电路基础-英文教学-1优质PPT.ppt
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要求一般理解与掌握的内容有:
5.时变与非时变的概念。
难点:
参考方向,受控源,功率计算。
1-1Introduction,1-2BasicConceptsandSystemofUnits,1-3ChargeandCurrent,1.4Voltage,1.5PowerandEnergy,1-6CircuitElements,1-9SummaryandReview,1-1Introduction,instrumentation,仪表,topology,拓扑,Theschematicdiagram,theInternationalSystemofUnits(SI),国际单位制,theGeneralConferenceonWeightsandMeasures,国际计量大会,原理图,1.Terms,electron,电子,proton,质子,neutron,anexternalelectromotiveforce(emf),外电动势,potentialdifference,电位差,instantaneouspower,瞬时功率,中子,First,areal-worldproblemisidentified;
second,theproblemismodeled;
third,themodelisanalyzed;
andfourth,theresultsareappliedtotheoriginalphysicalproblem.,2.Whystartwithcircuittheory?
Thesolutionofanengineeringproblemnormallyproceeds:
1-2BasicConceptsandSystemofUnits,1.2.1SystemofUnits,1.2.2BasicConcepts,Anelectriccircuitisaninterconnectionofelectricalelements.,Activeelements:
capableofgeneratingenergy,suchasgenerators,batteriesetc.,Passiveelements:
resistors,capacitorsandinductors,Idealcircuitelements:
理想电路元件Lumpedparameterelements集中参数元件Idealindependentsource理想电源元件Idealload理想负载元件Idealcouplingelements理想耦合元件Lumpedparameterelements&
distributedelements集中参数与分布参数,Chargeisanelectricalpropertyatomicparticlesofwhichmatterconsists,measuredincoulombs(C),Anelectrone=-1.6021019CIn1Cofcharge,thereare1/(1.60210-19)=6.241018electrons3.Thelawofconservationofcharge,Note,1-3ChargeandCurrent1.3.1Charge电荷,Electriccurrentisthetimerateofchangeofcharge,measuredinamperes(A).,1A=1C/1s(秒)1kA=1000A,1mA=10-3A,1A=10-6A,1nA=109A,1.3.2Current电流:
Analternativecurrent(ac)isacurrentthatvariessinusoidallywithtime.时变电流,Andre-MarieAmpere(1775-1836)安培,Adirectcurrent(dc)isacurrentthatremainsconstantwithtime.直流电流,Tospecifythecurrentinaconductor,weneedbothareferencedirectionandnumericalvalue,whichcanbepositiveornegative.,I0实际方向与参考方向相同I0实际方向与参考方向相反,1.3.3Currentreferencedirections电流的参考方向,Voltage(orpotentialdifference)istheenergyrequiredtomoveaunitchargethroughanelement,measuredinvolts(V).Uab=W/qV,kV,mV,V,AlessandroAntonioVolta(1745-1827)伏特,1.4Voltage1.4.1VoltageofPotential电位,Potentialreferencepolarity电位的参考极性(零电位点)参考点:
LetUb=0,Ua=U,Uab=U=Ua-Ub,pointaisatapotentialofUabvoltshigherthanpointb.,1.4.2Voltage电压,Voltagereferencedirections,Keepinmindthatelectriccurrentisalwaysthroughanelementandthatelectricvoltageisalwaysacrosstheelementorbetweentwopoints.,CheckYourUnderstandingWhatthedifferencebetweenUabandU?
