2017考研数学二真题解析：选择题第2题答案解析

解读2017考研数学三真题分析考查知识分布高等数学线性代数概率

2016年12月24日星期六和2016年12月25日星期日对于大多数人来说是一个休息的日子，但是这两天对于17年考研人来说是意义非凡的，这两天是交卷的时间，是收货的时节，预祝各位考研人考的都会，蒙的

新东方在线推荐：2018年考研一次顺利提分课程！！一科不过，全科免费Archaeologyasaprofessionfacestwomajorproblems.First,iti

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新东方在线推荐：2018年考研一次顺利提分课程！！一科不过，全科免费Theuseofheatpumpshasbeenheldbacklargelybyskepticismaboutadvertisers’claimsthatheatpumpscanprovideasmanyastwounitsofthermalenergyforeachunitofelectricalenergyused,thusapparentlycontradictingtheprincipleofenergyconservation.Heatpumpscirculateafluidrefrigerantthatcyclesalternativelyfromitsliquidphasetoitsvaporphaseinaclosedloop.Therefrigerant,startingasalow-temperature,low-pressurevapor,entersacompressordrivenbyanelectricmotor.Therefrigerantleavesthecompressorasahot,densevaporandflowsthroughaheatexchangercalledthecondenser,whichtransfersheatfromtherefrigeranttoabodyofair.Nowtherefrigerant,asahigh-pressure,cooledliquid,confrontsaflowrestrictionwhichcausesthepressuretodrop.Asthepressurefalls,therefrigerantexpandsandpartiallyvaporizes,becomingchilled.Itthenpassesthroughasecondheatexchanger,theevaporator,whichtransfersheatfromtheairtotherefrigerant,recingthetemperatureofthissecondbodyofair.Ofthetwoheatexchangers,oneislocatedinside,andtheotheroneoutsidethehouse,soeachisincontactwithadifferentbodyofair:roomairandoutsideair,respectively.Theflowdirectionofrefrigerantthroughaheatpumpiscontrolledbyvalves.Whentherefrigerantflowisreversed,theheatexchangersswitchfunction.Thisflow-reversalcapabilityallowsheatpumpseithertoheatorcoolroomair.Now,ifundercertainconditionsaheatpumpputsoutmorethermalenergythanitconsumesinelectricalenergy,hasthelawofenergyconservationbeenchallenged?No,notevenremotely:theadditionalinputofthermalenergyintothecirculatingrefrigerantviatheevaporatoraccountsforthedifferenceintheenergyequation.Unfortunatelythereisonerealproblem.Theheatingcapacityofaheatpumpdecreasesastheoutdoortemperaturefalls.Thedropincapacityiscausedbythelesseningamountofrefrigerantmassmovedthroughthecompressoratonetime.Theheatingcapacityisproportionaltothismassflowrate:thelessthemassofrefrigerantbeingcompressed,thelessthethermalloaditcantransferthroughtheheat-pumpcycle.Thevolumeflowrateofrefrigerantvaporthroughthesingle-speedrotarycompressorusedinheatpumpsisapproximatelyconstant.Butcoldrefrigerantvaporenteringacompressorisatlowerpressurethanwarmervapor.Therefore,themassofcoldrefrigerant—andthusthethermalenergyitcarries—islessthaniftherefrigerantvaporwerewarmerbeforecompression.Here,then,liesagenuinedrawbackofheatpumps:inextremelycoldclimates—wherethemostheatisneeded—heatpumpsareleastabletosupplyenoughheat.1.Theprimarypurposeofthetextisto[A]explainthedifferencesintheworkingofaheatpumpwhentheoutdoortemperaturechanges.[B]contrasttheheatingandthecoolingmodesofheatpumps.[C]describeheatpumps,theiruse,andfactorsaffectingtheiruse.[D]advocatethemorewidespreaduseofheatpumps.2.Theauthorresolvesthequestionofwhetherheatpumpsruncountertotheprincipleofenergyconservationby[A]carefullyqualifyingthemeaningofthatprinciple.[B]pointingoutafactualeffortinthestatementthatgivesrisetothisquestion.[C]supplyingadditionalrelevantfacts.[D]denyingtherelevanceofthatprincipletoheatpumps.3.Itcanbeinferredfromthetextthat,inthecourseofaheatingseason,theheatingcapacityofaheatpumpisgreatestwhen[A]heatingisleastessential.[B]electricityratesarelowest.[C]itscompressorrunsthefastest.[D]outdoortemperaturesholdsteady.4.Iftheauthor’sassessmentoftheuseofheatpumps(lines1-4)iscorrect,whichofthefollowingbestexpressesthelessonthatadvertisersshouldlearnfromthiscase?[A]Donotmakeexaggeratedclaimsabouttheproctsyouaretryingtopromote.[B]Focusyouradvertisingcampaignonvagueanalogiesandveiledimplicationsinsteadofonfacts.[C]Donotusefactsinyouradvertisingthatwillstraintheprospectiveclient’sabilitytobelieve.[D]Donotassumeinyouradvertisingthattheprospectiveclientsknoweventhemostelementaryscientificprinciples.5.Thetextsuggeststhatheatpumpswouldbeusedmorewidelyif[A]theycouldalsobeusedasairconditioners.[B]theycouldbemovedaroundtosupplyheatwhereitismostneeded.[C]theirheatoutputcouldbethermostaticallycontrolled.[D]peopleappreciatedtheroleoftheevaporatorintheenergyequation.