Edexcel A-Level Physics Resistivity

Practise Edexcel A-Level Physics resistivity with R = ρl/A, wire measurements, graph gradients, cross-sectional area and material identification.

Exam points

calculate resistivity from resistance, length and cross-sectional area of wires or cubes
use graph gradients and p.d.-length data to determine resistivity of nichrome wire
identify a metal by comparing calculated resistivity with values in a data table

[Maximum number: 3]

The circuit contains three identical resistors and switches X and Y. Each resistor is wire of diameter $0.181\,\mathrm{mm}$ and length $55.0\,\mathrm{cm}$ , with resistivity $1.10\times10^{-6}\,\Omega\,\mathrm{m}$ at room temperature.

Figure for Question 2.4.71 - Resistivity question 1 — Edexcel A-Level Physics AS

Show that the resistance of one resistor at room temperature is about $24\,\Omega$ .

Use $A=\pi r^2$ and $R=\rho l/A$ .
$A=\pi(0.0905\times10^{-3})^2=2.57\times10^{-8}\,\mathrm{m^2},$ $R=\frac{(1.10\times10^{-6})(0.550)}{2.57\times10^{-8}}=23.5\,\Omega.$

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2.4.71 - Resistivity question 1