Introduction to 9TH EDITION Electric Circuits James A. Svoboda ClarksonUniversity Richard C. Dorf University of California PUBLISHER DonFowley EXECUTIVE EDITOR DanSayre CONTENT MANAGER KevinHolm PRODUCTION EDITOR Tim Lindner EXECUTIVE MARKETING MANAGER Chris Ruel MARKETING ASSISTANT MarissaCarroll DESIGNDIRECTOR HarryNolan PRODUCTDESIGNER JennyWelter EDITORIAL OPERATIONSMANAGER MelissaEdwards EDITORIAL OPERATIONSASSISTANT CourtneyWelsh SENIORDESIGNER MadelynLesure PHOTOEDITOR SheenaGoldstein SENIORCONTENT EDITOR WendyAshenberg EDITORIAL PROGRAM ASSISTANT Jessica Knecht CONTENT ASSISTANT HelenSeachrist PRODUCTION MANAGEMENTSERVICES BruceHobart/Laserwords Maine CoverPhotos:#JivkoKazakov/iStockphoto.com;AlbertoPomares/GettyImages;#choicegraphx/iStockphoto.com; #mattjeacock/iStockphoto.com Thisbookwassetin10/12ptinTimesNewRomanbyLaserwordsMaine,andprintedandboundbyRRDJeffersonCity. ThecoverwasprintedbyRRDJeffersonCity. 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Montogomery Scott (Scotty), USS Enterprise Dedicated to our grandchildren: Ian Christopher Boilard, Kyle Everett Schafer, and Graham Henry Schafer and Heather Lynn Svoboda, James Hugh Svoboda, Jacob Arthur Leis, Maxwell Andrew Leis, and Jack Mandlin Svoboda About the Authors JamesA.Svobodaisanassociateprofessorofelectricalandcomputerengineer- ing at Clarkson University, where he teaches courses on topics such as circuits, electronics, and computer programming. He earned a PhD in electrical engineering fromtheUniversityofWisconsinatMadison,anMSfromtheUniversityofColorado, and a BS from General Motors Institute. Sophomore Circuits is one of Professor Svoboda’s favorite courses. He has taught this course to 6,500 undergraduates at Clarkson University over the past 35 years. In 1986, he received Clarkson University’s Distinguished Teaching Award. ProfessorSvobodahaswrittenseveralresearchpapersdescribingtheadvantages ofusingnullorstomodelelectriccircuitsforcomputeranalysis.Heisinterestedinthe way technology affects engineering education and has developed several software packages for use in Sophomore Circuits. RichardC.Dorf,professorofelectricalandcomputerengineering at the University of California, Davis, teaches graduate and under- graduate courses in electrical engineering in the fields of circuits and control systems. He earned a PhD in electrical engineering from the U.S. Naval Postgraduate School, an MS from the University of Colorado, and a BS from Clarkson University. Highly concerned with the discipline of electrical engineering and its wide value to socialandeconomicneeds,hehaswrittenandlecturedinternationally on the contributions and advances in electrical engineering. Professor Dorf has extensive experience with education and industry andisprofessionallyactiveinthefieldsofrobotics, automa- tion,electriccircuits,andcommunications.Hehasservedasavisiting professorattheUniversityofEdinburgh,Scotland,theMassachusetts Institute of Technology, Stanford University, and the University of California at Berkeley. A Fellow of the Institute of Electrical and Electronic Engineers and the American Society for EngineeringEducation,Dr.DorfiswidelyknowntotheprofessionforhisModernControlSystems, twelfth edition (Pearson, 2011) and The International Encyclopedia of Robotics (Wiley, 1988). Dr. Dorf is also the coauthor of Circuits, Devices and Systems (with Ralph Smith), fifth edition (Wiley,1992).Dr.DorfeditedthewidelyusedElectricalEngineeringHandbook,thirdedition(CRC Press and IEEE press), published in 2011. His latest work is Technology Ventures, fourth edition (McGraw-Hill 2013). ix Preface The central theme of Introduction to Electric Circuits is the concept that electric circuits are part of the basic fabric of modern technology. Given this theme, we endeavor to show how the analysis and design of electric circuits are inseparably intertwined with the ability of the engineer to design complex electronic, communication, computer, and control systems as well as consumer products. Approach and Organization Thisbookisdesignedforaone-tothree-termcourseinelectriccircuitsorlinearcircuitanalysisandis structured for maximum flexibility. The flowchart in Figure 1 demonstrates alternative chapter organizations that can accommodate different course outlines without disrupting continuity. The presentation is geared to readers who are being exposed to the basic concepts of electric circuitsforthefirsttime,andthescopeoftheworkisbroad.Studentsshouldcometothecoursewiththe basic knowledge of differential and integral calculus. Thisbookendeavorstopreparethereadertosolverealisticproblemsinvolvingelectriccircuits. Thus,circuitsareshowntobetheresultsofrealinventionsandtheanswerstorealneedsinindustry,the