Concept of Temperature
Everybody of us has the feeling of hot and cold. So, the measure of how much hot or cold a body is apparently called temperature of that body. Temperature is a measure of the intensity or degree of hotness in a body. Technically, it is determined by getting the average speed of a body’s molecules. That means, it can apparently be said that temperature means the degrees of hotness of a body. Suppose, there are two bodies; one is ‘A’ and the other one is ‘B’. If it is found by touching that body A is warmer than the body B then we can say that the body temperature of the body A is more and that of body B is less. Perfect definition of temperature may be given as:
Temperature is the thermal state of a body which controls the flow of heat from one body to another body and determines the direction of flow of heat.
In order to make the instrument for measurement of warmness or temperature, we need materials whose particular property changes significantly due to the change of temperature. For example, it can be said that in resistance thermometer platinum resistance is used and observing the thermometric property of electric resistance temperature is measured. On the other hand, in thermocouple thermometer junctions of two different metals are used and observing the property of thermal electromotive force temperature is measured. Again, in high-temperature radiation pyrometer, using the radiation property of a heated body temperature above 5000C is measured.