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1、CHAPTER35ACCircuitsRecommendedclassdays:2BackgroundInformationACcircuitsareanimportantapplicationofelectricityandmagnetism,butnonewphysicsisrequired.ThisisanextensionofthestudyofDCcircuitsinChapter31,andthesamemisunder-standingsaboutcurrentandvoltagewillcontinuetohauntstudentsunlessthosemis
2、understandingsweresuccessfullydealtwithinChapter31.Thetitleofthischapter,althoughconventional,issomewhatofamisnomer.Ratherthanbeingabout“householdelectricity,”asmoststudentswouldsurmise,thephasoranalysisandthemajorityoftopics(e.g.,resonancecircuits)aremorerelevanttoradiofrequencycircuits.Ph
3、asoranalysiswillbeanewideafornearlyallstudents,andmanyfindtheidearatherdifficult.Studentsdon’treadilydistinguishbetweeninstantaneousvalues(vandi),peakvalues(VandI),andrmsvalues(aVIrmsndrms),andthey’reoftennotsurewhichtouse.StudentLearningObjectives•TouseaphasoranalysistoanalyzeACcircuits.•T
4、ounderstandRCfiltercircuits.•TounderstandtheseriesRLCcircuitandresonance.•TocalculatepowerlossinanACcircuitusingthepowerfactor.35-1PedagogicalApproachAllresultsinthischapterarederivedfromthegeometryofaphasordiagram.Compleximpedancesarenotintroduced.Studentsneedtoseecarefulexplanationsofphas
5、ors,thedistinctionbetweenpeakandinstantaneousvalues,andtheideaofphaseleadsandlags.ACcircuitsaremuchhardertodemonstratethanDCcircuits,butit’swellworthusingadual-traceoscilloscopetoshowsimultaneouslyboththevoltageacrossandcurrentthroughacircuitelement(usingvoltagethroughaseriesresistorasthecu
6、rrenttrace).InanRCcircuit,forexample,youcanshowthatchangingtheamplitudedoesnotchangetheratioVVRC/,butchangingthefrequencydoes.FrequencyisusuallythemostimportantparameterforunderstandingACcircuits.UsingClassTimeThisisverymuchanoptionalchapter.Instructorsshouldconsideromittingittoprovidemoret
7、imeforothertopics.Day1:Thisisachaptereasilycoveredintwodays.Day1shouldconcentrateonwhataphasoris,distinguishbetweenpeakandinstantaneousvalues,andusephasorstounderstandresistor,capacitor,andRCfiltercircuits.The90°phasedifferencebetweenpositionandvelocityi
