$A$ capacitor of capacitance $C$ is charged to a potential difference $V$ from a cell and then disconnected from it. $A$ charge $+Q$ is now given to its positive plate. The potential difference across the capacitor is now:

Find the potential difference between points $A$ and $F$,and $F$ and $B$.

$27$ identical drops are charged at $22 \ V$ each. They combine to form a bigger drop. The potential of the bigger drop will be............ $V$.

$A$ capacitor of $50 \,\mu {F}$ is connected in a circuit as shown in the figure. The charge on the upper plate of the capacitor is $......\,\mu {C} .$

$A$ capacitor $C_1 = 1.0 \, \mu F$ is charged up to a voltage $V = 60 \, V$ by connecting it to a battery $B$ through switch $(1)$. Now,$C_1$ is disconnected from the battery and connected to a circuit consisting of two uncharged capacitors $C_2 = 3.0 \, \mu F$ and $C_3 = 6.0 \, \mu F$ in series through a switch $(2)$ as shown in the figure. The sum of the final charges on $C_2$ and $C_3$ is ...... $\mu C$.

The diagram shows four capacitors with capacitances and breakdown voltages as mentioned. What should be the maximum value of the external emf source such that no capacitor breaks down? (in $kV$)