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The Genius of Thomas Edison ___________________________________ A Look at His Inventions and the Man He Was Figure #1 Jeffrey D. Carbine John W. Davis Jose C. Estrada Bradley G. Pettet Physics 1010 Salt Lake Community College The Genius of Thomas Edison | 2 Abstract Thomas Edison did not so much invent as he did improve existing systems and products to make them more efficient and practical for everyday use. With these products and systems, he started multiple businesses that made him very wealthy and powerful. His influence is still felt today from all of this work. The Genius of Thomas Edison | 3 Introduction He profited greatly from his inventions such as DC generators and transformers, parallel circuits, the phonograph, and the reinvention of the light bulb. These inventions and innovations are a part of everyday life and are, to this day, used on a regular basis. They affect our economy and our lifestyle and we have grown very dependent on them. This paper expounds on these inventions and the physics behind them. Edison and AC/DC Power Thomas Edison was a very successful businessman and inventor that had over 1,000 patents to his name. He built an empire of reputation and businesses that helped him invent and develop these many devices and concepts. Multiple people challenge his ideas and disagree with him, Nikola Tesla was a person that Edison actually hired to work for him and eventually resigned because of disagreements he had with Edison. George Westinghouse was an engineer and entrepreneur who backed the development of the AC power network and clashed with Edison and his DC system. DC electrical current has its benefits for a variety of things, and Thomas Edison was a huge supporter for this standard and succeeded in commercializing it to an extent. AC electrical current eventually became the standard of the world for electrical distribution. It was adopted by the community for three main reasons: It can easily be stepped up to high voltages for long-distance transmission with small heat losses then stepped down to convenient voltages where the energy is consumed, the distribution transformers are much cheaper The Genius of Thomas Edison | 4 for the mass population, and the generating plants could be made much larger to serve a much larger area of population. Electrical current is the flow of electric charge across different substances, usually metal wires. The electrons, which hold a negative charge in the atoms that make up a metal wire, are able to move easily from atom to atom. Whereas the protons, which hold a positive charge, stay in their respective places inside the nuclei of the atoms. The electrons that are able to move freely across the wire are called conduction electrons. The rate at which the charge flows from one side of the connection to the other side is measured in amperes or amps. Voltage is the measurement of the potential difference of the opposite sides of the connection and is measured in volts. These values can be simply described in the design of a common automobile. The battery that stores electrical energy is used to turn over the engine to help it start and run off the energy created from the gasoline burning. The battery usually holds a charge of around 12 volts, which is the measurement of the potential difference of the positive and negative connections from the battery. It also needs around 300 amps of current to have enough power to turn the DC electric starter motor that turns the engine crank over to start the car. A Direct Current (DC) electric system is a fairly simple system whereas the electronic flow of electrons only happens in one direction like it is show in the picture to the left. They flow from the negatively charged side of the power source to the positively charged side. This allows the voltage Figure #2 The Genius of Thomas Edison | 5 to stay at a constant value thus simplifying the system. Thomas Edison was a huge supporter for the DC Current, most of his early inventions and patents used DC currents. One of Edison’s most famous innovations, the light bulb, was more of a practical revision of an invention that many people before him had already invented. It worked extremely well with direct current. When Edison was making the light bulb commercially available to the public, there wasn’t another product out there that used nearly as much electricity as the light bulb did. For that reason DC current was accepted by the community on a relatively large scale. There was no efficient, low-cost technology that could reduce a high voltage needed for long distance transmission down to a steady 100 volts that was needed to power the mass produced light bulbs that Edison developed and sold. Generating plants that supplied electricity to the homes and businesses had to be within a mile or so because the voltage dropped too much over long distances. Edison