----- Original Message ----- From: "Jonathan Johnson" To: Sent: Monday, January 06, 2003 10:29 PM Subject: Re: [EE]:Flashover voltage in Air? [snip] > So I think that the higher the airpressure the > higher the air density and thus the shorter the > gap?, Yes, vaccum is the best electric isolator. > the higher the humidity the smaller the gap?, Yes, humidity, water, or salinity in suspension, favors the electric jump. > the higher the rate of charge the shorter the gap? No, it is reverse. If you start to charge (increase) the jumping voltage slowly, the metal plugs start to product ions in the air, those ions can create an easy flow for the eletric jump. This is exactly what happens in nature's eletric discharges, part of the path of the thunderbolt was previously created by ions, mostly ozone, the rest of the path is done in "real time" and by the shorten way, lower resistance, etc. Sometimes during the discharge, the bolt is so heavy and the area below offers high impedance, it charges all the area and the easy path is upwards to other direction than downwards again where it offers lower impedance, then you can see those strange thunderbolts that travels horizontally to other directions. > the lower the altitude and thus higher air density the lower the gap? > temp>=gap i am presuming the probe density affects it largely due to the ionic charge > of the material and its conductivity > > It is more related to the format of the probe, when pointed (needle) it spread ions much easier than a round surface. This is why wind can interfere in the gap function, since ions can be taken away what can cause a curved jump, or no jump at all. One interesting point, observed during many experiences, FIRE, fire plasma, fire glow, etc, does not interfere in the ionization of in the jump path. By all I knew, I was expecting that FIRE plasma and its potent carbon conversion mechanism would be an easy path for the electric jump, but it is not, and I don't know why. Try to play with a car's coil and spark plug... increase voltage, big discharge, open the gap and see a 10 to 15mm jump, straight blue (cold, normal, just electrons) or RED (hot - ripping off burning metal particles along with the electrons) and aproach a fire plasma, nothing changes. Then open the gap wide (no spark happens), then insert fire in the middle, it should complete the jump path, but no, it does not. A simple toothpick in the middle favors the jump, but not bare plasma fire. Wagner. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu