电子受静电力及磁力作用的偏折

按一下以編輯母片標題樣式,按一下以編輯母片,第二層,第三層,第四層,第五層,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,V,1,),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,(cathode ray tube,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,:,Lorentz force,F,=,q,(,E,+,v,x,B),SI unit:N=C,(V/m)=,C(m/s).T,陰極射線管,CRT,的內部結構,陰極射線管的工作原理,Operation Principle of CRT,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,C(9),加熱放出熱電子,經控制柵極,G(1),聚焦陽極,F(2),及加速陽極,A(3)(,總電位,V,1,),後,電子往,Z,方向,(6),做等速運動，,mv,z,2,/2=,eV,1,v,z,=(2,eV,1,/,m,),1/2,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,m,=9.11 x 10,-31,kg,電荷,q,=-,e,=-1.60 x 10,-19,C,As V,4,=0 V,5,=0,Commonly used to obtain a visual display of electronic information in oscilloscopes,radar systems,televisions,etc,.,Be a vacuum tube in which a beam of electrons is accelerated and deflected under the influence of electric or magnetic fields.,The electrons are deflected in various directions by two sets of plates.,The placing of charge on the plates creates the electric field between the plates and allows the beam to be steered.,Cathode Ray Tube(CRT),Cathode Ray Tube(CRT),-is one of the main elements of an oscilloscope.,A CRT is commonly used to obtain,a visual display of electronic information,in oscilloscopes,radar systems,televisions,etc.,The CRT is a vacuum tube in which a beam of electrons is,accelerated,and,deflected,under the influence of electric or magnetic fields.,The tubes are produced with,electrostatic,and,electromagnetic control,where electrostatic or magnetic fields deviate the electron beam respectively.,The principle scheme of CRT has electrostatic control as well as the motion of the electrons in the beam drawing a,sinusoid,on the screen of oscilloscope.,Configuration of CRT,CRT consists of 6 sections:,Glass bulb evacuated to a high vacuum(,真空管,),Cathode(a source of electrons,，電子槍陰極,),Cathode heater(,陰極加熱器,),Electrodes for brightness and focus control,several accelerating anodes(,亮度、聚焦、加速控制柵極,),Pairs of horizontal and vertical capacitor plates deviating the electron beam,Fluorescing screen(,螢光幕,),Discharge Tube,It was observed that whenever the glass tube filled with air at low pressure and,sealed with electrodes at both the ends was subjected to about,10,000 volts,of electricity,a strange glow was produced around the edges of the wide end of the glass tube,irrespective of the type of gases present in it.,The glass tube with sealed electrodes is called discharge tube.,Discharge Tube,Electron Gun,Electron guns,Electron beams,Focusing coils,Deflection coils,Anode connection,Mask for separating beams for red,green,and blue part of displayed image,Phosphor layer with red,green,and blue zones,Close-up of the phosphor-coated inner side of the screen,Cutaway rendering of a color CRT,CATHODE-RAY TUBE(CRT)-,is one of the main elements of an oscilloscope.,One of anodes,which accelerate the electrons,is placed close to the screen.,The high positive voltage is applied to this electrode.,Under the action of the applied voltage the electrons are movedwith acceleration from cathode to anode.,In the absence of the voltage applied to deviating plates of the capacitor the electron beam will be incident on the screen in the center brightening a point in the fluorescing layer.,In oscilloscope the analyzed signal after amplification is applied to vertical deviating plates,while the periodic,sawtooth,signal is applied to horizontal plates.,http:/physics-, a result the electron beam draws the dependence of the investigated signal on time on the screen of the tube.,Reaching the right side of the screen the beam has to be returned to an initial point at the left side.,Thus,if CRT is not blanked during this retrace,then the beam will leave a track crossing the image of investigated signal.,For this reason,during retrace a negative voltage is applied to control electrode situated near to cathode and electrons are locked by such a way at the electron gun.,As a result,the electron beam will be discontinuous,as shown in animation.,Related Web Sites for CRT Animation,http:/highered.mcgraw- Cathode Ray Tube site:,http:/members.chello.nl/h.dijkstra19/page3.html,How Television Works:,http:/ V,f,=60 Hz,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,S,B,(,S,m,),螢光幕,(XY,面,)Y,軸上,S,B,有一亮點,5.,同時在電場及磁場的作用下,並使電子不偏折,S,E,+,S,B,=0,eE,=,ev,z,B,v,z,=E/B,代入,S,E,或,S,B,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,(X=60 mm,Y=54 mm,D=115 mm,L=11 mm,d=1.65 mm),插入,CRT,基座,(,Unilab 031.502,),X,為,X,電板輸入端,Y,為,Y,電板輸入端,A,1,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,(tube supply),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,(amplifier)(2)(,032.842,),接,CRT,電源供應器,(1),(,032.332,),之,aux unit,直流電源,(6 V),2.,產生交流電場,:,電源供應器,(1),之交流電壓,(6 V,rms,),接到放大器之,交流耦合,A(alternating coupling),輸入端,+,共用端,C(common),AC:,只有,ac,信號進入,(,串聯電容器,),DC:,直流耦合,D,(di