want to know about expansion of material

Dear student,

When heat is added to most materials, the average amplitude of the atoms' vibrating within the material increases. This, in turn, increases the separation between the atoms causing the material to expand. If the material does not go through a phase change, the expansion can be easily related to the temperature change. The linear coefficient of thermal expansion ( a) describes the relative change in length of a material per degree temperature change. As shown in the following equation, a is the ratio of change in length ( Dl) to the total starting length (l_i) and change in temperature ( DT).

By rearranging this equation, it can be seen that if the linear coefficient of thermal expansion is known, the change in components length can be calculated for each degree of temperature change. This effect also works in reverse. That is to say, if energy is removed from a material then the object's temperature will decrease causing the object to contract.