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Registered Member #3922
Joined: Thu Jun 02 2011, 06:24AM
Location:
Posts: 23
me and my science teacher have been talking about high voltage and atoms and such, specifically why an arc from a MOT will be orange-ish in color and larger, while the higher voltage arcs are blue and small.
we have talked about how it could be heat difference that makes it change, or voltage, but he thinks there has to be something more... like how if you put less energy through a florescent tube it simply glows dimmer.
I looked all over the internet, but nothing i could find told me anything other than adding chemicals to achieve a different color.
Could it just be different levels of excitement in the atoms?
If anyone could point me in the right direction, has a document to show me, or even a simple answer i would greatly appreciate it. :)
PS: in this case we are simply talking about an arc through air.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Generally, the colors of plasma (or salts burned in air) is related to the elemental identity of the atoms in question. Some of that orange your seeing may be Fe (l,ll,lll) from the steel (as steel is mostly iron).
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
wELL someone with more chemistry experience may have to explain this further, but remember the ions can be stripped out of solid electrodes, then accellerated buy E-field and thermal forces, so the color could be differ by location throughout the arc.
Im pretty sure this is largely or entirely atomic spectra were seeing here.
Registered Member #2063
Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352
when the atoms/molecules of you electrode is in their excited state, they whould drop back down to its ground state, and a photon would be released during the drop in energy level.
so depending on your electrodes you will have different colors, if you have a light prism with you, you can try a quick experiment. direct the arc's light into the prism and you should see a series of bright lines coming out of the prism, instead of a full spectrum of colors (BTW this is called bright line spectroscopy).
dip your electrodes in salt water then arc to it, you should see bright orange arcs
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Yeah youre right to question why sparks are white/bule/purple yet arcs are orange and yellow.
i believe the explanation is that atomic nitrogen - oxygen are white blue and easy to excite with lower current, while higher powers (more curretn like arcs) are able to pruduce more energy intensive nitrogen oxide molecular compounds, like a nuclear weapon, which dims 1-10 seconds after detonation due to generation of nitric oxide (which is brown as a vapor) which is then burned off and it brightens again.
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electrical arc colors, what causes different colors?
