My Second Essay's Second Draft

Josiah Janyszek
Professor Kerr
EN101-23
October 5, 2011

AC and DC

    Thomas Edison had over one hundred power stations across many residential areas supplying DC, which was the standard source of power during the late 1800s (“Teacher’s”). Nikola Tesla, who had just arrived in New York, noticed wires were being exposed and hanging around everywhere (“The Current”). Tesla, who knew this was a result of Edison’s DC system, desired to fix the wires being exposed (“The Current”). Edison allowed Tesla to work in his laboratory since Tesla had asked to be given a chance to use an AC motor in order to make the system better (“The Current”). George Westinghouse, a Pittsburgh industrialist, heard about Tesla’s invention and thought he could use this invention to solve problems with long-distance power transmission (“PBS: Tesla - Master of Lightning: War”). Westinghouse bought the patents from Tesla, and an industrial war started as a result of the breakthrough from the patents (“PBS: Tesla - Master of Lightning: War”). After many demonstrations and propaganda war, the ‘War of the Currents’ was ended once Westinghouse and Tesla proved their AC system was better than Edison’s DC system at the Columbian Exposition (“The Current”). The direction of current flow, the generation, and advantages of being used in the transmission system cause AC and DC to differ greatly yet still be needed.
    The direction of the current flow of AC differs from that of DC. DC, which stands for direct current, flows in only one direction whereas AC, which stands for alternating current, can flow in more than one direction (“Teacher’s”). The direction AC travels can be change many times every second (“Teacher’s”). When AC changes the direction it travels, it also changes between positive and negative values (“PBS: Tesla - Master of Lightning: Understanding”). A constant voltage being expelled from a source until the source has been depleted most likely means that the source is DC ("What Is Alternating Current?" ). DC electricity travels from a negative source to a positive source (“Direct”). A DC circuit, which includes a batter or other source of electrical energy and a conducting wire that travels from the positive end to the negative end, is needed for the electrons to travel between the two different sources (“Direct”). The electrical charges can only flow through a circuit once voltage, the push that causes the charges to flow, has been applied (“Teacher’s”). Before AC and DC can travel through a circuit, they need to be generated.
    AC and DC are generated in different ways and from two different generators. Inside of an AC generator, magnets create a magnetic field which has an armature (a wire that is wrapped to form several coils) moving through or spinning within it (“The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?: Inside”). The movement created by the armature or any sort of spinning wire within the magnetic field causes the electrons to move in two directions creating AC (“The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?: Inside”). DC generators use a brush to make contact with the coils which, in turn, creates direct current (“What Is Alternating Current (AC)? “).  Batteries are also used to produce DC electricity (“Teacher’s”). Along with flowing in different directions and being generated in different ways, AC and DC also have different advantages in the transmission system.
    The efficiency and cost of AC and DC traveling through the transmission system allow them both to have an advantage over the other. Transformers within the transmission system can easily ‘step up’ or ‘step down’ AC allowing it to travel at high voltages and used at a lower voltage ("The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?: Inside “). Because AC is constantly changing direction, the transformers can change the level of voltage at which the AC is traveling through (“Teacher’s”). When DC was originally used in the transmission system, it would lose its power after traveling for about a mile (“The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?“). A lot of the produced power was lost as heat due to the amount of resistance it met while traveling through the wires (“Teacher’s”). Heat loss causes a lot of inefficiency in electrical equipment (“Teacher’s”). Although using AC in the transmission system is more efficient, using DC costs less (“Why”). The DC power transmission system requires half as much land, a smaller tower, and cheaper wires (“Why”). DC also has a higher controllability, operators on both sides to control the load flow, and an inherent overload capability whereas AC is uncontrolled, relies on the network, and has a very low overload capability (“Why”).  The DC system can be used underground enabling it to reach locations that are hard, if not impossible, for the AC system to reach (“Why”). Nevertheless, AC is still the main standard for transmission (“AC”).
    AC and DC transmission systems have advantages the other does not, are produced by different generators in different ways, and flow in different directions. AC is used the most in the transmission system, yet most devices run on DC (“AC”). AC has an advantage over DC regarding circuits, generators, and efficiency in the transmission system, but DC receives the advantage over AC when the size of the transmission tower and the cost of the land and wires are considered. Even though AC has more advantages over DC, neither one can do all of the work. They both serve different purposes and are both needed for electricity.

Works Cited

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"PBS: Tesla - Master of Lightning: Understanding Electricity - AC and DC." PBS: Public Broadcasting Service. Web. 02 Oct. 2011. http://www.pbs.org/tesla/ins/ins_acdc.html.
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"The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?: Inside Generator." PBS: Public Broadcasting Service. Web. 02 Oct. 2011. http://www.pbs.org/wgbh/amex/edison/sfeature/acdc_insideacgenerator.html.
"The Current War." Classroom Web Page Information. Web. 03 Oct. 2011. http://staff.fcps.net/rroyster/war.htm.
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"Why Are Utilities Switching to High Voltage DC Transmission over Long Lines?" Find Science & Technology Articles, Education Lesson Plans, Tech Tips, Computer Hardware & Software Reviews, News and More at Bright Hub. Web. 02 Oct. 2011. http://www.brighthub.com/engineering/electrical/articles/81644.aspx.