profited largely by this, selling many generating plants that were feeding heavy distribution conductors. Alternating Current (AC) electric power is a system where the current flows in one direction until the load gets drawn down to Figure #3 zero. Then, because of the polarity switching by the source of power, it switches and flows in the opposite direction like it is shown in the picture above. This action of the current polarity changing direction happens in a very uniform way and endlessly continues like it is shown in the picture to the right. This switching is a measurable property that is called hertz. Hertz (Hz) is the measurement of cycles per second. In one cycle, the current travels in one direction, then The Genius of Thomas Edison | 6 switches and travels in the opposite direction. AC power usually is operated at a rate of 60 Hz in North America. DC power cannot be measured in Hz because it does not switch polarities and therefore has no measureable cycle, like shown in the picture Figure #4 to the left. AC power is in reality harder to handle and harder to harness for practical uses (motors, light bulbs, etc.) So why use AC instead of DC? Unfortunately for Edison, the answer ultimately came down to cost. DC worked well with small components like a light bulb and small DC motors, both of which he designed and sold through his company Edison General Electric (later merged with Thomson-Houston Electric Company to form General Electric that is now one of the largest corporations in the world). DC was a terrible choice though for transmitting electricity long distances both within and between cities and towns. It had to use large spinning rotary converters which were very expensive, inefficient, and required much maintenance. AC power can easily be converted to much higher voltages for long distance transmission by using a simple transformer that had no moving parts. This allowed the electric companies to build generating plants far away from the cities and mass populations. It also allowed them to build larger scale generating plants that could cover a much larger number of people and buildings. Not only was it much cheaper and easier to generate massive amounts of volts needed for long distance transmission, but it was much easier to convert that high voltage down to a safe voltage (120 volts) for the wiring in a home or The Genius of Thomas Edison | 7 business. Transformers, like the one that is pictured to the left, that convert the high voltage down to 120 volts are simple non-moving devices that require little to no maintenance and are relatively cheap compared to the expensive transformers needed convert DC power. Nikola Tesla was an inventor and electrical engineer that was hired by Edison in 1882 to help Figure #5 improve the many electrical components that Edison and his company were designing. Tesla was young and ambitious and just 3 years after working for Edison, he claimed that he could redesign his motors and generators to make significant improvements in efficiency and economy. To that statement, Edison said, “There’s fifty thousand dollars in it for you – if you can do it.” 1 He took that bet literally and accomplished the task several months later. When he went to Edison to demand pay, Edison claimed that it was joke and offered him a raise. Tesla refused it and left the company. Two years later, he started the Tesla Electric Company, which focused on developing AC motors and generators. He went on to acquire many patents related to AC electricity. He sold many of them to George Westinghouse who was in a so-called ‘War of Currents’ with Edison, who was stubborn to change his systems from DC to AC. Thomas Edison and his company were heavily invested in the DC system, because of this news of a new, more efficient AC system, it was difficult for them to see the community catch on and eventually stop buying their products. He The Genius of Thomas Edison | 8 started a campaign that failed to discourage the use of AC using propaganda to try to convince the public that AC was much more dangerous. To demonstrate this, he helped develop the first electric execution chair that uses AC power for murder convict, William Kemmler. They miscalculated the first shock which did not kill him, and it eventually took them 8 minutes to execute him. Witnesses said that it was cruel and they would’ve been better off with an axe. They also failed with their efforts to lobby against the use of AC in the state legislatures, by trying to pass a law that would limit the voltage allowed over power lines to 800 volts, which would've hampered the AC system greatly. DC power was widely used well into the 1960’s in the United States, but General Electric eventually adopted the AC standard and it continues today as the world’s standard for mass transmission of electricity. Edison’s Influence in Circuits As mentioned before, an electrical circuit is a system