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RegisterforInterviewGuidanceatwww.engineersinstitute.comQ.Whatisthedifferencebetweenironandsteel?Ans.Ironisanelementthatwhencombinedwithcarbonandotherelementsmakessteel.Q.Whatistheuseofhydrogeninautomobile?Ans.Lowemissions.EssentiallynoCOorHCintheexhaustasthereisnocarboninthefuel.MostexhaustwouldbeH2OandN2Fuelavailability.Thereareanumberofdifferentwaysofmakinghydrogen,includingelectrolysisofwater.Q.DifferencebetweenYieldStressandYieldStrength?Ans.Stressisameasureoftheloadappliedtoasamplerelativetoacrosssectionalareaofthesample.Strengthisaquantificationofthesamplesabilitytocarryaload.Theterms"yieldstrength"and"yieldstress"ofamaterialareusuallyusedinterchangeably(correctornot).Itisthestresswhichwilljustcausethematerialtoplasticallydeform.Ifamaterialyieldsat30,000psi,theyieldstressis30,000psi.Ifthepartinquestionhasacrosssectionalareaof2squareinches,thestrengthatyieldwouldbe60,000pounds,butusuallywejustsaytheyieldstrengthis30,000psi.Q.WhatisthedifferencebetweenYieldandUltimatetensilestrength?Ans.TheyieldstrengthisreachedwhenthematerialbecomesNonlinear(thatisnonelastic)andtakesapermanentsetwhenloadisreleased.Materialstretchesbutdoesnotbreak.Ultimatestrengthiswhenitbreaksandishigherthanyieldstrength.Q.Doesdieselenginepoweredautomobileuseunitpumpandunitinjector?Ans.Inthecaseoftheenginespoweredbydieselfuelsupplysystems,unitpump&unitinjectorareoperatedbycamshaft&thuspressureofinjectedfueldependsonenginespeed.Whereas,incommonrailsystemsitisindependentofenginespeed.Q.Ifweusegasolineindieselengine,whatwillhappen?Ans.Addinggasolinetothedieselenginemayblastofftheengine.Compressionratioofthepetrolengineis6to10anddieselengineis15to22.Thusgasolinewillgetveryhighlycompressedandmightresultinblastoffengine.


Q.WhatisthedifferencebetweenFlexuralstrengthandTensilestrength?Ans.Flexuralstrengthisresistanceofferedagainstbending.Tensilestrengthisresistanceofferedagainsttensileforce.Q.WhatisthedifferencebetweenShearandTensilestrength?Ans.TensileStrengthforaBoltisdeterminedbyapplyingaForcealongitlongaxis.ShearStrengthforaBoltisdeterminedbyapplyingaForceacrossitsdiameter,asitwouldbeloadedinalugjoint.Tensilestrengthisstrengthintensionwhenpullingforceisapplied.Andshearstrengthisstrengthagainstcuttingforcewhichisknownasshearforce.Q.WhatisthedifferencebetweenTensilestrengthandTensilemodulus?Ans.Tensilestrengthistheultimatecapacityofthematerialtoresistatensileloadregardlessofdeflection.TensilemodulusalsoknownasYoungsmodulusisameasureofthestiffnessofanisotropicelasticmaterial.Itisdefinedastheratiooftheuniaxialstressovertheuniaxialstrain.Itisdeterminedfromtheslopeofastressstraincurvetracedduringtensiletestsconductedonasampleofthematerial.Q.Whatisthereasonforemittingthewhiteexhaustsmokeduringstartofthevehicle?Howwillyoupreventthis?Ans.Themaincauseofwhitesmokeiswaterorantifreezeenteringthecylinder,sotheenginestartstoburnitwiththefuel.Thatwhitesmokeisnothingbutsteam.Preventionmeasures:Therearespecialgasketsi.e.headgasketsandprimarygasketsthatpreventtheantifreezefromenteringintothecylinderarea.Thisantifreezewillproduceawhitesteamwhichwillaccumulateatthetailpipearea.Q.Whatistherangeofengineefficiencyincaseoftwostrokeengine?Ans.Thetwostrokeengineshaveveryhighrangetobecomparedtothefourstrokeengines.Becausepowerstrokeisgeneratedeverytworevolutionwhileinfourstroke,powerstrokeisgeneratedeveryfourrevolutions.Q.WhatdoyouunderstandbyCCofengine?Ans.ThemeaningofCCiscubiccentimeters.Itrepresentsthetotalvolumeoftheenginecylinder.ThisreflectsthattheengineswithmoreCCcangeneratemorepowersthantheotherengines.CCcanalsoberelatedasinverselyproportionaltothefuelconsumption.Q.Whatisthesignificanceofentropy?Ans.Asperthesecondlawofthermodynamics,anyheatinputtothesystem(Heatengine)cannotbeconvertedcompletelyintousefulwork.Someenergyislostandthatiscalled'unavailablework'.Theamountofunavailableworkincreasesastheentropyincreases.


