Electron Beam Experiment to get the set of V and I values that will produce a beam of radius 5 cm. watch this short video show all work
https://www.youtube.com/watch?v=CyEMzKbWqjo
VERY short lab.There is a link to do lab all info is there for lab. please show work clearly and do conclusion.
The conclusion should include what was done in the lab. how the lab was accomplish. what is the lab results indicate. what you learned , what you already knew and how the lab can be applied to real life. please at least put one example for used in everyday life.
Microsoft Word - 6A-E-over-M 08-14-09.doc Electron E/M Ratio - 1 - 6A-E-over-M 08-14-09.doc The purpose of this lab is to determine the charge to mass ratio of the electron. Pasco Model SE-9638 E/M Apparatus Digital Multi-Meter, DMM Power Supply, Elenco Lead, Banana/Banana (7) Power Supply, Pasco Model SF-9585A Computer - for analysis Typical Setup Purpose Equipment Name Lab 9: Finding e/m ratio Electron E/M Ratio - 2 - 6A-E-over-M 08-14-09.doc The PASCO Model SE-9638 e/m Apparatus provides a simple method for measuring e/m, the charge to mass ration of the electron. The method is similar to that used by J. J. Thompson in 1897. A beam of electrons is accelerated through a known potential, so the velocity of the electrons is known. A pair of Helmholtz coils produces a uniform and measurable magnetic field at right angles to the electron beam. This magnetic field deflects the electron beam in a circular path. By measuring the accelerating potential (V), the current to the Helmholtz coils (I), and the radius of the circular path of the electron beam (r), e/m is easily calculated: 22 2 rB V m e = . (The calculations are explained in a later section of this hand out.) IMPORTANT: The circular electron beam should be large enough (adjust magnet current) so that it extends equally above and below the scale. This will be a judgment call on your part but it is a crucial part of the lab experiment. The path of the beam should cross the scale at a right angle to it. Introduction Figure 1 Electron E/M Ratio - 3 - 6A-E-over-M 08-14-09.doc Equipment Description The e/m Tube—The e/m tube (see Figure 2) is filled with helium at a pressure of 10 -2 mm Hg, and contains an electron gun and deflection plates. The electron beam leaves a visible trail in the tube, because some of the electrons collide with helium atoms, which are excited and then radiate visible light. The electron gun is shown in Figure 3. The heater heats the cathode, which emits electrons. The electrons are accelerated by a potential applied between the cathode and the anode. The grid is held positive with respect to the cathode and negative with respect to the anode. It helps focus the electron beam. The Helmholtz Coils—The geometry of Helmholtz coils—the radius of the coils is equal to their separation—provides a highly uniform magnetic field. The Helmholtz coils of the e/m apparatus have a radius and separation of 15 cm. Each coil has 130 turns. The magnetic field (B) produced by the coils is proportional to the current through the coils. The Controls—The control panel of the e/m apparatus is straightforward. All connections are labeled. The hook-ups and operation are explained in the next section. Cloth Hood—The hood can be placed over the top of the e/m apparatus so the experiment can be performed in a lighted room. Mirrored Scale—A mirrored scale is attached to the back of the rear Helmholtz coil. This scale is illuminated by lights, which automatically turn on when the heater to the Caution: The voltage to the heater of the electron gun should NEVER exceed 6.3 volts. Higher voltages will burn out the filament and destroy the e/m tube. Figure 2 Figure 3 Electron E/M Ratio - 4 - 6A-E-over-M 08-14-09.doc electron gun is powered. By lining up the circular electron beam with its image in the mirrored scale, you can eliminate the effect of parallax in the measurement of the radius of the beam path. Procedure Measuring e/m 1. If you will be working in a lighted room, place the hood over the e/m apparatus. 2. Flip the toggle switch up to the e/m MEASURE position. 3. Turn the current adjust knob for the Helmholtz coils to the OFF position. 