through which an electrical current flows. This current can be used to transfer the needed voltage to an electrical device in order to make it work. There are two basic ways to connect circuit components, and those are series circuits and parallel circuits. Thomas Edison was responsible for the invention of the latter, the parallel circuit. The parallel circuit had many advantages over the common, series circuit. An example of a series circuit is as follows: A circuit must start and end with a voltage source ( ), such as a battery, in order to work. A series circuit (or current-coupled circuit) sends the current through every single component on the system. Since there is only one path in The Genius of Thomas Edison | 9 the circuit for current to flow, that means that every component carries the same current. This also means, however, if one component fails in the system, the current will be interrupted and the system will stop operating, much like the bulbs on a strand of older Christmas-tree lights. The symbol ( ) in the circuit diagram to the right represents a resistor. A resistor is anything in a circuit that required power to operate, such as a lightbulb or a Figure #6 television set. The total resistance (R) of resistors in a series is equal to the sum of their individual resistances. Resistance is important to consider, because the higher the resistance, the more voltage is required. The resistance of a series circuit can be written as: Rtotal = R1 + R2 + … Rn This means that the sum of all resistance througout the system will determine how much voltage you will have to provide in order to adecuately deliver enough power to each resistor. Thomas Edison was responsible for the invention of the parallel circuit, which solved many inherent problems with the series circuit. The diagram below maps out a simple parallel circuit, and you can see that it provides more than one path for the current to follow. Figure #7 The Genius of Thomas Edison | 10 This allows many resistors to be placed independently one from another in the circuit. Which makes it possible that if one of the resistors fail in the circuit, the other ones will remain active. This is why that when one light bulb burns out in your front room, the whole room doesn’t go dark. However, this is not the only advantage to the parallel circuit. The total resistance in a parallel circuit is very different from that in a series circuit. In a series circuit, the total resistance was equal to the sum amount of each induvidual resistor. In a parallel circuit, the resistance is found through the following equation: 1/Rtotal = 1/R1 + 1/R2 + … 1/Rn Resistance is represented by the Omega (Ω) symbol, which stands for ohms. Simply stated, the greater the ohms in a circuit, the greater the voltage needed. For example, in a series circuit with varying resistors of 10, 20, 30, and 40 Ω, total resistance would be be as follows: Rtotal = 10 + 20 + 30 + 40 = 100 Ω In a parallel circuit with the exact same resistors, the equation to find total resistance would be as follows: 1/Rtotal = 1/10 + 1/20 + 1/30 + 1/40 1/Rtotal = .1 + .05 + .033 + .025 = .208 Rtotal = 4.80 Ω This means that you can power all resistors adecautely in a parallel circuit with far less voltage than a series circuit. This effects you daily because the less The Genius of Thomas Edison | 11 voltage that is required, the less you will have to pay when your electric bill shows up at the end of the month. These types of circuits are found everywhere to this day, and proved to be quite useful when paired with the rennovation of the light bulb that Edison is so famous for. Edison’s Re-invention In Menlo Park, New Jersey between the period of 1878 to 1880 Edison along with some associates worked on about three thousand different ideas to develop an efficient incandescent lamp. Incandescent lamps function by using electricity to heat a small strip of material (filament) until it gets hot enough that it glows. Many other inventors had tried to perfect incandescent lamps by making them smaller and weaker than the existing arc lamps were, which were just too bright to be used for small spaces such as rooms and such. Contrary to popular belief, Edison did not invent the light bulb but rather just improved the already existing Arc lamps to be more compact and suitable for smaller spaces. The basic design that Edison developed for this incandescent lamp was a simple one. It consisted of a filament housed in a glass bulb. As he had to try it out so many times, Edison had his own glass blowing shed in the back of his home where the bulbs for his experiments were carefully blown and shaped for the tests. The goal that Edison was trying to reach was that of creating a high resistance system that required a lot less electrical power than the currently existing arc lamps. This would allow for the making of smaller bulbs that could and would be used as a light form