Electric+Light+Bulb

__**Electric Light bulb**__ A Scottish chemist called Joseph Swann tried passing electricity through fine wires (filaments) to make them glow white hot in 1860. Despite enclosing them in bulbs and pumping out the air, they quickly broke or blackened and Swann abandoned the idea. 17 years later, finding a better vacuum pump, he tried again. With no air left inside, the filament light bulb became a realistic possibility The American inventor Thomas Edison patented the light bulb in 1880 and then sued Joesph Swann who had not applied for patents. However, Thomas Edison had missed one essential aspect, lighting the air while the air was being pumped out. This was quickly patented by Swann and eventually they formed a joint company. The first light bulbs had filaments made of carbon, which has a higher melting point than any metal. Swann carbonized (burnt without air) his visiting cards. Edison used slivers of bamboo. carbon filament bulbs are still popular in Germany as porch lights. Later filaments were made from tungsten which at 2500 degrees Celsius the tungsten slowly deteriorates and evaporates, so ordinary bulbs only have a 1,000 hour life. Thicker filaments and extra supports extend their life but reduce their light output, as they increase heat losses. Nowadays an ordinary bulb only gives out about 10% of its electricity as light. The rest is wasted as heat. Tungsten halogen bulbs give out about twice as much light,and fluorescent tubes twice as much again. Sodium street lights are more efficient still. Before the invention of the light bulb, lighting up the world after the sun went down was a messy and hazardous task. It took a bunch of candles or torches to fully light up a good-sized room, and oil lamps, while fairly effective, tended to leave a residue of soot on anything in their general vicinity.

By Jordan Madeira and Tom Walters 9G