Consider a point charge Q at origin O. Let P be a point at a distance r from it.
Take Q to be positive charge. For Q > 0, the work done against the repulsive force on the test charge is positive.
If the charge Q is negative, the potential is also negative as the test charge will have a force of attraction.
The electrostatic potential is inversely proportional to r and electrostatic field is inversely proportional to the square of r.
At some intermediate point P′ on the path, the electrostatic force on a unit positive charge is
where ˆr′ is the unit vector along OP′.
Work done against this force from r′ to r′ + ∆r′ is
Total potential at P due to the charge Q