SECOND_LAW_FALL_07

SECOND_LAW_FALL_07 - THERMODYNAMICS FOURTH EDIIICN J P...

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Unformatted text preview: THERMODYNAMICS FOURTH EDIIICN J. P Holmon- . o r c e . ) : ' o ' M - . h o . . o 1 . a , . - - . . n > o u l h e r n M e l h o d r s l U n v e , - r t y r*r"4':f!"h.j*f -,t".*;fi:;ilff#+*,!,: I 5 THE SECOND LAW OF THERMO- DYNAMICS I82 csrprrn s 5-I INTRODUCTION Wc havc already noted in Chap. I that thc second law of thermodynamrc\ relatcs to the direction of cnergy-exchange proce\ses. Some energy transtitr- ntittions are allowcd. whereas others are not. In Chap. 2 a more precisc expla nation of thc conservation of encrgv principlc has becn given antl rclated ro prcvious studics in mechanics. Insofar as the firsr law of: t hermodynamics is conccrned. all lbrms ofencrgy arc equally usetul; no prcf.erence is given for the different typcs of cnergy. and the Only concern is thirt in an i\otatcd sy!tem energy musl be conscrved. Evcn though no prefercncc is given. the differcnt types of energ! are distinguished from one anorher: Work is a force acting through a distance and represenls an inttraction bctwecn system\: internal energy is a firnction of statc. thc change of which is defined in terms ot work: and heat is subsequently dcfined in tcrms of *.ork and internal energy. Nothing in the conscryalion ofcnergy principle states that heat and work are not equi\, alent forms of energy: in fact. thc cyclic cquation 0.1'Q r Ol'w : ( - 5 l ) carries a casual implication that they a,,e equivalent. Thc second law of thermt> dynamlcs recognizes the tact thal heal and work are not equivalcnt and evcnlu_ ally establishes a set of lbrmal rclationships u,hich may bc used to supplement the firsl law in the stud! of thermodvnamic systems. I llil il I ilillil ill 5-2 P H Y S I C A L D E S C R I P T I O N O F T H E SECOND LAW A brief summary of a set of phenomcna talling into the realm of the second principle has bccn givcn in Chap. l. Thcse phenomena are restatcd herc fi)r c o n v e n i c n c e . Heat flows tiom a high temperature 1()) a low tcmperature in the absence ot olher cffects. This means that a hot botly u.ill cool down when brought lnto contact \r'i1h a body at a lower temperature. and not the opDosite 'f wo gases. whcn placed in an irolared e hamber. u ill mir uniformly throughoul thc chamber but will nol separate spontaneously once mixed. A battery will discharge through a resistor releasing a certain amount of encrgy. but it is not possible to make the revcrse of this happen. i.e., to acld cnergy to thc resistor by heating and. thus. cause the batteq/ to charge l l \ e l l . It is not possible to construct a machine or device which will operate contin_ uLllr\l\ $ h ile rcecir ing hcal frum a .inBle r.c.crvoir rnd p|r,tJu..jng 1n .rr1, ., lcnt amount of work. IHE SECOND LAW OF THERMODYNAMICS I83 r",:,r",,.i!:;iil,Ji;li,:T;:::l,iil,_x,.,1,::,:*JT:':i seem ro bc a direcr conscquence,,f "rhc;";;;.,;;;";.n..ii....
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SECOND_LAW_FALL_07 - THERMODYNAMICS FOURTH EDIIICN J P...

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