Three parallel plate capacitors of capacitances $4 \mu F$,$6 \mu F$ and $12 \mu F$ are first connected in series and then in parallel. The ratio of the effective capacitances in the two cases is

Find the equivalent capacitance across $A$ and $B$ in $\mu F$.

Four capacitors,each of capacity $4\,\mu F$,are connected as shown in the figure. If $V_P - V_Q = 15\,V$,the energy stored in the system is . . . . . . $ergs$.

Two capacitors of capacitances $1 \ \mu F$ and $2 \ \mu F$ can separately withstand potentials of $6 \ kV$ and $4 \ kV$ respectively. The total potential they together can withstand when they are connected in series is (in $kV$)

The diagram shows three capacitors with their capacitances and their respective breakdown voltages. What should be the maximum value of the external $emf$ $(E)$ of the source such that no capacitor breaks down?

What is the equivalent capacitance of the system of capacitors between $A$ and $B$?