All you need to do is to take a piece of fine steel wool – the finer the better (I use 0000 grade), pull it apart a little to separate a few threads. Then to light it, take the steel wool threads and short circuit a battery by connecting the wool to both battery terminals. Be careful because the steel will immediately turn red hot. Blow on it a little and it will burst into flame. You can make it even more effective by mixing in a little dryer lint.
Once you have done it with a 9 volt battery and see how easy it is, you can take the back off a flashlight, turn it on and use the battery and the metal flashlight case to do the same thing. As you can see from the video you can even do it with a cell phone battery.
How does it work?
The basic principle is that there is more electrical current that wants to flowing through the fibers, than the fibers can handle – the resistance to the current causes the wool to get hot. If the steel wool is not fine enough, the electricity will just flow through it. This will drain your battery without giving you the heat. If this is the case, increase the current.
Another factor is the total voltage that is applied to the strands. The higher the voltage, the hotter the wires will get. (The relationship between current and voltage is linear – double the voltage, to get twice the current.) This means, the more cells that you run in “series” the hotter the wires will get.
