AWG D.C. OHMS WIRE DIAM APPROX. TURNS PER FEET PER SIZE PER 1000 FT INCHES INCH, SOLID ENAMEL POUND COVERED 1 .1264 .2893 X 3.947 2 .1593 .2576 X 4.977 3 .2009 .2294 X 6.276 4 .2533 .2043 X 7.914 5 .3195 .1819 X 9.980 6 .4028 .1620 X 12.58 7 .5080 .1443 X 15.87 8 .6405 .1286 7.6 20.01 9 .8077 .1144 8.6 25.23 10 1.018 .1019 9.6 31.82 11 1.284 .0907 10.7 40.12 12 1.619 .0808 12.0 50.59 13 2.042 .0720 13.5 63.80 14 2.524 .0641 15 80.44 15 3.181 .0571 16.8 101.40 16 4.018 .0508 18.9 127.90 17 5.054 .0453 21.2 161.3 18 6.386 .0403 23.6 203.4 19 8.046 .0359 26.4 256.5 20 10.13 .0320 29.4 323.4 21 12.77 .0285 33.1 407.8 22 16.20 .0253 37.0 514.2 23 20.30 .0226 41.3 648.4 24 25.67 .0201 46.3 817.7 25 32.37 .0179 51.7 1031 26 41.02 .0159 58.0 1300 27 51.44 .0142 64.9 1639 28 65.31 .0126 72.7 2067 29 81.21 .0113 81.6 2607 30 103.7 .0100 90.5 3287 31 130.9 .0089 101 4145 32 162.0 .0080 113 5227 33 205.7 .0071 127 6591 34 261.3 .0063 143 8310 35 330.7 .0056 158 10480 36 414.8 .0050 175 13210 37 512.1 .0045 198 16660 38 648.2 .0040 224 21010 39 846.6 .0036 248 26500 40 1079 .0031 282 33410 41 1323 .0028 42 1659 .0025 43 2143 .0022 44 2593 .0020 45 3348 .00176 46 4207 .00157 47 5291 .00140 ************************************************************************ For winding Tesla secondary coils the general consensus is to use number 22 AWG, or larger diameter, CLOSE WOUND MAGNET WIRE. Often surplus partial spools of odd wire sizes are found, so I took time to post a more complete chart of AWG numbers and fractional diameters than is usually available. All information above is approximate despite the decimal places. Wire diameter, turns per inch, resistance, feet per pound, etc. all vary slightly from one manufacturer to another. Insulation thicknesses will vary depending upon type and the supplier. Turns per inch will also vary with the quality of the winding. In practice, Tesla coil windings are not perfect (nor do they need to be) so expect some slight variations from the specification table above. Magnet wire coatings from Phelps-Dodge: All data pertain to 18 AWG magnet wire. Build = thickness of coating Coating What's it made of Build DC ---------- ----------------- ----- breakdown Thermaleze-T (TZT) polyester-imide 2.8mils 11kV Armored Polythemaleze 3.05mils 11kV (APTZ) modified polyester& modified polyamide-imide Imideze (ML) Aromatic polyimide 2.9mils 12kV Formvar modified polyviynyl 3.0mils 10kV formal Sodereze modified polyurethane 2.9mils 8.5kV Nyleze Polyurethane 2.9mils 8.5kV & polyamide * Note: for the dielectric breakdown - These numbers are much bigger than for bulk materials because they are very thin coatings. The breakdown field increases as the thickness goes down. {a similar effect happens in gases and liquids and was studied by Paschen} Anyway, here's the dielectric constant/DF numbers for these matearials: Material Dielectric Const. / DF x 10^-3 1kHz 100kHz 1Mhz Rating TZT 3.7/5.6 3.56/16.4 3.58/21.5 3rd APTZ 3.86/6.9 3.69/22.1 3.67/26.6 5th ML 3.34/0.9 3.3/5.7 3.36/9.8 2nd to teflon Formvar* 3.6/11.2 3.41/25.2 3.37/28.4 5th Soldereze 3.85/11.3 3.66/20.7 3.66/23.1 4th Nyleze 4.07/19.7 3.78/27.1 3.75/27.2 6th * This shows that Formvar is far from an ideal coating for magnet wire used in Tesla Coils when compared to something like Polyimide coatings If this looks like Greek to you please don't dispare. Even the worst wire coating is acceptable, though noticable improvements in secondary coil performance will be obtained if you use magnet wire coated with ML, TZT, or Soldereze. Formvar coated wire is frequently found surplus on bulk rolls and is cheap by the pound, so don't feel bad if you end up using it.