Q.Whatisthedifferencebetweenheattransferandthermodynamics?Ans.Heattransferdealswiththeenergyanalysiswhichintransitionandanddependsonthemodesofheattransferlikeconduction,convectionandradiationorcombinationofanymodes.Heattransferdealsinnonequilibriumdomainandconditionswhilethermodynamicsdealswithstudyofsystematequilibriumanddoesnotdependonhowheattransferiscalculated.Q.Whatisbackcompressorinengines?Ans.Backcompressionmeansthecompressioncapabilityoftheengine.Andieselenginecancompressattheratioof14:1toashighas25:1.Thusthehighercompressionleadstobetterefficiencyoftheengine.Thickblacksmokeisemittedwhentheenginescompressionisreducedwhichleadstothedeformedeadgasketleadintocrankcase.Q.Howairconditionersworkincars?Ans.Airconditionersarebasedontheprinciplesofevaporationandcondensationandthencompressionandexpansion.Thehotairofthecarisremovedbytheprocessofevaporationandthenthecondensationoftheevaporatedairtakesplaceswhichisthenfurthercompressedbythecompressorandthenfinallyexpandedtousintheformofcoldbreeze.Somehow,Airconditioningreducestheaverageofthecar,astheenergyisrequiredtoremovethehotairandthencompressionandexpansion.Q.Howdoesthethermostatwork?Ans.Whentheengineistoocoldthethermostatclosesthemainvalve,thusstoppingtheflowtotheradiator.Whentheengineistoohot,itopensthemainvalvefornormalcirculationthroughtheradiator.Q.Whatisapressurecapintheradiator?Ans.Itisasealintheradiatorthatmaintainstheselectedpressureinthecoolingsystemwhentheengineishot.Q.Explainthereasonthatwhybigtyresareusedinrearofvehicles.Ans.Largetyresprovidelargersurfaceareatouchingtheground,thusprovidingthemorepullingpower.Basicallytractorshavelargerreartyresbecausetractorsdonthavetooperateathigherspeeds,thusgettingthesamegroundspeedwithlargertyres.Moreovergearratiosdonthavetobeashighasb/cofthetyres.Q.Whatiskingpinoffset?Statesomeofitsapplication.Ans.Thekingpinoffsetisthepart,basicallycalledaspivotusedinthesteeringofthevehicles.Thisoffsethelpsinrotatingofthesteeringandthusitsveryusefulinsteeringmechanismofthecars.Applications:Thisisalsousedtomeasurescrubradiuswiththehelpofgeometricparametersofwheelplaneaboveandbelowgroundlevel.Itprovidesdirectionalstabilitytothevehicleswheniticombinedwiththecaster.


