Thermal Expansion
Observe how a metal rod expands when heated and contracts when cooled. The micrometer measures the precise change in length caused by thermal expansion.
At room temperature, the metal rod maintains its original length. The micrometer shows no expansion.
The Science Behind Thermal Expansion
Thermal expansion occurs when materials expand upon heating and contract when cooled:
- Atomic vibration: Heat increases atomic vibrations, causing atoms to take up more space
- Linear expansion: The change in length (ΔL) is proportional to temperature change (ΔT)
- Coefficient of expansion: Each material has a characteristic expansion rate per degree temperature change
Thermal expansion must be accounted for in bridges (expansion joints), railways (gaps between tracks), and piping systems. Bimetallic strips in thermostats use differential expansion of two metals.
ΔL = α × L₀ × ΔT
Where:
ΔL = change in length
α = coefficient of linear expansion
L₀ = original length
ΔT = change in temperature
