How does it work? (From Steve Spangler's Website)
When you touch the free ends of the alligator clips to your "super battery," you form a complete circuit. That means electricity flows freely through the entire apparatus that you have just built. This flow of electricity channels through the graphite-based mechanical pencil refill that is connected by alligator clips. The flowing electricity has a noticeable effect on the pencil refill. The thin refill begins to glow and give off smoke. This happens because the electricity heats the graphite refill to an incredible temperature. So, if you are hoping to save some money by using your own homemade light bulbs around the house,stick with the store bought ones. It's not as cool, but it is safer.
Amazing! Click here to build one yourself (or on the Homemade Light Bulb link on the Homemade Light Bulb link to the right). Kids, remember to always have adult supervision and protective eye wear handy!