nagle_phys2020_fa07_lecture20

nagle_phys2020_fa07_lecture20 - Clicker Question Reading...

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1 70 Clicker Question Is equation (D) correct? A) D is correct B) D is incorrect 71 • Reading for this week: Chapter 19.4-19.5 and 19.7-19.8 • Reading for next week: Chapter 20 (Magnetism) + advanced notes posted • Note that Exam #2 is approaching – October 23 (Tuesday 7:30-9:15 pm in Duane G-1B30) • CAPA #8 is now available. This material will be included on the second examination. 72 Problem looks straightforward. Power = V 2 /R Thus, with R = 2.23 Ohms, if Power is delivered at higher Voltage, then more Power is wasted as heat in the transmission lines. But it is not! 73 If that were true, then why do we transmit electricity over long distances at very very high Voltage? Maybe the experts don’t know what they are doing! Or maybe there is something more subtle to this problem. 74 V A =2000 Volts V B =1900 Volts i=100 Amps Power delivered = V i = # Watts Which Voltage? V B . Power as heat in the line = V i. Which Voltage? Δ V = 100 V But easier to solve P = i 2 R Power Station Town If we lose less energy in heat at higher Voltage, why
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nagle_phys2020_fa07_lecture20 - Clicker Question Reading...

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