电子受静电力及磁力作用的偏折.ppt

實驗2電子受靜電力及磁力作用的偏折課本實驗15/16,,,,,,陰極射線管CRT的內部結構控制柵極G聚焦陽極F加速陽極A總電位V1水平偏壓偏折平行電極板垂直偏壓偏折平行電極板Z方向無偏折之電子束螢光幕陰極射線管CRT內的加熱燈絲陰極射線管CRT內的陰極C,目的觀察陰極射線管cathoderaytube,CRT中之電子束在電場E及磁場B中之偏折運動情形，並測量電子的荷質比e/m比原理LorentzforceFqEvxB[SIunitNCV/mCm/s.T],陰極射線管CRT的內部結構,陰極射線管的工作原理OperationPrincipleofCRT,,,,,I.在水平和垂直偏折平行電極板4,5無外加偏壓信號時陰極射線管內的加熱燈絲8將陰極C9加熱放出熱電子經控制柵極G1,聚焦陽極F2及加速陽極A3總電位V1後電子往Z方向6做等速運動，mvz2/2eV1vz2eV1/m1/2電子打到螢光幕XY面7上的中心位置，形成一亮點。,陰極射線管CRT的內部結構,電子質量m9.11x10-31kg電荷q-e-1.60 x10-19C,AsV40V50,Commonlyusedtoobtainavisualdisplayofelectronicinationinoscilloscopes,radarsystems,televisions,etc..Beavacuumtubeinwhichabeamofelectronsisacceleratedanddeflectedundertheinfluenceofelectricormagneticfields.,Theelectronsaredeflectedinvariousdirectionsbytwosetsofplates.Theplacingofchargeontheplatescreatestheelectricfieldbetweentheplatesandallowsthebeamtobesteered.,CathodeRayTubeCRT,CathodeRayTubeCRT-isoneofthemainelementsofanoscilloscope.,ACRTiscommonlyusedtoobtainavisualdisplayofelectronicinationinoscilloscopes,radarsystems,televisions,etc.TheCRTisavacuumtubeinwhichabeamofelectronsisacceleratedanddeflectedundertheinfluenceofelectricormagneticfields.Thetubesareproducedwithelectrostaticandelectromagneticcontrol,whereelectrostaticormagneticfieldsdeviatetheelectronbeamrespectively.TheprincipleschemeofCRThaselectrostaticcontrolaswellasthemotionoftheelectronsinthebeamdrawingasinusoidonthescreenofoscilloscope.,ConfigurationofCRT,,CRTconsistsof6sectionsGlassbulbevacuatedtoahighvacuum真空管Cathodeasourceofelectrons，電子槍陰極Cathodeheater陰極加熱器Electrodesforbrightnessandfocuscontrol,severalacceleratinganodes亮度、聚焦、加速控制柵極PairsofhorizontalandverticalcapacitorplatesdeviatingtheelectronbeamFluorescingscreen螢光幕,DischargeTube,Itwasobservedthatwhenevertheglasstubefilledwithairatlowpressureandsealedwithelectrodesatboththeendswassubjectedtoabout10,000voltsofelectricity,astrangeglowwasproducedaroundtheedgesofthewideendoftheglasstube,irrespectiveofthetypeofgasespresentinit.Theglasstubewithsealedelectrodesiscalleddischargetube.,DischargeTube,ElectronGun,ElectrongunsElectronbeamsFocusingcoilsDeflectioncoilsAnodeconnectionMaskforseparatingbeamsforred,green,andbluepartofdisplayedimagePhosphorlayerwithred,green,andbluezonesClose-upofthephosphor-coatedinnersideofthescreen,CutawayrenderingofacolorCRT,CATHODE-RAYTUBECRT-isoneofthemainelementsofanoscilloscope.,Oneofanodes,whichacceleratetheelectrons,isplacedclosetothescreen.Thehighpositivevoltageisappliedtothiselectrode.Undertheactionoftheappliedvoltagetheelectronsaremovedwithaccelerationfromcathodetoanode.Intheabsenceofthevoltageappliedtodeviatingplatesofthecapacitortheelectronbeamwillbeincidentonthescreeninthecenterbrighteningapointinthefluorescinglayer.Inoscilloscopetheanalyzedsignalafteramplificationisappliedtoverticaldeviatingplates,whiletheperiodicsawtoothsignalisappliedtohorizontalplates.,http//physics-,Asaresulttheelectronbeam“draws“thedependenceoftheinvestigatedsignalontimeonthescreenofthetube.Reachingtherightsideofthescreenthebeamhastobereturnedtoaninitialpointattheleftside.Thus,ifCRTisnotblankedduringthisretrace,thenthebeamwillleaveatrackcrossingtheimageofinvestigatedsignal.Forthisreason,duringretraceanegativevoltageisappliedtocontrolelectrodesituatedneartocathodeandelectronsarelockedbysuchawayattheelectrongun.Asaresult,theelectronbeamwillbediscontinuous,asshowninanimation.,RelatedWebSitesforCRTAnimation,http//highered.mcgraw-,,,2.電子在直流電場中之偏折利用水平電板X4及垂直電板Y5所提供的電壓，產生均勻電場E，使電子束偏折，如電板Y長L,兩板距離d,直流電位差V2EV2/d，電子離開電板後距螢光幕D，則電子在Y方向偏折SE，使螢光幕XY面在Y軸SE處產生一亮點。,,X,Y等速直線運動,,X等速直線運動Y等加度運動,,,3.電子在交流電場中之偏折若在電板Y加交流電頻率f/21/T因高頻，電子在螢光幕成一長為l的亮線Note一般家電Vrms110V,f60Hz,,,4.電子在磁場中之偏折利用共軸雙線圈螺線管之均勻磁場B來偏折電子束如磁場在x方向長L，電子離開磁場後距螢光幕D則電子在Y方向偏折SBSm螢光幕XY面Y軸上SB有一亮點5.同時在電場及磁場的作用下並使電子不偏折SESB0eEevzBvzE/B代入SE或SB即可求電子的荷值e/m比,,,實驗步驟I.陰極射線管電源1.陰極射線管X60mm,Y54mm,D115mm,L11mm,d1.65mm插入CRT基座Unilab031.502X為X電板輸入端Y為Y電板輸入端A1為最後加速陽極Z接柵極2.CRT基座接CTR電源供應032.332之五腳CRT插座tubesupply注意高壓電源接電路前,確定電源供應器開關為關off燈暗3.調整CRT亮點之亮度brill加速陽極及焦距focus聚焦陽極,,,II、電場偏折1.放大器amplifier2032.842接CRT電源供應器1032.332之auxunit直流電源6V2.產生交流電場電源供應器1之交流電壓6Vrms接到放大器之交流耦合Aalternatingcoupling輸入端共用端CcommonAC只有ac信號進入串聯電容器DC直流耦合Ddirectcouplingac/dc信號均可進入3.放大器之X/Y輸出端接CRT基座3031.502之垂直Y電板輸入4.利用放大器之增益gain及移動shift鈕，觀察及調整Y方向之亮線位置及長度/電壓振幅值l2Vm校正後Y靈敏度sensitivity23V/1cmQ如何量週期T,1,2,3,,,III.交流電壓波形及頻率1.時基產生器2產生掃描鋸齒波掃描週期可調2.時基產生器2同步掃描鋸齒波掃描週期可調輸出接水平放大器3輸入DC端下頁3.水平放大器3之輸出端接CRT基座之水平電板輸入5水平輸入為時間t校正後,,,3.5垂直Y電板輸入不變但垂直放大器4輸入接DC端垂直輸入為電壓V4.放大器輸入A端同步接時基產生器2032.892timebasegenerator同步輸入端sync5.觀查CRT之波形YXVt,量振幅Vm及週期T,1,2,3,4,5,,IV.磁場偏折產生磁場直流電源供應器5接到共軸雙線圈螺線管2031.402，線圈數為N3000圈3000圈。利用可變電阻4及安培計3調整及測量電流I大小，因磁場BNI，所以可求算B值。3.共軸雙線圈螺線管放於CRT基座1之CRT上。4.利用不同方式測量電子的e/m比值。,1,2,3,4,5,