Question

When is potential difference between two points said to be 1 Volt

Answer 1

when 1 joule of work is done to move 1 coloumb of charge from one point to another, then the potential difference is said to be 1 volt

Answer 2

We know that
V = W/Q,

so when 1 joule work done by 1 coulomb then we said potential difference between two points is 1 V

like put value in formula
V = W /Q
V = 1 joule / 1 coulomb
V = 1 v