专业英语复习题.doc

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1、1、Chargeisanelectricalpropertyoftheatomicparticlesofwhichmatterconsists,measuredincoulombs。2、Wealsoknowthatthechargeeonanelectronisnegativeandequalinmagnitudeto1.60210×10--19Cwhileaprotoncarriesapositivechargeofthesamemagnitudeastheelectron3.、Auniquefeature

2、ofelectricchargeorelectricityisthefactthatitismobile;thatis,itcanbetransferredfromoneplacetoanother,whereitcanbeconvertedtoanotherformofenergy.4、Althoughwenowknowthatcurrentinmetallicconductorsisduetonegativelychargedelectrons,wewillfollowtheuniversallyacce

3、ptedconventionthatcurrentisthenetflowofpositivecharges.5、ThewaywedefinecurrentasiinEq.(1-l)suggeststhatcurrentneednotbeaconstant-valuedfunction,chargecanvarywithtimeinseveralwaysthatmayberepresentedbydifferentkindsofmathematicalfunctions.6、Thevoltageuabbetw

4、eentwopointsaandbinanelectriccircuitistheenergy(orwork)neededtomoveaunitchargefromatob。7、Thepowerabsorbedorsuppliedbyanelementistheproductofthevoltageacrosstheelementandthecurrentthroughit.8、Anidealindependentsourceisanactiveelementthatprovidesaspecifiedvol

5、tageorcurrentthatiscompletelyindependentofothercircuitvariables.9、ThesymbolforavoltagesourcehavinguvoltsacrossitsterminalsisshowninFig.1-4(a).10、Anothersymbolthatisoftenusedforaconstantvoltagesource,suchasabatterywithUvoltsacrossitsterminals,isshowninFig.1-

6、4(b).11、WemightobserveatthispointthatthepolaritymarksonFig.1-4(b)areredundantsincethepolaritycouldbedefinedbythepositionsofthelongerandshorterlines.12、Thusifuisthevoltageacrossthesourceanditscurrentiisdirectedoutofthepositiveterminal,thenthesourceisdeliveri

7、ngpower,givenbyp=ui,totheexternalcircuit.13、Sincethecontrolofthedependentsourceisachievedbyavoltageorcurrentofsomeotherelementinthecircuit,andthesourcecanbevoltageorcurrent,itfollowsthattherearefourpossibletypesofdependentsources,namely:14、Itshouldbenotedth

8、atanidealvoltagesource(dependentorindependent)willproduceanycurrentrequiredtoensurethattheterminalvoltageisasstated,whereasanidealcurrentsourcewillproducethenecessaryvoltagetoensurethestatedcurrentflow