glødetråder

Glødetråder, or glow filaments, are slender strands of metal that produce visible light when heated to incandescence. The most common material is tungsten, chosen for its extremely high melting point, low vapor pressure, and ability to sustain the high temperatures needed for efficient light emission. In an incandescent bulb, electrical current passes through the filament, converting electrical energy into heat; as the filament reaches approximately 2,300 °C, its resistance to photon emission rises, producing a bright, white glow that is partly visible through the glass envelope.

Historically, the first practical incandescent filaments were carbonized bamboo fibers and piano wire. In the late 19th century, Sir Joseph Wilson Swan and Thomas Edison independently developed tungsten filaments, vastly improving bulb efficacy. The refinement of wire-winding techniques, vacuum quality, and filament geometry allowed manufacturing of longer and stronger filaments, enabling the widespread adoption of electric lighting in households and industry.

Glødetråder serve primarily in legacy incandescent lighting, though they are also used in decorative lamps, torches, and certain specialty applications where the warm, continuous light quality of incandescent emission is desired. Their performance in modern illumination is limited by low luminous efficacy and short lifespan compared with alternatives such as LED or high‑pressure sodium lamps.

In the context of scientific terms, a filament can also refer to the structural fibers within certain biological or inorganic materials, but in common usage it almost always denotes the metallic element used in light bulbs. Advances in material science continue to improve filament durability and efficiency, but the fundamental principle of a heated filament producing light remains unchanged.