On Fri, 10 Jun 2005, Michael Foster wrote: > So by drying the interior of the PVC pipe with forced hot air, I had > removed the conductive layer of water, thereby allowing the voltage > to rise to several tens of kilovolts. Mildly interesting, but no > new principle:(
But something weird is still going on. If conductive water on the pipe's inner surface gives a second "capacitor plate" with an equal and opposite (positive) charge, then as this water evaporates and the thickness of the layer decreases... nothing should electrically change. The layer still contains a positive charge equal to the negative one on the outside pipe surface. As the water finally dries out, the positive charge should remain on the plastic surface, strongly attracted there by the nearby negative charge. You've apparently created a fluid-stream VandeGraaff machine, where somehow the positive ions which cling strongly to the plastic are being injected into the air blast, so the layer of positive charge is pushed far away, leaving the negative charge behind on the outer plastic surface. > However, I have had a number of successful charge-by-evaporation > experiments. These did not involve water or other polar solvents, > which I have not yet been been able to make work. I have used > a non-polar alkane hydrocarbon which has been heat evaporated to > make and transport an electrostatic charge. There was no spray > involved here, merely evaporation and condensation. As far as > I can tell, this is a simple triboelectric phenomenon, which I can > describe in detail if anyone is interested. Nevertheless, it is > a heat pipe electric generator. Very interesting! Someone sent me an email years ago about strong charging caused by solvent evaporating (in some sort of industrial cleaning setup.) Also: Evaporative charging caused by salt crystals http://web.archive.org/web/20001016120655/http://www.geocities.com/CapeCanaveral/Lab/8063/colin.htm ALso: http://www.esdjournal.com/techpapr/prevens/article.htm http://www.esdjournal.com/techpapr/prevens/flow1.pdf > Keep in mind, the Armstrong and subsequent Faraday experiments involved > high pressure steam and fairly high heat. One can assume that at > least partial condensation into water droplets was necessary to effect > a charge transport. On the other hand, the setup I use can be driven > by a fairly low heat difference. Whether anything useful can be made > of this is open to question. I've never seen ANY serious claim that evaporation can produce electrostatic charging. If you've discovered a liquid which exhibits this effect, it's at least worth a physics paper (or an archivx preprint, or a personal webpage!) Lots of science-fair physics students could have fun with it. (((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-789-0775 unusual phenomena, tesla coils, weird sci
