Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx> At 11:47 AM 4/11/2006, Tesla list wrote:
Original poster: "Thomas Coyle" <zxcasd@xxxxxxxxx>I'm not sure I agree with this - I have trouble believing that the sparks we're seeing are getting the air up to 10,000K, which is what would be required to get the characteristic blue color if it's just blackbody radiation.
Why wouldn't they be that hot? It's just a matter of current/energy. The former is determined by the inductance of the discharge path, the latter by the topload C and voltage.
There's a huge amount of literature on the temperature of sparks of all sorts, measured in all sorts of ways (spectral line spreading being one).
Indeed, there IS some radiation from the ionization of the air (just as in corona discharge), but for real "sparks" (as opposed to wispy little feelers), I think it's incandescent gas.
Certainly this would be the case for any sparks that are "daylight visible".
Of course, there's a "simple" way to test it - just enclose a coil in plexi, evacuate it, and replace it with neon (for example). Of course, that sounds an awful lot like a plasma globe, which colors definitely aren't caused by blackbody radiation.
Most plasma globes are running at low powers, with gas mixtures and pressures chosen specifically for color.
Run several hundred watts or a few kilowatts through a plasma globe, and I'll bet the sparks look bluewhite, just like air sparks.
On 4/10/06, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote: Original poster: Jim Lux <<mailto:jimlux@xxxxxxxxxxxxx>jimlux@xxxxxxxxxxxxx> At 08:04 AM 4/10/2006, Tesla list wrote: >Original poster: BunnyKiller <<mailto:bunikllr@xxxxxxx>bunikllr@xxxxxxx> > >Hi Langer... > >we see it pretty much the same way we see a neon tube glowing... Folks.. all this talk of ionization levels and such are fine, and there's no doubt that some of the light coming of the sparks on a TC is from excited nitrogen. Nitrogen has a whole raft of lines all the way from red to blue. However, the dominant source of light is going to be blackbody radiation from hot gas, at least for any spark that's reasonably bright.