Pressure-Volume or P-VWork Vi Pa 8w=-Pextdv always gas V W=- xdV P .Isobaric Change:Pext=const. w=-Pext(V-Vi)=-PexAV PDF文件使用"pdfFactory Pro”试用版本创建m,fineprint.com,cn
Pressure-Volume or P-V Work Vi , Pgas Pext w = -PextdV always =- ò f V i V dV ext w P d •Isobaric Change: Pext = const. w = -Pext(Vf - Vi ) = -PextDV PDF 文件使用 "pdfFactory Pro" 试用版本创建 fwww.fineprint.com.cn f
Pressure-Volume or P-V Work .Reversible expansion A reversible change is one that can be reversed by an infinitesimal modification of a variable. 8w=-PexdV--(Pin+dP)dV=-PindV W=一 [P.dV V. in .For an ideal gas in an isothermal expansion T W=-nRTIn(V/V)=-nRTIn(P/P) PDF文件使用"pdfFactory Pro”试用版本创建ww.fineprint.com.cn
•Reversible expansion Pressure-Volume or P-V Work A reversible change is one that can be reversed by an infinitesimal modification of a variable. d w = -PextdV=-(Pin±dP)dV= -PindV =- ò f V i V dV in w P •For an ideal gas in an isothermal expansion T Wr =-nRTln(Vf /Vi )=-nRTln(Pi /Pf ) PDF 文件使用 "pdfFactory Pro" 试用版本创建 ÿwww.fineprint.com.cn
area-nRT In (Vr/Vi) Fig.2.4.The reversible isothermal work of expansion of a perfect gas is 1larca=pex△V given by the area beneath the isotherm.Note that it is greater than the irreversible work done against Pex=Pin =nRTIV constant pressure. isothermal, reversible expansion Pe=constant irreversible expansion PDF文件使用"pdfFactory Pro”试用版本创建癱m,fineprint.com,cn
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Reversible process In a reversible process the system passes through a sequence of states only infinitesimally removed from equilibrium states(where for example,expansion and compression tendencies just balance) .The maximum work available from a system operating between specified initial and final states,and passing along a specified path,is obtained when it is operating reversibly. .In a reversible process,not only the system,but also the surroundings can recover,no change left in the surroundings. PDF文件使用"pdfFactory Pro”试用版本创建m,fineprint..com,cn
Reversible process • In a reversible process the system passes through a sequence of states only infinitesimally removed from equilibrium states(where ,for example, expansion and compression tendencies just balance) •The maximum work available from a system operating between specified initial and final states, and passing along a specified path, is obtained when it is operating reversibly. •In a reversible process, not only the system, but also the surroundings can recover, no change left in the surroundings. PDF 文件使用 "pdfFactory Pro" 试用版本创建 fwww.fineprint.com.cn f
Path Functions Path Functions These are properties which depend on how the system was prepared (or how a change was effected).Work,w,and heat, Q,are examples of path functions. Because we do not speak of a system as possessing a particular amount of 'work or heat',or of its 'work or heat'having a particular value.Properties that depend on the path we call path functions PDF文件使用"pdfFactory Pro”试用版本创建剑，fineprint.com,cn
Path Functions These are properties which depend on how the system was prepared (or how a change was effected). Work, w, and heat, Q, are examples of path functions. Path Functions Because we do not speak of a system as possessing a particular amount of ‘work or heat’, or of its ‘work or heat’ having a particular value. Properties that depend on the path we call path functions PDF 文件使用 "pdfFactory Pro" 试用版本创建 餳ÿ www.fineprint.com.cn