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Thomas Alva Edison (1847 - 1931): In 1878, Edison began work
on an electric lamp and sought a material that could be electrically
heated to incandescence in a vacuum. At first he used platinum wire
in glass bulbs at 10 volts. He connected these bulbs in series to
utilize a higher supply voltage; however, he realized that
independent lamp control would be necessary for home and office use.
He then developed a three-wire system with a supply of 220 volts DC.
Each lamp operated at 110 volts, and the higher voltage required a
resistance vastly greater than that of platinum. Edison conducted an
extensive search for a filament material to replace platinum until,
on Oct. 21, 1879, he demonstrated a lamp containing a carbonized
cotton thread that glowed for 40 hours. |
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Thomas Alva Edison
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1882
Edison installed the first large central power station on Pearl
Street in New York City in 1882; its steam-driven generators of 900
horsepower provided enough power for 7,200 lamps.
He consistently
fought the use of alternating current AC, and continued to market
direct current DC systems.
This eventually destroyed this arm of his
marketing empire due to inadequate technology. During his
experiments on the incandescent bulb, Edison noted a flow of
electricity from a hot filament across a vacuum to a metal wire.
This effect, known as thermionic emission, or the Edison effect, was
the foundation of the work later refined by Lee De Forest to create
the Audion. |
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