IGCSE Physics / Electrical resistance
Electricity calculations: choosing the right equation
Edexcel International GCSE Physics (4PH1), chapter 8: Electrical resistance, specification point 2.4, 2.5, 2.13, 2.15, 2.21. Part of the full course.
Read the revision notes · IGCSE Physics past papers
Electricity calculations use five equations linking charge, current, time, voltage, resistance, power and energy. Choose an equation that links the values you know to the value you need, and chain two equations if one is not enough.