When matter is heated, it normally expands and when cooled, it normally contracts. The atoms in a solid vibrate about their mean position. When heated, they vibrate faster and force each other to move a little farther apart. This results into expansion.
The molecules in liquid or gas move with certain speed. When heated, move faster and force each other to move a little farther apart. This results in expansion of liquids and gases on heating. The expansion is more in liquids than in solids; gases expand even more.
A change in temperature of a body causes change in its dimensions. The increase in the dimensions of the body due to an increase in its temperature is called thermal expansion.
- Linear expansion.
- Areal expansion.
- Volume expansion.
The increase in the volume due to heating is called volume expansion or cubical expansion.The expansion takes place in 3 dimensions.
Calculating change in volume(ΔV ) due to application of heat :
The change in volume ΔV is very nearly ΔV = 3αVΔT. This equation is usually written as ΔV = βVΔT, where β is the coefficient of volume expansion and β ≈ 3α.
Applications of thermal expansion:
- Linear expansion property of mercury is used in thermometers.
- Ever thought that in winter when a cap of metal container gets jammed, and how it’s losened up again after appication of heat, that’s an example of areal expansion.
- The thermostat is a heat-regulating device which works on the principle of thermal expansion.
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