inside of homes and places of that size. The Genius of Thomas Edison | 12 After all his trials, errors, and time put in, finally by January of 1879 Edison had finished building his first successful high resistance incandescent electric light structure, as seen in the picture to the right. The way that this worked was by allowing an electric current to go through a filament that was constructed out of platinum. This filament was mounted Figure #8 inside of the glass bulbs mentioned earlier. The glass bulb's purpose was to delay the time that it took the filament to melt by absorbing its heat energy. With this first design Edison's bulb still only burned for a few hours before the filament melted and burned out. This was frustrating to him, and his patience was put to the test. His response to all this failure was illustrated in a statement he was quoted saying, "I am not discouraged, because every wrong attempt discarded is another step forward." So with all that persistence that he had acquired years prior in his lab at home from all his previous trials and errors he was able to continue to try out different products and materials for the filament. Literally thousands upon thousands of different materials were tested in place of the originally used platinum filament. It was his attitude that drove him to keep trying after many failed attempts. At one point he even thought about using tungsten for the filament. Tungsten is what we use in our light bulbs now a days. He was, The Genius of Thomas Edison | 13 however, not able to use tungsten due to the unavailability to the proper tools to work with it at that time. I love how positive he was towards his project. With all this failure, I would find myself discouraged but he rather said, "I have not failed, I've just found 10,000 ways that won't work" "Many of life's failures are men who did not realize how close they were to success when they gave up." It was words like these that ran through his mind that pushed him forward to greater discoveries. Edison went on to test out more filaments out of vegetation, such as bamboo and all sorts of other vegetation and trees. He would make the filaments out of the material and then carbonize them. He made one out of a cotton thread that burned for about fifteen hours but it did so with a very dim glow. He persisted with test after test that would burn longer then the last. In the end he tested over 6,000 vegetation made filaments. Edison ended up patenting his lamp under the US Patent #223,898. Even though Edison's main focus was to find the best possible material to use for a long lasting filament, he also ended up inventing seven system elements that were critical to the practical application of electric lights as an alternative to the gas lights that were prevalent in that day.2 The Phonograph Edison’s invention of the phonograph begun with his curiosity to record sound and have it play back. He played around with the inventions of the telegraph and telephone. Thomas Edison used something similar to what the phonograph has now. He used a diaphragm and a stylus, to try and record sound The Genius of Thomas Edison | 14 on paper using the telegraph to imprint dots. Later, he decided to combine the two and make a machine to record sound and play it back. He proved sound could be recorded when he spoke into his new machine and it indented on the paper, but only static was heard when he attempted to play it back. Finally Thomas Edison did it! In November of 1877, Thomas Edison announced his invention of the phonograph. The first words Edison successfully played back were “Mary had a little lamb.” 3 The Phonograph is the grand-daddy of all music recording devices today. Without the Phonograph, we wouldn’t see the inventions that make up most of the music recording industry today that came afterwards. Before we see how the Phonograph works, it may help us to better appreciate the Phonograph if we take a closer look at sound. The better we understand how sound works, the more we’ll understand how it’s captured. When an object vibrates, it creates sound. Vibrations set in motion the nearest molecules, transferring energy to the next molecules and so on. This causes waves of motion like the picture to the left portrays. The more energy put into the sound, the higher the Figure #9 volume. Its true for the opposite effect, if you put less energy into the wave, the lower the volume. Within sound waves are two things, known as compressions and rarefactions. Compressions are caused with outward movements of vibration. In compressions, the molecules are closer together. Rarefactions are the opposite, they are vibrations that move inward, causing the molecules to be pulled back The Genius of Thomas Edison | 15 apart like it is shown in the picture to the left. Simply put, sound is waves that travel through a medium. Sound must have a medium to travel through, Figure #10 otherwise no