Driving down the road yesterday they were repairing some electrical lines and I guess one of them sparked and it left a trail of blue sparks on the ground. But when I hook up a battery and short it with a wire sparks appear an orangish-yellow color.
Anyone know why?
In: Engineering
Electricity has no colour. The plasma created by the electric field releases light when it reforms into normal atoms. The colour changes depending on the plasma too. If you do welding and hit a copper object e.g. wiring, you would see the arc to be greenish.
When atoms split into the nucleus and electrons they require a specific amount of energy and when recombined they shoot out the exact same energy in one single packet. So the colour depends solely on how much energy in that packet of light emitted. When light is higher energy the more blue it seems, and thats not even the limit. The light can be ultraviolet. Thats why if you weld without proper equipment, you get sunburns.
The blue or purple is superheated air letting of photons because the air cant hold that much energy. The sparks are usually the ends of the wires melting off because of the arc. Superheats the end till it melts and increases in resistance and then they boil off and that’s the spark you see. It’s all happening extremely quickly though.
As discussed in several comments in this thread, this is due to ionization of the molecules (in particular, nitrogen) in the air whose emission spectra have peaks in the blue or violet.
In other gases, ionization leads to different colored emission – this video shows this perfectly using a Tesla coil.
[Gases near a Tesla Coil](https://www.reddit.com/r/blackmagicfuckery/comments/b0ozcn/gases_near_a_tesla_coil/?utm_source=share&utm_medium=ios_app&utm_name=iossmf)
The discharge also forms O3 (ozone) which is why people often claim to smell rain, as distant storms can create enough to be smelled at a distance. St. Elmo’s fire – Walter Lewin has a video on his MIT EM Physics channel. RIP you wonderful genius.
Electricity is actually invisible. When it arcs through the air, it ionises the gasses, and since the air is mostly nitrogen, and nitrogen ionises violet, lightning and sparks appear blue.
If the sparks were travelling through a different gas, they would be a different color.
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