A capacitor of capacitance 2 µF is charged to 10V and another capacitor of capacitance 3 µF is charged to 20V. Now their opposite polarities are connected, the loss of total stored electrical potential energy in this process is

540 µJ

$H=U_i-U_f $

$=\left(\frac{1}{2} \times 2 \times 10^2+\frac{1}{2} \times 3 \times 20^2\right)-\left(\frac{1}{2} \times 2 \times 8^2+\frac{1}{2} \times 3 \times 8^2\right)$

= 540 µJ