Q.Explainthereasonthatwhythetyresarealwaysblackincolour?Ans.Tyrescolourisblackduetotheproportionofcarbonmixedinitduringthevulcanizationoftherubber,tomakethetyreshearresistant.Withoutvulcanizationtyreswon'tbeabletobearthefrictionheatandstressoftheroad.Thuscarbonisresponsibleforgivingtyrestheprominentblackcolour.Addingofcarbonpreventstyresfromrapidlydeterioratingbecausewhenozonecombineswiththeultravioletlightfromthesun.Itattacksthepolymerofthetyre.Q.WhathappensifgasolineisusedinaDieselengine?Dieselenginewillwork?Ans.No,Itwillnotwork,astheCompressionratioofPetrolengineis6to10&thatofDieselengineis15to22.Thusonsuchhighcompression,gasolinegetshighlycompressed&itmayblast.Q.WhatisthedifferencebetweenCriticalSpeedandWhirlingSpeed?Ans.InSolidmechanics,inthefieldofrotordynamics,thecriticalspeedisthetheoreticalangularvelocitywhichexcitesthenaturalfrequencyofarotatingobject,suchasashaft,propellerorgear.Asthespeedofrotationapproachestheobjectsnaturalfrequency,theobjectbeginstoresonatewhichdramaticallyincreasessystemvibration.Theresultingresonanceoccursregardlessoforientation.WhirlingSpeedisduetotheunbalancedforcesactingonarotatingshaft.Q.Howisoilpressuremaintainedwhenstartingorstoppingamediumsizedturbine?Ans.Anauxiliarypumpisprovidedtomaintainoilpressure.Someauxiliarypumpsareturnedbyahandcrank;othersaremotordriven.Thispumpisusedwhentheintegralpumpisrunningtooslowlytoprovidepressure,aswhenstartingorsecuringamediumsizedturbine.Q.HowaDieselEngineWorksasGenerator?Ans.Dieselengineisaprimemover,foragenerator,pump,andforvehiclesetc.generatorisconnectedtoenginebyshaft.mostlyinthermalpowerplat,thereisanengineisusedtodrivegeneratortogeneratepower.Q.ExplainSecondLawofThermodynamics?Ans.Theentropyoftheuniverseincreasesovertimeandmovestowardsamaximumvalue.Q.CompareBraytonCycleandOttoCycle?Ans.TheheatadditionandrejectionprocessesinOttocycleareofconstantvolume,whereasinBraytoncycle,theyareofconstantpressure.Ottocycleistheidealcycleforsparkignitionengines.Braytoncycleistheidealcycleforgaspowerturbines.Q.WhatisthepurposeofScrapperRing?Ans.scraptheexcesslubeoilfromthecylinderwalls.therebypreventingoilfromenteringcombustionzone.


Q.WhatisDTSITechnology?Ans.DTSIstandsforDigitalTwinSparkPlugIgnition.ThevehicleswithDTSITechnologyuse2sparkplugswhicharecontrolledbydigitalcircuit.Itresultsinefficientcombustionofairfuelmixture.DigitalSincethesparkgenerationwillbeinitiatedbyamicrochip.TwinSincetwosparkplugswillbeused.SparkignitionSincetheignitionwillbedoneviaaspark.Q.HowtoFind,DuctileBrittleTransitionTemperatureinMetals?Ans.ThepointatwhichthefractureenergypassesbelowapredeterminedpointforastandardImpacttests.DBTTisimportantsince,onceamaterialiscooledbelowtheDBTT,ithasamuchgreatertendencytoshatteronimpactinsteadofbendingordeforming.Q.WhatistheimportanceofThermodynamics?Ans.Allthemechanicalengineeringsystemsarestudiedwiththehelpofthermodynamics.Henceitisveryimportantforthemechanicalengineers.Q.WhatisthedifferencebetweenP11andP12Pipes?Ans.P11thechromiummolybdenumcompositionthatis1%ofchromiumand1/4%ofmolybdenum.P12thechromiummolybdenumcompositionthatis1%ofchromiumand2%ofmolybdenumQ.StatedifferencebetweenAntifrictionBearingandJournalBearing?Ans.Generally,journalbearingshavehigherfrictionforce,consumehigherenergyandreleasemoreheat,buttheyhavelargercontactsurface,sonormallyusedinlowspeedhighloadapplications.Inantifrictionbearingsfrictionisless.Oneobjectjustrollsovereachother.Q.WhatisthedifferencebetweenTechnologyandEngineering?Ans.Engineeringisapplicationofscience.TechnologyshowsvariousmethodsofEngineering.Abridgecanbemadebyusingbeamstobeartheload,byanarcorbyhanginginacable;allshowsdifferenttechnologybutcomesundercivilengineeringandscienceappliedislawsofforce/loaddistribution.Q.HowtoMeasureTemperatureinWetBulbThermometer?Ans.Wetbulbtemperatureismeasuredinawetbulbthermometerbycoveringthebulbwithawickandwettingitwithwater.Itcorrespondstothedewpointtemperatureandrelativehumidity.


