Please be advised that this entry will probably grow slowly, over time, meaning that it will change much -- especially today, Nov. 30th 2011. I have been looking for electrical resistivity data in various places on the web, although I probably have books around here somewhere with tables of data. So far the data I have seen has been either variable or I have not been able to understand it. "Ohm meter" has units that so far have boggled my mind to try to imagine them, for example. Anyway, one site that seems useful: http://epg.modot.org/index.php?title=901.12_Electrical_Components. I am trying to calculate the number of amperes that I might expect to flow out of a 30 AWG copper wire that is some 3300 feet long. First I have to understand some of the figures that I am getting off the web, but also I have gone back to basic electricity formulas, and am reviewing some basic principles of electricity. I must also be wary of the average website's data. For example, www.ohmslawcalculator.com does not state which metal the AWG applies to. I assume that the website designer is referring to copper, but I am somewhat accustomed to finding comparisons among metals so the lack of the explicit naming of the element from which the wire is made makes me uneasy. The modot site above says that the smaller the diameter of the wire, the greater the voltage. This makes sense from the perspective that the greater the diameter of the wire, the greater the conductivity, which is inversely proportional to resistivity. The ohmslawcalculator site indicates that 3000 feet of 30 AWG wire should have approximately 310 ohms resistance. Mind you, I will not believe this until I can confirm it somehow.... I have other things to do today, but I am interested in getting back to the modot site as soon as possible to finish reading there.... What I have been obsessing about of late has to do with getting too little amps. Using the I = V/R formula I was getting only 0.01 amps for a $35 spool of 30 AWG wire, based on a 1700 ohms figure I had derived from some website for 3300 feet of wire. The site I found this morning has 310 ohms for 3000 feet of wire, which gives 0.06 amps if 18 volts are in fact produced. This is still not much, especially since AC gives even less power than the straight DC calculations. I have started working toward reducing the diameters of my spools in order to get more turns per foot. This takes me back to the smaller magnets, by the way, and spacing them closer together so that more coils can be gotten onto the outside perimeter. My next mapping project will be working with the 2 lb lift, 1 inch high horseshoe magnets. But first I must clear off a table that has no metals in it. I finally realized that my previous magnetic field mapping might have been affected by metal fasteners in my table, so I will be rechecking all of those maps before displaying them here. Also, I get "funny" shapes sometimes that may or may not be caused by the differences between the South and North poles. Certainly the fields are different when another magnet is nearby, so I will have to examine a completed rotor some day. Perhaps I will find inconsistencies among the magnets due either to differences in their manufacture or how they were stored.... Certainly I do not subject my magnets to any great heat that would explain their difference field shapes. |