A hollow cylinder has a charge of ' $q$ ' $C$ within it. If $\phi$ is the electric flux associated with the curved surface B, the flux linked with the plane surface A will be

A conducting sphere of radius ' R ' is given a charge ' $Q$ ' uniformly. The electric field and the electric potential at the centre of the sphere are respectively [ $\varepsilon_0=$ permittivity of free space]

' n ' small spherical drops of same size which are charged to ' $V$ ' volt each coalesce to form a single big drop. The potential of the big drop is

The electric potential ' V ' is given as a function of distance ' $x$ ' (metre) by $V=\left(4 x^2+8 x-3\right) V$. The value of electric field at $x=0.5 \mathrm{~m}$, in $\mathrm{V} / \mathrm{m}$ is