WhatisaFieldUBCPhysicsampAstronomyOutreachHome大學物理和天文學是一場宣傳家課件

Legend-WhitebackgroundisforTeachertoseeasinstructions.-BluebackgroundisfortheStudenttosee

Legend-Whitebackgroundisfor1Mypresentationismoregeartowardupperlevelhighschoolphysicsstudent(i.e.Physics11,Physics12andPhysics12AP).Mypresentationismoregeart2MaterialsneededforthedemonstrationsMaterialsneededfortheconstructionofthedemosPliersSandpaperGluegun#1CathoderaytubedemoCathoderaytubeset#2Batterydemo9Vbatterythincopperwiresrubberbandaneodymiummagnet(orderonlinegrand-illusions/toyshoporebay)#3Ferromagneticlevitationborrowalevitationdevicefromayear2

MechanicalEngineering2019friend#4Diamagneticlevitation4neodymiummagnetsapieceofpyrolyticcarbon

Materialsneededforthedemos.Instructionswillbegiveninlaterslides#5MaglevtrainStrongmagneticstripsthinplexiglassthesupporttrackMaterialsneededforthedemon3ElectromagnetismUniversityofBritishColumbiaPhysics420By:JasonCheungElectromagnetismUniversityof4WhatisaField?AregionofspacecharacterizedbyaphysicalpropertyhavingadeterminablevalueateverypointintheregionExamples:gravitationalfield,Electricfield,andmagneticfieldWhatisaField?Aregionofsp5ExplanationofField(#1)

(forslide5)Thismeansifweputanythingappropriateinafield,wecanthencalculate“something”outofthatfieldBeforegoingfurtherwithElectricfieldandMagneticfield,mentiontherearesomethingcalledtheElectricandMagneticfield.Usegravitationalfieldasastart,becauseG-fieldthemosteasytounderstandLinkElectricfieldandMagneticfieldafterexplainingtheGravitationalfieldExplanationofField(#1)

(fo6GravitationalFieldDefinedasA=accelerationG=gravitationalconstantm=massofbigobjectr=distancetothecenterofthebigobjectGravitationalFieldDefinedas7WhatisaFieldUBCPhysicsampAstronomyOutreachHome大學物理和天文學是一場宣傳家課件8ExplanationofField(#2)

(forslide8)IfweputBobinthegravitationalfield,wecancalculatetheForceactingonhimbytheEarth.HewillfollowthegravitationalfieldlinesandfalltothesurfaceoftheEarth.Essentially,ifweputanythingthathasamassintheGravitationalfield,wecancalculatethat“something”Imentionedbefore.That“something”isthe“gravitationalforce”inthiscase.Emphasizethatwedeterminedifferentkindsofforcewithdifferentkindsoffield.ThiscanbridgetoElectricandMagneticFieldonfollowingslides.ExplanationofField(#2)

(for9ElectricFieldElectricfieldisdefinedastheelectricforceperunitChargeItisthesurroundingchargesthatcreateanelectricfieldE=ElectricFieldF=ElectricForceq=ChargeEismeasureinForce/CoulombElectricFieldElectricfieldi10ExplanationofElectricField(E-field)(forslide10)#0 Explainwhatisacharge,q -TheyshouldhaveenoughPhysicstoknowwhatisa+/-chargeis -OppositechargesattracteachotherandLikechargesrepeleachother#1 ExplainEisdefinedasF/q -Ifweputa+/-(positiveornegative)chargeinaelectricfield,the+/-chargewill experienceaforce.Thisforceiscalled“ElectricForce” -(IMPORTANT!!)RecallfromG-field.G-fieldrequiresanobjectwithaMASStohavea force.E-fieldrequiresa+/-chargetohaveaforce#2 HowdoyoudrawtheE-fieldlineswithdifferentcharges? -Electricfieldlinesalwayscomesoutofthepositivechargeintothenegative charge -NegativechargealwaysabsorbtheE-fieldlines

