Physics of Incandescent Light bulbs :: physics light bulb

The incandescent light bulb, since its fairly recent invention, has quickly become a basic essential of modern technological life as we know it. It took many years to create an practical bulb despite the simplicity of its structure. I believe a majority of us take them completely for granted as a normal part of life. Early man knew the sun as his lightsource and when the sun set, he knew the moon and the stars. As his intelligence increased and he learned about the world in which he lived he became associated with fire. Fire could be used for warmth, cooking, protection, and light. Man lived with this for years, elaborating and improving the way the fire was created and burned for light, until the year of 1809 when one man, an English chemist by the name of Humphrey Davy began the search for a usable incandescent light source using electricity. Using a high powered battery to induce a current between two high powered strips he produced an intense incandescent light, which became known as the first arc lamp. Although it was a first step it was not yet a practical light source. The first known attempt to make a actual bulb didn't come until 1920 when Warren De la Rue enclosed a coil of platinum wire in an evacuated tube and passed an electrical current through it. Although a platinum light bulb was not practical the idea behind his design was. A metal with a high melting point to achieve high temperature and thus bright light, as well as an evacuated tube that contained less particles to react with the metal and thus an elongated bulb life. Throughout the next few decades scientists labored to create their "efficient" light bulb. Their main hurdle was finding a low cost, long lived, high temperature filament material that would glow with high intensity. In 1879 two scientist, Joseph Wilson Swan and Thomas A Edison, had independent breakthroughs for a longer lasting incandecent bulb with their use of a carbon fiber filament derived from cotton. It lasted a maximum of 13.5 hours. In 1880 Edison also developed a filament derived from bamboo which lasted up to 1200 hours. This was good, but to create a truly efficient bulb something different was need to creae a filament with very high temperatures but without degeneration and loss of heat. Many elements were experimented with, a few of the most popular which were carbon, osmium, and tantalum.