Question

In the video of the lecture Nº4, minute 42 aprox the vandergraph gives the electric field to the fluorescent tube to produce light, but ¿where does the electrons come from? Because even with electric field you need current to make de tube work ¿electrons come from the vandegraph? ¿from the air? If they come from the vandregraph ¿is the air ionized to be a good conductor of the current? ¿whould we have the same effect in the vacuum, without any ionized air?
Someone answer me that “electrons do not come from vandergraf or from earth but are already present in the flourescent tube” but I think it

Answer 1

....would work only for an instant, if you have a continuous flux of electrons (you have light for several seconds) then you would need to get new electrons from somewhere (in the case of the negative side) and the electrons would need to go out of the tube to somewhere (in the case of the positive side).

Answer 2

There are always a few ionized atoms (thus electrons)in the gas within the tube from collisions with cosmic rays, etc which will be accelerated by the electric field. Collisions will excite other atoms which release light as their electrons transition back to lower energy levels. If you notice, the lights are turned off to view this - the number of emissions is less than you would see if it were connected in a circuit. Sufficient ionization takes place that the glow does not go out in an instant

Answer 3

@stan Are you sure? You may be right, but I still think that the ground should have something to do with the effect. And would you conclude that eventually the glow would turn of when all positive ions go from high electric field to low electric field and electrons go from low electric field to high electric field? I mean: if you only consider the electrons and ions within the tube eventually all electrons would be at one side and positive ions in the other.

Answer 4

no, because of cosmic rays and the collisions within the gas causing additional ionization