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Charge-to-Mass of Electrons

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This is the device to measure the charge-to-mass ratio of electrons. The electron tube is right here, it's a big bulb and it's evacuated. The filament that the electrons are boiled off of is back here you can't see it. In order to boil the electrons off we have 6.3 volt power supply attached to it right there so that heats up the filament and some of the electrons are freed. Now once the electrons are free they can be accelerated this way with an accelerating potential. So we have right here with this wire, this is a high voltage connection its high voltage positive; so the electrons are accelerated this way. They leave the accelerating field right there and here they enter the main part of the tube. And you can see there are the deflecting plates right here. So those plates are set up so we can deflect the electrons this way. We have a high positive direction on this plate and a zero potential on this plate. Alright so, now the first thing I'll do is turn this on and we'll just create the deflection of the electron beam this way, under the action of an electron field only. Alright so I'll turn on my power supply and turn it up to about 3000 volts we'll zoom in here on the scale so we can take a reading of the voltage as precisely as possible. And then we'll swing over and take a look at the electron beam on the tube. You can see that the electron tube curves upward. What you're seeing are not electrons what your seeing are the electrons striking the phosphorescent screen and emitting a glow. Same kind of thing that happens when electrons strike the TV set. Okay we're going to turn the lights off so you can get a better view of that path; so that should be a parabola.


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