电子信息与通信工程专业英语lesson2-1(太原理工大学版)001

2024/7/1可编辑1

Chapter2

CircuitSystemandDesign

第二章电路系统与设计

Outline大纲2.1CircuitandSystem电路与系统2.2AnalogandDigitalCircuitsDesign

模拟与数字电路设计2.3RadioReceiverCircuit无线电接收机电路

2024/7/1可编辑22.1CircuitandSystemOutline大纲Basicconcepts基本概念CircuitandSystem电路与系统

2024/7/1可编辑3Terminology术语chargen.负荷,电荷,费用,主管,充电,充气,装料conductivityn.传导性,传导率insulatorn.绝缘体,绝热器gravitationaladj.重力的voltagen.[电工]电压,伏特数voltsn.直流电压amperen.安培ohmn.[物]欧姆coulombn.[电]库仑(电量单位)diametern.直径inductancen.感应系数,自感应2024/7/1可编辑4dielectricn.电介质,绝缘体adj.非传导性的faradn.[电]法拉(电容单位)polarityn.极性potentialdifference[电]电位差，电势差equivalentresistance等效电阻SuperpositionTheorem叠加定理Thevenin'sTheorem戴维南定理Norton'sTheorem诺顿定理2024/7/1可编辑5IntheBohrtheoryoftheatom(namedafterNielsBohr,1885–1962),electrons

orbitanucleuscontainingneutronsandprotons.Electricchargeismeasuredincoulombs.IntroductionTexttour文本浏览Basicconcepts

Chargeandconductivity

2024/7/1可编辑6Thisrelativemobilityofelectronswithinamaterialisknownaselectricconductivity.Conductivityisdeterminedbythetypesofatomsinamaterial(thenumberofprotonsineachatom'snucleus,determiningitschemicalidentity)andhowtheatomsarelinkedtogetherwithoneanother.2024/7/1可编辑7Itshouldalsobeunderstoodthatsomematerialsexperiencechangesintheirelectricalpropertiesunderdifferentconditions.Whilethenormalmotionof"free"electronsinaconductorisrandom,withnoparticulardirectionorspeed,electronscanbeinfluencedtomoveinacoordinatedfashionthroughaconductivematerial.Thisuniformmotionofelectronsiswhatwecallelectricity,orelectriccurrent.2024/7/1可编辑8Therecanbeelectriccurrentonlywherethereexistsacontinuouspathofconductivematerialprovidingaconduitforelectronstotravelthrough.Ifthepathisblocked,the"flow"willnotoccur.2024/7/1可编辑9

Electriccircuits,voltageandcurrent

Anelectriccircuitisformedwhenaconductivepathiscreatedtoallowfreeelectronstocontinuouslymove.Thiscontinuousmovementoffreeelectronsthroughtheconductorsofacircuitiscalledacurrent,anditisoftenreferredtointermsof"flow,"justliketheflowofaliquidthroughahollowpipe.Theforcemotivatingelectronsto"flow"inacircuitiscalledvoltage,whichtechnicallyisameasureofpotentialenergyperunitchargeofelectrons.

Themoremasssomethinghasandthehigherweliftit,themorepotentialenergyithas.2024/7/1可编辑10Onevoltisdefinedasthatmagnitudeofelectromotiveforcerequiredcauseacurrentofoneamperetopassthroughaconductorhavingaresistanceofoneohm.CurrentflowisrepresentedbythelettersymbolI.Thebasicunitinwhichcurrentismeasuredistheampere(amp).Oneampereofcurrentisdefinedasthemovementofonecoulombpastanypointofaconductorduringonesecondoftime.2024/7/1可编辑11Freeelectronstendtomovethroughconductorswithsomedegreeoffriction,oroppositiontomotion.Thisoppositiontomotionismoreproperlycalledresistance.TheresistanceofamaterialthatfollowsOhm'slawisconstant,orindependentofvoltageorcurrent,andtherelationshipbetweencurrentandvoltageislinear.Wheneveranelectricvoltageexistsbetweentwoseparatedconductors,anelectricfieldispresentwithinthespacebetweenthoseconductors.Electricalenergycanbestoredinanelectricfield.Thedevicetobecapableofdoingthisiscalledacapacitororacondenser.

