Three charges $-q, Q$ and $-q$ are placed respectively at equal distances on a straight line. If the potential energy of the system of three charges is zero, then what is the ratio of $Q: q$ ?

What is the potential energy of the equal positive point charges of $1\,\mu C$ each held $1\, m$ apart in air

Explain electrostatic potential energy difference and give the noteworthy comments on it.

A particle of charge $q$ and mass $m$ is subjected to an electric field $E = E _{0}\left(1- ax ^{2}\right)$ in the $x-$direction, where $a$ and $E _{0}$ are constants. Initially the particle was at rest at $x=0 .$ Other than the initial position the kinetic energy of the particle becomes zero when the distance of the particle from the origin is

Mass of charge $Q$ is $m$ and mass of charge $2Q$ is $4\,m$ . If both are released from rest, then what will be $K.E.$ of $Q$ at infinite separation

The charge $q$ is fired towards another charged particle $Q$ which is fixed, with a speed $v$. It approaches $Q$ upto a closest distance $r$ and then returns. If $q$ were given a speed $2 v$, the closest distance of approach would be