathrm{~V}$
$400 \mathrm{~V}$
Solution
Let the unknown potential be $\mathrm{V}_{\mathrm{u}}$
Energy of a capacitor $=\frac{1}{2} \mathrm{CV}^2$
$\begin{array}{ll}
& \Rightarrow \frac{1}{2} C_1 V_1^2=\frac{1}{2} C_2\left(V_u\right)^2 \\
& \frac{1}{2} \times 900 \times 10^{-6} \times(100)^2=\frac{1}{2} \times 100 \times 10^{-6} \times\left(V_u\right)^2 \\
& \left(V_u\right)^2=9 \times 100^2 \\
\therefore \quad & V_u=300 \mathrm{~V}
\end{array}$