Electric potential difference ( ΔV ) is the difference in electric potential between the final and the initial location. It is also called voltage.
The power law equation is:
P = I * V ( P - power, I - current and V - voltage )
Therefore: V = P / I
V = 5 W / 5 A
V = 1 V.
Answer: The potential difference across a resistor is 1 V.