My Second Essay's First Draft

Josiah Janyszek
Professor Kerr
EN101-23
October 4, 2011

AC and DC

    Hundreds of Thomas Edison’s power stations were being used across the country to supply DC, which was the standard source of power during the late 1800s (“Teacher’s”). Nikola Tesla had arrived in New York when he noticed wires were exposed and hanging low everywhere (“The Current”).  He was shocked to see this and desired to fix it (“The Current”). He knew this was a result of Thomas Edison’s DC system so he asked to work in Edison’s laboratory (“The Current”). Tesla had the idea of using an AC motor, and Edison knew this but decided to hire him anyway (“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 for the invention from Tesla, and an industrial war started as a result of the breakthrough from the patents (“PBS: Tesla - Master of Lightning: War”). Propaganda and demonstrations were being used to defend both AC and DC (“The Current”).  The war would be brought to an end once Westinghouse and Tesla’s DC or Edison and the General Electric Company’s AC won the competition for deciding which one would be used to power the Columbian Exposition in Chicago (“The Current”). Demonstrations for both AC and DC were given, and AC won (“The Current”). However, Tesla decided to show the safety and beauty of AC along with Edison showing DC, and Tesla with his AC came out on top and won the war (“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”). Smooth changes are made when an AC power source of electricity constantly changes amplitude and regularly changes polarity, and these changes never stop repeating in continuations of identical cycles ("What Is Alternating Current?").  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 two different sources (“Direct”). DC electricity traveling through a circuit has the same concept as water flowing through a pipe and requires a battery or DC generator in order to be generated for travel (“Direct”). The electrical charges can only flow through a circuit once voltage, the push that cause 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’s 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 wire within the magnetic field causes the electrons to move in two directions creating AC as a result (“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, create direct current (“What Is Alternating Current (AC)? “).  Even to this day, DC is still produced by batteries as well as being produced by DC generators (“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”). The more current put through the wires results in more heat loss, and the only way to decrease the current yet maintain the same amount of power is to increase the voltage (“Teacher’s”). The more voltage that is applied will cause the power transmission to be more efficient (“Teacher’s”). Although using AC in the transmission system is more efficient, using DC costs less (“Why”). The DC power transmission system requires fifty percent less land and tower that is thirty percent as great as the size of a tower required for AC (“Why”).  Along with the smaller towers and smaller areas of land, the lines also save money since they cost thirty-three percent less since the DC system requires a shorter break-even system (“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 power transmission system can also reach and help in places in which AC cannot such as offshore farms or energy platforms (“Why”). This system is also beneficial for back-to-back transmission since it restricts the spread of cascading disturbances and does not increase short circuit power, and the overhead lines using the DC system also lowers the cost since the lines require narrow transmission corridors (“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 being considered. Even though AC may have 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

"AC or DC? Should We Switch Our Electric Current? : Greentech Media." Green Technology | Cleantech and Renewable Energy News and Analysis. Web. 02 Oct. 2011. http://www.greentechmedia.com/articles/read/ac-or-dc-should-we-switch-our-electric-current/.
"Direct Current (DC) Electricity by Ron Kurtus - Succeed in Understanding Physics: School for Champions." School for Champions: Online Lessons for Those Seeking Success. Web. 03 Oct. 2011. http://www.school-for-champions.com/science/dc.htm.
"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.
"PBS: Tesla - Master of Lightning: War of the Currents." PBS: Public Broadcasting Service. Web. 02 Oct. 2011. http://www.pbs.org/tesla/ll/ll_warcur.html.
"Teachers' Domain: AC / DC: What's the Difference?" Teachers' Domain: Home. Web. 02 Oct. 2011. http://www.teachersdomain.org/resource/phy03.sci.phys.mfw.acdc/.
"The American Experience | Edison's Miracle of Light | AC - DC: What's the Difference?" PBS: Public Broadcasting Service. Web. 02 Oct. 2011. http://www.pbs.org/wgbh/amex/edison/sfeature/acdc.html.
"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.
"What Is Alternating Current?" Welcome to Play-Hookey! Web. 03 Oct. 2011. http://www.play-hookey.com/ac_theory/.
"What Is Alternating Current (AC)? : BASIC AC THEORY." All About Circuits : Free Electric Circuits Textbooks. Web. 03 Oct. 2011. http://www.allaboutcircuits.com/vol_2/chpt_1/1.html.
"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.