| MadSci Network: Physics |
In a lightbulb, an electric current is forced through a thin wire, called the filament, causing it to become extremely hot. The filament becomes hot because of resistance to electric current flow. All wires have some resistance to current flow. Some materials have more electrons that are available to conduct current, thus these materials have less resistance. Gold, silver and copper have lots of electrons so they are good conductors. Also, the thickness of the wire is a factor. Thicker wires have less resistance because there is more of the conductive material. When there are not enough electrons to conduct all of the electric current, then the wire material begins to absorb the excess energy. This process is called resistive heating and it is used in most electric heaters to convert electricity to heat. The filament in a light bulb conducts some of the electricity, but absorbs most of it. Resistive heating causes the filament in a 100 watt bulb to become about 3,000 degrees C. The filament is tiny, so the total amount of heat produced seems like only a little for something that is so hot.
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