Question: how to calculate resistance using potential difference and current?
Answer: To find the resistance of a component, you need to measure:
The resistance is the ratio of potential difference to current. ... 
For example, 3 A flows through a 240 V lamp. ... 
resistance = 240 ÷ 3 = 80 Ω
If you plot a graph of current against potential difference for a wire, you get a straight line.