Chapter 5 - I u ._ £7, 3 4 ‘ VMQcfig/m m 5 (s; ‘

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Unformatted text preview: I u ._ £7, 3 4 ‘ VMQcfig/m m 5 (s; ‘ ”""""”*j""*" r- ---~~~-~»...m . ... m M i “7‘” WW, m". f» 1 3M “Md W m " ._ _ +653 6W3 mng ...... _. A ['- ! NL‘ . f”. H375 6t ,V ..... _, Mk3 I M w .V W _ @ 13x2 [ff 2 w. W. 6 m W. M M W W w w w W‘QW O W q; ’ ' / mg: m 4% SM * ~ 1%»[ a 3 M 1; NW, -- - w w _ 13%;?» Wm «375 We; ,,,,,,, .A / i ,. ,, W : [f [7f]:.,I[fii::T“W w m _ : TMJ H,iii? : ” w wile) W W H _. 8’3, _ i ‘ ME,._&<=5M ¥ gmmmg ,.,:T{:,.__£S____.1@. gig/gm... ._ Mm _ _, .._ -h N ,, , ‘_ _ _ .‘ 0r WWM W .. ¥,, ,, _ _ ,, _ _,.‘ gwfy ._ u _. m - .._. h__ m V ._ fl a _____ m _ _. ... .3 W. Si‘vgi/(T’fiej AQQWCGA _ _ a m a: we t. w *_ g M V: .Imgf;WW‘,}§W.&W§ 1:: .... _. V0 ,, , .. .. u _ . 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Work ‘3 Work \ .__ ________________ __.__J C 3% Cold reservoir, Tc Figure 5.12 Carnot vapor powar cycle Carnot, Sadi (in full Nicholas~Leonard~Sadi) Developer of Heat Engine Theory 1796—1832 Life and Work adi Carnot propOSed the theory of how heat engines operate. He mathematically connected the efficiency of heat engines to measures of work, disorder, probability, and information. Carnot was born in Paris, France, in 1796 to a prominent family; his father Lazare was a well—known leader in the French Revolution, and his nephew, also named Sadi, became president of the French Republic. \Vhen he graduated from the elite Ecole Polytechnique in Paris in 1814, Great Britain was a long— term enemy of France and the greatest power in the world. Carnot realized that the steam engine, invented and improved in Great Britain, was one of the most important sources of that country’s strength. Carnot committed to study how steam engines WORLD Events CAanor’s LIFE French Revolution 1789 1796 Sadi Carnot is born Napoleonic Wars 1.8Q3—15 in Europe l 1814 Carnot graduates from school and begins his engineering career 1824 Reflection: 071 [be ‘ . ' Motive Pen/er osz're, V in which. Carnot presents his ideas on heat engines, is published 1832 Carnot dies 1849 Carnot’s work is 1 discovered by Lord Kelvin Germany is united 1871 operate in hopes that France might catch up with, or even surpass, Great Britain. Carnot began by comparing the flow of heat through a steam engine with the flow of water through a waterwheel. He assumed that heat was material substance, commonly called caloric by scientists of his time. (We know now that heat is a form of vibrational motion and not a separate substance. Remarkably, though, Carnot’s logical descrip~ tion of heat flow was so thorough that his the— ory was easily corrected after his death.) His great discovery was that the operation of a heat engine, a device that converts heat into motion just as water turns a waterwheel. did not depend on what fluid was used: any gas (a form of fluid) would follow the same laws as steam. His work was later interpreted to show that there is a limit to how much work any heat engine can do, even if it had perfect bear— lugs and parts with no friction. in 1824 he published the results of his study in a book, Rrflecriom an the Motive Power of Fire. Six hundred copies were printed at his own expense and went practically unnoticed. Eight years later he contracted cholera as an epidemic swept Paris, and he died on August 24, 1832, only 36 years old. Legacy Carnot’s ideas became the starting point for thermodynamics, the field dealing with mathematical relationships that connect the efficiency ofheat engines to measurements of work available from their fuel. A year after Carnot’s death, another French engineer, Emile Clapeyron, found and read Carnotls book. Clapeyton simplified the main ideas and published them in 1854, after several journals had refused to print the article. Finally in 1849 the great British scientist William Thomson (later known LORD KEVIN) read Clapeyron’s article, became aware of Carnot’s work, and recognized its importance. Carnot’s work was eventually widely under~ srood and appreciated; it became the basis of the Second Law of Thermodynamics, which states that heat will never flow on its own from a colder object to a warmer one. Carnot also came close to developing the First Law, which asserts that the amount of energy in the uni— verse is constant, but he died before he could For Further Reading: get his notes in order and present his work. His surviving brother did not publish