office,andthehome.Althoughthetoolsofelectriccircuitanalysismaybepartiallyabstract,electric circuitsarethebuildingblocksofmodernsociety.Theanalysisanddesignofelectriccircuitsarecritical skills for all engineers. What’s New in the 9th Edition RevisionstoImproveClarity Chapter 10, covering AC circuits, has been largely rewritten to improve clarity of exposition. Inaddition,revisionshavebeenmadethroughthetexttoimproveclarity.Sometimestheserevisions are small, involving sentences or paragraphs. Other larger revisions involved pages or even entire sections. Often these revisions involve examples. Consequently, the 9th edition contains 36 new examples. MoreProblems The9theditioncontains180newproblems,bringingthetotalnumberofproblemstomorethan1,400. This edition uses a variety of problem types and they range in difficulty from simple to challenging, including: (cid:1) Straightforward analysis problems. (cid:1) Analysis of complicated circuits. (cid:1) Simple design problems. (For example, given a circuit and the specified response, determine the required RLC values.) (cid:1) Compareandcontrast,multipartproblemsthatdrawattentiontosimilaritiesordifferencesbetween two situations. (cid:1) MATLAB and PSpice problems. (cid:1) Design problems. (Given some specifications, devise a circuit that satisfies those specifications.) (cid:1) How Can We Check . . . ? (Verify that a solution is indeed correct.) xi xii Preface Color Matrices, Code Determinants E A 1 2 3 4 ELECTRIC CIRCUIT RESISTIVE METHODS OF CIRCUIT ELEMENTS CIRCUITS ANALYSIS OF VARIABLES RESISTIVE CIRCUITS Complex Numbers B, C, D 9 10 11 12 THE COMPLETE SINUSOIDAL AC STEADY-STATE THREE-PHASE RESPONSE OF STEADY-STATE POWER CIRCUITS CIRCUITS WITH ANALYSIS TWO ENERGY STORAGE ELEMENTS FIGURE1 Flowchartshowingalternativepathsthroughthetopicsinthistextbook. Features Retained from Previous Editions Introduction Eachchapterbeginswithanintroductionthatmotivatesconsiderationofthematerialofthatchapter. Examples Becausethisbookisorientedtowardprovidingexpertiseinproblemsolving,wehaveincludedmore than260illustrativeexamples.Also,eachexamplehasatitlethatdirectsthestudenttoexactlywhatis being illustrated in that particular example. Various methodsofsolving problems are incorporatedinto selectexamples. Thesecases show studentsthatmultiplemethodscanbeusedtoderivesimilarsolutionsor,insomecases,thatmultiple solutionscanbecorrect.Thishelpsstudentsbuildthecritical thinking skillsnecessarytodiscernthe best choice between multiple outcomes. MuchattentionhasbeengiventousingPSpiceandMATLABtosolvecircuitsproblems.Two appendices, one introducing PSpice and the other introducing MATLAB, briefly describe the capabilities of the programs and illustrate the steps needed to get started using them. Next, PSpice Preface xiii PSpice F, G 5 6 7 8 CIRCUIT THE ENERGY THE COMPLETE THEOREMS OPERATIONAL STORAGE RESPONSE OF AMPLIFIER ELEMENTS RL AND RC CIRCUITS 14 LAPLACE TRANSFORM 16 FILTER CIRCUITS 13 14 15 16 17 FREQUENCY THE FOURIER FILTER TWO-PORT RESPONSE LAPLACE SERIES CIRCUITS NETWORKS TRANSFORM AND FOURIER TRANSFORM 6 17 THE TWO-PORT OPERATIONAL NETWORKS AMPLIFIER Legend: Primary flow Chapter Appendix Optional flow andMATLABareusedthroughoutthetexttosolvevariouscircuitanalysisanddesignproblems.For example,PSpiceisusedinChapter5tofindaTh(cid:1)eveninequivalentcircuitandinChapter15torepresent circuitinputsandoutputsasFourierseries.MATLABisfrequentlyusedtoobtainplotsofcircuitinputs andoutputsthathelpustoseewhatourequationsaretellingus.MALABalsohelpsuswithsomelong andtediousarithmetic.Forexample,inChapter10,MATLABhelpsusdothecomplexarithmeticthat wemustdoinordertoanalyzeaccircuits,andinChapter14,MATLABhelpswiththepartialfraction required to find inverse Laplace transforms. xiv Preface Ofcourse,there’smoretousingPSpiceandMATLABthansimplyrunningtheprograms.We payparticularattentiontointerpretingtheoutputofthesecomputerprogramsandcheckingittomake surethatitiscorrect.Frequently,thisisdoneinthesectioncalled“HowCanWeCheck...?”thatis included in every chapter. For example, Section 8.9 shows how to interpret and check a PSpice “Transient Response,” and Section 13.7 shows how to interpret and check a frequency response produced using MATLAB or PSpice. DesignExamples,aProblem-SolvingMethod,and “HowCanWeCheck . . . ?”Sections Eachchapter concludes witha designexample thatusesthe methods ofthatchaptertosolve adesign problem.Aformalfive-stepproblem-solvingmethodisintroducedinChapter1andthenusedineach of the design examples. An important step in the problem-solving method requires you to check your results to verify that