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Thermodynamics (Greek thermai, ‘heat’ + dunamikos, ‘powerful’) is the study of heat and temperature in relation to the mechanical power produced. The distinction between heat and temperature is that heat is a form of energy and temperature is the measure of hotness. For example, a pot of water placed on a stove receives energy and this increases its temperature.
Kinetic Energy is the form of energy corresponding to movement. For a body of mass m moving a velocity v the kinetic energy is 0.5 mv2.
Potential Energy corresponds to height above a base line: that is, the energy required to raise a body of mass—to a height h above base line is mgh where g is the acceleration due to gravity. Another form of potential energy corresponds to deformation—as in stretching an elastic band or putting gas under pressure.
There are two laws which have been established to explain the nature of thermo-dynamics. The first law states that if an interaction occurs between two bodies then energy is neither created nor destroyed. In other words if a quantity of heat is absorbed by one body this energy is equal to the sum of the increase in internal energy and any external work done by the body. This law is a direct consequence of the law of conservation of energy. This change in internal energy will be made up of an increase in both the kinetic and potential energy of the body. This change of energy may take any form, that is, thermal, mechanical, etc. This law states that it is possible to convert all work totally into a thermal change, such as heat.
The second law is that the reverse is not true; that is, all heat cannot be turned back into work. In other words, energy will not be transferred from a cooler body to a warmer body. This law was established by the French engineer Sadi Carnot (1796 - 1832) who worked on trying to establish the most efficient engine possible. This engine, the Carnot engine, established the upper limit of efficiency for turning thermal energy into mechanical energy. His sole publication, called Réflexion sur la Puissance Matrice de Feu, explains his concepts that became known as the Second Law of Thermodynamics. AA
Further reading M.W. Zemansky and , Richard Dittman, Heat and Thermodynamics. |
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