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What Is the Coefficient of Linear Expansion?
Expansion means to change or increase in length. If the change in length is along one dimension (length) over the volume, it is called linear expansion. Here the reason behind the expansion is the temperature change. Thus, it is implied that the temperature change will reflect in the expansion rate. How much material can withstand its original shape and size under the influence of heat radiation is well explained using this concept.
Assuming that the effect of pressure is negligible,
Coefficient of Linear Expansion is the rate of change of unit length per unit degree change in temperature
The coefficient of linear expansion can be mathematically written as
\(\begin{array}{l}\alpha _{L}=\frac{\frac{dL}{dT}}{L_0}\end{array} \) |
Where,
- \(\begin{array}{l}\alpha _{L}\,is\,the\,coefficient\,of\,linear\,expansion.\end{array} \)
- \(\begin{array}{l}dL \,is\,the\,unit\,change\,in\,length\end{array} \)
- \(\begin{array}{l}dT \,is\,the\,unit\,change\,in\,temperature.\end{array} \)
- \(\begin{array}{l}L_{0} \,is\,the\,intial\,length\,of\,the\,object.\end{array} \)
S.I. Unit
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How Does it Work?
- The linear expansion coefficient is an intrinsic property of every material.
- Hence it varies from one material to another.
- The rate at which a material expands purely depends on the cohesive force between the atoms.
- Cohesive force is the force that binds two or more atoms.
- In other words,
- The cohesive force resists the separation between the atoms.
- However, the greater the cohesive force, the expansion will be low for a given increase in temperature.
- Soft metals like Lead has a low melting point and can be compressed easily.
- On heating, the lead will expand faster with a unit rise in temperature.
Applications of Coefficient of Linear Expansion
The outcome of advancements in science and technology is immense. To march with this rapid growth in industrialisation and construction, one needs to be sure about using the material palette. Starting from constructing a building to constructing a satellite, The material used acts as a backbone.
A diverse variety of materials are readily available around us. Each of them has different thermal properties. Comparing the expanding ability with an increase in temperature for various materials is crucial to use them in an appropriate situation. Generally, the material with a higher linear expansion coefficient is strong in nature and can be used in building firm structures. This property can be modified to match the need by mixing the materials. Thus nowadays, metal alloys are getting popular.
Coefficient of Linear Expansion for Various Materials
This section mainly summarizes the coefficient of linear expansion for various materials. Some material shows huge variation in αL when it is studied against variation in temperature and pressure.
For hard solids αL ranges approximately around 10-7 K-1 and for organic liquids αL ranges around 10-3 K-1. Highest αL is observed for Ti-Nb alloy.
Below is the table of materials along with their αL values.
Watch the video and learn how linear expansion varies with the temperature change
Frequently Asked Questions – FAQs
What is the coefficient of linear expansion?
What is heat capacity?
Define thermal stress.
Define thermal conductivity.
What are the factors that affect the internal energy of a system?
- Heat passes into or out of the system,
- Work is done on or by the system, or matter enters or leaves the system.
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@8th grade student
Need any 3 applications of thermal expansion of liquids.
The three applications of thermal expansion of liquids are:
The rise in the level of mercury and alcohol in thermometers is due to the thermal expansion of liquids. These liquids expand ar different rates when compared to the tube, therefore, as the temperature increases, there is a rise in their level and when the temperature drops, the level of these liquids drop.
The second application is in the automobile engine coolant. The coolant that is used in the automobile is used to avoid the overheating of the engine.
The natural cooling of water in nature is the third application of the thermal expansion of the liquid. The existence of freshwater plants and animals is based on the thermal expansion of water.