Thermal expansion stretches a heated rod by ΔL = α·L0·ΔT. Pick a material and drag the sliders below to change the temperature change and original length, then watch the change in length respond — the drawing is exaggerated, but the readouts are true.
Heat a rod of aluminium and a rod of Invar by the same amount, and one lengthens while the other hardly stirs. That difference lives in a single material constant, α, the coefficient of linear expansion. This simulation lets you pick that constant from six buttons and watch it steer everything else. Choose Aluminium (α = 23), Brass (19), Copper (17), Steel (12), Glass (about 8), or Invar (1.2, in units of 10-6 per °C) and the rod's response resets instantly — aluminium expanding roughly 19 times as much as Invar for identical settings.
Two sliders supply the rest of the recipe. Temperature change ΔT can run positive for heating or negative for cooling, and Original length L0 sets the starting metre-scale. The readouts return the change in length ΔL, the original L0, and the final length L = L0 + ΔL. Everything traces to ΔL = α·L0·ΔT, a product of three factors: double either ΔT or L0 and ΔL doubles, while a negative ΔT contracts the rod.
Because α itself is only about 10-5 per °C, a real ΔL is tiny — a fraction of a millimetre up to a few millimetres per metre — so the drawing magnifies the motion ×200 while the numbers stay honest. Since ΔL grows with L0, long rails and bridge spans, not short offcuts, are what earn expansion gaps. Run the numbers in the thermal expansion calculator, then open the next experiment in our physics lab collection.
When a solid is heated it lengthens by ΔL = α·L0·ΔT, where α is the coefficient of linear expansion, L0 the original length and ΔT the temperature change. Cooling reverses it.
Each material has its own coefficient α. Invar (about 1.2 ×10^-6 per °C) barely moves, while aluminium (about 23) expands roughly nineteen times as much for the same length and temperature change.
Yes. The change in length is proportional to the original length L0, so a 2 m rod expands twice as much as a 1 m rod of the same material and temperature change — which is why long rails and bridges are built with expansion gaps.
A negative ΔT gives a negative ΔL, so the rod contracts, shrinking by the same rule ΔL = α·L0·ΔT. Heating and cooling are two directions of the same relation.