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

Three point charges $+q,+2 q$ and $+4 q$ are placed along a straight line such that the charge $+2 q$ lies at equidistant from the other two charges. The ratio of the net electrostatic force on charges $+q$ and $+4 q$ is

A particle of mass 2 g and charge $6 \mu \mathrm{C}$ is accelerated from rest through a potential difference of 60 V . The speed acquired by the particle is