IGCSE Physics Electricity Practice Test 2026 - Free Electricity Practice Questions and Study Guide

Resistance tells us how much a component opposes the flow of current. The unit used for this is the ohm, symbol Ω, defined as one volt per ampere. This comes from Ohm’s law, R = V / I, so the unit of resistance is volts per ampere, i.e., an ohm. The other quantities have different units: current is amperes, potential difference is volts, and power is watts. So the unit of resistance is the ohm.