4. Connect your power supplies and meters to the front panel of the e/m apparatus, as shown in Figure 4 (below). (Full picture—last page. Figure 5) Figure 4 5. Adjust the power supplies to the following levels. The voltmeter in Figure is not necessary because the meters on the Pasco SF-9585A power supply are of the same quality. (Note: Make sure all settings are in the zero position before turning on the power switch.): Electron E/M Ratio - 5 - 6A-E-over-M 08-14-09.doc Electron Gun Heater: 6.3 VAC or VDC Electrodes: 150 to 300 VDC HelmHoltz Coils: 6-9 VDC 6. Wait several minutes for the cathode to heat up. When it does, you will see the electron beam emerge from the electron gun. 7. Slowly turn the current adjust knob for the Helmholtz coils clockwise. Watch the ammeter and take care that the current does not exceed 2 A. The field from the Helmholtz coils will curve the electron beam. (Check that the electron beam is parallel to the Helmholtz coils. If it is not allow your instructor or lab tech to adjust it.) 8. Carefully read the current to the Helmholtz coils from your ammeter and the accelerating voltage from the voltmeter on the Pasco power supply. Record the values in the data table 9. Carefully measure the radius of the electron beam. Look through the tube at the electron beam. To avoid parallax errors, move your head (up-down and side-side) to align the electron beam with the reflection of the beam that you can on the mirrored scale. Measure the extent of the outer edge of the beam as you see it on both sides of the “zero” on the illuminated scale, and then average the results. This is your measured value of the radius. Record your results in the data table. Caution: The voltage to the heater of the electron gun should NEVER exceed 6.3 volts. Higher voltages will burn out the filament and destroy the e/m tube. Electron E/M Ratio - 6 - 6A-E-over-M 08-14-09.doc Note 1: To ‘line up’ of each beam. Move the head left to right and up and down. Note 2: By using the current adjust; try to make the line of sight on the beam cross the scale in a perpendicular manner. 10. There is only ONE correct value of the electron beam radius. It will be the same for every set of magnet current and electron gun voltage measurements. Your task is to achieve that radius, measure it accurately and precisely and to repeat the process for a total of five (5) sets of magnet current and beam voltage. Data Analysis Data Set Accel Voltage (V) Magnet Current (A) Current^2 (A 2 ) Beam Radius (cm) 1 2 3 4 5 GRAPHICAL ANALYSIS Plot a graph of V vs I^2 using Excel. Fit the data with a linear trendline and determine the slope and the uncertainty in the slope (using LINEST). The value of the slope is the value of V/I^2 that you will use to determine your experimental value of the electron’s e/m ratio. ( ) ( ) 3 2 2 2 0 5 2 4 ( / ) a e v V I m B r N rµ = = Report - This lab requires a full formal report. The lab report should be typed or neatly written and include the following sections: 1. Theory 2. Objective 3. Procedure 4. Results 5. Conclusions Slope of the “V” vs “I^2” graph Electron E/M Ratio - 7 - 6A-E-over-M 08-14-09.doc APPENDIX - Analysis of e/m Measurement The magnetic force ( mF ) acting on a charged particle of charge q moving with velocity v in a magnetic field (B) is given by the equation BqvFm ×= , (where F, v, and B are vectors and × is a vector cross product.) Since the electron beam in this experiment is perpendicular to the magnetic field, the equation can be written in scalar form as: evBFm = Equation 1 where e is the charge of the electron. Since the electrons are moving in a circle, they must be experiencing a centripetal force of magnitude r mv Fm 2 = Equation 2 where m is the mass of the electron, v is its velocity, and r is the radius of the circular motion. Since the only force acting on the electrons is that caused by the magnetic field, cm FF = , so equations 1 and 2 can be combined to give r mv evB 2 = or Br v m e = Equation 3 Therefore, in order to determine e/m, it is only necessary to know the velocity of the electrons, the magnetic field produced by the Helmholtz coils, and the radius of the electron beam. The electrons are accelerated through the accelerating potential V, gaining kinetic energy equal to their charge time the accelerating potential. Therefore 2 2 1 mveV = . Electron E/M Ratio - 8 - 6A-E-over-M 08-14-09.doc The velocity of the electrons is therefore: = m 1/2 2eV v Equation 4 The magnetic field produced near the axis of a pair of Helmholtz coils is given by the equation: [ ] a IN B 2 3 0 4 5 = µ Equation 5 A derivation for this formula can be found in most introductory texts on electricity and magnetism. Equations 4 and 5 can be plugged into equation 3 to get a final formula for e/m: ( )20 2 3 4 5 2 IrN aV Br v m e µ == where: =V the accelerating potential =a the radius of the Helmholtz coils = 15.0 cm =N the number of turns on each Helmholtz coil = 130 =0µ the permeability constant 7104 −×= π =I the current through the Helmholtz coils =r the radius of the electron beam path (e/m) accepted = 1.7589 x 10 11 C/kg Do not use this form of the equation