Thermal Expansion And Contraction:

Assume that we have a sample of solid material which expands whenever the temperature rises. This is the common case, though some solids enlarge more per degree Celsius than others. The extent to which the width, height, or depth of a solid changes per degree Celsius is termed as the thermal coefficient of linear expansion.

For most of the materials, in a reasonable range of temperatures, the coefficient of linear expansion is steady. This means that when the temperature changes by 2°C, the linear dimension will change twice as much as it would if the temperature variation were only 1°C. Though, there are limits to this, obviously. When you heat a metal up to a high adequate temperature, it will become soft and eventually will melt or even burn or vaporize. When you cool the mercury in a thermometer down sufficient, it will freeze. Then the simple length-versus-temperature rule no longer exerts.

In common, if s is the difference in linear dimension (in meters) generated by a temperature change of T (in degrees Celsius) for an object whose linear dimension (in meters) is d, then the thermal coefficient of linear expansion, represented by the lowercase Greek letter alpha (α), and is given by the equation:

α = s/(dT)

Whenever the linear dimension raises, consider s to be positive; whenever it decreases, consider s to be negative. The rising temperatures generate positive values of T; falling temperatures generate negative values of T. The coefficient of linear expansion is stated in meters per meter per degree Celsius. The meters cancel out in this expression of units; therefore the technical quantity is per degree Celsius, represented by /°C.