Last post I mentioned my new hobby, classic car restoration. This involves replacing rusted metal with shiny new metal and that means welding so I bought a welding machine. It's a MIG welder which stands for metal inert gas. The principal is that a thin wire is fed out of a nozzle onto the workpiece. The wire is at about 30 V and the workpiece is earthed so a current flows, the size of the current depends on the resistance of the wire which is related to it length so the longer the length of wire the lower the current and since power = VI, less current means less heat per second resulting in a lower temperature and a poor weld.