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# Mod 1 - Module 1 Thermodynamics Thermodynamics...

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Module - 1: Thermodynamics Thermodynamics: Thermodynamics (Greek: thermos = heat and dynamic = change) is the study of the conversion of energy between heat and other forms, mechanical in particular. All those problems that are related to the inter- conversion of heat energy and work done are studied in thermodynamics. In thermodynamics, we discuss different cycles such as Carnot cycle, Rankine cycle, Otto cycle, diesel cycle, refrigerator, compressors, turbines and air conditioners. Thermal equilibrium and Temperature: The central concept of thermodynamics is temperature. Temperature is familiar to us all as the measure of the hotness or coldness of objects. We shall learn afterwards that temperature is a measure of the average internal molecular kinetic energy of an object. It is observed that a higher temperature object which is in contact with a lower temperature object will transfer heat to the lower temperature object. The objects will approach the same temperature, and in the absence of loss to other objects, they will then maintain a constant temperature. They are then said to be in thermal equilibrium. Thermal equilibrium is the subject of the Zeroth Law of Thermodynamics. The Zeroth Law of Thermodynamics: The "zeroth law" states that if two systems are in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other. This law states that if object A is in thermal equilibrium with object B , and object B is in thermal equilibrium with object C , then object C is also in thermal equilibrium with object A . The message of the zeroth law is: “Every body has a property called temperature”. Two objects are defined to have the same temperature if they are in thermal equilibrium with each other. This law allows us to build thermometers. For example the length of a mercury column (object B ) may be used as a measure to compare the temperatures of the two other objects. The zeroth law, which has been called a logical afterthought, came to light only in 1930s, long after the first and second laws of thermodynamics had been discovered and numbered. Because the concept of temperature is fundamental to those two laws, the law that establishes temperature as a valid concept should have the lowest number-hence the zero. The zeroth law has a fairly straightforward statistical interpretation and this will allow us to begin to establish the equivalence between the statistical definitions and the conventional thermodynamic ones. Temperature and Heat: If you take a can of cola from the refrigerator and leave it on the kitchen table, its temperature will rise- rapidly at first but then more slowly – until the temperature of the cola equals that of the room(the two are then in thermal equilibrium).

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