Plus traditional bulbs use a filament high in resistance (like tungsten) that produces light from said resistance. The way HIDs work is that 12V source is then bumped up to about 800V at the ballast/ignitors and then goes from point within the HID bulb then jumps the air gap (like points ignition in a distributor cap) to the other point, and in doing so creates light. This is the corona style HID there are one or two other styles but I can't remember the names at time of text.

Justin