Question

Two identical capacitors are joined in parallel charged upto a potential $V$ and than separated, after that again connected in series i.e. the positive plate of one is connected to negative of the other, then

• A. the charges on the free plates connected together are destroyed.
• B. the charges on the free plates are enhanced.
• C. the energy stored in the system increases.
• D. the potential difference in the free plates becomes 2V.

Answer 1

The correct option is D the potential difference in the free plates becomes 2V.

When charged to V potential through battery
$Q_1=CV$
and
$Q_2=CV$
After connecting them in series the potential difference in each capacitor is taken as $V_1$ and $V_2$
Applying charge conservation
$C{V}_1+C{V}_2=Q_1+Q_2$
$\Rightarrow C{V}_1+C{V}_2=2CV\Rightarrow V_1+V_2=2V$