专业英语复习题.docx
- 文档编号:29893610
- 上传时间:2023-08-03
- 格式:DOCX
- 页数:9
- 大小:20.73KB
专业英语复习题.docx
《专业英语复习题.docx》由会员分享,可在线阅读,更多相关《专业英语复习题.docx(9页珍藏版)》请在冰豆网上搜索。
专业英语复习题
专业英语复习题
1、Chargeisanelectricalpropertyoftheatomicparticlesofwhichmatterconsists,measuredincoulombs。
2、Wealsoknowthatthechargeeonanelectronisnegativeandequalinmagnitudeto1.*****×10-19Cwhileaprotoncarriesapositivechargeofthesamemagnitudeastheelectron
3.、Auniquefeatureofelectricchargeorelectricityisthefactthatitismobile;thatis,itcanbetransferredfromoneplacetoanother,whereitcanbeconvertedtoanotherformofenergy.
4、Althoughwenowknowthatcurrentinmetallicconductorsisduetonegativelychargedelectrons,wewillfollowtheuniversallyacceptedconventionthatcurrentisthenetflowofpositivecharges.
5、ThewaywedefinecurrentasiinEq.(1-l)suggeststhatcurrentneednotbeaconstant-valuedfunction,chargecanvarywithtimeinseveralwaysthatmayberepresentedbydifferentkindsofmathematicalfunctions.
6、Thevoltageuabbetweentwopointsaandbinanelectriccircuitistheenergy(orwork)neededtomoveaunitchargefromatob。
7、Thepowerabsorbedorsuppliedbyanelementistheproductofthevoltageacrosstheelementandthecurrentthroughit.
8、Anidealindependentsourceisanactiveelementthatprovidesaspecifiedvoltageorcurrentthatiscompletelyindependentofothercircuitvariables.
9、ThesymbolforavoltagesourcehavinguvoltsacrossitsterminalsisshowninFig.1-4(a).
10、Anothersymbolthatisoftenusedforaconstantvoltagesource,suchasabatterywithUvoltsacrossitsterminals,isshowninFig.1-4(b).
11、WemightobserveatthispointthatthepolaritymarksonFig.1-4(b)areredundantsincethepolaritycouldbedefinedbythepositionsofthelongerandshorterlines.
12、Thusifuisthevoltageacrossthesourceanditscurrentiisdirectedoutofthepositiveterminal,thenthesourceisdeliveringpower,givenbyp=ui,totheexternalcircuit.
13、Sincethecontrolofthedependentsourceisachievedbyavoltageorcurrentofsomeotherelementinthecircuit,andthesourcecanbevoltageorcurrent,itfollowsthattherearefourpossibletypesofdependentsources,namely:
14、Itshouldbenotedthatanidealvoltagesource(dependentor
independent)willproduceanycurrentrequiredtoensurethattheterminalvoltageisasstated,whereasanidealcurrentsourcewillproducethenecessaryvoltagetoensurethestatedcurrentflow.
15、Allthesimplecircuitelementsthatwillbeconsideredintheworkthatfollowscanbeclassifiedaccordingtotherelationshipofthecurrentthroughtheelementtothevoltageacrosstheelement.
16、Furthermore,weshallneedtodefinespecialkindsofsourcesinwhichthesourcevoltageorcurrentdependsuponacurrentorvoltageelsewhereinthecircuit;suchsourceswillbetermeddependentsourcesorcontrolledsources.
17、Thecircuitelementusedtomodelthecurrent-resistingbehaviorofamaterialistheresistor.
18、Obviously,astraightlineistheonlygraphpossibleforwhichtheratioofu(t)toi(t)isconstantforalli(t).
19、Resistorswhoseresistancesdonotremainconstantfordifferentterminalcurrentsareknownasnonlinearresistors.
20、Inreality,allpracticalresistorsarenonlinearbecausetheelectricalcharacteristicsofallconductorsareaffectedbyenvironmentalfactorssuchastemperature.
21、"Resistors"maybeeasilypurchasedormanufactured,butitissoonfoundthatthevoltage-currentratioofthisphysicaldeviceisreasonablyconstantonlywithincertainrangesofcurrent,voltage,orpoweranddependsalsoontemperatureandotherenvironmentalfactors.
22、Adifferentclassofrelationshipoccursbecauseoftherestrictionthatsomespecifictypeofnetworkelementplacesonthevariables.Stillanotherclassofrelationshipisonebetweenseveralvariablesofthesametypewhichoccursastheresultofthenetworkconfiguration,i.e.,themannerinwhichthevariouselementofthenetworkareinterconnected.
23、
24、Kirchhoff'sCurrentLaw(KCL)statesthatthealgebraicsumofcurrentsenteringanode(oraclosedboundary)iszero.
25、AnalternativeformofKCL:
Thesumofthecurrentsenteringanodeisequaltothesumofthecurrentsleavingthenode.
26、Kirchhoff'sVoltageLaw(KVL)statesthatthealgebraicsumofallvoltagesaroundaclosedpath(orloop)iszero.
27、Thesignoneachvoltageisthepolarityoftheterminalencounteredfirstaswetravelaroundtheloop.
28、Withthetwotechniquestobedevelopedinthissection,wecananalyzealmostanycircuitbyobtainingasetofsimultaneousequationsthatarethensolvedtoobtaintherequiredvaluesofcurrentorvoltage.
