Dave
Ø Jones, even at 40 kHz it is going to be extremely difficult to get enough current to flow inside a coil of wire. Remember, they normally drive the expansive sheet of resistive metal that has an effective resistance that is much less than an ohm. The coils that we are using is in the vicinity of 10 ohms. Yes, that is true but don’t forget that the tube fill mix can be made conductive as well. This is the reason I suggested to Jack to use Fe3O4 instead of Fe2O3 as the bulk fill (or support material) with an inductor setup. The former is 6 orders of magnitude more electrically conductive than the later. So, you have a magnetic field that enters a much larger area of resistive metal when a pan is placed upon the unit than with the small coil. Then, the length of wire used in the coil has a large series resistance whereas the pan is more of a parallel resistance and much less in total value. Both of these effects are working against you. I agree but Fe3O4 is highly conductive - although we do not know what happens at elevated temperature in the presence of reducing compounds, but as long as it is not further oxidized, Fe3O4 should be in the few Ohm range, no? Not to mention acting as a transformer coil, to an extent. Jones
