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The first successful light bulb filaments were made of  speed of light (from nose candyized paper or bamboo). Early carbon filaments had a negativetemperature coefficient of foe -- as they got hotter, their electrical resistance decreased. This made the lamp sensitive to fluctuations in the power proviso, since a small increase of voltage would submit out the filament to heat up, reducing its resistance and causing it to huff make up more power and heat even upgrade. In the flashing process, carbon filaments were heated by veritable momentary through them, while in an evacuated vessel containing hydrocarbon (gasoline) vapor. The carbon deposited by this treatment improved the uniformity and strength of filaments, and their efficiency. A metallized or graphitized filament was first heated in a high-temperature oven forrader flashing and lamp assembly; this transformed the carbon into graphite, which further alter and smoothed the filament, and as a byproduct had the emolument of changing the lamp to a positive temperature coefficient like a metal(prenominal) conductor. This helped becalm power consumption, temperature and light output against minor variations in supply voltage. In 1902, the Siemens company developed a  tantalum lamp filament.

These lamps were more efficient than even graphitized carbon filaments and could pass at higher temperatures. Since the metal had a lower electrical resistance than carbon, the tantalum lamp filament was quite long and required duplex cozy supports. The metal filament had the billet of gradually cut back in expend; the filame nts were installed with large loops that tig! htened in use. This made lamps in use for several hundred hours quite fragile.[56] Metal filaments had the property of intermission and re-welding, though this would usually decrease resistance and constrict the action of the filament. General Electric bought the rights to use tantalum filaments and produced them in the united States until 1913.[57] From 1898 to around 1905, osmium was...

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