IB Physics IA idea · Electricity and electronics
IB Physics IA idea: how the resistance of a metal wire changes with temperature
A copper coil heats up and its resistance climbs. Measure the temperature coefficient yourself.
These ideas are starting points, not an IA to copy. Never copy an idea blindly: make the question, method and analysis your own, and check your plan with your teacher.
Example research question
How does the resistance of an insulated copper coil depend on temperature from 20 °C to 85 °C in eight steps in a water bath, measured by a four-wire method, and what temperature coefficient of resistance follows?
Change the system, the range or the method so the question is yours. Check it against the research question checklist in our Physics IA guide.
Variables
- You change
- wire temperature, 20 to 85 degrees C in 8 steps
- You measure
- resistance of the coil, about 5 to 7 ohm
- You keep the same
- wire material
- current (low to avoid self-heating)
- bath volume
- stirring
Method
Immerse an insulated copper or constantan coil in a water bath and measure resistance with a four-wire method as the bath cools. Allow time at each temperature to equilibrate.
Data analysis
Plot R against T. The gradient divided by R0 gives alpha; compare with the accepted value for copper. Use max/min gradients and discuss the effect of a thermal gradient inside the coil.
How it works
You change Wire temperature (°C) and measure Resistance of coil (Ω) in Coil in water bath, keeping Measuring current, Time to equilibrate, Same coil, Stirring the same. Expect a graph of Resistance / Ω against Temperature / °C: The gradient divided by R₀ gives α.
Make it yours
Compare copper with constantan or nichrome, or run the set-up with a thermistor beside it.
Extended Essay angle
A resistivity model combining Matthiessen's rule with experimental data for different alloys.
Safety
Take care with: heat and hot liquids, mains or high-voltage electricity.
Hot water: low-voltage supply, careful handling; protect leads from water.
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