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. Each one has a worked solution and a mark scheme showing where the marks go.