Chapter 28131Q28.16A wire or cable in a transmission line is thick and made of material with very low resistivity. Onlywhen its length is very large does its resistance become significant. To transmit power over a longdistance it is most efficient to use low current at high voltage, minimizing the IR2power loss in thetransmission line. Alternating current, as opposed to the direct current we study first, can be steppedup in voltage and then down again, with high-efficiency transformers at both ends of the powerline.Q28.17Car headlights are in parallel. If they were in series, both would go out when the filament of onefailed. An important safety factor would be lost.Q28.18Kirchhoff’s junction rule expresses conservation of electric charge. If the total current into a pointwere different from the total current out, then charge would be continuously created or annihilatedat that point.Kirchhoff’s loop rule expresses conservation of energy. For a single-loop circle with two
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .