On rotating a point charge having a charge $q$ around a charge $Q$ in a circle of radius $r$. The work done will be

Define an electrostatic potential energy.

A point charge $Q$ is placed in uniform electric field $\vec E = E_1 \hat i + E_2\hat j$ at position $(a, b)$. Find work done in moving it to position $(c, d)$

The work done to take an electron from rest where potential is $-60\, V$ to another point where potential is $-20\, V$ is given by.....$eV$

$(a)$ In a quark model of elementary particles, a neutron is made of one up quarks [ charge $\frac{2}{3}e$ ] and two down quarks [ charges $ - \frac{1}{3}e$ ]. Assume that they have a triangle configuration with side length of the order of ${10^{ - 15}}$ $m$. Calculate electrostatic potential energy of neutron and compare it with its mass $939$ $Me\,V$. $(b)$ Repeat above exercise for a proton which is made of two up and one down quark.

Two charges of magnitude $5\, nC$ and $-2\, nC$, one placed at points $(2\, cm, 0, 0)$ and $(x\, cm, 0, 0)$ in a region of space, where there is no other external field. If the electrostatic potential energy of the system is $ - 0.5\,\mu J$. The value of $x$ is.....$cm$