Question

Consider two 100𝜇𝐹 capacitors. One is charged to 10V, disconnected from the power supply, 

and then connected across the other. Calculate the energy stored by the combination

Answer 1

$W=\frac{C_0 U_0^2}{2},$

$C_0=C_1+C_2=2C,$

$U_0=U_1=U_2=U,$

$W=CU^2,$

$W=100\cdot 10^{-6}\cdot 10^2=0.01~J.$