The volume of a solid substance increases if its temperature is increased. It is called volume expansion.

Let, the initial volume of a substance be V_{1} and initial temperature be **θ _{1}**. When the temperature is raised to

**θ**, its volume becomes V

_{2}_{2}after being increased.

There increase in volume is V_{2} – V_{1} and increase of temperature = **θ _{2} – θ_{1}**

Now if the coefficient of volume expansion is represented by

**γ = [(V _{2} – V_{1}) / V_{1}(θ_{2} – θ_{1})] ….. ………. ………(1)**

**[Increase in surface area / (Initial area x increase of temperature)]**

In equation (1) if the initial volume V_{1} = 1 m^{3} and increase of temperature, **θ _{2} – θ_{1}** = 1K, then

**γ = V _{2} – V_{1 }= increase in volume.**

Therefore, the increase in volume of a solid of volume 1 m^{3} for a rise of temperature 1K is called the coefficient of volume expansion of the material of the solid. The coefficient of volume expansion of copper is **50.1 x 10 ^{-4} m^{3}** means that if the temperature of a copper body with a volume of 1 m

^{3}increases through 1K then its volume will increase by

**50.1 x 10**.

^{-4}m^{3}**The relations among α, β, and γ are as follow: γ = 3α and β = 2α**