电路分析英文Lectu

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1、ECTE170–Lecture8/111Chapter14–BoylestadSinusoidalresponseofresistor,inductorandcapacitorLowandhighfrequencyresponseofinductorsandcapacitorsAveragepowerandPowerFactorBasicElementsandPhasors2IntroductionTheresponseofthebasicR,L,andCelementstoasinusoidalvoltageandcurrentwillbee

2、xaminedwithaspecialnoteofhowfrequencywillaffectthe“opposing”characteristicofeachelement.Phasornotationwillthenbeintroducedtoestablishamethodofanalysis.3TheDerivativeTounderstandtheresponseofthebasicR,L,andCelementstoasinusoidalsignal,youneedtoexaminetheconceptofthederivative

3、.Thederivativedx/dtisdefinedastherateofchangeofxwithrespecttotime.Ifxfailstochangeataparticularinstant,dx=0,andthederivativeiszero.Forthesinusoidalwaveform,dx/dtiszeroonlyatthepositiveandnegativepeaks(wt=p/2and3p/2)sincexfailstochangeattheseinstantsoftime.45TheDerivativeThed

4、erivativedx/dtisactuallytheslopeofthegraphatanyinstantoftime.Thegreatestchangeinxwilloccurattheinstantswt=0,p,and2p.Forvariousvaluesofwtbetweenthesemaximaandminima,thederivativewillexistandwillhavevaluesfromtheminimumtothemaximuminclusive.Thederivativeofasinewaveisacosinewav

5、e;ithasthesameperiodandfrequencyastheoriginalsinusoidalwaveform.67SinusoidalResponse:ResistorForaresistorthevoltageandcurrentareinphaseandarerelatedbyOhm’slaw8Thevoltageandcurrentofaresistiveelementareinphase.9SinusoidalResponse:InductorsForaninductorthecurrentlagsthevoltage

6、by90degreesXL=Liscalledtheinductivereactance-unit10SinusoidalResponse:WaveformsInductor11SinusoidalResponse:CapacitorsForacapacitorthecurrentleadsthevoltageby90degreesXc=1/Ciscalledthecapacitivereactance–unit12SinusoidalResponse:WaveformsCapacitor13SinusoidalResponseT

7、hecurrentthrougha5ohmresistorisi=40sin(377t+30°)A.Findtheexpressionforvoltageacrossit.14SinusoidalResponseThecurrentthrougha0.1Hcoilisi=7sin(377t–70°)A.Findthevoltageacrossit.1516CapacitorExample1718Morequestions192021LowandHighFrequencyResponseforInductorsInductors:XL=ωLA

8、tlowfrequencies,andespeciallyDC,thereactanceofainductorisverylow(zeroforDC)