The formula for the thermal expansion of solids

You can work out the amount that a solid expands when its temperature is raised by a certain amount by using the following formula:

The linear expansivity is a constant for a material and is how much a unit length of the material would expand for a 1^o rise in temperature — it is a very small number: 0.000 0012 for iron.

This means that an iron rod one metre long would expand by 0.000 0012 m when its temperature is raised by 1^o C. If the 1m iron rod had its temperature raised by 1000 ^oC it would still only expand by just over 1 mm!