Q.WhataretheAdvantagesandDisadvantagesofusingLPGinCar?Ans.Advantages1.Completecombustion2.Fuelsaving3.HomogenouscombustionDisadvantages1.Ascompletecombustionisoccurring,moreheatliberated,notadvisedforlongjourney,enginewillbeoverheated2.Installationisdifficult3.ReduceenginelifeefficiencyQ.WhatisthedifferencebetweenSpeedandEconomicSpeed?Ans.Theratedspeedtellsusaboutthemaximumspeedwhichcanbeachievedbyavehicleorsomeothermachinebuttheeconomicalspeedmeansthespeedlimitatwhichthemachineworksefficientlywithleastconsumptionoffuel.eginnormalbikes(notracing),themax.speedlimitshownonspeedometerisupto120kmphbutcompaniesalwaysadvicetheircustomerstodrivesuchbikesataround60kmphtohavemaximummileage.Q.WhenCrudeOilisHeated,WhichHydroCarboncomesfirst?Ans.Naturalgas(Gasoline)at20CelsiusQ.HowtocalculateBearingnumbertiDiameteroftheinnerandouter?Ans.Dividetheshaftdiametersizeby5,itwillgivelasttwodigitofthebearingno.andaccordingtotypeofloadwehavetochoosethetypeofbearingandthatwillgivepriornumberofthebearing.Q.TheFatiguelifeofapartcanbeimprovedby?Ans.ImprovingthesurfacefinishbyPolishing&providingresidualstressbyShotpeening.Q.WhatisPowderTechnology?Ans.Powdertechnologyisoneofthewaysofmakingbearingmaterial.Inthismethodmetalslikebronze,Al,Fearemixedandcompressedtomakeanalloy.Q.WhatarethelawsofThermodynamics?Ans.Therearethreelawsofthethermodynamics.FirstLaw:Energycanbeneithercreatednordestroyed.Itcanonlychangeforms.Inanyprocessinanisolatedsystem,thetotalenergyremainsthesame.SecondLaw:Whentwoisolatedsystemsinseparatebutnearbyregionsofspace,eachinthermodynamicequilibriuminitself,butnotinequilibriumwitheachotheratfirst,areatsometimeallowedtointeract,breakingtheisolationthatseparatesthetwosystems,andtheyexchangematterorenergy,theywilleventuallyreachamutualthermodynamicequilibrium.Thesumofthe


