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Could nothing happen when fork in socket

  1. Aug 5, 2017 #1
    Hi
    right now I do not have school but I was thinking about what my chemistry teacher said last year.
    he was telling us about electrons and how they move from negative to positive. he said something along the line of: lets you would put a fork in a wall socket and by chance you first hit the positive side nothing happens and when you hit the negative side the system is closed and still nothing will happen because only now the electrons will start moving in an already completed track.

    sometimes when I correct one of my science teachers they tell me that they do not always tell the whole story or lie to make it easier for the class to understand the general line.

    so I was thinking is this a real possibility?
     
  2. jcsd
  3. Aug 5, 2017 #2

    Filip Larsen

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    Gold Member

    Putting forks in AC wall socket can potential lead to fatal accidents so never do this and never play around with high voltage (say, above 24V) electric circuits without being certified to do so. If you touch any electric conducting part of a high voltage system your body (or parts thereof) may be included in the electrical system conducting power to the ground or worse. Modern installation have some protection against ground faults [1], but even with this there is potential for fatal electric shock when your body is used as an electrical short circuit to ground.

    Also, the words from your chemistry teacher implies he do not know how AC wall sockets "works". Normally such sockets have a ground and a lead wire (see [2] and [3] for US), not a positive or negative wire. The lead wire is an obvious shock hazard, but the neutral wire can also provide shock in faulty installations or in other special situations. Even the ground wire (for sockets that have this) can provide electrical shock if the installation is sufficiently old or messed up.

    All that said, it is true that in order to get an electrical shock your body or parts of it must act as an electrical conduct between a high and low electrical potential. For instance, birds sitting on high voltage lines are sufficiently small so their body do not act to conduct electrical power. But if they get close to two wires at once they are likely to be rather quickly toasted.

    Note that the "reverse" situation can also be true. For instance, if you walk on a flat ground near where a live high voltage line has dropped to the ground you may think you are safe because there is only one high voltage potential and it is on the ground, but that thinking is wrong. The decrease in electrical potential per distance away from where the wire touch ground is enough to draw fatal power through both your legs when you take a large enough step to get away from the wire.

    So again, in general do not ever think you can "outsmart" electrical circuits. Electricity know much better and faster than you when your body will act as a convenient short circuit.


    [1] https://en.wikipedia.org/wiki/Residual-current_device
    [2] https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets
    [3] https://en.wikipedia.org/wiki/Electrical_wiring_in_North_America
     
  4. Aug 5, 2017 #3
    thank you for your quick and comprehensive reply.

    to begin with, i want to make sure I never intended anything having to do with this question.
    this teacher has a history of making up stories so things tend to fit with our study material. let alone that we (the Netherlands) also use mostly grounded sockets.
    it still is a little bit of a bummer, it could have been one heck of an urban legend.

    once again thank you for the extensive research:bow:
     
  5. Aug 5, 2017 #4

    CWatters

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    1) If a piece of metal touches just the positive side of a battery then nothing will happen because a circuit has not been formed. If the metal is moved so that it touches both the positive and negative then a circuit is formed and current will flow through the metal.

    2) If a piece of metal touches just the live terminal in a socket then nothing will happen because a circuit has not been formed. If the metal is moved so that it touches both the live and neutral then a circuit is formed and current will flow through the metal.

    WARNING: ALL of these situations can be dangerous for different reasons. Do not try this yourself. Mains sockets contain high voltages, so if the metal also touches you by accident current can flow from the power station, through the live terminal, through the metal, through you to the ground/earth and back to the power station forming a circuit. This can kill you. With a small battery the voltage is not usually dangerous. However some batteries can deliver very high currents that can cause metal to get very hot or even explode.

    So I suspect your teacher was trying to explain (badly) that a circuit is needed for current to flow. Make sure you are never part of the circuit!
     
  6. Aug 5, 2017 #5

    fresh_42

    Staff: Mentor

    The question of the OP has been answered. This was done in a very responsible way, stressing the danger that comes along with those [the teacher's] statements, which must not be seen in any way as an appropriate setup for an experiment.
    sums it up pretty well. That is what we invented instruments for. But even those can fail, if they are not designed to handle the values they are applied to. A fork is certainly one of the worst instruments.

    So I'll close this thread before less responsible people can chime in. Or as my Latin teacher used to say: Better five minutes a coward than a brave dead for the entire life.
     
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