I work in a museum and we have a large plasma tube (I do not know any details of the current used within the tube). When I place my hand on the tube and then hold out my finger and touch another human being (who's not touching the tube) we can pass a current at times large enough to make a small spark. Both of us are insulated from the ground with rubber shoes.
How is this possible?
Does it have anything to do with the fact that even though we are somewhat insulated we are not completely insulated and current can dissipate into the air around us and thus we are at a relatively close to a grounding potential compared to potential on the outer surface of the plasma tube?
Answer
If the plasma tube works on the same principle as plasma bowl, then there must be Tesla transformer which generates high voltage at high frequency. The high voltage (like 10kV to 1MV) would be enough to travel through your body. However there is also so called skin effect which ensures that high frequency current is conducted in a thin layer on the surface of your skin and not through muscles and internal organs.
The fact that you wear shoes is irrelevant first because the floor itself is not conductive and second because you care about the current between you and the other person not you and ground.
As for the dissipation it is kinda like that. The Tesla transformer creates high frequency alternating current which moves electrons in the gas towards it and back so that you see sparks but you don't get electricaly charged when you touch it. You can read about it on wikipedia: https://en.wikipedia.org/wiki/Tesla_coil#Air_discharges
You don't even need plasma tube to pass spark to another person try rubbing your rubber shoes on the carpet. You will genenerate static electrical charge which you can then pas to another person. It's a little different principle but it is similar.
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