Question

A 600 pF capacitor is charged by a 200V supply. It is then disconnected from the supply and is connected to another uncharged 600 pF capacitor. How much electrostatic energy is lost in the process?

Answer 1

Initial energy, $E=\frac{1}{2}C{V}^2$
$E=1.2\times {10}^{-5}J$
when another capacitor is connected,
$\frac{1}{C_1}=\frac{1}{C}+\frac{1}{C}$
$C_1=300pF$
$E_1=\frac{1}{2}{C}_1{V}^2=0.6\times {10}^{-5}$
$\Delta E=E-E_1=6\times {10}^{-6}J$