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What Is a Tungsten Filament?

Inventor Thomas Edison used tungsten filament to create his light bulb.
Light bulbs with a tungsten filament.
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  • Written By: Dale Marshall
  • Edited By: Jessica Seminara
  • Last Modified Date: 06 September 2014
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A tungsten filament is a thin strand of the metal which glows very brightly when an electric current is passed through it. When coiled and sealed inside a glass container filled with an inert gas, a tungsten filament can glow brightly enough to light up a room. It was the inclusion of a tungsten filament in his electrical lighting system that resulted in the world giving Thomas Edison credit for inventing the electric light bulb when in fact dozens of scientists had been experimenting with electric light.

Tungsten is an element (Symbol: W; Atomic Number 74) discovered in the late 18th century. Almost twice as dense as lead, it has the highest melting point of all the metals at 6192 ° F (3422 ° C); of all the elements, only carbon’s melting point is higher. These properties make tungsten very useful not only in electric technology, but also for military applications such as hardening weapons. Another use of tungsten is as a component of jewelry, where it’s combined with other materials to form very hard and lustrous compounds, although they can be brittle.

When Thomas Edison and other scientists were working on developing the electric light bulb, they experimented with a number of materials for the light-producing filament. Until the early 20th century, the most successful incandescent light bulbs utilized a filament of carbonized bamboo, which lasted about 1,200 hours. Edison wasn’t the first to use tungsten, which was introduced as an incandescent light bulb filament in Europe in 1904.

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In 1906, Edison's company General Electric (GE) developed a process for making pure tungsten flexible enough to draw into a coiled wire. Using a coiled wire allowed GE to increase the surface area of tungsten that would be inside the bulb. By 1911, the company was manufacturing and selling light bulbs using the new filaments, which outlasted all others. Advances in this technology continued almost uninterrupted, so that the cost of operating an incandescent bulb by the turn of the 21st century was less than 5% of what it was in 1911.

Despite its success as the light source for incandescent bulbs, tungsten filament is remarkably inefficient in producing light. About 90% of the power used in operating an incandescent light bulb is emitted as heat, not light. As more efficient methods of producing light have been developed, most notably fluorescent lighting and light emitting diodes (LEDs), some have called for the banning of incandescent bulbs as an energy conservation measure.

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