Friday, January 2, 2015

Temperature and its Measurement

Heat and temperature

Heat is a format of energy. In the nature there are different forms of energy’s like sound, light and heat. All forms of energy’s satisfy a concept called law of conservation of energy. According to this law energy is neither created nor destroyed and it just converts from one form to another form. Heat is a disordered format of energy. It is because of internal random collisions of molecules. Measuring the hotness or coldness of a body directly without the concept of temperature is very difficult. The human perception never gives the correct understanding of hotness or coldness of a body as it is just comparative. We always compare the hotness or coldness of the body with respect to the another body and it will never give you correct results.

To measure heat, we have a physical quantity called a temperature. Temperature is a measure of heat energy. Heat is the cause and the temperature is its effect. Heat always flows from a body of higher temperature to your body of lower temperature. Temperature is treated as a fundamental physical quantity and it does not depend on any other physical quantities.

To measure temperature we have different kinds of scales like centigrade scale, Foreign heat scale and Kelvin scale. There is a simple relation among all this scales. Though the scales are different, they are measuring the temperature of the same body and it shall be the same. Just because the scale is different the number appears like different one but the original temperature of the body is same. The following is the relation between different kinds of scales.

It could be easily noticed that difference in the temperature is in degrees centigrade is similar to that of the degree Kelvin.

We can solve a small problem where we are going to identify at what temperature the Kelvin scale and the foreign heat scale are going to show the same reading ?

To measure the temperature we have different kinds of thermometers. Each of this thermometers works basing on a certain principle. For example ,mercury Thermometer works on the principle that when the temperature is increase, the volume expansion of the mercury is a uniform and proportional. Similarly the volume of a gas like hydrogen increases proportionately with temperature at constant pressure and this concept is used in designing gas Thermometer.

For a ohmic material,with respect to the increase of the temperature resistance increases in the proportionally and this concept also can be used to designing a Thermometer called resistance Thermometer.

We can derive a small formula to find the temperature of a body using any of these Thermometers as shown below.

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