07_AC_electricity

001 ohms per meter times 200 km 0001 m 2 105 m 20

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Unformatted text preview: timate resistance of power lines: say 0.001 Ohms per meter, times 200 km = 0.001 /m 2 105 m = 20 Ohms 20 /m 10 We can figure out the current required by a single bulb using P = VI so I = P /V = V I so 120 Watts/12 Volts = 10 Amps (!) 2R = 10 2 20 = 2,000 Watts!! Power in transmission line is P = I 10 20 “Efficiency” is = 120 Watts/4120 Watts = 0.3%!!! Efficiency” 120 What could we change in order to do better? Winter 2008 2 3 – P = V I so less current demands higher voltage • Solution is high voltage transmission – Repeating the above calculation with 12,000 Volts deliv...
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