I've been trying to understand how plasma lamps (or plasma globes, according to Wikipedia) work and why you don't die a horrible fiery death when you touch them. What I've got so far is that the center electrode is fed a high voltage and high frequency input. Due to the high voltages, the gas ionizes and you get the plasma filament thingies. All this makes sense, but I have some questions I can't answer (or find the answer to online). Firstly, related to how current kills:
What current is needed to harm you? I've heard of the milliamp current that causes fibrillation, but I'm talking about actual burns and people on fire. Human bodies are resistors typically on the MOhm range (as confirmed by my multimeter and me). Even with main voltages (220 where I live), that's a ridiculously small current, not even milliamps. Also, the power you dissipate is like 0.1W, which shouldn't be terribly harmful. Can you be severely burnt (in dry conditions) with mains voltage?
Now onto the Plasma Ball part:
What is a good equivalent circuit for the ball? Maybe if someone could supply an equivalent circuit, I could understand it better.
Why does it need to be high-frequency?? Wouldn't a few kV ionize the gas just the same?
Which parts of the lamp are grounded? It does seem to make a difference whether you're grounded or not when you touch it. Also, why does the filament concentrate on your finger when you touch it? It seems as though you're closing a circuit with ground, but this seems weird because of question 1.
Why isn't this extremely dangerous?!?! Under right, but not too unlikely circumstances, if you're standing on the ground and offer a low resistance, the center electrode on the kV range would output a current on the amps range or even more (assuming the reference of the center electrode is actually grounded). This should at least fry you right where you stand, if it doesn't cause fibrillation before. I understand it would be pretty stupid to touch one of these lamps standing bare foot on the ground and wet, but you wouldn't get just shocked, a few amps would make for a gruesome spectacle, right? How can you sell such a thing to the public? I've heard people say it's not that harmful because of the high frequency but how can that be the case? Does the human body stop behaving like a resistor at high frequencies?
On a similar note, if I had the lamp on a metal table and someone were to tip it over, a few kilovolts short circuited to ground have got to create some fireworks. Isn't this really dangerous? I know that probably the power supply inside won't be able to supply the amperage and the voltage will drop, causing a smaller current, but again, isn't this really dangerous anyway?