Re: [Vo]:Triboelectric metals
On Sep 11, 2007, at 10:22 AM, Michael Foster wrote: I am always amused by triboelectric series tables. The people who put these out usually have absolutely no idea what they are talking about. The position of lead on this table is complete nonsense. Yes, it was surprising to see lead up there with the notorious cat fur. I've never seen any static effects whatsoever associated with lead. It must be active with some material? Other gross errors include acrylic, polyester and styrene on the negative side. The vast majority of acrylics, and there are thousands, tend to go positive when rubbed with almost anything, including cat fur and rabbit fur. Styrene is interesting because in can go either way depending on the conditions, however, it usually goes positive. Styrofoam tends to go negative whereas crystal styrene almost always tends positive, even though they are chemically identical. Glass is interesting. Most modern glasses are difficult to charge. One of the best ways to charge glass is to use aluminum foil, much better than those materials listed on the negative side of Wikipedia's series. Of course you have to keep the glass against a conductive surface, wood, Formica, metal, etc., while you are rubbing the glass so that the charge is kept at low voltage. You then pick up the sheet of glass and it hisses its positive charge into the nearest grounded object. Sounds like you have done a lot of experimenting along these lines. Any experience with gasses that have triboelectric effects? That's clear glass. Frosted, ground, or sandblasted glass tends to go negative. The only reason I bring all this up is that the conventional ideas as to what constitutes electron sources are not necessarily valid. Several metals and other substances dutifully listed on triboelectric series are in their positions based on assumptions, hearsay, and errors. It also seemed to me strange zinc, one of the more electrochemically active metals, was not even listed. So goes the rest of science and most other human endeavors. The problem with the triboelectric tables is they are subjective, not quantitative, and thus probably haven't had use or scrutiny. They are not even in my 74th Edition CRC Handbook of Physics and Chemistry. Most of the other stuff in there seems pretty reliable. It has to be for the most part, because it is used for engineering and lives can be at stake. There is someting fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. --Mark Twain Gee, I thought that was a good thing! 8^) It is indeed surprising how such a large amount of physics, especially 19th century physics, is based on so few experiments. It is also wonderful how understanding such a few basic laws gives us so much insight unavailable to generations past. Horace Heffner http://www.mtaonline.net/~hheffner/
Re: [Vo]:Triboelectric metals
--- Horace Heffner [EMAIL PROTECTED] wrote: It is surprising that lead is a powerful electron donor, as powerful as cat fur: http://www.school-for-champions.com/science/static_materials.htm Also noted as a weak donor is aluminum. This seems somewhat consistent with the electron affinity table: http://en.wikipedia.org/wiki/Electron_affinity because lead is 35 and Al is 42, but the *extreme* donating ability of lead is surprising. The problem remaining then is to find a good transport molecule for interacting with lead. Odd there was no mention of zinc. Lead is the metal also at the top of the Wikipedia list at http://en.wikipedia.org/wiki/Triboelectric_effect and is listed just above cat fur. Though not a metal, silicon is listed as better than gold or platinum as an electron acceptor. If doped silicon works as well in that role as silicon then it might be worth considering. It may also be possible to add materials to ebonite or silicone rubber to make them sufficiently conducting to work, but neither would be good for high temperatures, nor would lead. Either CO2 or nitrogen must be a good transport molecule, I'm not sure which: http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=10120574 I guess it would be CO2 that transports because CO2 could then neutralize the coal by acting as a quasi conductor. The other interpretation might be that nitrogen is a contact transporter that charges coal in the first place. Neither would necessarily be inconsistent with the dry pile operation. I bet on CO2 as the transporter because dry nitrogen is a terrific insulating gas. Horace Heffner http://www.mtaonline.net/~hheffner/ I am always amused by triboelectric series tables. The people who put these out usually have absolutely no idea what they are talking about. The position of lead on this table is complete nonsense. Other gross errors include acrylic, polyester and styrene on the negative side. The vast majority of acrylics, and there are thousands, tend to go positive when rubbed with almost anything, including cat fur and rabbit fur. Styrene is interesting because in can go either way depending on the conditions, however, it usually goes positive. Styrofoam tends to go negative whereas crystal styrene almost always tends positive, even though they are chemically identical. Glass is interesting. Most modern glasses are difficult to charge. One of the best ways to charge glass is to use aluminum foil, much better than those materials listed on the negative side of Wikipedia's series. Of course you have to keep the glass against a conductive surface, wood, Formica, metal, etc., while you are rubbing the glass so that the charge is kept at low voltage. You then pick up the sheet of glass and it hisses its positive charge into the nearest grounded object. That's clear glass. Frosted, ground, or sandblasted glass tends to go negative. The only reason I bring all this up is that the conventional ideas as to what constitutes electron sources are not necessarily valid. Several metals and other substances dutifully listed on triboelectric series are in their positions based on assumptions, hearsay, and errors. So goes the rest of science and most other human endeavors. There is someting fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. --Mark Twain M. Shape Yahoo! in your own image. Join our Network Research Panel today! http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7
