Can someone please explain to me how a plasma ball works? I think I kind of get it. I get that the current flows through the gas inside of the ball because there is a large enough electrical potential difference between the two points. I'm not sure why the sparks follow you finger around the surface, but I suspect this is due to you fingers presence changing the potential at that point in space. I'm also interested in how large is the power consumption for one of these things and what physical factors it depends on.