The mass of a particle is $400$ times that of an electron and its charge is double that of an electron. The particle is accelerated by a potential difference of $5 \; V$. If the particle was initially at rest,what will be its final kinetic energy in $eV$?

Four identical charges $+50\,\mu C$ each are placed,one at each corner of a square of side $2\,m$. How much external energy is required to bring another charge of $+50\,\mu C$ from infinity to the centre of the square? (Given $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9\,\frac{N\cdot m^2}{C^2}$)

$A$ hollow metallic sphere of radius $10 \; cm$ is charged such that the potential at its surface is $80 \; V$. The potential at the centre of the sphere would be (in $; V$)

Two small equal point charges of magnitude $q$ are suspended from a common point on the ceiling by insulating massless strings of equal lengths. They come to equilibrium with each string making an angle $\theta$ from the vertical. If the mass of each charge is $m$,then the electrostatic potential at the centre of the line joining them will be $\left( \frac{1}{4\pi \epsilon_0} = k \right).$

Charges of $+ \frac{10}{3} \times 10^{-9} \, C$ are placed at each of the four corners of a square of side $8 \, cm$. The potential at the intersection of the diagonals is

Charges of $2 \mu C$ and $-3 \mu C$ are placed at two points $A$ and $B$ separated by a distance of $1 \ m$. The distance of the point from $A$ where the net potential is zero is: (in $m$)