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Foolishly trying to fish a burning piece of bread from a toaster with a metal butter knife, a man comes into contact with 120-V AC. He does not even feel it since, luckily, he is wearing rubber-soled shoes. What is the minimum resistance of the path the current follows through the person?
Question by OpenStax is licensed under CC BY 4.0.
Final Answer

$120 \textrm{ k}\Omega$

Solution Video

OpenStax College Physics Solution, Chapter 20, Problem 89 (Problems & Exercises) (0:54)

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Video Transcript

This is College Physics Answers with Shaun Dychko. We're going to figure out the minimum resistance of this person's rubber-soled shoes by dividing both sides by current here in Ohm's Law. We get <i>R</i> equals <i>V</i> over <i>I</i>. Now we know the voltage is 120 volts and we also know the current because we'll take -- this is the smallest current that a person could perceive flowing through their body. Currents greater than this can become dangerous and currents less than this don't matter at all, you don't even notice them. This is the threshold of perception of the current. So we have 120 volts divided by that minimum that one can sense, one times ten to the minus three amps. That is 120 kilo ohms is the minimum resistance to avoid getting hurt or even sensing the current.