define thermal expansion
Answers
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The expansion or change in shape, area or volume of the of matter due to heat is called Thermal Expansion.
The word thermal means relating to temperature.
When there is change in length of substance due to heat, it is called Linear Expansion.
When there is change in area of substance due to heat, it is called Superficial Expansion.
When there is change in volume of substance due to heat, it is called Cubical Expansion.
Applications of thermal expansion are:
♣ Thermometer
It is a device which uses linear expansion to measure the temperature of the body. When it comes in the contact with body the mercury rises up by which we can know body temperature.
♣ Pendulum clock
It also works on principle of thermal expansion. The metal rod used in it expands and its length increases during summers because of sun's heat and in winters, it winters the length decreases and made time of it wrong. It is made up of special type of steel called invar which have negligible expansion.
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