Resistance,capacitanceandinductance2024/7/1可编辑12Ifacondenserisconnectedtoabattery,theelectronswillflowoutofthenegativeterminalofthebatteryandaccumulateonthecondenserplateconnectedtothatside.Thusthecondenserissaidtobecharged.Thecapacitanceisdirectlyproportionaltothedielectricconstantofthematerialandtotheareaoftheplatesandinverselytothedistanceoftheplates.Thelargertheplatearea,thesmallerthespacebetweenthem,thegreaterthecapacitance.Wheneverelectronsflowthroughaconductor,amagneticfieldwilldeveloparoundthatconductor.Thiseffectiscalledelectromagnetism.Magneticenergycanbestoredinamagneticfield.Thedevicetobecapableofdoingthisiscalledaninductor.2024/7/1可编辑13Tostoremoreenergyinaninductor,thecurrentthroughitmustbeincreased.Thismeansthatitsmagneticfieldmustincreaseinstrength,andthatchangeinfieldstrengthproducesthecorrespondingvoltageaccordingtotheprincipleofelectromagneticself-induction.Whenthecurrentthroughaninductorisincreased,itdropsavoltageopposingthedirectionofelectronflow,actingasapowerload.Inthisconditiontheinductorissaidtobecharging,becausethereisanincreasingamountofenergybeingstoredinitsmagneticfield.Notethepolarityofthevoltagewithregardtothedirectionofcurrent.2024/7/1可编辑142.CircuitandSystemOhm'sLawThefirst,andperhapsmostimportant,relationshipbetweencurrent,voltage,andresistanceiscalledOhm'sLaw,discoveredbyGeorgSimonOhmin1827.Ohm'sprincipaldiscoverywasthattheamountacircuitisdirectlyproportionaltothevoltageofelectriccurrentthroughametalconductorinimpressedacrossit,foranygiventemperature.Ifweknowthevaluesofanytwoofthethreequantities(voltage,current,andresistance)inacircuit,wecanuseOhm'sLawtodeterminethethird.

2024/7/1可编辑15Kirchoff’sCurrentLawandKirchoff’sVoltageLaw

Kirchoff’sCurrentLawisthetotalchargeflowingintoanodemustbethesameasthetotalchargeflowingoutofthenode.Kirchhoff'sVoltageLaw(orKirchhoff'sLoopRule)isaresultoftheelectrostaticfieldbeingconservative.Itstatesthatthetotalvoltagearoundaclosedloopmustbezero.Ifthiswerenotthecase,thenwhenwetravelaroundaclosedloop,thevoltageswouldbeindefinite.2024/7/1可编辑16IntroductiontonetworktheoremsInelectricnetworkanalysis,thefundamentalrulesareOhm'sLawandKirchhoff'sLaws.Whilethesehumblelawsmaybeappliedtoanalyzejustaboutanycircuitconfiguration(evenifwehavetoresorttocomplexalgebratohandlemultipleunknowns),therearesome“shortcut”methodsofanalysistomakethematheasier.2024/7/1可编辑17SuperpositionTheoremThestrategyusedintheSuperpositionTheoremistoeliminateallbutonesourceofpowerwithinanetworkatatime,usingseries/parallelanalysistodeterminevoltagedrops(and/orcurrents)withinthemodifiednetworkforeachpowersourceseparately.Then,oncevoltagedropsand/orcurrentshavebeendeterminedforeachpowersourceworkingseparately,thevaluesareall“superimposed”ontopofeachother(addedalgebraically)tofindtheactualvoltagedrops}currentswithallsourcesactive.2024/7/1可编辑18Thevenin'sTheoremThevenin'sTheoremstatesthatitispossibletosimplifyanylinearcircuit,nomatterhowcomplex,toanequivalentcircuitwithjustasinglevoltagesourceandseriesresistanceconne