Write the definition of electric potential. Calculate the electric potential due to a point charge Q at a distance r from it. Draw a graph between electric potential V and distance r for a point charge Q.
Electric potential is the amount of electric potential energy that a unitary point electric charge would have if located at any point in space, and is equal to the work done by an external agent in carrying a unit of positive charge from the arbitrarily chosen reference point (usually infinity) to that point without any acceleration.
Electric potential due to point charge Q at a distance r is
V=−∫r∞Edr
=∫r−∞Q4πϵ0r2dr
=Q4πϵ0r