Although many people contribute the invention of the light bulb to Thomas Edison, the first design was produced by Sir Humphry Davy in 1801. His design used a platinum strip that was heated by an electric current. However, this first light bulb was impractical because the metal strip burned up quickly. Many others tried to produce a practical light bulb, but their designs either used expensive materials like platinum, or did not burn long enough. After many years of work, Joseph Swan, an English physicist, developed a light bulb using a carbon filament in a vacuum. He applied for a British patent in 1878, and started his own company. At the same time, Thomas Edison was also trying to make a practical bulb. He tried thousands of different materials for the filament, finally deciding on carbon from bamboo, allowing his bulbs to burn for 1200 hours. Swan sued Edison for patent infringement and won. (Edison had applied of a patent a year later than Swan.) As part of the settlement, he was made a partner in the “Edison and Swan United Electric Company”.

The electric light bulb consists of a filament contained within a glass bulb. Electric current is passed through the filament, which causes it to become hot and glow. The glass bulb allows the low pressure gases to be placed in the bulb. Halogen and noble gases are used in most bulbs to prevent evaporation of the filament, and the low pressure reduces chemical reactions between the filament and the gases and slows the conduction of heat away from the filament, keeping the bulb cooler.

Despite their low efficiency – less than 10% - light bulbs were a very important invention. Their low cost and easy use makes them very practical for many applications from flashlights to home lighting.

*Picture from Encarta Encyclopedia