Plasma!


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munfai

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what is that?
 

roygoh

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Jan 18, 2002
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Originally posted by munfai
what is that?
A plasma ball...I guess that's what it's called.

One of those glass balls with a near vacumm inside and a very high voltage electrode.

The high voltage causes the gas to become conductive and as the electrons travel from the electrode to the inner surface of the glass, they form purplish trails.

- Roy
 

ckhaos

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Originally posted by roygoh
A plasma ball...I guess that's what it's called.

One of those glass balls with a near vacumm inside and a very high voltage electrode.

The high voltage causes the gas to become conductive and as the electrons travel from the electrode to the inner surface of the glass, they form purplish trails.

- Roy
I never understood why the high voltage causes trails to form. If the gas becomes conductive, shouldn't the electrons travel isotropically? What causes the trails to form and not a spreading ball??? :confused:
 

roygoh

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#5
Originally posted by ckhaos
I never understood why the high voltage causes trails to form. If the gas becomes conductive, shouldn't the electrons travel isotropically? What causes the trails to form and not a spreading ball??? :confused:
Hehe...this will bring the discussion way off the topic of photography.

Base on my limited knowledge in physics, I would guess that the following are the reasons:

1. The E-field in the chamber is never perfectly uniform. Neither the electrode nor the glass ball is perfectly shaped, and there are other factors like contamination etc to consder. This is also why touching the glass ball's outer surface would attract the trails towards the aread touched because of the change in potential on the inner surface.

2. Avalanch effect. I don't know how to describe this, but the analogy is lightning streaks. Once the lowest energy path is found, the accumulated charge will follow this path for discharging.

I have no physics degree, so I am just as curious and only guessing here.

What do you think?

- Roy
 

#6
Saw a nice one in UK selling for less than S$60. It also reacts with sound! Put the subwoofer beside it and watch the plasma ball thump along. I'm still considering whether I should buy it or save the money for more photography accessories.
 

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