The electric field intensity $E$ at a distance of 3 m from a uniform long straight wire of linear charge density $0.2 \mu \mathrm{~cm}^{-1}$ is

A point charge $q \mathrm{C}$ is placed at the centre of a cube of a side length $L$. Then, the electric flux linked with each face of the cube is

Three equal electric charges of each charge $q$ are placed at the vertices of an equilateral triangle of side of length $L$. Then, potential energy of the system is

Eight drops of mercury of equal radii and possessing equal charge combine to form a big drop. If the capacity of each drop is $C$, then capacity of the big drop is