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Unformatted text preview: gainst it and so we are susceptible to parallax errors. But there is some additional equipment on the apparatus that will help you avoid these errors—we’ll ask you to figure out how rather than describe the procedure here. Heathkit power supply Helmholtz coils 6 VDC power supply - + - i ammeter (Fluke) Figure 3: Connections in the e/m experiment. Procedure
• Connect the power supplies to the baseboard as shown in Figure 3. Switch the Heathkit power supply to “B+” voltage: this is the voltage difference V between the anode and the cathode, and you will read its value from the top (red) scale. Set this voltage to zero and turn on the power supply. Turning on the Physics 7B Charge-to-mass: e/m p. 7 power supply applies an alternating current to the cathode heater in the glass bulb, which will glow orange after a few seconds. (Note: “B+” is a bizarre historical term for the voltage between an anode and a cathode. Don’t get it confused with the magnetic field, B.) 1. Prediction: You are now going to turn up the voltage and the electron beam will appear. Will it be curved or straight? Why? • Turn up the voltage until you can see a glowing blue...
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