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The concept of temperature is rooted in qualitative ideas based on our sense of touch.  A body that feels “hot” usually has a higher temperature than a similar body that feels “cold.”

Many properties of matter that we can measure i.e. :—

  • the length of a metal rod
  • steam pressure in a boiler
  • the ability of a wire to conduct an electric current
  • the color of a very hot glowing object

depend on temperature.


Temperature and kinetic energy

Temperature is also related to the kinetic energies of the molecules of a material. We will discuss the relation between kinetic energy of the molecules of a material and its temperature in Kinetic Theory of Gases.

In this article we’ll develop a macroscopic definition of temperature :-

“It is the quantity by the aid of which the hotness or coldness of a body can be determined.”


To use temperature as a measure of hotness or coldness, we need to construct
a temperature scale. To do this, we can use any measurable property of a system that varies linearly over a wide range with its “hotness” or “coldness.”

For example, the length of mercury column filled in the thermometer, changes linearly with temperature.

Temperature - Curio Physics


When the system becomes hotter, the liquid (usually mercury or ethanol) expands and rises in the tube, and the value of L increases.

Another simple system to measure temperature, is a quantity of gas in a constant volume container. The pressure p, measured by the gauge, increases or decreases as the gas becomes hotter or colder.

Temperature - 2 - Curio Physics

A third example is the electrical resistance R of a conductor wire, which changes when the wire is hot or cold (the changes must be linear).

Each of these properties gives us a number (L, p, or R) that changes linearly with warmth and coolness, so each property can be used to make a thermometer.


About the author

Manoj Kumar Verma

Hi, I'm Manoj Kumar Verma, a physics faculty having 7 years of teaching experience. I have done B.Tech (E.E.). I am also a YouTuber and Blogger. This blog is dedicated to help students learn the physics concepts easily.

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