Question

draw equipotential surface for a pair of negative charge

Answer 1

in an equipotential surface the potential is same in all points on the surface so concentric circles are applicable for single charges .In the acsd of like charges the same applies but with a biconcave over the 2 charges..with field lines outward or inward based on nature of charge..
Thanks for asking!!
$v = 1 \div 4\pi(e0) \times q \div r$