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Potential Difference and electric shock

  1. Sep 6, 2015 #1
    Electricity travels from higher potential to lower potential then why don't we get an electric shock while holding aa high potential wire without touching the earth ( we are also at lower potential)
     
    Last edited: Sep 6, 2015
  2. jcsd
  3. Sep 6, 2015 #2
    Because while not touching the earth, you are floating in the air which it is an insulator thus you have an open circuit.
     
  4. Sep 6, 2015 #3
    Isn't our body's potential at lower level than the high potential wire to make the electrons flow from there inside us
     
  5. Sep 6, 2015 #4
    Yes, but you need a closed circuit to make the current flow
     
  6. Sep 6, 2015 #5
    But when we connect an object to any one of the terminals of a battery , it gains the same potential (maybe due to static electricity), we should at least feel some sort of shock
     
  7. Sep 6, 2015 #6
    You have to connect a circuit in order to detect the potential. For example if you connect a capacitor to only 1 terminal of a battery it will not charge.
     
    Last edited: Sep 6, 2015
  8. Sep 6, 2015 #7
    You are instantly at the same potential as the hot wire you have touched, but as their is no connection by your body to a lower potential no current flows and therefore you feel no shock.
     
  9. Sep 6, 2015 #8

    davenn

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    yes it is

    careful with those answers, ... they are not correct ..... there is an initial flow of current into you till you gain the same potential as the wire you touch. Depending on the voltages involved will be what determines if you feel the zap or not

    watching helicopter guys working on EHT power lines is a classic example of this. The helicopter isn't grounded, yet there is a large flow of current between the helicopter and worker as they come up to the potential of the power line
    see this video......





    Dave
     
  10. Sep 6, 2015 #9

    davenn

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    The problem here is that with smaller voltages around 40V or less, there is not enough voltage to overcome the body's skin (dry) resistance and allow a current to flow

    hence you don't feel anything from a say 12V car battery
    wet skin is a different matter and maybe you have briefly touched a small PP3 9V battery to your tongue and felt the sharp tingling ??


    Dave
     
  11. Sep 7, 2015 #10

    sophiecentaur

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    We can and do. When we connect our(isolated)selves to ANY potential not at our own, a charge will flow until we are at that potential. IF the potential is high enough (different enough from where we started) there will be enough charge flowing to give us a shock. For lower potentials, the charge will be small and the current flowing onto us will be very small because I = V/R. The charge that flows onto us will be proportional to the Capacitance of our bodies (as in charging any capacitor). The capacitance of a human body is around 100pF and the contact resistance can be high or low depending on how moist our skin is or if we're standing in a bucket of salt water!. 100pF is pretty low in terms of circuit components - compare it with a super capacitor with 1F capacitance or one of 1000μF in a hi fi amplifier. We just don't take much charge on board except from a very high potential object.
    The way our body reacts to 'shocks' in general is very complicated and the effects can be very variable.
    Having played with high voltages (safely engineered ones, I must add) I can tell you that touching a charged Van Der Graaff ball or a Tesla Coil is much less unpleasant if you make actual contact via a metal rod. This is because the shock is particularly noticeable when the area of contact is small. Holding a metal rod will spread the contact all over your palm and you may not feel a thing,
     
  12. Sep 7, 2015 #11

    sophiecentaur

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    It's all proportional. Not 'no current' - just a small current.
     
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