his notes until 1878, well after other scientists had understood the nature of heat energy. Many aspects of contemporary technology employ applications of Carnot’s discoveries. Steam engines are still in use today, although they have become less visible than in Carnot’s time. All electric power plants that burn coal, oil, or gas, along with all nuclear power plants, are actually steam engines. Those fuels supply eat to boil vast quantities of water into steam and force it through giant pinwheels, called turbines. The turbines spin and force enor~ mous generators to turn and produce electric— ity. The engines that power modern cars, buses, trains, and planes all use the same prin« ciples that Carnot discovered, but with hot, expanding gases as the working fluid rather than Steam. Unfortunately, the inherent problems that Carnot discovered in the theory of heat engines remain. Carnot’s work was interpreted to show that the absolute maximum efficiency of any heat engine, whether fueled by steam, gasoline, or anything else, is limited by the difference in temperature between the source of heat entering the engine and its exhaust. The exhaust from gasoline engines is very hot and that represents wasted heat. Only about one~third of the fuel is actually put to use, and we can not improve that figure very much without running into the theoretical limits discovered by Carnot. Straw Commoner, Barry. “Thermodynamics, the Science of Energy.” 111 The Paverzy of Power, New York: Knopf, 1976. Segre, Emilio. From Billing Bodies to Radio Waves. New York: Freeman, 1984, / A . ‘v v 7 . . 40 ' 1.2226: and Legumes: .Sczmrzsn', Ilflar/aemerzcmm, and Inventors Clausius, Rudolf Founder of Thermodynamics 1822—1888 and War/e Rudolf Clausitrs formalized the laws of thermodynamics and helped to establish thermodynamics as a field of study. Born on January 2, 1822, in Koslin, Prussia. Rudolf Clausius was the son ofa pastor who also served as principal of the local school. t the University of Berlin, Clausius was at first attracted [0 history, but gradually became more interested in science. Because of financial diffi~ culties. he had to work as a teacher in Berlin while he finished his own education. receiving his doctorate in 1848. in 1850‘ he tool: a profes- sorship at the Royal Artillery School anti in that same year presented his first paper on thermody— namics, the study of how energy moves and transforms from one form to another. He taught at several other universities. finally settling at the University of Bonn, Germany, in 1869, where he remained for the rest of his life. Many scientists had studied heat during the first half of the nineteenth century and had reached some important conclusions. For example, SAD! CAI-{NOT described the way hear flows in a steam engine, and JAMES JOULE showed that heat is equivalent to mechanical energy. Clausius clarified their terminology, improved their mathematics, For Further Reading: and unified their ideas into the two great laws of thermodynamics. Clausius tackled a prohlem in Carnot’s worlt on heat engines: Carnot had considered only ide” Hil‘ifll, perfectly reversible processes. in fact. all of classical physics assumed that laws of nature worlt equally well running forward or haclcward. like watching a movie in reverse. Clausius found a term in the mathematical equations used to describe heat engines that increases with time, making: reversing the process impossible. He developed the concept concerning this new term lry l85l, and in 1865 finally introduced it by name. He called it entropy, from the Greek word trope, meaning “transformation.” Entropy is a measure of disorder or randomness in a system. in Clausius's new terms, the two laws of thermo— dynamics are: l) the energy of the universe is constant 2) the entropy of the universe tends toward a maximum. The British scientist \William Thomson (later named LORD Klan/IN) developed the same laws at about the same time. Clausius stated them more simply and succinctly, and he was the one who conceived of the name, entropy, for the fundamental change that occurs in a system over time. Tragedy struck Clausius in 1875 when his wife died delivering their sixth child. He spent most of the rest of his life raising his family and died in Bonn on August 24, 1888. Legacy Rudolf Ciausius's two laws of thermody— namics created the groundwork for the field of thermodynamics. lie analyzed the worlt of Joule and Carnot. synthesized their