29、Aconvenientchoiceofvoltagesformanynetworksisthesetofnodevoltages.
30、Frequentlythereferencenodeischosentobethenodetowhichthelargestnumberofbranchesareconnected.
31、Thechassismaythenbecalledground,anditbecomesthelogicalchoiceforthereferencenode.
32、Clearly,simplificationinwritingtheresultingequationsispossiblewhenthereferencenodeischosentobeanodewithalargenumberofelementsconnectedtoit.
33、identifyingitbythegroundconnectionshown.
34、Thesetwovoltagesaresufficient,andthevoltagebetweenanyotherpairofnodesmaybefoundintermsofthem.
35、Wedothisbyequatingthetotalcurrentleavingthenodethroughtheseveralconductancestothetotalsourcecurrententeringthenode.
36、Usingmeshcurrentsinsteadofelementcurrentsascircuitvariablesisconvenientandreducesthenumberofequationsthatmustbesolvedsimultaneously.
37、Aplanarcircuitisonethatcanbedrawninaplanewithnobranchescrossingoneanother;otherwiseitisnonplanar.
38、Ameshcurrentisindicatedbyacurvedarrowthatalmostclosesonitselfandisdrawninsidetheappropriatemesh,asshowninFig.1-16.
39、Althoughthedirectionisarbitrary,weshallalwayschooseclockwisemeshcurrentsbecauseacertainerror-minimizingsymmetrythenresultsintheequations.
40、Impedanceisnotaphasorandcannotbetransformedtothetimedomainbymultiplyingbyejωtandtakingtherealpart.
41、WecanproceedtooursimplificationofsinusoidalsteadyCstateanalysisbyestablishingtherelationshipbetweenthephasorvoltageandphasorcurrentforeachofthethreepassiveelements.
42、WeshouldnotefromEq.(1-24)thatthevoltageandcurrentrelationisinphase,asillustratedinthephasordiagraminFig.1-18.
43、Thephasesequenceisthetimeorderinwhichthevoltagespassthroughtheirrespectivemaximumvalues.Thephasesequenceisdeterminedbytheorderinwhichthephasorspassthroughafixedpointinthephasordiagram.
44、Thisisduetotheeasewithwhichloadsmaybeaddedorremovedfromeachphaseofadelta-connectedload.
45、Ontheotherhand,delta-connectedsourcesarenotcommoninpracticebecauseofthecirculatingcurrentthatwillresultinthedelta-meshifthethree-phasevoltageareslightlyunbalanced.
46、Thewyesourceconnectionisusedforlongdistancetransmissionofelectricpower,whereresistivelosses(I2R)shouldbeminimal.
47、Thisconversionsfromthree-phasetosingle-phaseisrequiredinresidentialwiringbecausehouseholdlightingandappliancesusesingle-phasepower.
48、Ineveryaspectofourincreasinglytechnologicalsociety―whetheritisscience,engineering,medicine,music,maintenance,orevenespionage―theroleofelectronicsislarge,anditisgrowing.
49、Thisinformationmightinvolvespeechandmusic,asinradiobroadcasting,aphysicalquantitysuchasthetemperatureoftheairinaroom,ornumericaldata,suchastherecordofstockmarkettransactions.
50、
51、Asignal-processingsystemisaninterconnectionofcomponentsanddevicesthatcanacceptaninputsignaloragroupofinputsignals,operateonthesignalsinsomefashioneithertoextractorimprovethequalityoftheinformation,andpresenttheinformationasanoutputintheproperformatthepropertime.
52、Analogelectronicspertainstothosesystemsinwhichtheelectricalvoltageandelectricalcurrentareanalogoustophysicalquantitiesandvarycontinuously.
53、Analogelectroniccircuitsarecarefullydesignedtomaketheelectricalvoltagesandcurrentsfollowtheinputsignal.
54、Thebodyofthoughtthatisknowncollectivelyassymboliclogicestablishedtheprinciplesforderivingmathematicalproofsandsingularlymodifiedourunderstandingandthescopeofmathematics.
55、Booleandotherswereinterestedindevelopingasystematicmeansofdecidingwhetherapropositioninlogicormathematicswastrueorfalse,butweshallbeconcernedonlywiththevalidityoftheoutputofdigitaldevices.
56、Indevelopingdigitalsystemstheeasiestprocedureistoputtogetherconceptuallythegatesandconnectionstoperformtheassignedtaskinthemostdirectway.
57、Theequivalentsimplifiedcombinationofgateswillprobablybemuchlessexpensiveandlessdifficulttoassemble.
58、Therearemanydifferentwaystobuildelectroniccircuitswithinput-outputcharacteristicsthatcorrespondtothevariousdigitaloperations.
59、Occasionally,onemustmakeconnectionsbetweendigitalcircuitsconstructedfromlogicfamilieswithinputandoutputvoltagerangesthatarenotcompatiblewithoneanother.
60、Thedigitalrepresentationofthevaluesisimportantfordigitalprocessingandanalysis,forregulationandcontrol,andforrecordingandtransmittingthedatathatquantizethem.
61、Theclarityandfidelityoflaser-readdigitalrecordingsofmusicandspeechandthefreedomoftheserecordingsfrombackgroundnoisearerecentadvancements,butthehumanearcannotconvertbinarydatarecordedonadisctomusicorspeech.
62、Thetransduceristhenameofthedev
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 专业 英语 复习题