2013-2-27 Overview:Laws of Thermodynamics First law of thermodynamics an expression of conservation of energy principle >En-Eout=△Esystem >for closed system: Q=△U+W 6Q=dU+6W(differential form) (conservation of energy principle:energy can neither be created,nor be destroyed;it can change from one form to another,but the total amount of energy remains constant) The first kind of perpetual motion machine is impossible! Overview:Laws of Thermodynamics Second law of thermodynamics >Kelvin-Planck statement:It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work >Clausius statement:It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower-temperature body to a higher- temperature body. The second kind of perpetual motion machine is impossible 62013-2-27 6 First law of thermodynamics an expression of conservation of energy principle ¾Ein – Eout = △Esystem ¾for closed system： Q=△U+W δQ=dU+δW (differential form) (conservation of energy principle: energy can neither be created, nor be destroyed; it can change from one form to another, but the total amount of energy remains constant) 11 The first kind of perpetual motion machine is impossible! Overview: Laws of Thermodynamics Second law of thermodynamics ¾Kelvin-Planck statement: It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work ¾Clausius statement: It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower-temperature body to a higher￾temperature body. 12 Overview: Laws of Thermodynamics The second kind of perpetual motion machine is impossible!