An engineer is investigating how the resistance of a uniform constantan alloy filament varies with its length and cross-sectional area.
To determine the cross-sectional area, the engineer must first obtain a precise measurement of the filament's diameter, which is approximately 0.25 mm0.25\text{ mm}0.25 mm.
Identify one measuring instrument that would allow the engineer to measure this diameter with suitable accuracy.
59 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.