contributions, and created a universal theory that benefited future generations. immediate applications of his laws resounded in all fields of sciencewfiom the study of gases under real conditions. to elccw trochemistry. to boiling, melting. and vaporiz- ing, to capillary action, and especially to industrial chemistry. The l ws took chemists, in particular, from trial and error methods to understanding theoretically what can and can not be accomplished. Clausius lived to see his own work taken to yet another level. In 1875 the great American scientist J. Willard Gibbs used Clausius’s two laws of thermodynamics as the opening words Critdwell, D. S. L. From Wart m Cr'auriur: The Rise qukw-modymzmrtt in l/rr Early [Minn/(11 Age. ADkC’S: Iowa . Hecht, E. Phys/ct in Perspective. Addison rWesley, 1979. . ; University Press, l989. Segre, Emilio. Pram Falling Bodies m Rat/in Warm. New York: Freeman, 1984. in his paper on the theory ofcl'lemical equilib— rium, which states that a point exists in the progress of a reversible chemical reaction Where no net change occurs in the amounts of original or resulting chemicals. Chemical equir libriurn proved to he a tremendously useful tool for chemists in hoth explaining chemical processes and predicting their outcomes. The laws that Clausius developed had extensive impact on fundamental questions regarding the universe. They began one of the longestrlasting controversies in physics: how will the universe end? The first law claims that energy, whatever it is, is a special, conserved quantity in the universe; however much energy there was at the beginning of time, that energy is still around us today and always will he, in one form or another. The second law sets lim— its on the transformation of energy: heat must flow from hotter places to cooler ones, and if all the parts of a system are at the same tem— perature, no energy transformations can hap— pen. These laws suggest the theory of the “heat death” of the universe: the universe will end in continual expansion, as the stars burn out one by one. It is proposed, however, that this won’t happen for dozens of billions of years. Our Sun alone has enough fuel to last for five bil- lion years or more. Seraur WORLD EVENTS Cmusros’s LIFE Napoleonic \Wars 1803— 15 in Europe 822 Rudolf Clausius is born 1 848 Clausius receives ‘ doctorate from University of Berlin 850 l Ciausius presents , first paper on thermodynamics 85] Clausius develops laws of thermodynamics . 865 Ciausius coins the term entropy and applies it to second law ‘ 869 Clausius takes a l professorship at University of Bonn Germany is no 1888 Clausius dies Spanish—American 1898 lar Liver and Legacies: Scientists, erzt/wmrzticiam, and [mentors ' 7 Kelvin, Lord (William Thomson) Pioneer in Electromagnetism, Heat, and Mechanics 18241907 Life and Wine/6 Ed Kelvin accomplished groundbreaking eorencal and technical work that advanced and synthesized the studies of heat, electricity, magnetism, and mechanics. Kelvin was born William Thomson on june 26, 1824, in Belfast, lreland. (He adopted the name Kelvin when he became a baron in 1892.) From his father, a university mathematics protes— sor, he learned recent, advanced mathematics that was not yet taught at British schools. He entered the University of Glasgow at age 10, where he was introduced to Joseph Fourierls application of abstract mathematics to investigate heat flow, which was controversial at the time. After transferring to Cambridge University in 1841 , Thomson published two papers defending Fourier’s approach and became the first to sug~ gest that the approach he used in other fields, including the study of fluids and electricity. Graduating From Cambridge in 18115, he was elected the following year to become head of the natural philosophy later physics) department at the University of Glasgow. He held the position for 53 years. Kclvin's scientific approach was shaped by his belief that physical theories of matter and energy were converging toward one unified theory, an For Further Reading: idea based on evidence hinting that all forms of energy are related. Studying othersi experimental results, he extracted generalizations about variv ous physical phenomena and developed theories on hydrodynarnits, elasticity, and the electrody~ namic properties of metals. Applying mathemat» ics Formulated by lrish physicist George Stokes to models of rotating elastic solids, he was able to discuss some of the Forces acting between