Q 12-02-033NEETJEE MainMedium
The plates of an isolated charged capacitor are pulled apart to twice their separation. The work done by the external agent equals
Answer: (B) the initial energy stored
$Q$ is fixed and $C$ halves, so $U = \dfrac{Q^2}{2C}$ doubles. The external work equals the increase: $2U - U = U$.
Solution by Sreeraj P, M.Sc Physics