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Concept of Heat and Temperature
Kelvin, a British Physicist, was born in Belfast in 1824. He worked in the field of thermodynamics. He restated the second law of thermodynamics in 1850, and introduced the absolute scale of temperature. Jule-Kelvin effect was developed by him in collaboration with Joule.
The words "Temperature" and "Heat" are not new
in our daily life. We use the words cold, cool, warm, hot etc. many times which are related with heat and temperature. When we touch ice we may say "Oh cold!" and when we stand outside our home in the summer day we may say "Oh! its very hot today." The cause of these sensations is nothing but heat. Previously it was thought that heat was a fluid which when transferred in cold objects makes them hot. But this concept was unable to explain many experimental phenomena. The quantity of heat has a meaning only when we define it in terms of energy. Transfer of energy takes place from a hot to a cold body by conduction, convection or radiation. Heat, unlike other forms of energy, arises due to the molecular motions of the matter. Temperature measure the degree of hotness of a body. It also determines the direction of flow of heat when two bodies are placed in thermal contact. Temperature of a body is associated with the average kinetic energy of the molecules of the matter. The sense was use when we touch an object is temperature which determines body may produce a sense of cold for one person and a sense of hot for another person, at the same time. A familiar example is, if we place our one hand in cold water and another hand in hot water then we place bother hands in water at room temperature, we will find that the hand which was previously placed in cold water feels hot and the other hand feels cold.
in our daily life. We use the words cold, cool, warm, hot etc. many times which are related with heat and temperature. When we touch ice we may say "Oh cold!" and when we stand outside our home in the summer day we may say "Oh! its very hot today." The cause of these sensations is nothing but heat. Previously it was thought that heat was a fluid which when transferred in cold objects makes them hot. But this concept was unable to explain many experimental phenomena. The quantity of heat has a meaning only when we define it in terms of energy. Transfer of energy takes place from a hot to a cold body by conduction, convection or radiation. Heat, unlike other forms of energy, arises due to the molecular motions of the matter. Temperature measure the degree of hotness of a body. It also determines the direction of flow of heat when two bodies are placed in thermal contact. Temperature of a body is associated with the average kinetic energy of the molecules of the matter. The sense was use when we touch an object is temperature which determines body may produce a sense of cold for one person and a sense of hot for another person, at the same time. A familiar example is, if we place our one hand in cold water and another hand in hot water then we place bother hands in water at room temperature, we will find that the hand which was previously placed in cold water feels hot and the other hand feels cold.