sound is produced. Without a medium, there is nothing for the energy to transfer through. One of the most common mediums sound uses to travel, is air. 4 A good example of this, is talking. We make lots of noise when we talk, and this starts in the throat. Inside the throat is the larynx, and inside the larynx are vocal cords, which are two small pieces of tissue that stretch across the larynx, with an opening between them. When we speak, muscles in our throat tighten and the opening between cords becomes smaller. Air from our lungs proceeds through the tightened cords and a vibration occurs. From this vibration, we get vocal sounds. The tighter the cords, the higher the pitch. The opposite is true as well, when the cords are looser, the lower the pitch.5 When sounds travel, what we’re actually hearing is the effect the vibrations have on air molecules. If you think about the way the ear works, it helps us to understand sound better. Sound travels through our ear canals and to the ear drum. There, the vibrations hit the ear drum and are processed from the ear drum to the brain through electric impulses. What we understand as sound is really the squeezing and stretching of molecules. One of the ways to best demonstrate this is by holding a slinky and moving it back and forth.6 The Genius of Thomas Edison | 16 Now let’s look into how the Phonograph works. The makeup of the phonograph is pretty simple as it is pictured to the left. A horn is connected to a diaphragm, and the diaphragm is likewise connected to a stylus, which presses against a cylinder covered in wax or tin foil. When you speak, sound causes the Figure #11 air to vibrate within the horn and these vibrations travel through the horn down to the diaphragm. This in turn causes the diaphragm to vibrate as well. Turn the handle and the cylinder will start to rotate at a very slow pace. Vibrations then cause the stylus to move up and down slightly with the sound. The stylus pushes into the wax on the cylinder, and makes impressions or grooves. The sound is recorded in those grooves within the wax. The stylus comes in handy when you want to playback the sound. The stylus, which is linked to the diaphragm, rides in the grooves in accordance to the recorded vibrations on the waxed cylinder. It basically traces back over the recorded sound. The vibrations travel back to the diaphragm and into the air within the horn, to reproduce the original sound. Walla! Recorded sound! Thomas Edison’s invention of the phonograph lasted for a good decade, until other inventions and improvements were made on it, including the gramophone , etc. However the Phonograph is still so important to us today, and sometimes we don’t realize it. It literally set the way for recorded music. Almost The Genius of Thomas Edison | 17 everyone who has a phone or computer today has access to music that they can listen to instantly. Artists around the world are constantly making new records and songs. These could not be produced without the foundation of Thomas Edison’s invention of the Phonograph. Conclusion From his tactics in business, to his ideas and practices in engineering, Thomas Edison is a well known figure in history that definitely succeeded in making a name for himself. He was stubborn and patient, smart and innovative, and very successful. He made an immediate and long lasting impact in the field of electricity, telecommunications, sound, electrical lights, and the distribution of electricity. He wowed people in his time with his inventions and profited much from his ability to create and sell products for the consumer and for the commercial corporations. His inventions and concepts that he either created himself or greatly improved upon are still being used in today's society. The Genius of Thomas Edison | 18 Bibliography 1 Tesla: Man Out of Time pg. 54 (2001) Margaret Cheney 2 http://www.about.com 3 http://www.personal.psu.edu/jtk187/art2/phonograph.htm 4 http://www.sound-physics.com/Sound/Longitudinal-Wavelength 5 The Physics of Sound: How We Produce Sounds by Tina Marie Diamantini 6 http://www.youtube.com/watch?v=kbmnGj-C4SY Figure Credits #1: http://www.menloparkmuseum.org/files/old-age-thomas-edison-full.jpg #2: http://www.play-hookey.com/ac_theory/fundamentals/images/basic_dc_ circuit_sch.gif #3: http://www.play-hookey.com/ac_theory/fundamentals/images/basic_ac_ circuit_sch.gif #4: http://www.play-hookey.com/ac_theory/fundamentals/images/ac_graph.gif #5: http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Polemountsinglephase-closeup.jpg/220px-Polemount-singlephase-closeup.jpg #6: http://www.school-for-champions.com/science/images/dc_circuits-series.gif #7: http://www.eng.cam.ac.uk/DesignOffice/mdp/electric_web/DC/00083.png #8: http://symonsez.files.wordpress.com/2008/12/edisonbulb.jpg #9: http://www.sound-physics.com/s.gif #10: http://www.sound-physics.com/s.gif #11: http://memory.loc.gov/ammem/edhtml/home.jpg