Uab=U=US+RIUab=-Uba=UU=USRI,Poweristhetimerateofexpendingorabsorbingenergy,measuredinwatts(W).,Instantaneouspower,1.5PowerandEnergy,Indccircuit:
P=IU,Powerunit:
W,kW,1MW106W,Whenthecurrententersthroughthepositiveterminalofanelement,p=+ui.Ifthecurrententersthroughthenegativeterminal,p=-ui.,p0PowerabsorbP0Powersupply,Accordingtolawofconservationofenergy,wehave,Inasourceset,thecurrentreferencedirectionisdirectedoutofthe+polaritymarking(orthefirstsubscript)ofthevoltage.Inaloadset,thecurrentreferencedirectionisdirectedintothe+polaritymarking(orthefirstsubscript)ofthevoltagereferencedirection.,fromEQ(1-1),theenergyabsorbingorsuppliedbyanelementfromtimet0totis,Unitisjoules(J),1Wh=3600J,Example:
TheelectronbeaminaTVpicturetubecarries1015electronspersecond.Asadesignengineer,determinethevoltageU0neededtoacceleratetheelectronbeamtoachieve4W.Solution:
1-6CircuitElements,(Chapter6),Passiveelements(无源元件),Activeelements(有源元件),Resistors电阻,Inductors电感,Capacitors电容,Independentsource独立电源,dependentsource受控源,Voltagesource电压源,currentsource电流源,CCCSCCVSVCVSVCCS,Summary:
1.Current,2.Voltage,3.Potential,4.Power,2.P0absorborexpendpower(吸收功率)P0supplypower(发出功率),Emphasis重点,1.currentandvoltagereferencedirection,Anidealindependentsourceisanactiveelementthatprovidesaspecifiedvoltageorcurrentthatiscompletelyindependentofothercircuitvariable.,1.6.1IdealIndependentSources,1、理想电压源IdealVoltageSource,Theidealvoltagesourcemaintainsitsprescribedvoltage,independentofitsoutputcurrent.Generalsymbolforavoltagesource,graphicalcharacteristicofadcvoltagesource:
thecurrentisdeterminedbytheload(负载)U=0,Shortcircuit,maintainsitsvoltage,Theidealcurrentsourceproducesitsprescribedcurrent,independentofitsoutputvoltage.Generalsymbolofacurrentsource,2、独立电流源IdealCurrentSource,graphicalcharacteristicofadccurrentsource,maintainsitscurrent,thevoltageisdeterminedbytheload(负载),Anidealdependent(orcontrolled)sourceisanactiveelementinwhichthesourcequantityiscontrolledbyanothervoltageorcurrent.,1.6.2、受控电源CONTROLLEDSOURCES,CCCS:
Acurrent-controlledcurrentsource:
currentgain,dimensionless,VCCS:
Avoltage-controlledcurrentsourceg:
transconductance(S),VCVS:
Avoltage-controlledvoltagesource:
voltagegain,dimensionless,CCVS:
Acurrent-controlledvoltagesource:
r:
transresistance(),Example:
R1=1,R2=2,R3=3,=3,US3=3V.Findopen-circuitvoltageU22(开路电压),Solution:
22开路:
Io=0,Io=0,,1.6.3电阻、电感、电容元件Resistors,InductorsandCapacitors,一、电阻元件Resistors,R=,开路/断路Opencircuit:
acircuitelementwithresistanceapproachinginfinity.RR=0,短路Shortcircuit:
acircuitelementwithresistanceapproachingzero.R0,Ohmslawstatesthatthevoltageacrossaresistorisdirectlyproportionaltothecurrentflowingthroughtheresistor.,u(t)=Ri(t)U=RI,I=GU,GeorgSimonOhm(1787-1845),欧姆,P=UI=RI2=U2/R=GU2,CheckYourUnderstandingUab=?
Uad=?
Uac=?
Ucd=?
Ua-R1I1+E1=Ub;
Uab=R1I1-E1;
Uad=R1I1-E1-R3I3-E3;
Uac=R1I1-E1+E2-R2I2;
Ucd=R2I2-E2-R3I3-E3;
二、电感器Inductors,(t)=Li(t)-(Wb)(韦伯)L-(H)亨利I-(A)(安培),graphicalcharacteristic(Wb-A),Thevoltage-currentcharacteristicsofaninductor,Theenergystoredintheinductor:
三、电容器Capacitors,Circuit-theorydefinitionofacapacitor:
q(t)=Cu(t),C-法拉(F),1F=10-6F,1pF=10-12Fq-库仑(C)V-伏特(V),MichaelFaraday(1791-1867),法拉弟,线性电容,(C-V曲线),Theenergystoredinthecapacitor:
Thevoltage-currentcharacteristicsofancapacitor:
小结,IdealCurrentSource(IS,iS)
(1)Current不随Load变化而变化。
(2)Voltage随Load变化而变化。
2.IdealVoltageSource(IS,iS)
(1)Voltage不随Load变化而变化。
(2)Current随Load变化而变化。
3.Controlledsourses受控电源,4.ResistorOhmslaw,5.Inductor,6.Capacitor,1.9Summary,Anelectriccircuitconsistsofelectricalelementsconnectedtogether.TheInternationalSystemofUnits(SI)istheinternationalmeasurementlanguage,whichenablesengineerstocommunicatetheirresults.Fromthesixprincipalunits,theunitsofotherphysicalquantitiescanbederived.Currentistherateofchargeflow.Voltageistheenergyrequiredtomove1Cofchargethroughanelement.,5.Poweristheenergysuppliedorabsorbedperunittime.Itisalsotheproductofvoltageandcurrent.,6.Accordingtothepassivesignconvention,powerassumesapositivesignwhenthecurrententersthepositivepolarityofthevoltageacrossanelement.,7.Anidealvoltagesourceproducesaspecificpotentialdifferenceacrossitsterminalsregardlessofwhatisconnectedtoit.Anidealcurrentsourceproducesaspecificcurrentthroughitsterminalsregardlessofwhatisconnectedtoit.,8.Voltageandcurrentsourcescanbedependentorindependent.Adependentsourceisonewhosevaluedependsonsomeothercircuitvariable.,9.TwoareasofapplicationoftheconceptscoveredinthischapteraretheTVpicturetubeandelectricitybillingprocedure.,