Thermal expansion describes the tendency of an object to change its dimension either in length, area or volume due to heat. Heating up a substance increases its kinetic energy. Depending on the type of expansion thermal expansion is of 3 types– Linear expansion, Area expansion, and Volume expansion.
Linear expansion is the change in length due to heat. Linear expansion formula is given as,
Where,
L0 = original length,
L = expanded length,
α = length expansion coefficient,
ΔT = temperature difference,
ΔL = change in length
Volume expansion is the change in volume due to temperature. Volume expansion formula is given as
Where,
V0 = original volume,
V = expanded volume,
αv = volume expansion coefficient,
ΔT = temperature difference,
ΔV = change in volume after expansion
Area expansion occurs is the change in area due to temperature change. Area expansion formula is given as,
Where,
A = original area,
ΔA = change in the area,
αA = area expansion coefficient,
ΔT = temperature difference,
A0 = expanded area.
Solved Examples
Example 1
A rod of length 5 m heated to 40°C. If the length of increases to 7 m after some time. Find the expansion coefficient. Room temperature is 30°C.
Solution:
Given:
Initial length Lo = 5 m,
Expanded length L = 7 m
Change in length Δ L = 7 – 5 = 2 m
Temperature difference Δ T = 40°C – 30°C  = 10°C
  Absolute temperature T = 10°C +273=283 K
The linear expansion formula is given by,
∴  Length expansion coefficient is given by,
   = 2 / 5 x 283
  Â