electri- cal current and magnetism. in 18/18 Kelvin introduced the scale of. tem~ perature that starts at absolute zero, the theoret-i ically lowest possible temperature. The scales unit, the ltelvin (K). corresponds in caloric value to one degree Celsius (C): no negative numbers exist on the Kelvin scale, and the temperature of melting ice at atmospheric pressure is 273.15°K, which corresponds to OlC. Kelvin was intrigued by iAMES PRESCOTI’ JOULE’s proposition stating that heat is a form of mechanical motion, which opposed accepted doctrine that heat is a special substance that has no fixed relationship to the amount of mechan— ical worh generated by it. in l851 Kelvin offered mathematical support for Joule’s theory with the influential paper “On the Dynamical Theory of Heat. ” The following year Kelvin and ionic collaborated and developed ideas on worl: and heat, including that when a gas expands without doing work (not moving a piston or a turbine, for example). the gas cools slightly. Their ideas opened the area of low—temperature physics (cryogenics). Kelvin was also an inventor who used his suc— cessful patents to finance his research. in 1854 Kelvin became involved in Cyrus Field’s plan to lay submarine telegraph cable across the Atlantic Ocean. He formulated equations describing heat flow in a solid that gave the veiocity or electrical current flowing through cable wire. His inven— tions, the mirror galvanomcrer and siphon recorder, served as the telegraph—receiving mech— anism in most undersea telegraph cables. Queen Victoria granted him knighthood, primarily based on the success of the transatlantic cable, which stretched between Ireland and Newfoundland, Canada, the first cable to con- nect both sides of the Atlantic. in his later years Kelvin owned a yacht, and his sea-going adventures resulted in several naviga— tional patents: an improved compass, which com— pensared for the effects of iron and steel components of ships, a ride—measuring device, and farhomerers and sounding equipment, which measured water depth. He died at his estate near Largs, Scotland, on December 17, 907. Sharlin, Harold 1. Lord Kali/in: The Dynamic lr’irtm'irm. University Park: Pennsylvania State University Press, 19.79. Smith, Crosbie. Energy and Empire‘A Brogqnhicnl .S'runjr affair! Kelvin. Cambridge: Cambridge University Press, 1989. .0- . Legacy I i elvins acl'iievements represented significant irogress in nineteenth-century physics, resulting in the turn‘of—the—cenrury concept that all physical change is related to energy. Kelvinls contributions helped lay the ground— worlt for the First and Second laws of Thermo— dynamics, which are fimdamental to the modern understanding of nature. The First Law of Thermodynamics states that energy cannot be cre— ated or ctlesrroyecl; its quantity is constant. The Second law can be expressed in a number ofways, it states that a system’s entropy, a measure of its dis~ order, can never decrease; in other words, all sys tems tend toward a more disordered state. The law similarly posits that heat will flow spontaneously born a hotter system to a colder system) but will not [low in the opposite direction, Kelvirfs worlt on the relationship between elec— tricity and magnetism led directly to JAMES CLERK Msxwrufs 1865 theory that light is a form of electromagnetic radiation. This theory unified the understanding of light, electricity, and magnetism. The laying of transatlantic telegraph cables, to which Kelvin‘s electrical engineering skills con— tributed, resulted in an international submarine communication network by the end of the nine- teenth century. Kelvins nautical inventions had a direct impact on maritime safety. l'lis improved compass, tidal gauges and predictors, farhotneters, and sounders helped make navigation more accurate, thus sav— ing lives by reducing shipwrecks. Schuyler KnviN’s LIFE 1824 William Thomson is I i born WORLD EVENTS 1841 Kelvin enters Cambridge University 1846 Kelvin begins athliaa tion with University of Glasgow 1848 Kelvin introduces absolute temperature scale 1851 Kelvin completes i “On the Dynamical 1 Theory of Heat” ' United States 1861165 Civil War Germany is united 18l71 Spanisermerican 1898 War 1907 Kelvin dies Liver and Legacies: Scientists, ,M'rzt/r/emaricz’am, and Inventor‘s ' 11,9 ...
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Chapter 5 - I u ._ £7, 3 4 ‘ VMQcfig/m m 5 (s; ‘

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