Two insulated spheres have capacitances 3 and 5μF are charged to potentials 300 and 500 V respectively. What is loss of energy due to redistribution after they are charged to a common potential? 

3.75 X 10^-2 J 

$\text{Loss of Energy due to redistribution } \Delta U = \frac{C_1 C_2 (V_1 - V_2)^2}{2(C_1 + C_2)} = 3.75 \times 10^{-2} J$