A student measures two fixed resistors in series. The supply voltage is 6.0 V and the current is 0.20 A. The voltage across resistor X is 2.0 V. The student calculates the resistance of X as 30 Ω. Which correction is needed?
Use 2.0 V2.0\ \mathrm{V}2.0 V and 0.10 A0.10\ \mathrm{A}0.10 A to obtain 20 Ω20\ \Omega20 Ω
Use 4.0 V4.0\ \mathrm{V}4.0 V and 0.20 A0.20\ \mathrm{A}0.20 A to obtain 20 Ω20\ \Omega20 Ω
Use 2.0 V2.0\ \mathrm{V}2.0 V and 0.20 A0.20\ \mathrm{A}0.20 A to obtain 10 Ω10\ \Omega10 Ω
Use 6.0 V6.0\ \mathrm{V}6.0 V and 0.40 A0.40\ \mathrm{A}0.40 A to obtain 15 Ω15\ \Omega15 Ω
81 exam-style questions on Edexcel GCSE Physics 10.2 Resistance, covering 10.2.1 Current in a circuit and conservation at junctions, 10.2.2 Resistance and variable resistors, 10.2.3 Series and parallel resistance, 10.2.4 I–V characteristics of components, and 10.2.5 LDRs and thermistors. Each one has a worked solution and a mark scheme showing where the marks go.