# Formula Linear thermal expansion Initial length    Initial temperature    Final temperature    Coefficient of thermal expansion

## Length difference

Unit
Length of a metallic body (metal rod) which has changed after heating. If the metal rod is heated, it becomes longer!$$\Delta l ~=~ l_1 ~-~ l_0$$

## Initial length

Unit
Length of the metal rod before heating.

## Initial temperature

Unit
Temperature of the metal rod before heating.

## Final temperature

Unit
Temperature of the metal rod after heating.

## Coefficient of thermal expansion

Unit
Coefficient of thermal expansion is a material-dependent constant that tells how much a body expands when the temperature changes $$\Delta T ~=~ \class{red}{T_1} ~-~ \class{violet}{T_0}$$.