IB Physics IA idea · Heat and thermal physics
IB Physics IA idea: how much does a heated metal rod grow?
Rails buckle in summer. Measure how much a rod stretches per degree.
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 change in length of a 0.5 m metal rod in a circulating-water jacket depend on temperature from 20 °C to 80 °C in eight steps, measured with a dial gauge, and what linear expansivity 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
- temperature, 20 to 80 degrees C in 8 steps
- You measure
- change in length, 0 to 1 mm for 0.5 m
- You keep the same
- rod material
- dial gauge zero
- bath stirring
- insulation
Method
Place a metal rod in a jacket of circulating water and measure its length with a dial gauge or optical lever for each temperature. Repeat on cooling.
Data analysis
Plot change in length against temperature; the gradient divided by L0 gives alpha. Compare with the data-book value and discuss the thermal gradient and contraction of the support.
How it works
You change Rod temperature (°C) and measure Change in length (mm) in Rod in water jacket, keeping Rod material, Starting length, Reading method the same. Expect a graph of Change in length / mm against Temperature / °C: The gradient divided by L₀ gives α.
Make it yours
Compare aluminium, steel and brass; try a bimetallic strip.
Safety
Take care with: heat and hot liquids.
Hot water: handle carefully.
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