they are correct. Each chapter includes a section entitled “How Can We Check . . . ?”thatillustrateshowthekindofresultsobtainedinthatchaptercanbecheckedtoensure correctness. KeyEquationsandFormulas Youwillfindthatkeyequations,formulas,andimportantnoteshavebeencalledoutinashadedboxto help you pinpoint critical information. SummarizingTablesandFigures Theproceduresandmethodsdevelopedinthistexthavebeensummarizedincertainkeytablesand figures. Students will find these to be an important problem-solving resource. (cid:1) Table 1.5-1. The passive convention. (cid:1) Figure 2.7-1 and Table 2.7-1. Dependent sources. (cid:1) Table 3.10-1. Series and parallel sources. (cid:1) Table 3.10-1. Series and parallel elements. Voltage and current division. (cid:1) Figure 4.2-3. Node voltages versus element currents and voltages. (cid:1) Figure 4.5-4. Mesh currents versus element currents and voltages. (cid:1) Figures 5.4-3 and 5.4-4. Thévenin equivalent circuits. (cid:1) Figure 6.3-1. The ideal op amp. (cid:1) Figure 6.5-1. A catalog of popular op amp circuits. (cid:1) Table 7.8-1. Capacitors and inductors. (cid:1) Table 7.13-2. Series and parallel capacitors and inductors. (cid:1) Table 8.11-1. First-order circuits. (cid:1) Tables 9.13-1, 2, and 3. Second-order circuits. (cid:1) Table 10.5-1. Voltage and current division for AC circuits. (cid:1) Table 10.16-1. AC circuits in the frequency domain (phasors and impedances). (cid:1) Table 11.5-1. Power formulas for AC circuits. (cid:1) Tables 11.13-1 and 11.13-2. Coupled inductors and ideal transformers. (cid:1) Table 13.4-1. Resonant circuits. (cid:1) Tables 14.2-1 and 14.2-2. Laplace transform tables. Preface xv (cid:1) Table 14.7-1. s-domain models of circuit elements. (cid:1) Table 15.4-1. Fourier series of selected periodic waveforms. IntroductiontoSignalProcessing Signalprocessingisanimportantapplicationofelectriccircuits.Thisbookintroducessignalprocessing intwoways.First,twosections(Sections6.6and7.9)describemethodstodesignelectriccircuitsthat implementalgebraicanddifferentialequations.Second,numerousexamplesandproblemsthroughout thisbookillustratesignalprocessing.Theinputandoutputsignalsofanelectriccircuitareexplicitly identified in each of these examples and problems. These examples and problems investigate the relationship between the input and output signals that is imposed by the circuit. InteractiveExamplesandExercises Numerousexamplesthroughoutthisbookarelabeledasinteractiveexamples.Thislabelindicatesthat computerizedversionsofthatexampleareavailableatthetextbook’scompanionsite,www.wiley.com/ svoboda. Figure 2 illustrates the relationship between the textbook example and the computerized exampleavailableontheWebsite.Figure2ashowsanexamplefromChapter3.Theproblempresented bytheinteractiveexampleshowninFigure2bissimilartothetextbookexamplebutdifferentinseveral ways: (cid:1) The values of the circuit parameters have been randomized. (cid:1) The independent and dependent sources may be reversed. (cid:1) The reference direction of the measured voltage may be reversed. (cid:1) A different question is asked. Here, the student is asked to work the textbook problem backward, using the measured voltage to determine the value of a circuit parameter. Theinteractiveexampleposesaproblemandthenacceptsandcheckstheuser’sanswer.Studentsare provided with immediate feedback regarding the correctness of their work. The interactive example choosesparametervaluessomewhatrandomly,providingaseeminglyendlesssupplyofproblems.This pairingofasolutiontoaparticularproblemwithanendlesssupplyofsimilarproblemsisaneffective aid for learning about electric circuits. The interactive exercise shown in Figure 2c considers a similar, but different, circuit. Like the interactive example, the interactive exercise poses a problem and then accepts and checks the user’s answer. Student learning is further supported by extensive help in the form of worked example problems, available from within the interactive exercise, using the Worked Example button. Variations of this problem are obtained using the New Problem button. We can peek at the answer,using theShow Answer button. Theinteractive examples and exercisesprovide hundredsof additionalpracticeproblemswithcountlessvariations,allwithanswersthatarecheckedimmediately by the computer. Supplements and Web Site Material ThealmostubiquitoususeofcomputersandtheWebhaveprovidedanexcitingopportunitytorethink supplementary material. The supplements available have been greatly enhanced. BookCompanionSite Additional student and instructor resources can be found on the John Wiley & Sons textbook companion site at www.wiley.com/college/svoboda.