1、2021/9/51大学物理（热学）1)Review2)Carnots cycle3)Entropy2006-12-21用热做功存在限制否？Carnots ideasQW“The necessary condition of themaximum is,then,that in the bodiesemployedbyrealizethemotivepower of heat there should not occurany change of temperature whichmay not due to a change of volume.”Carnots ideasCarnots Cy
2、cle“All reversible engines operatingbetweenthesametwoconstanttemperatures TH and TL have the sameefficiency.Any irreversible engine operatingbetween the same two fixed temperatureswill have an efficiency less than this.”Carnots theoremClausuis statementNot possibleClapeyrons Graph(1834)绝热绝热绝热绝热e=W/Q
3、H=1-QL/QH=1-TL/THClausius deduction(1865)QL/TL=QH/TH,QH/TH-QL/TL=0(Q/T)=0=0TdQrev=?TdQrev=0TdQrevT1T2T3T4T5T6T7(Q1/T1+Q2/T2)+(-Q2/T2+Q3/T3)+(-Q6/T6+Q7/T7)=0熵的引入克劳修斯R.ClausiusTdQdS=baTdQbaTdQIII)()(0)()(=+abTdQbaTdQIIIIrreversible:e=W/QH=1-QL/QHQH/TH(Q/T)0 0TdQrevBAABTdQSS0)()(+abTdQbaTdQIIIbaTdQbaTd
4、QIII)()(BAABTdQSSR&IRFor isolated system:S 0“The energy of the universe is aconstant.The entropy of the universeapproaches a maximum.”Clausius Statement2021/9/51大学物理（热学）1)Review2)Examples3)Order and Disorder2006-12-27e=W/QH=1-QL/QH=1-TL/THClausius deduction(1865)QL/TL=QH/TH,QH/TH-QL/TL=0(Q/T)=0=0TdQ
5、rev=?TdQrev=0TdQrevT1T2T3T4T5T6T7(Q1/T1+Q2/T2)+(-Q2/T2+Q3/T3)+(-Q6/T6+Q7/T7)=0TdQdS=baTdQbaTdQIII)()(0)()(=+abTdQbaTdQIIIIrreversible:e=W/QH=1-QL/QHQH/TH(Q/T)V1.Calculate the change in entropy(a)ofthe gas and(b)of the surroundingenvironment.(c)Evaluate S for 1.00mole,with V2=2.00 V1.Example 20-8=BAABTdQSSBAABTdQSS“Natural processes tend to movetoward a state of greater disorder.”Second Law等几率假定等几率假定S=kBlnW
