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The first successful light bulb filaments were made of  hundred (from carbonized paper or bamboo). Early carbon filaments had a negativetemperature coefficient of opponent -- 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 make out the filament to heat up, reducing its resistance and causing it to huff even more power and heat even further. In the flashing process, carbon filaments were heated by current 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 advantage of changing the lamp to a positive temperature coefficient like a metallic 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 operate at higher temperatures. Since the metal had a lower resistivity than carbon, the tantalum lamp filament was quite long and required multiple cozy supports. The metal filament had the property of gradually shortening in expend; the filaments were installed with large loops that tightened 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 shorten 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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