ExplanationofElectricField11ExplanationofElectricField(E-field)(forslide10)#3 Whatdirectionistheelectricforce? -ThedirectionoftheElectricforceisparalleltotheelectricfield. -LookatthePOINTPonthediagramonslide10.Thearrowinthediagramrepresents thedirectionoftheelectricforce Q: Whatisthecharge,positiveornegative,ifthedirectionofthe forceispointingoutwardlikeinthediagramonslide10 A: Positivebecauseitispointawayfromthestationarypositive charge Q: Whatisthecharge,ifthedirectionoftheforceonthediagram switched?? A: NegativechargeExplanationofElectricField12WhatisaFieldUBCPhysicsampAstronomyOutreachHome大學物理和天文學是一場宣傳家課件13CathodeRayTubeDemo(CRT)InstructionandexplanationfortheCRTDemo#1 TurnonthePowersupplyandElectricplatecontroller,andwaitandcalibratetheelectronstothe centerofthescreen#2 AdjusttheelectricplatebyturningtheXknobortheYknob.Thisistodemonstratethatthe electricplatecancontrolwheretheelectronwillhitonthescreen.QuestionsandFunfactsQ: WhatdoyouthinkistheapplicationofaCRTandwhatdotheelectricplatesdointheCRT?A: Our“OLD”TV(beforeLCDandPlasma)usethistechniquetoviewimagesonourTV!CathodeRayTubeDemo(CRT)Ins14MagneticFieldMagneticfieldisafieldthatexertsaforceonamovingchargeAmagneticfieldcanbecausedeitherbyanothermovingchargeorbyachangingofelectricfieldormagneticdipolesofmaterialsMagneticFieldMagneticfieldi15ExplanationofMagneticfield

(forslide15)Inordertohaveamagneticforce,weneedamoving+/-charge.MagneticfieldlinescomeoutofNandgointoS(seediagramonslide15)Emphasizethe3componentstoproduceamagneticfield #1Moving+/-charge #2ChangingofE-field #3Dipoleofmaterial(seediagramtoexplain)

ExplanationofMagneticfield

16MagneticFieldismeasureinTeslaAsimpleformulatocalculateMagneticFieldB= magneticfieldF= MagneticForceQ= chargeV= velocityofthemovingchargeMagneticFieldismeasureinT17ExplanationofMagneticfieldcon’t

