Thermodynamics

An important characteristic of a material is how much it expands for a given increase in temperature. The amount that a rod of material lengthens is given by L=L₀ [1+ α (T-T₀)], where L₀ is the length of the rod at some temperature T₀, and L is the length at some other temperature T; α (Greek alpha) is called the coefficient of linear expansion. Some typical values for α ×10⁶ (per °C) are: aluminum, 24.0; copper, 16.8; glass, 8.5; steel, 29.0 (this notation means that, for example, aluminum expands at a rate of 24.0/1,000,000 for each degree Celsius change in temperature). Volumes, of course, also expand with a rise in temperature, obeying a law similar to that for linear expansion; coefficients of volume expansion are approximately three times as large as that for linear expansion for the same material. It is interesting to note that, if a hole is cut in a piece of material, the hole expands just as if there were the same material filling it!