792_Physics ProblemsTechnical Physics

792_Physics ProblemsTechnical Physics - 132 Direct Current...

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132 Direct Current Circuits Q28.23 So long as you only grab one wire, and you do not touch anything that is grounded, you are safe (see Question 28.11). If the wire breaks, let go! If you continue to hold on to the wire, there will be a large—and rather lethal—potential difference between the wire and your feet when you hit the ground. Since your body can have a resistance of about 10 k , the current in you would be sufficient to ruin your day. Q28.24 Both 120-V and 240-V lines can deliver injurious or lethal shocks, but there is a somewhat better safety factor with the lower voltage. To say it a different way, the insulation on a 120-V line can be thinner. On the other hand, a 240-V device carries less current to operate a device with the same power, so the conductor itself can be thinner. Finally, as we will see in Chapter 33, the last step- down transformer can also be somewhat smaller if it has to go down only to 240 volts from the high voltage of the main power line.
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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 .

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