(forslide15)TheunitofTeslaisaverySMALLunit -Earthmagneticfieldhasaround10^(-5)Tesla -AverygoodFerromagnethasaround0.5to1TeslaItisveryhardtomakematerialthathasaverystrongmagneticfield,andIwillexplainitinmoredetaillaterSinceIamdoingaqualitativestudyonmagnetism,Ijustgavethemoneofthemostbasicequationformagneticforce -EmphasizeontheCROSSPRODUCT,itisnottreatedasatimesoperator.Velocityofa +/-chargeneedstobe90degreetothemagneticfieldinordertohaveamagneticforceExplanationofMagneticfield18ConstructionofBatterydemoMaterialneededcopperloop9Vbatteryrubberbandcopperearsx2Stepone:pinchthecooperearsontothebatterySteptwo:tietheearsontothebatterywithrubberbandStepthree:putthecopperloopthroughtheholesonthecopperearsFinishproductCopperears9VbatteryRubberbandCopperloopConstructionofBatterydemoMa19VideoofbatterydemoShowBatteryDemovideounder“Videos”VideoofbatterydemoShowBatt20BatteryDemoInstructionofhowtousethebatterydemo #1Setupdeviceasabove #2Bringtheneodymiummagnetclosetotheloop #3GiveakickstartfortheloopbyflickingitThingstotellthestudents -Withoutthemagneticfield,theloopwillnomove -ItisduetotorqueprovidedbythemagneticforcesothattheloopwillgoroundandroundBatteryDemoInstructionofhow21ExtrainterestingtopicforthebatterydemoQ:Whatisgoingonwiththebattery?Answer:Thepermanentmagnetsexertforcesontheelectricalcurrentsflowingthroughtheloopofwire.Whentheloopofwireisinaverticalplane,theforcesonthetopandbottomwiresoftheloopwillbeinoppositedirections.Theseoppositelydirectedforcesproduceatwistingforce,ortorque,ontheloopofwirethatwillmakeitturn.Whyisitsoimportanttosandhalfofoneprojectingwire?Supposethatthepermanentmagnetsaremountedwiththeirnorthpolesfacingupward.Thenorthpoleofthepermanentmagnetwillrepelthenorthpoleoftheloopelectromagnetandattractthesouthpole.Butoncethesouthpoleoftheloopelectromagnetwasnexttothenorthpoleofthepermanentmagnet,itwouldstaythere.Anypushontheloopwouldmerelysetitrockingaboutthisequilibriumposition.Bysandinghalfofoneendofthewire,youpreventcurrentfromflowingforhalfofeachspin.Themagneticfieldoftheloopelectromagnetisturnedoffforthathalf-spin.Asthesouthpoleoftheloopelectromagnetcomesclosesttothepermanentmagnet,theun-sandedwireturnsofftheelectriccurrent.Theinertiaoftherotatingcoilcarriesitthroughhalfofaturn,pasttheinsulatingpaint.Whentheelectriccurrentstartstoflowagain,thetwistingforceisinthesamedirectionasitwasbefore.Thecoilcontinuestorotateinthesamedirection.Extrainterestingtopicforth22ChargemovinginamagneticfieldobeystheRightHandRuleTherearetwotypesofRHRRightHandRule#1RightHandRule#2Chargemovinginamagneticfi23RightHandRule1ThethumbrepresentsthevelocityofwhichthechargeisgoingTheremainingfingerstellyouthedirectionofthemagneticfieldexample:RightHandRule1Thethumbrep24RightHandRule2I=directionofthechargeB=directionoftheMagneticFieldF=ForceactonthechargePalmPushPositive(*Remember!!)RightHandRule2I=direction25WhatisaFieldUBCPhysicsampAstronomyOutreachHome大學物理和天文學是一場宣傳家課件26Slide22

ThetwodiagramsshowthepathofamovingelectroninamagneticfieldUseRHR#2toverifythepathoftheelectronsinthediagramsarecorrectSlide22Thetwodiagramsshow27RightHandRuleQuestion

PutaFerromagnet(NorS)closetheturnedonCRTfromtheside.Notethattheelectronbeamwilleithergoupwardordownward Q:Whatisthemagneticfield(NorS)onthesidefacingtheCRT? A:ItdependsonwhichsideIputmymagnetclosetotheCRT,butIjustusedRHR#2to identifiedtheNorSfieldontheFerromagnetRightHandRuleQuestionPuta28Magnetismexampleofpairandunpaired: Nisunpaired, Oispaired(oneofthem)Whatismagnetism? Magnetismisoneofthephenomenabywhichmaterialsexertanattractiveorrepulsiveforceonothermaterials.Whatcausesmagnetisminmaterial? Itistheunpairedelectronsintheelectronorbitcausemagnetism

Magnetismexampleofpairandu29RememberSPDF??(Chem11)ElectronsfallintoelectronshellaccordingtoHund’srule.ExamplesRememberSPDF??(Chem11)Elect30ExplanationofMagnetism

(forslide29and30)#1Explainwhatarepairedandunpairedelectrons#2RecalltheirChemistry11,SPDF,electronorbital

-UsingHund’srulesandPauliExclusionPrincipletoplaceelectronsintoelectronorbital -Practiceplacingelectronsintotheirorbitalusingthediagramonslide30ExplanationofMagnetism

(for31Nitrogen-Electrons-ProtonsandNeutrons1s22p3ElectronConfigurationofNitrogenWrongWrong2s2RightNitrogen-Electrons-Protonsand32ExplanationofMagnetism

