Question

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Give few examples of thermal expansion and explain them. ​

Answer 1

Thermal expansion definition

Most of the substances solids, liquid, and gases expand on heating and contract on cooling. Their thermal expansions and contractions are usually small and are not noticeable. However, these expansions and contractions are important in our daily life.

The kinetic energy  of the molecules of an object depends on its temperature. The molecules of a solid vibrate with larger amplitude at a high temperature than at low temperatures. Thus, on heating, the amplitude of vibration of the atoms or molecules of an object increases. They push one another farther away as the amplitude of vibrations increases. Thermal expansion results in an increase in length, breadth, and thickness of a substance.

What is the difference between linear thermal expansion and volume thermal expansion?

Linear Thermal Expansion In Solids

It has been observed that solids expand on heating and their expansion is nearly uniform over a wide range of temperatures. Consider a metal rod of length L° at a certain temperature T°. Let its length on heating to a temperature T  becomes L. Thus

Increases in length of the rod = ΔL = L – L0

Increase in temperature = ΔT = T – T°

It is found that change in length ΔL of the solid is directly proportional to its original length L°, and the change in temperature Δ T. That is

ΔL ∝ L0ΔT

ΔL =αL0ΔT …….(1)

L – L0=αL0ΔT

or L =L0(1+αΔT) …..(2)

Where α is called the coefficient of linear thermal expansion of the substance. From equation (1) we get

α = ΔL/L°ΔT

Coefficient of linear expansion

 The coefficient of linear expansion α of a substance is the fraction increase in the length per kelvin rise in temperature.

Thermal expansion examples

Here Are Some Examples of thermal expansion in our Daily Life.

• Cracks in the road when the road expands on heating.
• Sags in electrical power lines.
• Windows of metal-framed need rubber spacers to avoid thermal expansion.
• Expansion joints (like joint of two railway tracks).
• The length of the metal bar getting longer on heating.
• Tire bursts in hot days when filled full of air due to thermal expansion.

I hope it helped you,

don by own, not copid.

Answer 2

1) If you have ever tried to unscrew a stuck lid off a glass jar, you'll appreciate this expansion effect. Simply run some hot water over the metal lid for a few seconds to heat the lid up. This will make the lid expand slightly and it should then be easier to unscrew.

2) Bridges have a long span and in hot weather the materials that the bridge is made of will expand. This could cause the bridge span 'sections' to buckle.To avoid this, expansion joints are designed into the bridge so that the bridge sections can expand freely without buckling.

3) A liquid, when heated, will expand and can be made to rise up a tube. Thermometers use the expansion of a liquid such as mercury or alcohol to measure the temperature using a calibrated scale.