Why does the steel wool catch on fire?
When the two terminals of the battery touch the steel wool a closed circuit is created. Normally as electricity flows through a closed circuit, the energy is used by a device that is connected to the circuit. This device could be a light bulb, television or anything else that is powered by electricity. These devices add resistance to the circuit and help to decrease the current (or in other words decrease the level of energy in the circuit). You can think of this way. If a dam is constructed in the middle of a fast flowing river, the rate at which that river flows will be decreased. So the devices in the circuit act as a dam would in a river. Since these devices resist the flow of the electricity, we call them resistors.
If there aren’t any resistors in the circuit, then the energy will simply flow back to the source (a battery in our case). This situation creates a short circuit. A short circuit results when the positive and negative terminals of a battery are connected by a conductor with a very low resistance, like a metal wire. The resistance is so low in a short circuit that the current will be extremely high. The current can get high that heat is being produced. The many thin wires of the steel wool create many very hot short circuits resulting in fire.
What is happening when the steel wool is on fire?
When the temperature gets hot enough a chemical reaction between the iron in the steel wool and the oxygen in the air will take place. This reaction is highly exothermic (produces heat) as we saw in the video. The reaction is described by the chemical equation shown below.
Are there any other ways to cause the steep wool to ignite?
Anything that will cause the steel wool to heat up enough will cause the reaction to occur. If you are in a survival situation and have a piece of flint, you could simply drop a spark into some steel wool and it should ignite very easily.
So next time you go on a camping trip, don’t forget to bring your box of Brillo Pads.