Question

Draw an equipotential surface for a system consisting of two charges Q,-Q separated by a distance r in air

Answer 1

Equipotential surface is the surface with same electric potential at every points.
Here +Q and -Q charge . For a spherical charged particle equipotential surface be the shape of circular . But for two dimensional system of charged particle , equipotential surface will be straight line.

Here two charged particle +Q and -Q are given ,
equipotential surface lies between given charges , and it is straight line . Also you have to know , equipotential surface is always perpendicular to electric lines of force . Here a rough daigram is shown. In middle line (straight line ) is not other than equipotential surface.