Thermal expansion is the phenomenon where materials increase in size when heated. There are three main types of thermal expansion: 1. Linear expansion is the increase in length of a material when heated. 2. Area expansion is the growth of a material's surface area due to heating. 3. Volume expansion is the increase in a material's overall volume from an increase in temperature. Thermal expansion occurs because the atoms and molecules in materials vibrate more when heated, causing the material to take up more space. Real-world examples of accounting for thermal expansion include building expansion gaps into bridges.

1. Thermal Expansion
Overview

2. Thermal Expansion
Thermal expansion is the phenomenon observed in
solids, liquids, and gases. In this process, an object or
body expands on the application of heat (change in
temperature). Thermal expansion defines the
tendency of an object to change its dimension either
in length, density, area, or volume due to heat.

3. What causes thermal expansion
With increased temperature, the atoms vibrate back and forth
over greater distances. With wider vibrations in all dimensions, the solid expands
as a whole.

4. This is atoms when heated

5. This is atoms when heated

6. This is atoms when heated

7. Thermal Expansion: In 3 ways
The change in one dimension of a
solid (length, width, or thickness) is
called
linear expansion.
Linear Expansion
The increase in volume of a solid
when heated is known as volume
expansion. Or a three-dimensional
material expansion.
Volume Expansion
Area Expansion is the growth of an
object's surface, or stretching its area
alone. An area expansion is a two-
dimensional material expansion. The
temperature of the thing determines
how much it expands.
Area Expansion

8. The change in one dimension of
a solid (length, width, or
thickness) is called
linear expansion.
Linear Expansion

9. Wherein, L or ∆L is change in length.
Lo is the original length,
α is the thermal coefficient
and ∆T is Change in temperature.
Linear Expansion

10. Area Expansion is the growth of an object's
surface, or stretching its area alone. An area
expansion is a two-dimensional material
expansion. The temperature of the thing
determines how much it expands.
Area Expansion

11. Wherein, A or ∆A is change in area.
Ao is the original Area,
α is the thermal coefficient
and ∆T is Change in temperature.
Area Expansion

12. The increase in volume of a solid
when heated is known as volume
expansion.
Volume Expansion

13. Wherein, V or ∆V is change in Volume.
Vo is the original Volume,
α is the thermal coefficient
and ∆T is Change in temperature.
Volume Expansion

14. Thermal expansion coefficient

15. Linear expansion, Area expansion and Volume expansion
Sample problems.

16. Linear Expansion
A steel is 40 cm long at 20 oC. The coefficient of linear expansion for steel is 12 x 10-6 (Co)-1. The
increase in length and the final length when it is at 70 oC will be…
Known :
The change in temperature (ΔT) = 70oC – 20oC = 50oC
The original length (L1) = 40 cm
Coefficient of linear expansion for steel (α) = 12 x 10-6 (Co)-1
Unkown : The change in length (ΔL) and the final length (L2)
Solution :
a) The change in length (ΔL)
ΔL = α L1 ΔT
ΔL = (12×10-6 oC-1)(40 cm)(50oC)
ΔL = 0.024 cm
b) The final length (L2)
L2 = L1 + ΔL
L2 = 40 cm + 0.024 cm
L2 = 40.024 cm

17. Area Expansion
At 20oC, the length of a sheet of steel is 50 cm and the width is 30 cm. If the coefficient of linear
expansion for steel is 10-5 oC-1, determine the change in area and the final area at 60oC.
Known :
The initial temperature (T1) = 20oC
The final temperature (T2) = 60oC
The change in temperature (ΔT) = 60oC – 20oC = 40oC
The initial area (A1) = length x width = 50 cm x 30 cm = 1500 cm2
The coefficient of linear expansion for steel (α) = 10-5 oC-1
Unknown : The change in area (ΔA) and the final area (A2)
Solution :
The change in area (ΔA) :
ΔA = 2 α A1 ΔT
ΔA = 2 (10-5 oC-1)(1500 cm2)(40oC)
ΔA = 1.2 cm2
The final area (A2) :
A2 = A1 + Δ A
A2 = 1500 cm2 + 1.2 cm2
A2 = 1501.2 cm2

18. Volume Expansion
At 30 oC the volume of an aluminum sphere is 30 cm3. The coefficient of linear expansion is 24 x
10-6 oC-1. If the final temperature is 260oC, what is the final Volume of the aluminum sphere?
Known :
The coefficient of linear expansion (α) = 24 x 10-6 oC-1
The initial temperature (T1) = 30oC
The initial volume (V1) = 30 cm3
The change in temperature (ΔT) = 260oC – 30oC = 230oC
Unknown: Change in Volume and final volume
Solution :
The change in Volume (ΔV) :
ΔV = 3 α V1 ΔT
ΔV = 3 (24 x 10-6 oC-1)(30 cm3)(230oC)
ΔV = 0.4968
ΔV = 0.5cm3
The final volume (V2) :
V2 = V1 + Δ V
V2 = 30cm3 + 0.5cm3
V 2 = 30.5cm2

19. Thermal
Expansion in
Real World
Expansion gaps are
built into bridge
roadways to
prevent contact
stresses produced by
thermal expansion.

20. THANK YOU!!!!