The amount by which the area of a material increases when the temperature is raised one degree is called the coefficient of superficial expansion. The unit of coefficient of superficial expansion is .
The coefficient of superficial expansion can be designated by the symbol (beta).
Areal expansion in solid
Consider a material with the area of at \(c\). And, the material is heated upto \(c\). Now, the length of the material is .
Let be the coefficient of linear expansion.
We know that,
The change in area \(ΔA\) is proportional to the original area , rise in temperature \(ΔT\), and material type.
Rearranging the above equation,
The will vary for different materials.