entropiesoftheinitial,isolatedsystemsislessthanorequaltotheentropyofthefinalexchangingsystems.Intheprocessofreachinganewthermodynamicequilibrium,entropyhasincreased,oratleasthasnotdecreased.ThirdLaw:Astemperatureapproachesabsolutezero,theentropyofasystemapproachesaminimum.Q.Atwhichtemperaturethermalradiationcanbecomezero?Ans.Notpossible.Becausethermalradiationbecomesonlyzeroatabsolutezerotemperaturewhichcanneverbeattainedbythethirdlawofthermodynamics.Q.StatethedifferencebetweenUnilateralandBilateralTolerance?Ans.Aunilateraltoleranceistoleranceinwhichvariationispermittedonlyinonedirectionfromthespecifieddirection.e.g.1800+0.000/0.060Bilateraltoleranceistoleranceinwhichvariationispermittedinbothdirectionfromthespecifieddirection.e.g.1800+0.060/0.060Q.Whatistheabbreviationofweldingrod7018?Ans.7018= 70=tensilestrength70000psi 1=weldingposition 8=currentfluxQ.WhatisdifferencebetweenWeldingandBrazing?Ans.InWeldingconcentratedheat(hightemperature)isappliedatthejointofmetalandfusetogether.InBrazinginvolvessignificantlylowertemperaturesanddoesnotentailthemeltingofbasemetals.Instead,afillermetalismeltedandforcedtoflowintothejointthroughcapillaryaction.Q.WhichhasmoreEfficiencyDieselEngineorPetrolEngine?Ans.Dieselenginehasthebetterefficiencyoutoftwo.Q.WhatisDifferencebetweenstaminaandstrength?Ans.StrengthiscapabilityoverashortlengthoftimeandStaminaistheabilitytokeepgoingcontinuously.Q.WhyCavitationwilloccurinCentrifugalPumpandnotinDisplacementPump?Ans.Theformationofcavities(orbubbles)isinducedbyflowseparation,ornonuniformflowvelocities,insideapumpcasing.Incentrifugalpumpstheeyeofthepumpimpellerissmallerthantheflowareaofpipe.Thisdecreaseinflowareaofpumpresultsinincreaseinflowrate.Sopressuredrophappenedbetweenpumpsuctionandthevanesoftheimpeller.Hereairbubblesorcavitiesareformedbecauseofliquidvapourduetoincreaseintemperatureinimpeller.Thisairbubblesaretransmittedtopumpwhichformscavitation.


Q.WhichPumpismoreEfficientCentrifugalPumporReciprocatingPump?Ans.Centrifugalpump.Becauseflowrateishighercomparedtoreciprocatingpump.Flowissmoothanditrequireslessspacetoinstall.Lowerinitialcostandlowermaintenancecost.Q.WhyCentrifugalPumpisnotcalledasaPositiveDisplacementTypeofPump?Ans.Thecentrifugalhasvaryingflowdependingonpressureorhead,whereasthePositiveDisplacementpumphasmoreorlessconstantflowregardlessofpressure.Likewiseviscosityisconstantforpositivedisplacementpumpwherecentrifugalpumphaveupanddownvaluebecausethehigherviscosityliquidsfilltheclearancesofthepumpcausingahighervolumetricefficiency.Whenthereisaviscositychangeinsupplythereisalsogreaterlossinthesystem.Thismeanschangeinpumpflowaffectedbythepressurechange.Onemoreexampleis,positivedisplacementpumphasmoreorlessconstantefficiency,wherecentrifugalpumphasvaryingefficiencyrate.Q.ExplainwhyBCC,FCCandCPHlatticepackingandfeaturesofgrainstructureaffecttheDuctilityandBrittlenessofparentmetallicmaterials?Ans.Ductilityisthemechanicalpropertyofamaterial.(Itisthematerialsabilitytodeformunderthetensilestresswithoutfracture).Soitisdependsontheatomshowtheyarrangedinalatticeanditsgrainsize.Theabilitytoabsorbtheenergyoftheimpactandfractureresistancedependsonthearrangementoftheatomsinalatticeandfeaturesofgrainstructure.Q.WhydoyouhaveTrussBridges?Ans.Trussbridgescarryloadintensionandcompressionratherthanbending(Selfweight+Theweightofvehiclescrossingit+Windloads).Atrusshastheabilitytodissipatealoadthroughthetrusswork.Thebeamsareusuallyarrangedinarepeatedtriangularpattern,sinceatrianglecannotbedistortedbystress.Q.WhyIsectionbeamispreferredforheavyloading?Ans.CrosssectionalshapeI,givingmanybenefits.Itisverygoodforgivingstiffness(lessdeformationonloading)andtowithstandhigherbendingmoments(asaresultofheavyloading)oncomparisonwithothercrosssectionalshapesofsamearea.Also,itisveryeasytomanufacture.Itwillhavemoremomentofinertia.Q.WhatisHydrostaticSystem?Ans.Hydrostaticsisthestudyoffluidbodiesthatare

Atrest Movingsufficientlyslowlysothereisnorelativemotionbetweenadjacentpartsofthebody

Forhydrostaticsituations Therearenoshearstresses Thereareonlypressureforcesthatactperpendiculartoanysurface.