(forslide32)ExerciseusingHund’srule -useNitrogenasanexample:thefirstelectronconfigurationisrightandthesecondand thirdexamplesoftheelectronconfigurationiswrongExplanationofMagnetism

(for33Therearefourtypesofmagnetism

1.Ferromagnetic2.Paramagnetic3.Diamagnetic4.Ferrimagnetic (Notgoingtocover)Therearefourtypesofmagnet34(forslide34)

TellstudentsthatFerrimagnetismistoohardtounderstand.TheyneedsomeuniversitylevelofPhysicsinordertounderstandit(forslide34)Tellstudentst35MaterialSusceptibilityχmVacuum0Water-1.2*10-5

Bi-16.6*10-5C-2.1*10-5O20.19*10-5Al2.2*10-5Fe200Co70Ni110MagnetismisMeasureinMagneticSusceptibility(χm)

Themoresusceptibilityofamaterialhas,themoremagneticpropertyitprocessesMaterialSusceptibilityχmVacuu36ExplanationofMagneticSusceptibility(forslide36)MagneticSusceptibilityistomeasurethemagneticpropertyofamaterial Q:Whatisthedifferencesbetweensomeofthematerialsinthechartinslide36? A:Theysplitoffintothreegroups: #1negativevaluewithsmallMagneticSusceptibility #2positivevaluewithsmallMagneticSusceptibility #3positivevaluewithrelativelybigMagneticSusceptibilitycomparetoabove #1and#2 #40MagneticSusceptibilityforVacuumbecausevacuumdoesnotcontain anymaterialExplanationofMagneticSuscep37FerromagneticAnymaterialthatpossessmagnetizationWITHOUTanexternalmagneticfieldisferromagneticlargeandpositivesusceptibilityExamplesofferromagneticmaterialsCobalt(Co)Susceptibility=70Iron(Fe)Susceptibility=200FerromagneticAnymaterialthat38ExplanationofFerromagnetic

(forslide38)Explainwhatisanexternalfield -example:currentrunningthroughasolenoidTheydonotneedanexternalfieldbecausethesematerialproducetheirownmagneticfield.Someferromagneticmaterialdoesnotproducetheirownmagneticfieldbecausethedomaininsideofthematerialdonotalign,whichIwillexplaininslide42.

ExplanationofFerromagnetic

(39IronelectronconfigurationFe:1s2,2s2,2p6,3s2,3p6,4s2,3d6

Fe:[Ar],4s2,3d6

Ar:1s2,2s2,2p6,3s2,3p6=[Ar]“Core”[Ar]-Theelectronsseemstoalignspontaneously-Purequantummechanicseffect

IronelectronconfigurationFe:40ExplanationofIron

(forslide40)AnotherexercisetofillintheelectronsintheelectronorbitalofIron.Discussthattherearefourunpairedelectronsinthe3dorbital #1ThisisoneofthereasonswhyIroncanproduceitsmagneticfield #2TheelectronsseemstoalignspontaneouslyduetoQuantumMechanicseffectsExplanationofIron

(forslid41WhyaresomeFerromagneticdoesn’tattractoneanother?HastodowiththemagneticdomainofthematerialWhyaresomeFerromagneticdoe42Explanationofdomainsofmaterial

(forslide42)Diagramontheleftshowsthedomainsofthematerialdonotalign.Thiscausesthemagneticfieldofthematerialcanceleachother,thereforeitcannotproduceitsownmagneticfieldDiagramontherightshowsthedomainsofthematerialdoalign.Therefore,itcanproduceamagneticfieldonitsown

