Question

A capacitor is charged with a battery and energy stored is $U$. After disconnecting battery another capacitor of same capacity is connected in parallel with it. Then energy stored in each capacitor is:

• A. $\frac U2$
• B. $\frac U4$
• C. $4U$
• D. $2U$

Answer 1

Answer: (B)

$\frac U4$

Answer 2

$Energy\ stored\ (U) =\frac {q^2}{2C}$

After connecting with another capacitor

$V_{common}=\frac {q_1+q_2}{C_1+C_2}=\frac {q+0}{C+C}=\frac {q}{2C}$

∴Energy on each capacitor =$\frac {1}{2} CV^2_{common}$ = $\frac 12 (\frac {q}{2C})^2$ = $\frac U4$

So, the correct option is (B): $\frac U4$