The capacitance of a parallel plate capacitor can be increased by

An electric field of magnitude $400 {\mathrm{NC}}^{-1}$ can be produced by applying a potential difference of $20 \mathrm{V}$ to a pair of parallel metal plates separated by

The distance between the circular plates of a parallel plate condenser $40 \mathrm{mm}$ in diameter, in order to have same capacity as a sphere of radius $1 \mathrm{m}$ is

Capacitance of a capacitor made by a thin metal foil is $2 \mathrm{\mu F}$. If the foil is folded with paper of thickness $0.15 \mathrm{mm}$, dielectric constant of paper is $2.5$ and width of paper is $400 \mathrm{mm}$, then length of foil will be

An air capacitor of capacity $C=10 \mathrm{\mu F}$ is connected to a constant voltage battery of $12 \mathrm{V}$. Now the space between the plates is filled with a liquid of dielectric constant $5$. The (additional) charge that flows now from battery to the capacitor is 

A parallel plate air capacitor is charged to a potential difference of $V$. After disconnecting the battery, distance between the plates of the capacitor is increased using an insulating handle. As a result, the potential difference between the plates 

A parallel plate air capacitor has capacity $C$, distance of separation between plates is $d$ and potential difference $ V$ is applied between the plates. Force of attraction between the plates of the parallel plate air capacitor is:

The insulated plates of a charged parallel plate capacitor (with small separation between the plates) are approaching each other due to electrostatic attraction. Assuming no other force to be operative and no radiation taking place, which of the following graphs approximately shows the variation with time $t$ of the potential difference $V$ between the plates?