Question

Name three types of thermal expansion?

Answer 1

Hint: When solids, liquids and gases are subjected to change in temperature, there is some change in their dimensions. Thermal expansion refers to the expansion or contraction of the dimensions of the solid, liquid or gas when their temperature is changed.

Complete answer:
Let us first understand what thermal expansion is. When solids, liquids and gases are subjected to change in temperature, there is some change in their dimensions. Thermal expansion refers to the expansion or contraction of the dimensions of the solid, liquid or gas when their temperature is changed. There are three types of thermal expansion depending on the dimension that undergo change and that are linear expansion, areal expansion and volumetric volume.
(i) Linear expansion: Linear expansion is the expansion in the length of the substance which is subjected to increasing temperature. Linear expansion mostly takes place in solids.
(ii) Areal expansion: Areal expansion is the expansion of the surface area of the substance which is subjected to increasing temperature. Areal expansion is also called superficial expansion.
(iii) Volume expansion: Volumetric expansion is the expansion in the volume of the substance which is subjected to increasing temperature. For an open solid, volumetric expansion refers to the expansion of the volume enclosed by it.

It is found that the ratio of expansion of a particular dimension is given by a solid to its original dimension is directly proportional to the change in its temperature.For linear expansion, ${\displaystyle \frac{\mathrm{\Delta }l}{l}}=\alpha \mathrm{\Delta }T$, where ${\displaystyle \frac{\mathrm{\Delta }l}{l}}$ is the fraction by which the length changes when the temperature is changed by $\mathrm{\Delta }T$.$\alpha$ is called the coefficient of linear expansion. For areal linear expansion, ${\displaystyle \frac{\mathrm{\Delta }A}{A}}=\beta \mathrm{\Delta }T$, where ${\displaystyle \frac{\mathrm{\Delta }A}{A}}$ is the fraction by which the area changes when the temperature is changed by $\mathrm{\Delta }T$.$\beta$ is called the coefficient of areal expansion. For volumetric linear expansion, ${\displaystyle \frac{\mathrm{\Delta }V}{V}}=\gamma \mathrm{\Delta }T$, where ${\displaystyle \frac{\mathrm{\Delta }V}{V}}$ is the fraction by which the volume changes when the temperature is changed by $\mathrm{\Delta }T$.$\gamma$ is called coefficient of volumetric expansion.

Note: The coefficients of linear, areal and volume expansion are related to each other. It is found that $\gamma =2\beta =3\alpha$. If the coefficient of linear expansion is given and it is asked to calculate the volume change then we can use this relation.