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Thread: How efficient was Thomas Edison's lightbulb?

  1. #1 How efficient was Thomas Edison's lightbulb? 
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    I was wondering, do we have any figures on how efficient the early light bulbs were? I cannot seem to find anything about this anywhere.


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    You may find this extract from Wikipedia helpful:

    Thomas Edison began serious research into developing a practical incandescent lamp in 1878. Edison filed his first patent application for "Improvement In Electric Lights" on 14 October 1878.[25] After many experiments with platinum and other metal filaments, Edison returned to a carbon filament. The first successful test was on 22 October 1879,[26][27] and lasted 13.5 hours. Edison continued to improve this design and by 4 November 1879, filed for a U.S. patent for an electric lamp using "a carbon filament or strip coiled and connected ... to platina contact wires."[28] Although the patent described several ways of creating the carbon filament including using "cotton and linen thread, wood splints, papers coiled in various ways,"[28] it was not until several months after the patent was granted that Edison and his team discovered that a carbonized bamboo filament could last over 1200 hours.

    Incandescent light bulb - Wikipedia, the free encyclopedia


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    According to the Wikipedia article:
    By 1964, improvements in efficiency and production of incandescent lamps had reduced the cost of providing a given quantity of light by a factor of thirty, compared with the cost at introduction of Edison's lighting system.
    From this we can deduce that the Edison light was 1/30th of the efficiency of a modern incandescent light (around 2%) which would give the Edison bulb an efficiency of somewhere around 0.07% of the electric power converted to light. This is just a rough estimate though, because it includes improvements in manufacturing.
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