1314EEMv2resitexam1314FINAL

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1、SBCYEAR2ENGINEERING2013–2014ElectronicEngineeringMaterialsExaminationSessionTimeAllowedResit2hours10minutes(Including10minutesreadingtime)NOTE:Themarkforeachquestionisindicatedinsquarebrackets[].Thetotalmarkforthispaperis60.INSTRUCTIONSTOSTUDENTS·Noanswersmustbewritteninthefirst10minutes.·Writey

2、ourCandidateNumberclearlyontheanswerbooksinthespaceprovided.·AnswerTHREEquestionsoutoffour.·Writeyouranswersintheanswerbooksprovided.Additionalsheetswillbeprovideduponrequest.·Nowrittenmaterialisallowedintheexaminationroom.·Nomobilephonesareallowedintheexaminationroom.·Anapprovedcalculatormaybeu

3、sedintheexamination.UsefulFormulaeAllsymbolsnotspecificallydefinedhavetheirnormallyacceptedmeaningsUniversalConstantsk=1.38´10-23JK-1or8.62´10-5eVK-1q=1.6´10-19Cm0=4p´10-7Hm-1e0=8.85´10-12Fm-1h=6.62´10-34Jsme=9.1´10-31kgMainEquationsIfneeded,assumethatthetemperatureis300Kunlessotherwisestated.An

4、swerTHREEQuestionsOnly.Question1(a)i.Withtheaidofasketch,describetheuseoftherighthandgripruleforacoil.ii.SketchtheshapeoftheB-Hcurveforaferromagneticmaterial.LabelyourdiagramwithremanenceBrandcoercivityHc.iii.Magneticmaterialsaresometimesdescribedas‘hard’or‘soft’.Whatarethemeaningsof‘hard’and‘s

5、oft’whenappliedtomagneticmaterials?iv.Wouldyouchoosea‘hard’or‘soft’materialforatransformeranywhy?v.Wouldyouchoosea‘hard’ora‘soft’materialforamagneticrecordingdeviceandwhy?[4][5][2][2](b)i.Ifthefluxdensityinacertainmaterialis0.5Tandtheareaofthematerialis500x10-6m2,whatisthefluxthroughthematerial?

6、ii.Mildsteelhasarelativepermeabilityof800.Calculatethereluctanceofamildsteelcorethathasalengthof10cmandhasacrosssectionof0.5cmby0.5cm.[2][5]Question2(a)i.Describetheprocessofconductionwithinamaterialbyconsideringelectronsoccupyinganumberofdiscreteenergybandsatroomtemperature.Startbyassumingsomek

7、indofenergyisprovidedtoavalenceelectron.ii.Describethedifferencebetweenafullbandandanemptybandintermsofelectrons.iii.Withtheaidofdiagramsillustratethedifferencebetweenann-typeandap-typesemiconductormaterial.[3][2][5](b)Twose