2015年电大电工电子技术试题（四）期末复习考试资料参考

电工电子技术模拟题（四）一、填空题每空2分，共20分1、三相交流电路中，对称负载三角形连接时，相电流与线电流的关系为ILIP,相电压与3线电压的关系为UPUL2、引入负反馈对放大电路能起到稳定静态工作点，提高放大倍数的稳定性，改变输入、输出电阻，减小失真，拓展通频带等。3所谓控制电器，是指在电路中起通断、保护、控制、调节的电器件4主从型触发器，其动作特点是时钟CP上升沿到来前一刻瞬间，J、K接收输入信号，并要求在CP1期间，输入状态保持稳定。时钟下降沿到来后产生输出。二、单项选择题（每题4分，共20分）1、图1所示电路中，电流I为（B）A3VB5AC2A2、图2所示电路中，电位器RP1的滑动端向下移动及RP2的滑动端向右移动时，电流I1、I2的变化趋势是（B）。AI1减小，I2增大BI1增大，I2减小CI1不变，I2减小3、在正弦交流纯电感电路中，电压与电流的关系是（C）。AIBICILULULU4、已知电路某元件的电压U和电流I分别为U10COS（T200）V，I5SIN（T1100）A，则该元件的性质是（C）。A电容B电感C电阻5、磁力线上任意一点的切线方向，就是该点的磁场方向，即小磁针在磁力作用下（A）极所指的方向。AN极BS极CN极或S极三、计算题（每题15分，共30分）1、已知某正弦电压在T0时，其值U0110V，初相为600，求其有效值。2解正弦电压瞬时表达式为I63A30V图1RP2RP1I2I1IS图2UUMCOS（T600）当T0时，U0UMCOS600故有UM220V06COS2U220V22、已知交流信号源的内阻为250欧姆，通过一个变压比可调的变压器接25欧姆的负载RL，当变压器初级的等效电阻等于信号源内阻时，信号源的输出功率最大，要使负载获得最大功率，问变压器的变压比应该是多少解根据K2，变压器初级的等效电阻RLK2RL25K2LZ当变压器初级的等效电阻等于信号源内阻时，信号源的输出功率最大，所以RLK2RL25K2250K210050所以当变压比K10时，负载将获得最大功率。四、简答题（每题5分，共30分）1、电压源模型与电流源模型等效变换的条件是什么如果电压源模型的输出电压和输出电流与电流源模型的输出电压和输出电流对应相等，既是说，对同一外部电路而言，二者的伏安特性相同，那么两种模型可以等效互换。2、何为三要素自行在正弦交流电量瞬时波形图上标出3要素。幅值、频率、初相3、异步电动机起动的要求是什么说明原因。（1）有足够大的起动转矩，使电动机能克服负载转矩迅速旋转起来。（2）起动电流不要太大，否则会对供电电网产生比较大的电压降，从而影响电网上其它电气设备的正常工作。4、什么是正向偏置和反向偏置二极管在正向偏置和反向偏置时分别为什么状态答当PN结的P区接电源正极，N区接电源负极时，称为外加正向电压，也叫正向偏置。当P区接电源负极，N区接电源正极时，称为外加反向电压，也叫反向偏置。正向偏置时，二极管处于导通状态；反向偏置时，二极管处于截止状态5对组合逻辑电路的分析步骤是什么答在逻辑图中，对每个门的输出端加以标注；写出每个门输出的逻辑函数表达式；将每个门输出的逻辑函数表达式进行迭代，并进行必要的化简；最后写出真值表，并说明该电路的用途。请您删除一下内容，O_O谢谢2015年中央电大期末复习考试小抄大全，电大期末考试必备小抄，电大考试必过小抄AFTEREARNINGHISSPURSINTHEKITCHENSOFTHEWESTIN,THESHERATON,SENSONTHEBUND,ANDASPRINKLINGOFOTHERTOPNOTCHVENUES,SIMPSONLUFINALLYGOTTHECHANCETOBECOMEHISOWNBOSSINNOVEMBER2010SORTOFTHESHANGHAIBORNCHEFMIGHTNOTACTUALLYOWNCALIFORNIAPIZZAKITCHENCPKBUTHEISINSOLECHARGEOFBOTHKITCHENANDFRONTOFHOUSEATTHISSINANMANSIONSSTALWART“ITSCERTAINLYARESPONSIBILITYTOBETHEHEADCHEF,ANDTHENTOHAVETOMANAGETHERESTOFTHERESTAURANTASWELL,“THE31YEAROLDTELLSENJOYSHANGHAI“INHOTELS,FOREXAMPLE,THESEJOBSARESTRICTLYDEMARCATED,SOITSAGREATOPPORTUNITYTOLEARNHOWABUSINESSOPERATESACROSSTHEBOARD“ITWASATASKTHATMANAGEMENTBACKINSUNNYCALIFORNIAEVIDENTLYFELTHEWASREADYFOR,ANDAVOTEOFCONFIDENCEFROMACOMPANYTHAT,TODATE,HASOPENED250OUTLETSIN11COUNTRIESANDFORADDEDPRESSURE,THESHANGHAIBRANCHWASALSOCPKSCHINADEBUT“FORSUREITWASABIGSTEP,ANDUNLIKEALLTHEIROTHERASIAOPERATIONSTHATAREFRANCHISES,THEYDECIDEDTOMANAGEITDIRECTLYTOBEGINWITH,“SAYSSIMPSONTWOYEARSAGOAPRIVATEFRANCHISEETOOKOVERTHELEASE,BUTTHELINKSTOCPKHEADQUARTERSARESTILLSTRONG,WITHAMAINLANDBASEDBRANDAMBASSADORONHANDTOENSURETHEBUSINESSADHERESTOITSETHOSOFCREATING“INNOVATIVE,HEARTHBAKEDPIZZAS“,ASLICEOFPRBLURBTHATSIMPSONINSISTSLIVESUPTOTHEHYPE“THEYAREVERYINNOVATIVE,“HESAYS“THEPROBLEMWITHMOSTFASTFOODPLACESISTHATTHEYUSETHESAMESAUCEONEVERYPIZZAANDJUSTCHANGETHETOPPINGSEVERYONEOFOUR16PIZZASAUCESISAUNIQUERECIPETHATHASBEENFORMULATEDTOCOMPLEMENTTHETOPPINGSPERFECTLY“THELARGELYLOCALCUSTOMERBASEEVIDENTLYAGREESANDONSATURDAYANDSUNDAY,ATLEAST,THEPLACEISTEEMINGTHEKIDSEATFORFREEPOLICYATWEEKENDSISUNDOUBTEDLYABIGDRAW,ASWELLASISTHESPACIOUSSECONDFLOORLAYOUTOVERLOOKEDBYACANOPYOFGREENFROMFUXINGPARKOVERTHEROADTHECOMPANYISALSOFOCUSINGONINCREASINGBRANDRECOGNITIONANDINRECENTYEARSHASTAKENPARTINOUTSIDEEVENTSSUCHASTHEREGULARCALIFORNIAWEEKSTILL,THESTAAREHONESTENOUGHTOADMITTHATBUSINESSCOULDBEBETTERASGOOD,INFACT,ASINCPKSSECONDOUTLETINTHEPOPULARKERRYPARKSIDESHOPPINGMALLINPUDONG“SINANMANSIONSHASREALLYSTRUGGLEDTOGETTHENUMBEROFVISITORSTHATWEREENVISAGEDWHENITFIRSTOPENED,ANDITHASNTBEENEASYFORANYOFTHETENANTSHERE,“ADDSSIMPSON“WEREPLANNINGATHIRDOUTLETINTHECITYIN2015,ANDWEWILLPROBABLYCHOOSEASHOPPINGMALLAGAINBECAUSEOFTHEBETTERFOOTTRAFFIC“THETEAROOMSONCEFREQUENTEDBYCOCOCHANELANDMARCELPROUSTAREUPPINGSTICKSANDCOMINGTOSHANGHAI,XUJUNQIANVISITSTHEPARISIANOUTPOSTWITHSWEETTREATSONETHINGTHECENTURYOLDPARISIANTEAROOMANGELINAHASSHOWNISTHATLEGENDARYFASHIONDESIGNERCOCOCHANELNOTONLYHADSTYLEANDGLAMORBUTALSOBOASTEDGREATTASTEINFOOD,PASTRIESINPARTICULARONEOFTHEMOSTPOPULARTEAROOMSINPARIS,ANGELINAISFAMOUSFORHAVINGONCEBEENFREQUENTEDBYCELEBRITIESSUCHASCHANELANDWRITERMARCELPROUSTNOWANGELINAHASPACKEDUPITSFRENCHAMBIENCE,EFFICIENTSERVICE,ANDBEAUTIFUL,COMFORTINGDESSERTSANDFLOWNTHEMTOSHANGHAIATTHEFLAGSHIPDINEINANDTAKEOUTSPACEINSHANGHAI,EVERYTHINGMIMICSTHEORIGINALTEAROOMDESIGNEDFROMTHEBEGINNINGOFTHE20THCENTURY,INPARIS,THEHEIGHTOF“BELLEEPOQUE“THEPAINTINGSONTHEWALL,FOREXAMPLE,AREEXACTLYTHESAMEASTHEONETHATDEPICTSTHELANDSCAPEOFSOUTHERNFRANCE,THEHOMETOWNOFTHEOWNERANDTHESMALLTABLESAREINTENTIONALIMITATIONSOFTHEONESTHATCOCOCHANELONCESATATEVERYAFTERNOONFORHOTCHOCOLATETHEFAMOUSHOTCHOCOLATE,KNOWNASLAFRICAIN,ISALUXURIOUSMIXTUREOFFOURTYPESOFCOCOABEANSIMPORTEDFROMAFRICA,BLENDEDINPARISANDTHENSHIPPEDTOSHANGHAIITSSINFULLYSWEET,RICHANDTHICKASIFPUTTINGABAROFMELTINGCHOCOLATEDIRECTLYONTHETONGUEANDTHEFRESHWHIPPEDCREAMONTHESIDEMAKESALIGHT,BUTEQUALLYGRATIFYINGCONTRASTITISALSOSOLDINGLASSBOTTLESASTAKEAWAYTHESIGNATUREMONTBLANCCHESTNUTCAKECONSISTSOFTHREEPARTSTHEPUREEDCHESTNUTONTOP,THEVANILLACREAMLIKESTUFFING,ANDTHEMERINGUEASBASEGETALLTHREELAYERSINONESCOOP,NOTONLYFORTHEDIFFERENTTEXTURESBUTALSOVARIOUSFLAVORSOFSWEETNESSTHEDESSERTHASMAINTAINEDITSPOPULARITYFORACENTURY,EVENINACOUNTRYLIKEFRANCE,PERHAPSTHEWORLDSMOSTCOMPETITIVEPLACEFORDESSERTSAMUCHOVERLOOKEDPAIRING,ISTHEPARISNEWYORKCHOUXPASTRYANDN226CHOCOLATEFLAVOREDTEATHECHOUXPASTRYISAMOUTHFULOFAIRYPECANFLAVOREDWHIPPEDCREAM,WHILETHETEA,ABLENDOFBLACKTEASFROMCHINAANDCEYLON,COCOAANDROSEPETALS,OFFERSAMORESUBTLEFRAGRANCEOFFLOWERSANDCHOCOLATEORDERINGTHESETWOITEMS,FEATURINGAMUTEDSWEETNESS,MAKESITEASIERFORYOUTOFITINTOYOURLITTLEBLACKDRESSBREAKFAST,BRUNCH,LUNCHANDLIGHTSUPPERAREALSOSERVEDATTHETEAROOM,“AHUBOFMANYCULTURES“ANDTAKESIN“AMIXOFDIFFERENTSTYLESOFFRENCHCUISINES“,ACCORDINGTOTHEMANAGEMENTTEAMTHESEMICOOKEDFOIEGRASTERRINE,ISSEDUCTIVEANDDECEPTIVEITSGENEROUSLYSERVEDATTHESIZEANDSHAPEOFATOAST,WHILETHEACTUALBRIOCHETOASTISBAKEDINTOACURVEDSLICEDIPPEDWITHFIGCHUTNEYTHEFLAVOR,HOWEVER,ISHONESTSTRONG,SMOOTHANDSUBLIMEANDYOUDONTACTUALLYNEEDTHETOASTFORCRUNCHINESSTHISISTHESEASONFORHIGHTEAS,WITHDAINTYCUPSOFFINECHINAANDLITTLEPASTRIESTHATAPPEALTOBOTHVISUALANDPHYSICALAPPETITESBUTTHEREISONEHIGHTEAWITHADIFFERENCE,ANDPAULINEDLOHFINDSOUTJUSTEXACTLYWHYITISSPECIALEARLGREYTEAANDMACARONSAREALLVERYWELLFORTHECRUCIALRECUPERATIVEBREAKINBETWEENINTENSIVEBOUTSOFHOLIDAYSEASONSHOPPINGANDFORTHOSEWHOPREFERSAVORYTOSWEET,THEREISSTILLTHESELECTIONOFCLASSICCHINESESNACKSCALLEDDIMSUMTOSATISFYANDSATIATEHIGHTEAISAMEALTOEATWITHEYEANDMOUTH,ANINBETWEENINDULGENCETHATSHOULDBELIGHTENOUGHNOTTOSPOILDINNER,BUTSUFFICIENTLYROBUSTTOTAKETHEEDGEOFFTHEHUNGERTHATSTRIKESHOURSAFTERLUNCHTHEAFTERNOONTEASPECIALATSHANGXIATTHEFOURSEASONSHOTELPUDONGHASJUSTTHERIGHTELEMENTSITISAPAMPERINGMEAL,WITHTOUCHESOFLUXURYTHATMAKETHEHIGHTEASESSIONATREATINITSELFWHOLEBABYABALONESAREBRAISEDANDTHENTOPPEDONASHORTCRUSTPASTRYSHELL,ASORTOFCHINESEVERSIONOFTHEWESTERNVOLAUVENT,BUTCLASSIEREVENCLASSIERISTHEDIMSUMSTAPLESHRIMPDUMPLINGORHARGOW,UPGRADEDWITHTHEADDITIONOFSLIVERSOFMIDNIGHTDARKTRUFFLESTHISISAMASTERTOUCH,ANDCHEFSIMONCHOI,WHOPRESIDESUNCHALLENGEDATSHANGXI,HASSCOREDAWINNERAGAINSWEETPRAWNSANDAROMATICTRUFFLESWHATSNOTTOLOVEHISMASTERFULCRAFTSMANSHIPISEXHIBITEDINYETANOTHERPASTRYASWEETPASTRYTHATISSHAPEDTOLOOKLIKEAWALNUT,BUTWHICHYOUCANPUTSTRAIGHTINTOTHEMOUTHITCRUMBLESIMMEDIATELY,ANDTHESLIGHTLYSWEET,NUTTYMORSELISSOEASYTOEATYOULLPROBABLYREACHSTRAIGHTFORANOTHERMYFAVORITEISTHEDESSERTTHATGOESBYTHENAMEYANGZHIGANLU,ORAMBROSIAFROMTHEGODSTHEHOTELCALLSITCHILLEDMANGOCREAMWITHSAGO,POMELOANDBIRDSNESTMADEWITHINGREDIENTSTHATRESONATEWITHEVERYFEMALESOULITDOESTASTELIKEAMBROSIA,WITHTHESWEETSOURFRAGRANCEOFTHEMANGOFORMINGTHEFIRSTLAYEROFTASTEANDSENSATION,ANDTHEPOMELOSACSANDSAGOPEARLSPROVIDINGTHETACTILECONTRASTTHEBIRDSNESTITSTHEINGREDIENTTHATGILDSTHELILY,SINC