Itsaclosedloophydraulicsystems.Itcomprisesofmotorandpump.Herepumpsuppliesenergytomotorandmotorgivesreturnenergytopumpsupply.Q.WhatisdifferencebetweenCenterofMassandCenterofGravity?Ans.Bothtermsaresamewhengravityisuniform.Whengravityisnonuniformfollowingaretheterms:Thecenterofmassisapointthatactsasifallthemasswascenteredthere(themassononesideofthepointisequaltothemassontheoppositeside).Ifsupportedatthecenterofmass,anobjectwillbebalancedundertheinfluenceofgravity.Thecenterofgravityisthepointatwhichwherethesum(vector)ofthegravitationalforcesactonanobjectwhichwillbebalancedonthatpoint.Q.WhatisthedifferencebetweenCenterofMassandCentroid?Ans.Ifthematerialcomposingabodyisuniformorhomogeneous,thedensityorspecificweightwillbeconstantthroughoutthebody,andthenthecentroidisthesameasthecenterofgravityorcenterofmass.Centroid:Centroidisthepoint,wherethewholeareaofplaneisgoingtobeact.Itisvalidonlyfor2Dproblemslikeplanefigures,squareplateetc.Thecenterofmassisapointthatactsasifallthemasswascenteredthere(themassononesideofthepointisequaltothemassontheOPPOSITEside).Ifsupportedatthecenterofmass,anobjectwillbebalancedundertheinfluenceofgravity.Q.WhatisCotterjoint?Ans.Acotterjointisusedtoconnectrigidlytwocoaxialrodsorbarswhicharesubjectedtoaxialtensileorcompressiveforces.Hereshaftislockedinplacebyasmallerpinthatpassesthroughthesideofthelugandpartlyorcompletelythroughtheshaftitself.Thislockingpinisnamedascotter.Q.Howistheexcessdischargepressureprevented?Ans.Dischargepressurepreventedbyapressurizedspikecushion.Herethesystememploysapressurizedcushionofairandatwooringpiston,whichpermanentlyseparatesthisaircushionfromthewatersystem.Whenthevalveclosesandthewaterflowissuddenlystopped,thepressurespikepushesthepistonupthearresterchamberagainstthepressurizedcushionofair.Theaircushioninthearresterreactsinstantly,absorbingthepressurespikethatcauseswaterhammer.Q.Whatisthedifferencebetweenastrainerandafilter?

Ans.Strainersandfiltersarebothproductsthatfilersolidsfromfluids.However,whenthesolidtobefilteredisvisibletothenakedeye(greaterthan40m)thenthetermstrainerisusedandwhenfiltrationissmallerthanorequalto40m,thetermfilterisused.


