Can a metal be used as a medium for dielectric?

A parallel plate air capacitor has a capacitance $C$. When it is half-filled with a dielectric of dielectric constant $5$, the percentage increase in the capacitance will be:-

The equivalent capacitance between the points $A$ and $B$ in the given diagram is :

In an adjoining figure, three capacitors $C_1, C_2$and $C_3$ are joined to a battery. The correct condition will be:

A number of capacitors, each of capacitance, $1 \mu \mathrm{F}$ and each one of which gets punctured if a potential difference just exceeding, $500 \mathrm{V}$ is applied, are provided. Then an arrangement suitable for giving a capacitor of capacitance, $3 \mu \mathrm{F}$ across which, $2000 \mathrm{V}$ may be applied requires at least:

The effective capacity of the network between terminals A and B is :

A series combination of two capacitances of value $0.1 \mu \mathrm{F}$ and $1 \mu \mathrm{F}$ is connected with a source of voltage $500 \mathrm{volts}$. The potential difference in volts across the capacitor of value $0.1 \mu \mathrm{F}$ will be:

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

The equivalent capacitance between points A and B of the circuit shown will be :