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Flow of elecltrons ?

  1. Aug 6, 2010 #1
    before i say this i am not going to try this , would you be shocked if you stuck a fork in a 120 volt 60Hz outlet . cause after watching walter lewin short out a car battery by holding
    the wrench in his hand i don't think so . electricity takes the path of least Resistance
    so wouldn't it just want to flow straight across to the other part of the outlet and not want to flow through your hand. I mean unless there is a potential difference between the fork and the ground . But i did a little test with a volt meter i hooked up a circuit with a light bulb in it and the checked the potential difference between the copper wire in the circuit and the ground and the voltmeter was zero . And yes this would pop the breaker and the fork would heat up until the 15amp breaker pops but would you get shocked ?
     
    Last edited: Aug 6, 2010
  2. jcsd
  3. Aug 6, 2010 #2
    Unless the resistance of your hand/neuronal system is less than that of the fork, I guess.
     
  4. Aug 7, 2010 #3
    seems very unlikely , i checked that with an ohm meter . I checked the Resistance of my body from my left arm to my right arm and it was way more resistive than a metal fork .
    When people get shocked are they completing the circuit with their body so it flows through them . But then i was thinking about an electric fence for cattle , when you touch the fence you get shocked so why is their a potential difference between the fence wire and the soil .
     
  5. Aug 7, 2010 #4

    alxm

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    Your body is more resistive, yes. But on the other hand you only need 100 milliamps to kill you, which is a small fraction of a 15A current.
     
  6. Aug 7, 2010 #5
    ok thanks for your answer alxm it cleared it up for me , i just wanted to make sure i understood the flow of electricity more so, than if you would die or not .
     
  7. Aug 7, 2010 #6
    Electricity does not JUST flow along a path of least resistance.
    There is still some current flowing in the higher resistance branch, unless the resistance is too high.
     
  8. Aug 7, 2010 #7

    Integral

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    As Pallidin said, electricity takes every path available. Body resistance is variable, it depends a lot on skin moisture and the surface you are standing on. If you are in a tub of bath water and attempted this the results may not be pleasant. Standing on a well insulated pad you may not feel anything.

    What ever else happens you may well earn a good burn, the fork will get hot.
     
  9. Aug 7, 2010 #8
    so will a wrench if you use it to connect the terminals of a car battery. I know this from first hand experience.

    My physics professor's explanation as to why I didn't get shocked was that the voltage supplied by the battery wasn't high enough to push the current through my body. I could grab both ends of the terminal with my bare hands and all I would feel was a slight tingling as the current tried and failed to pass through my body.
     
  10. Aug 7, 2010 #9

    Integral

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    That slight tingling was current passing through your body, just a very small current. No matter how small the voltage or how large the resistance SOME current flows.

    According to Ohm's law

    [tex] I = \frac E R [/tex]

    I have seen body resistance as low as 50KOhm, (it is commonly much greater) for nice numbers with 12V call it 60K. From Ohm's law we find the current to be .2ma This is barely detectable and way below dangerous levels.
     
  11. Aug 9, 2010 #10
    It's not all or nothing, taking "the" path of least resistance and ignoring any other path. A portion takes each path, in inverse proportion to their resistances. Look up rules for resisters in parallel. So, the direct metal path is very low resistance, and the path through your hand is larger, but you can calculate what percentage will take that branch.

    You'll also find AC effects that complicate matters.

    Personally, I've accidentally completed a circuit while working on a live outlet. I was wearing gloves, as a precaution. It took a bite out of my pliers, and I suppose the flying metal might be more of a hazard than the direct electrocution.
     
  12. Aug 9, 2010 #11
    The bathtub experiment would probably be fatal. People do get shocked from 115 volts and usually it is very unpleasant but not lasting. In an outlet one lead is connected to 115 volts and the other to ground. Thus if the fork first connected to ground there would be no current through you unless in pulling away you kept the 115 connection and broke the ground connection. In this case you would need to be grounded to get shocked.
     
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