Three condensers each of capacitance $2 \ F$ are connected in series. The resultant capacitance is ......... $F$.

Two equal capacitors are first connected in series and then in parallel. The ratio of the equivalent capacities in the two cases will be

The minimum value of effective capacitance that can be obtained by combining $3$ capacitors of capacitances $1 \ pF, 2 \ pF$ and $4 \ pF$ is

Three parallel plate air capacitors are connected in parallel. Each capacitor has plate area $A/3$ and separation between the plates is $d$, $2d$, and $3d$ respectively. The equivalent capacity of the combination is ($\epsilon_0$ is the permittivity of free space).

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?

Four identical metal plates are arranged in air at equal distances from each other as shown in the figure. Each plate has an area $A$. Find the equivalent capacitance of the system between points $A$ and $B$.