[engineerman]

I am trying to create a safer way of starting the Goldschmidt reaction so that it can be more safely used in welding.  My idea is to take a disposable "filament" of tungsten and attach it to a battery by means of two copper wires, one of which has a switching mechanism allowing the welder to start the reaction by switching on the circuit.  When the electricity goes through the tungsten filament, it will heat it to the 1200+ degrees C necessary to start the Goldschmidt reaction.  The idea is essentially the same as an incandescent bulb, except that since the reaction cannot be produced in a vaccuum the tungsten filament will likely be destroyed either by the Goldschmidt reaction or by oxidizing from its own heat.  This will allow the welder to keep a safe distance at all times during the procedure, start the reaction with more accuracy, and avoid most of the dangers and difficulties associated with the other common methods of starting the Goldschmidt reaction (namely, a magnesium ribbon fuse (which may start the reaction too early) or a potassium permanganate + glycerin reaction (which has a chance, albeit small, of explosion)).

The problem is, it has been a little while since I calculated the heat generated by an electric current, and I don't remember how.  How would I go about calculating the temperature generated by a specified current through a copper wire, a tungsten filament, and another copper wire of specified lengths and diameters.  Most importantly I need to know where the heat will be generated (as I don't want the copper wires or the battery to get too hot).