Q.WhatisthepositionofPistonRing?Ans.In180degreeangletheTopring,SecondringandOilringarefixed.Positiontheringapproximately1inchgapbelowtheneck.Q.IntheThermalPowerPlantwhyDeaerator(D/A)placedonheight?Ans.TobuildaVeryhighpressureandthetemperatureforaboilerfeedwaterpumpanditdischargehighpressurewatertotheboiler.AndtoprovidetherequiredNetPositiveSuctionHead(NPSH)fortheBFWpumpandtoserveasastoragetanktoensureacontinuoussupplyoffeedwaterduringrapidchangesinBFP.Q.WhatdoyoumeanbyOneTonnAirConditioner?Ans.1tonrefrigerationmeans210kJ/minextractsheatfromthesystem.Q.WhatistheimportanceoftheThermodynamicsinthefieldofMechanicalEngineering?Ans.Allthemechanicalengineeringsystemsarestudiedwiththehelpofthermodynamics.Henceitisveryimportantforthemechanicalengineers.Q.StateLawsofconservationofenergy?Ans.Accordingtothelawsofconservationofenergy,energycanneitherbecreatednorbedestroyed.Itcanonlybetransformedfromoneformtoanother.Q.Istheboileraclosedsystem?Ans.Yesdefinitelytheboilerisaclosedsystem.Q.WhatisCarnotengine?Ans.ItwasbeingdesignedbyCarnotandletmetellyouthatCarnotengineisanimaginaryenginewhichfollowstheCarnotcycleandprovides100%efficiency.Q.WhatisHessLaw?Ans.AccordingtotheHesslawtheenergytransferissimplyindependentofthepathbeingfollowed.Ifthereactantandtheproductofthewholeprocessarethesamethensameamountofenergywillbedissipatedorabsorbed.Q.Whichhasmoreefficiency:DieselengineorPetrolengines?Ans.Dieselenginehasthebetterefficiency.Givefurtherexplanationsifinterviewwanttoknow.Q.WhyEntropydecreaseswithincreaseintemperature?Ans.ds=dQ/TEntropyisinverselyproportionaltothetemperatureso,astemp.Increases,entropydecreases.


Q.Whydifferenttypesofsoundareproducedindifferentbikes,thoughtheyrunonSIEngines?Ans.EnginespecificationsaredifferentindifferentmanufactureslikeasBoreDiameter(CC),Ignitiontiming.Alsotheexhaustpassagetakesmoreresponsibleforsound.Q.HowmuchWattmeans1Hp?Ans.746.2WattQ.ExplainBicycleRearWheelSprocketworking?Ans.Rearwheelsprocketworksundertheprincipleofratchetandpawl.Q.DefinitionofOctaneNumberandCetaneNumber?Ans.OctaneNo.Octanenumberisdefinedasthepercentage,byvolume,ofisooctaneinthemixtureofisooctaneandhheptane.ItisthemeasureofratingofSIengine.CetaneNo.Cetanenumberisdefinedasthepercentage,byvolume,ofncetaneinthemixtureofncetaneandalphamethylnaphthalene.ItisthemeasureofratingofCIengine.Q.WhichMechanismisusedinAutomobilegearingSystem?Ans.DifferentialmechanismQ.WhathappensifgasolineisusedinaDieselEngine,SieselEnginewillwork?Ans.No,Itwillnotwork,astheCompressionratioofPetrolengineis6to10&thatofDieselengineis15to22.Thusonsuchhighcompression,gasolinegetshighlycompressed&itmayblast.Q.Whatarethreemethodsofheattransfer?Ans.Threemethodsofheattransferareconduction,convectionandradiation.Conduction:Thetransferofenergybycollisionsbetweentheatomsandmoleculesinamaterial.Convection:Transfersheatwhenparticlesmovebetweenobjectsorareasthatdifferintemperature.Radiation:Thetransferofenergybywaves.Q.Explainthesignificanceofgovernorinautomobiles?Ans.Governorisanimportantcomponentofautomobileengine.Itisusedtoregulatethemainspeedofengineduringthevariationsinloads.Withthevariationsintheload,fuelsupplyhastobemaintained.Thistaskisperformedbythegovernor.Inthecaseofhighloadontheengine,speeddecreases,hencefuelsupplyhastobeincreasedandsimilarlywhenloaddecreasesthenthefuelsupplyhastobedecreased.


Q.PoissonsRatioisHigherin,Rubber/Steel/Wood?Ans.Whenamaterialiscompressedinonedirection,itusuallytendstoexpandintheothertwodirectionsperpendiculartothedirectionofcompression.ThisphenomenoniscalledthePoissoneffect.PoissonsratioisameasureofthePoissoneffect.Forrubber=0.5Forsteel=0.288Forwood