How the Light Bulb Changed History

How the Light Bulb Changed History — page 3 — THOMAS EDISON Thomas Edison was born in Ohio in 1847 The Edison family moved to Michigan in 1854 Young Edison was a bright student and tended to exasperate his teachers with his constant questions His mother took over the job of teaching him and Edison later credited her with his interest in learning Soon he developed an interest in the sciences as well as in making money By age 12 Edison was selling newspapers and snacks on a nearby train that ran between Port Huron and Detroit His interest in telegraphy and learning from telegraph operators along the railroad line led to his first telegraph job Edison learned Morse code a system of tapping in dot and dash patterns that correspond to letters By age 16 Edison had come up with his first invention a machine that would automatically transmit the Morse code used by telegraph machines Edison never attended college but he went on to invent many other machines ultimately collecting more than 1 000 patents His favorite invention was the phonograph which could record and produce sounds He married twice his first wife died and had six children Two of them had the nicknames Dot and Dash after his work with Morse code The reporters returned to New York and published Edison s claim When the news went public the gas companies that supplied the fuel for the gaslights that lit most of the United States took a hit on the stock market which tracks the financial worth of various companies Then everyone settled in to wait Six weeks passed No light bulb Six months passed No light bulb 8

How the Light Bulb Changed History — page 4 — Finding a Filament As the weeks and then months passed Edison was far behind his original schedule but he was not discouraged He did not believe failure was a setback Rather he saw it as a necessary step on the path to success This problem however had many thousands of steps Edison was not the first inventor to experiment with incandescent light The idea was already 40 years in development by the time he turned his attention to it Incandescent lights operate by passing an electric current through a material called a filament The flow of electrons produces heat and as the filament gets hotter it glows The whole apparatus is encased in a glass bulb from which the air has been removed By creating this vacuum environment the materials in the filament are unable to chemically react with the surrounding air and break down The heat itself though causes the filament to deteriorate and most of the early incandescent lamps lasted only a short time before the filament burned through These early light bulbs were novel interesting things to look at but they weren't very practical No one could read a book or mend a shirt or do anything else useful in the few minutes some of the lamps provided light The ones that did last longer were expensive to manufacture and distribute Edison knew he had to find a way to make a working light bulb that would last considerably longer while also staying affordable His first task was to create efficient vacuum 9

How the Light Bulb Changed History — page 5 — technology that would preserve the materials in the bulb The next task was to identify a good filament During his first year of research Edison focused on platinum and learned it was not the best choice Edison came to believe the ideal filament could be made of carbon the primary element in living things because carbon could withstand the high heat generated by incandescence He carbonized various materials burning them until all that remained was the carbon itself and then shot an A CO2 electric current through each one Nothing stood out Some materials burned longer than others but nothing burned long enough Edison was more than a year into his experiments when his team tried a simple substance on October 22 1879 It had been in his house the whole time cotton thread The filament glowed and then it kept glowing Hour after hour after hour the carbonized cotton thread stayed lit Eventually what put out the A replica of Edison s incandescent lamp the first practical light bulb 10

How the Light Bulb Changed History — page 6 — light bulb was not fizzling filament but the bulb breaking By then it a had been lit more than 14 hours Two months later Edison was ready to unveil his new invention Shortly after Christmas and into the new year he gave demonstrations of his light bulb for reporters and the public He may have underestimated how much time it would take but he had succeeded in his goal to improve the light bulb CHOOSING CARBON With its resistance to high temperatures carbon seemed ideal for making a light bulb filament Plus it was readily available because it is a fundamental ingredient in plant life The team at Menlo Park believed filaments needed to be twisted and formed into spirals so a longer length of material could fit into a bulb They thought the shape would be more energy efficient by keeping more heat in the spiral But carbon was fragile and it was difficult to form these carbonized materials into spirals Edison s team experimented with straight lengths of carbon These carbon wires demonstrated a naturally high resistance and were stable within the vacuum lamp This simpler design proved successful in creating a working bulb The lamps Edison presented used cardboard filaments They were cheap but not optimal in terms of life The cotton thread had shown Edison carbon could work in his bulb Next he needed to find a more stable long lasting carbon material Simply Light Over time Edison steadily bettered his bulb Cardboard was an improvement lengthening the glow time to 100 hours Eventually 11

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