A portable inspection lamp is connected in series with a variable resistor to a 12 V supply. The variable resistor is adjusted until the current is 0.60 A. At this current, the lamp has a resistance of 4.0 Ω.
Calculate the resistance of the variable resistor.
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.