Resistivity of a Wire: Virtual Required Practical
A virtual resistivity practical: micrometer or vernier caliper, zero error, diameter readings along and around the wire, ammeter inside or outside the voltmeter's span, meter ranges and wire heating. Plot R against L and see why the gradient method cancels the contact resistance.
About this simulation
- What
- An interactive Physics simulation of Resistivity of a Wire: Virtual Required Practical.
- Who
- Designed for AP, IB, and A‑Level Physics students.
- How
- Runs in any modern browser — drag, adjust, and explore in real time.
Updated 2026-10-11
Key Concepts
Resistivity
R = ρL/A. Resistivity ρ is a property of the material; R also depends on the wire's length and cross-sectional area.
Diameter matters most
A = πd²/4, so the percentage uncertainty in d counts twice. Use a micrometer, correct its zero error, and take readings along the wire and at right angles.
Gradient of R against L
The gradient is ρ/A. Constant extra resistance — the clip contacts, or the ammeter if it is inside the voltmeter's span — only moves the intercept.
Small current, brief readings
Current heats the wire and raises its resistance. Keep it small and open the switch between readings.
What This Resistivity Lab Teaches
Determining the resistivity of a wire is AQA A-level required practical 5 and a standard experiment in the Chinese textbook (测量金属丝的电阻率). The physics is R = ρL/A; the marks are in the measurements: the diameter with a micrometer and its zero error, the circuit, the current, and finding ρ from a graph.
Here you measure a real-feeling wire: it is slightly oval and tapered, the micrometer has a zero error, the clips have contact resistance, and current heats the wire. Measure the diameter, build the circuit, record U and I at several lengths, then plot R against L.
The analysis compares the gradient method with the mean of RA/L, shows the intercept that the contact resistance produces, and builds the uncertainty from 2 × %d plus the gradient's uncertainty — so you can see why the diameter matters most.
Frequently Asked Questions
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