Explanationofdomainsofmate43Ferromagneticmaterialdemo

Materialneeded -neodymiummagnet -coupleofpaperclipsInstructions #1Showthemthepaperclipsdonotattracttoanymaterialeventhoughtheyare ferromagnetic(domainsarenotalign). #2Attractoneofthepapercliptotheneodymiummagnet #3usethepaperclipthatisontheneodymiummagnettoattractanotherpaperclip Q:Howcomeitattractsnow? A:Theneodymiummagnethelpalignthedomaininthepaperclip #4Gentlyremovetheneodymiummagnetandshowthatthepaperclipcanstillattractto eachother Q:Why? A:ItstaysalignuntilyoupullthemawayFerromagneticmaterialdemoMa44ParamagneticAnymaterialthatpossessmagnetization(i.e.attractionwithothermagnetizedmaterial)WITHanexternalmagneticfieldisparamagneticsmallandpositivesusceptibilityExamplesofparamagneticmaterialsAluminumAlSusceptibility=2.2*10-5

PlatinumPtParamagneticAnymaterialthat45Paramagneticmaterialdemo

(forslide45)Trytoattractanaluminumcanwithaneodymiummagnet.Itcannot Q:Why? A:ItisbecauseoftheMagneticSusceptibilityofparamagneticmaterialsaretooweak comparedtoFerromagneticParamagneticmaterialdemo

(fo46Aluminumelectronconfiguration[Ne].3s2.3p1ComparetoIron(Fe)[Ar]Fe:[Ar],4s2,3d6thedipolesdonotinteractwithoneanotherandarerandomlyorientedintheabsenceofanexternalfieldduetothermalagitation,resultinginzeronetmagneticmoment

Whatisthedifferencesbetweenthetwo?!Aluminumelectronconfiguratio47ParamagneticandFerromagneticDemo(magnetsandlevitation)Instructionsofhowtousethelevitationdevice

#1Setupthedevice #2Placeorangestudwiththemagnetsidefacingawayfromthesolenoid #3Placethestudsoyoucanfeelthesolenoidisattractingthestud #4GentlyremoveyourhandsothedeviceanddoitsworkExplanationofhowitworks -solenoidprovidethemagneticfield,sothemagnetwillattractupward (paraandferromagneticproperty). -detectorinthebottomistosenseifthestudismovingupordown.Ifitmoves toohigh,thedetectorwillcutthecurrentsothestudwillcomebackdownby gravity.Ifitmovestoolow,thedetectorwillsendcurrentinthesolenoidto generateamagneticfield,sothestudwillgoupagainbytheattractionbetweenthemagnet andmagneticfieldParamagneticandFerromagnetic48VideoofferromagneticlevitationShowFerromagneticlevitationvideounder“Videos”Videoofferromagneticlevitat49Diamagneticveryweakandnegativesusceptibilitytomagneticfields.Negativesusceptibility=repelagainstmagneticfields(diamagnetism)Positivesusceptibility=attracttomagneticfields(para+ferromagnetism)Diamagneticveryweakandnegat50DiamagnetismExamplesofdiamagneticmaterialsGoldCopperHuman(mostly)DiamagnetismExamplesofdiamag51DiamagneticLevitationDemoInstructionsofhowtousethemagnets #1Setupthemagnets #2GentlyplacethepyrolyticcarboninthemiddleofthefourmagnetsDiamagneticLevitationDemoIns52ApplicationsofMagnetismMRI(magneticresonanceimages)SuperconductorsApplicationsofMagnetismMRI(53ApplicationofMagnetism

(forslide53)?MagneticResonanceImages(MRI)

-Thesemachinescanproducedupto7Teslatomakeverygoodimagesofthebody

Q: Howtoproduceastrongmagneticfield? A: Buildagiantsolenoid Q: Whatistheproblemwithproducingastrongmagneticfield A: #1Materialcannotstandthemagneticforcewiththemagneticfield;resultingin collapsingthematerial #2Highvelocityofcurrentrunningthroughthesolenoidproducealotofheat. Thiscanresultinmeltingthesolenoidifthemagneticfieldistoostrong?Superconductors -superconductorsareveryusefulbecauseitdoesnothaveanyresistantwithother material -allsuperconductorsarediamagnetic?Animals -Animalssuchassh