Naked Science Forum
Non Life Sciences => Technology => Topic started by: ScientificSorcerer on 08/02/2014 00:03:11
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Imagine the plasma power of a Tesla coil, with an electrically conductive gas being sprayed out by a hose at the top of the Tesla coil would the conductive gas carry the plasma farther? depending on the gas used would it change the color or properties of the plasma? I know neon and the Nobel gases are conductive gasses under a vacuum, but what gas would be more conductive then air at room pressure?
basically what i'm asking is can you make a ghost busters plasma pack with just a Tesla coil gun and a conductive gas or different gas like neon.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Ffancydresscostumes.co.uk%2Fblog%2Fwp-content%2Fuploads%2F2012%2F07%2FGhostbusters-proton-packs.jpeg&hash=b9b77d6629108c172be6ae3285928d0c)
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Mercury vapours are good gaseous conductor
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All gases become more conductive when they are ionised - the negative electrons move towards the +ve electrode, while the positive ion moves towards the -ve electrode. If the current & voltage are high enough, the electrons gain enough energy to strip electrons off other atoms with which they collide, forming a sustained arc.
To sustain an arc, you really need a DC supply - a Tesla coil is an AC voltage, so the current drops to zero thousands of times per second, allowing the cold external air to extinguish the arc. You need to apply a high voltage before the arc starts again, probably in a different place.
Presumably, if you increased the frequency to the MHz region, the arc would not completely cool down before the voltage reversed.
Initiating an arc requires voltages of about a million volts per meter - let's say 10 million volts for an indoor ghostbusters gun.
Once the arc is initiated, the resistance drops to near zero, so you need to deliver currents of hundreds of amps.
This is a massive power supply, with some difficult insulation requirements.
A focussed arc really needs to flow between two electrodes attached to the same power supply - having a concentrated stream of electricity just going into the air is unlikely. The magnetic fields inside the arc tend to tear it apart very quickly unless it is controlled and focussed, such as by strong magnetic fields.
Uncontrollable electric arcs has been an ongoing problem for nuclear fusion researchers (http://en.wikipedia.org/wiki/Fusion_power#Magnetic_Confinement_Fusion).
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You can, of course make a Jacob's Ladder (http://deskarati.com/2012/02/03/the-physics-behind-the-jacobs-ladder/).
By creating a plasma, it changes the conductivity of the air. So, while you may only have enough power to create a small arc in air, the plasma can maintain a much longer arc, as demonstrated by the rising arc.
As mentioned, you need to have a the arc jump between two electrodes, or between the electrode and "ground". An uncontrolled arc would be extremely dangerous. No capturing ghosts like on ghostbusters.
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you guys mentioned some good information, I am perticularly interested as to how the plasma will look in a different more conductive atmosphere of gas for example
NEON PLASMA
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.arborsci.com%2Fwordpress%2Fwp-content%2Fuploads%2F2013%2F03%2F04-neon-bulb-close.png&hash=1899349e6bec464bb857e4668c46afe3)
KRYPTON PLASMA
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fteslaboys.com%2FPlasma%2FMorePlasmaGlobes%2FKryptonXenon001.jpg&hash=fea72913acb413eddbe64bf05ab5d450)
AIR PLASMA
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwonders.physics.wisc.edu%2Fimages%2FTesla_2.jpg&hash=833a5908f2c08ed6c298eac70639b02b)
I wonder IF a different more conductive gas would change how it arcs through air.
The plasma would flow farther and strike at a much longer distance without the need for higher voltages if it were put in a different atmosphere of gas.
One of you guys said something about mercury gas would be a good canidate, how would that kind of lightning look like. I found a picture of a mercury lightbulb.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2F3%2F3c%2FMercuryVaporLamp.jpg&hash=33c395cc49026cbffcc60b5d849183d7)
If I sprayed out mercury gas at high pressure on the tip of a tesla coil would it alter the color of the plasma? would the gun shoot blue-green/turquoise lightning? cause that would be awesome. but what if for example you use neon gas instead. would it give off plasma like the picture above?
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Releasing Mercury into the atmosphere should be avoided, as it causes brain damage (and other organ toxicity) if inhaled.
The colours of an ionised gas depend on the mixture of gases, and their pressure. Often the gas is held under a lower pressure than atmospheric pressure. You could start by putting two electrodes in a vacuum chamber, filling the chamber with a desired gas mixture, and starting the vacuum pump to reduce the pressure. You could also try changing the current and frequency of the voltage source.
As soon as you try putting the gas into the air, you are limited to atmospheric pressure, with a lot of nitrogen and oxygen mixed in. You are also limited in your placement of the second electrode.
Noble gases are not known for being particularly conductive - one measure of this is the first ionisation energy (http://en.wikipedia.org/wiki/Ionization_energies_of_the_elements). Noble gases are more difficult to ionise (ie higher resistivity) than other gases of similar atomic mass, for example:
- Neon is 2080 kJ·mol−1
- Oxygen is 1313 kJ·mol−1
If you use Helium, it is likely to rise up towards the ceiling, while Argon is likely to fall towards the floor as it spreads out.
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evan_au
You said that noble gasses arent very conductive compared to other gases, I didn't know that. Thanks for the tip.
You also said that putting the gas in a vacuum chamber would help the arcs get bigger without more power.
But using a vacuum chamber isnt really the point. The main Idea is can you increase the range of electric arcs by spraying a conductive gas in the air, and dose the color of the electric arcs change because of the gas type.
Imagine a mix between a tazer and mace spray. The end result is plasma hits a target at a longer range by flowing through the conductive gas.
It would look similar to the ghost busters blaster in my mind. It's just a large tesla coil and a hose that shoots a conductive gas out of the top. It would look like the movie weapon and have similar properties because the color of the plasma would be a different and it would be a big backpack mounted weapon.
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Imagine a mix between a tazer and mace spray. The end result is plasma hits a target at a longer range by flowing through the conductive gas.
This might end up blinding the person in question, I imagine eyeballs being more conductive than the rest of your skin, and I am sure that high voltage + eyeballs = bad.
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SorryDnoodle
Huuu... Never thought about that, but I think the lightning would probably go for the hands because fingers are pointy, and lightning likes pointy things believe it or not. also a "target" is likely to have some kind of weapon like a knife "which is both conductive and pointy".
That knife would act like a lightning rod :) guns would act the same way because they are oftely made of conductive metal.
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You might be able to get a longer arc with lower voltage by using a powerful laser to ionize the air. see: http://www.gizmag.com/laser-induced-plasma-channel/23117/
http://en.wikipedia.org/wiki/Electrolaser
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ChiralSPO.
That laser would take up many more times the power needed to make an electrical arch. The power need ed for that laser would be somewhere in the megawatt range That is a huge amount of power. you would sooner vaporize someone in half with the laser then electrocute them.
I did a cool experiment with a helium balloon and a taser. I just deflated the helium on the taser spark gap and the lightning turned a bright red! But I think it's range decreased because the taser became nearly silent as if less power was passing through.
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How about mist or steam? what if you sprayed mist or steam out the front? Water is known for it's electrical conductivity and there's no risk of toxicity, unlike if I sprayed mercury vapor. I saw this video on you-tube were they used a water gun to get long ranges take a look.
the important part of the video is the last part, when the shot the water from the gigantic Tesla coil, If you look closely the arch is red, more importantly it's focused, that's a bit how the taser looked when I put helium through the spark gap like a week ago.