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1、重庆大学《专业其语》课程试卷2005-2006学年第二学期开课学院：电气工程学院考试日期：考试方式：□开卷目闭卷口其他考试时间：12U分钟题号—・二三四五六七八九十总分得分一、Readingcomprehension(20points):PASSAGEONEConsiderthesituationshowninFig丄Therateofelectricalenergyflow(power)fromnetworkAtonetworkBisp=vi•Lowercase①lettersareusedtoindicateinstantaneousvalues,
2、thatis,thatp,v,andimayvarywithtime.Highpowerlevelsrequirehighvoltageandcurrentvalues.Foragivenvalueofcurrent,higherpowerflowsmaybeobtainedbyincreasingthevoltage,andviceversa.Unfortunately,theexistingtechnologysetspracticalupperlimitsonallowablecurrentsandvoltages.Whatarethelimit
3、ingfactorsforcurrent?Wefabricate②powerconductorsUSingmaterialsWithhighconductivity,Figipowertransmissionbetween•x■•■■▲•▲twonetworksappropriatemechanicalcharacteristics,andthatareeconomical:aluminumisthemostcommonchoice,withcopperusedforsomeapplicationSeThecurrent-carryingcapacit
4、yofaconductorisrelatedtoitsmaximumallowablecurrentdensityanditscross・sectionalarea③:maxmaxThemaximumcurrentdensityJmaxisdeterminedbythemaximumconductortemperaturethatwillnotdamagetheconductororitsinsulationsystem.Whatarethelimitingfactorsonvoltage?Thefundamentalconsiderationisto
5、provideelectricalisolation④(orinsulation)betweenadjacentpartsthatcanconductcurrent-thatis,toconfinecurrenttothepathsthroughwhichitwasintendedtoflow.Whenthevoltageexceedsthebreakdown®strengthforagiveninsulationsystem,undesirableconductionpathswillbecreatedandthesystemwillbeeither
6、temporarilyorpermanentlydisabled*Fluidinsulationtendstobe"self-healing：⑥”(thesystemwillrecoverfromabreakdownifitisde-energized)forashorttimeandthenre-energized,whereassolidinsulationispermanentlydamagedbyabreakdown^LAnswerthefollowingquestions:(1)Foragivenvalueofvoltage,howtoobt
7、ainthehighenergyflows?(2)Whatarethelimitingfactorsoncurrentandvoltage?2.ExplaintheunderliningwordsmChinese①lowercase②fabricate③cross-sectionalarea④isolation⑤breakdown⑥self-healingPASSAGE命是人Withthewidespreaduseofthepersonalcomputer,manyauthoritiesinthefieldof｛①｝havepointedoutthen
8、eedforcomputerliteracy.Unfortunately,thereisno｛
