1202_LabManual.pdf

# Read sternheim kane sections 161 5 167 168 review

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leaving the electron gun region of the CRT affects the position of the beam spot. Read Sternheim & Kane sections 16.1-5, 16.7 & 16.8. Review Kinematics if necessary. E QUIPMENT You have a Cathode Ray Tube. You also have a Cenco power supply, banana cables, DMM and an 18v/5amp power supply. The applied electric field is created by connecting the internal parallel plates to the power supply. Note: The CENCO power supplies can have transient AC voltage in the DC output, making it less than ideal for creating an electric field – use the 18volt/5amp supplies . If you need assistance, send an email to [email protected] . Include the room number and brief description of the problem. W ARM UP If you have done the problem Deflection of an Electron Beam by an Electric Field , you can refer to back to the Warm-up questions and Prediction for that problem. Numbers 1-8 below are identical for that problem 1. Draw a picture of the important components of the CRT. Only include one set of the deflection plates as shown in the appendix. Draw the trajectory the electron would take if there were no electric field between the plates. If there is an electric field between the deflection plates, will there be regions where different forces act on the electron? Label these regions. Draw the trajectory the electron would take when there is electric field between the plates. On the trajectory, draw and label arrows representing the electron’s velocity and acceleration for each region. The distance between where the non-deflected beam hits the CRT screen and where the deflected beam hits is the deflection . 2. What forces cause electrons to accelerate in each region? On your picture, draw an arrow representing each force. (Are there any forces you can assume to be negligible?) For each region, label the electron's trajectory and the electron’s velocity 114

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DEFLECTION OF AN ELECTRON BEAM AND VELOCITY – 1202Lab4Prob6 and acceleration as it enters the region, while it is in the region, and when it leaves the region. Qualitatively describe the shape of the electron's trajectory in each region. 3. The magnitude of the electric field (in Newtons per Coulomb) between two equally charged parallel plates is equal to the voltage between the two plates (in Volts) divided by the distance between the plates (in meters). What is the direction of the electric field between the two accelerating plates? See the appendix for the position of the accelerating plates. How much energy is transferred to the electron by this field? Using conservation of energy, write an equation for the electron’s velocity as it leaves the electron gun in the CRT. What is the direction of the electron as it leaves the accelerating field? What assumptions have you made? 4. What is the net force exerted on an electron as it travels through the region between the deflecting plates? Use Newton’s second law to write an equation for the acceleration of an electron as it travels through this region. You will need to define a coordinate system if you have not already done so. Does the electric field vary in the region between the deflecting plates? What does that tell you about the
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