132 Direct Current CircuitsQ28.23So 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 alarge—and rather lethal—potential difference between the wire and your feet when you hit theground. Since your body can have a resistance of about 10 kΩ, the current in you would be sufficientto ruin your day.Q28.24Both 120-V and 240-V lines can deliver injurious or lethal shocks, but there is a somewhat bettersafety factor with the lower voltage. To say it a different way, the insulation on a 120-V line can bethinner. On the other hand, a 240-V device carries less current to operate a device with the samepower, 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 highvoltage 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 .