The value of equivalent capacitance of the combination shown in the figure between the points $P$ and $Q$ is

Seven capacitors,each of capacitance $2 \mu F$,are connected in a configuration to obtain an effective capacitance of $\frac{6}{13} \mu F$. The combination that will achieve this is:

Four capacitors with capacitances $C_1 = 1\ C$,$C_2 = 2\ C$,$C_3 = 3\ C$,and $C_4 = 4\ C$ are connected to a battery of potential $V$ as shown in the figure. Find the ratio of charges on $C_2$ and $C_4$.

From the circuit given below, the capacitance between terminals $A$ and $B$ is . . . . . . $\mu\text{F}$. (Take $C_1 = C_2 = C_3 = 1\text{ }\mu\text{F}$ and $C_4 = 2\text{ }\mu\text{F}$.)

In the circuit,two capacitors $C_1$ and $C_2$ are connected as shown in the figure. The potential at point $A$ is $V_1$ and at point $B$ is $V_2$. What is the potential at point $D$?

Two capacitors each of capacity $2\,\mu F$ are connected in parallel. This system is connected in series with a third capacitor of $12\,\mu F$ capacity. The equivalent capacity of the system will be......$\mu F$