Thermal Expansion & Bimetal Strip
Heat or cool a metal bar and see how much it grows, then bend a bimetal strip.
Drag the thermometer up to heat the bar and down to cool it. Then switch to the bimetal strip to see it bend.
About the Thermal Expansion & Bimetal Strip
Free thermal expansion & bimetal strip. Heat or cool a metal bar and see how much it grows, then bend a bimetal strip. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the thermal expansion & bimetal strip runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Heat or cool a metal bar and see how much it grows, then bend a bimetal strip. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Thermal Expansion & Bimetal Strip
- Use the controls to change Material, Temperature, Length at 20 °C. The simulation reacts instantly.
- Pick an option such as Steel, Aluminium, Copper, Glass to switch modes or load an example.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Compare steel with invar at 500 °C.
- Cool the bar to -50 °C.
- Show the bimetal strip and heat it, then cool it.
Key ideas you can learn
- ΔL = α × L₀ × ΔT.
- Different materials have different expansion coefficients α.
- A bimetal strip bends because one metal expands more.
- Bridges and railways need expansion gaps.
Where this is used in the real world
Thermostats, expansion joints in bridges, railway tracks, glass cookware and precision instruments all depend on thermal expansion.
Who is this simulation for?
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is the coefficient of linear expansion?
The fractional change in length per degree of temperature change.
Why does a bimetal strip bend?
The two bonded metals expand by different amounts, so the strip curves toward the metal that expands less.
Is the Thermal Expansion & Bimetal Strip free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Thermal Expansion & Bimetal Strip work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.