Four capacitors are arranged as shown in below figure. All are initially uncharged. A 30 V battery is placed across terminal PQ to charge the capacitors and is then removed. The voltage across the terminals RS is then (in volt)

In the given figure capacitors $3 \mathrm{\mu F}$, $3 \mathrm{\mu F}$ and $3 \mathrm{\mu F}$ (between Rand S) are in series. If Q is the charge on each of these capacitors, then

                              $30 =\frac{\mathrm{Q}}{3}+\frac{\mathrm{Q}}{3}+\frac{\mathrm{Q}}{3}$

                              $\mathrm{Q}=30 \mathrm{\mu C}$

Potential difference between R and S

                              $\mathrm{V}=\frac{\mathrm{Q}}{\mathrm{C}}=\frac{30}{3}$

$\Rightarrow$                         V = 10 V