改变世界的物理学二.pptx

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1、Zeroth lawFirst lawSecond lawTUSdU=dQ+dWdQ TdS1(P1,V1)=2(P2,V2)第1页/共78页“To understand a science it is necessary to know its history.”August Comte (1789-1857)in“Positive Philosophy”第2页/共78页The purview of science grows rapidly with time.It is the responsibility of each generation to join new insights

2、to old wisdom,and to distill the key ideas for the next generation.James P.Sethna第3页/共78页 The pursuit of rigor involves almost inevitably abandoning the historical approach.Great ideas are more often arrived at by a combination of intuition and a judicious disregard of niceties than by a systematic

3、and logical development of explicitly formulated premises,But once the goal has been attained it is possible to go back over the road and see how the same end could have been reached more logically.A.B.Pippard第4页/共78页1 1.“热热”究竟是什么究竟是什么？第5页/共78页冷热的感觉冷热的感觉第6页/共78页伽利略Galileo Galilei温度计的发明第7页/共78页第8页/共7

4、8页 “By the use of these instruments we have learned,that if we take 1000 or more different kinds of matter,such as metals,stones,salts,woods,cork,feathers,wool,water and a variety of other fluids,although they be at first of different heats,let them be placed together in the same room without a fire

5、,and into which the sun does not shine,the heat will be communicated from the hotter of these bodies to the colder,during some hours perhaps,or the course at a day,at the end of which time,if we apply a thermometer to them all in succession,it will point precisely to the same degree.”Black（17281799)

6、第9页/共78页热质？热质？第10页/共78页焦 耳 James Prescott Joule热量能量？热量能量？第11页/共78页第12页/共78页第13页/共78页dU=dQ+dW第14页/共78页瓦特 J.Watt蒸汽机蒸汽机用热做功用热做功存在限制否？存在限制否？第15页/共78页2.Carnot2.Carnot循环循环第16页/共78页卡 诺Sadi Carnot卡卡诺循环诺循环第17页/共78页(1824)第18页/共78页Carnots ideas QW第19页/共78页“The production of motive power is then due in steam-en

7、gines not to an actual consumption of caloric,but to its transportation from a warm body to a cold body,that is,to its re-establishment of equilibrium-an equilibrium considered as destroyed by any cause whatever,by chemical action such as combustion,or by any other.”Carnots ideas第20页/共78页“According

8、to this principle,the production of heat alone is not sufficient to give birth to the impelling power:it is necessary that there should also be cold;without it,the heat would be useless.”第21页/共78页“The necessary condition of the maximum is,then,that in the bodies employed by realize the motive power

9、of heat there should not occur any change of temperature which may not due to a change of volume.”第22页/共78页第23页/共78页Carnots Cycle第24页/共78页“All reversible engines operating between the same two constant temperatures TH and TL have the same efficiency.Any irreversible engine operating between the same

10、 two fixed temperatures will have an efficiency less than this.”Carnots theorem第25页/共78页 Q1 Q1Original proof of Carnots theoremWWWW第26页/共78页(1834)(1850)第27页/共78页Clapeyrons Graph第28页/共78页(1834)(1850)第29页/共78页A careful examination shows that the new method does not stand in contradiction to the essent

11、ial principle of Carnot,but only to the subsidiary statement that no heat is lost,since in the production of work it may very well be the case that at the same time a certain quantity of heat is consumed and another quantity transferred from a hotter to a colder body,and both quantities of heat stan

12、d in a definite relation to the work that is done.Clausius ideas第30页/共78页第31页/共78页W=WT1Q1 Q1在热力学第一定律的基础上：在热力学第一定律的基础上：第32页/共78页Clausuis statement Not possible第33页/共78页在热力学第一定律的基础上：在热力学第一定律的基础上：第34页/共78页 第35页/共78页熵的引入熵的引入克劳修斯R.Clausius第36页/共78页e=W/QH=1-QL/QH=1-TL/THClausius deduction(1865)QL/TL=QH/TH

13、,QH/TH-QL/TL=0(Q/T)=0第37页/共78页第38页/共78页T1T2T3T4T5T6T7(Q1/T1-Q2/T2)+(Q2/T2-Q3/T3)+(Q6/T6-Q7/T7)=0第39页/共78页第40页/共78页Irreversible:e=W/QH=1-QL/QH QH/TH(Q/T)0第41页/共78页R&IRFor isolated system:S 0第42页/共78页“The energy of the universe is a constant.The entropy of the universe approaches a maximum.”Clausius S

14、tatement第43页/共78页Thermodynamic system第44页/共78页Thermal Equilibrium 第45页/共78页第46页/共78页第47页/共78页第48页/共78页第49页/共78页第50页/共78页第51页/共78页第52页/共78页第53页/共78页第54页/共78页第55页/共78页第56页/共78页第57页/共78页第58页/共78页第59页/共78页第60页/共78页3.Maxwell3.Maxwell分布律分布律第61页/共78页 Krnig(1856)第62页/共78页 对任何领域的学生来说，阅读相关对任何领域的学生来说，阅读相关的原始文献

15、都是极有益处的，因为的原始文献都是极有益处的，因为处在雏形中的科学最容易被消化。处在雏形中的科学最容易被消化。James Clark Maxwell第63页/共78页Phil.Mag.19(1860)19第64页/共78页第65页/共78页第66页/共78页第67页/共78页Equilibrium distributiondn is the number of moleculesvy vy+dvyinni the number of molecules ofnear v第68页/共78页among N molecules,how many are near vprobability that

16、one molecule is near v proportional to dvx.Meaning of dn/N第69页/共78页Isotropic assumptionThe solution isThe probability should be normalized第70页/共78页12aaeach normalized第71页/共78页Known while第72页/共78页For unit volumeMaxwell velocity distribution第73页/共78页Maxwell speed distributionFor one molecule,what speed is most possible?Most probable speedAmong N molecules,what is the speed most molecules have in unit interval?第74页/共78页Maxwellian can be written as第75页/共78页The average speed第76页/共78页第77页/共78页感谢您的观看！第78页/共78页