$A$ moving positive charge approaches a negative charge. What will happen to the potential energy of the system?

Three charges $Q, +q$ and $+q$ are placed at the vertices of a right-angled isosceles triangle as shown in the figure. If the net electrostatic potential energy of the system is zero,the value of $Q$ is

The electrostatic potential due to an electric dipole at a distance '$r$' varies as:

Three charges $Q$,$+q$,and $+q$ are placed at the vertices of a right-angled triangle as shown. The net electrostatic potential energy of the configuration is zero. The value of $Q$ is

Two equal charges $q$ of opposite sign separated by a distance $2a$ constitute an electric dipole of dipole moment $p$. If $P$ is a point at a distance $r$ from the centre of the dipole and the line joining the centre of the dipole to this point makes an angle $\theta$ with the axis of the dipole,then the potential at $P$ is given by $(r \gg 2a)$ (where $p = 2qa$).

Three charges $Q, +q$ and $+q$ are placed at the vertices of a right-angled isosceles triangle with legs of length $a$ as shown in the figure. The net electrostatic potential energy of the configuration is zero. The value of $Q$ is: