100CHAPTER 18 Answers to Even Numbered Conceptual Questions 2.4.(a)ii (b)i 6.(a)ii (b)i 8.A short circuit can develop when the last bit of insulation frays away between the two conductors in a lamp cord. Then the two conductors touch each other, opening a low resistance branch in parallel with the lamp. The lamp will immediately go out, carrying no current and presenting no danger. A very large current will be produced in the power source, the house wiring, and the wire in the lamp cord up to and through the short. The circuit breaker will interrupt the circuit quickly but not before considerable heating and sparking is produced in the short-circuit path. 10.A wire or cable in a transmission line is thick and made of material with very low resistivity. Only when its length is very large does its resistance become significant. To transmit power over a long distance it is most efficient to use low current at high voltage, minimizing the power loss in the transmission line.
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Resistor, Electrical resistance, Short circuit, Series and parallel circuits, lamp cord