Define one volt from power (P=VI)

 In the equation P = VI, where P is power, V is voltage, and I is current, we can rearrange the equation to solve for voltage V:

V = P / I

If we assume that the power P is 1 watt and the current I is 1 ampere, then we can define one volt as the voltage required to maintain a power of 1 watt with a current of 1 ampere:

1 volt = 1 watt / 1 ampere

So, one volt is the amount of electric potential difference between two points in a circuit that would be required to maintain a power of 1 watt with a current of 1 ampere.