In the figure,the area of each plate is $A$ and the distance between consecutive plates is $d$. What is the effective capacitance between points $A$ and $B$?

$A$ parallel plate capacitor of capacity $C_0$ is charged to a potential $V_0$.
$(i)$ The energy stored in the capacitor when the battery is disconnected and the separation is doubled is $E_1$.
$(ii)$ The energy stored in the capacitor when the charging battery is kept connected and the separation between the capacitor plates is doubled is $E_2$.
Then the value of $E_1/E_2$ is:

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 $kV$)

The figure shows two identical parallel plate capacitors $A$ and $B$ of capacitances $C$ connected to a battery. The key $K$ is initially closed. The switch is now opened and the free spaces between the plates of the capacitors are filled with a dielectric of dielectric constant $K=3$. Then which of the following statement$(s)$ is/are true?

For the given circuit,find the potential at point $a$. (in $V$)

In the given figure,the capacitors $C_1, C_3, C_4, C_5$ have a capacitance of $4\,\mu F$ each. If the capacitor $C_2$ has a capacitance of $10\,\mu F$,then the effective capacitance between $A$ and $B$ will be.....$\mu F$.