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Lets say theoretically electron flow is captured in a vacuum and not allowed to exit then where would they go? I do not want to know the practical impossibilities of it. And also what would happen if that vacuum was in a glass container?

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  • $\begingroup$ You should clarify your question a bit. Do you mean an infinite vacuum or inside of a box ? If it is a box, the awnser depends on its shape and the material the walls are made of. Also, are your electrons at rest initially or not ? $\endgroup$
    – Dimitri
    Feb 19, 2016 at 9:12
  • $\begingroup$ No they are not at rest. And how would the shape matter ? lets assume the material to be glass $\endgroup$
    – user104591
    Feb 19, 2016 at 9:22
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    $\begingroup$ The electrons will repel each other and scatter towards the edges of the box, so the shape of the edges will influence their distribution. If the box was metallic the current of electrons would create induced currents that slow down the flow of electrons. $\endgroup$
    – Dimitri
    Feb 19, 2016 at 9:27
  • $\begingroup$ That's called space charge and it can do all kinds of nasty stuff. In experiments one usually tries to avoid it, which is pretty hard, actually... so your assumption that it is something hard to make is pretty much the opposite of reality... if you have a vacuum and any kind of electrical activity, you usually have a space charge problem. $\endgroup$
    – CuriousOne
    Feb 19, 2016 at 9:52

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That's essentially what particle accelerators are doing (even a symple cyclotron). You need magnetic field to curve the path of a moving electron into a circle.

Of course, once the electron is allowed to touch the surface, it's over. So you need to keep it in there. Yes, electrons feel repulsive forces, but moving electron beams also produce magnetic fields and self-focus (they attract laterally) - this is called plasma pinch and is what makes the lightning bolt so narrow and concentrated. When you have a lot of electrons stored in a vacuum ring (or a Tokamak, if you're building a fusion reactor -- although, plasma also contains positive ions, so at least repulsive forces aren't that big of a problem), they themselves are creating a lot of complex electrogmanetic field, and adaptive control is a good idea to keep things confined.

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  • $\begingroup$ what happens when they touch the non metallic or insulator surface? $\endgroup$
    – user104591
    Feb 19, 2016 at 10:03
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    $\begingroup$ @user104591: Electrons will sit on insulator surfaces and move around in electric field, producing very hard to control electric fields themselves. That's why it's a bad idea to have perfect insulators in vacuum. One will usually try to make the surfaces semiconducting, so that any charges on them can flow to either ground or a specific potential (like a positive getter electrode). $\endgroup$
    – CuriousOne
    Feb 19, 2016 at 10:23
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The old style tv tubes with an electron gun and a phosphorescent screen had to have a conducting path from the screen to earth to prevent the build up of negative charge on the screen. If this was not done a reduction of picture brightness would result. Even with this return path for the electrons charges did accumulate on the screen with the result that dust particles were attracted to the outside of the screen.

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