Question

how can we define 1 volt potential

Answer 1

one volt is the potential difference between two points in a current carrying conductor when 1joule of work is done to move a charge of 1 coloumb from one point to another.

Answer 2

when 1 joule of work is done by 1 coulomb of charge, from an infinity to a point in the electric field then the potential at that point is called 1 volt.