Electrical Lay Person.

Discussion in 'Homework Help' started by vol2011, Jun 24, 2011.

  1. vol2011

    Thread Starter New Member

    Jun 24, 2011
    2
    0
    Good day to all and may I appologies up front for my lack of knowledge in all that is electrical, but I am in need of some advice regarding what may well be bread and butter basics to you chaps, here goes:

    Situation 1. Man makes contact with a 240 volt circuit where the resistance of the person and the floor they are stood on is 4000 ohms.

    Situation 2. Man makes contact with 110 volt circuit where the resistance of the person and the floor they are stood on is 4000 ohms.

    Which of the two situations is more likely to lead to a more serious electric shock? and why? and what effect did Ohm's law have on the outcome?

    I can hear you lot sniggering now!!:D but I have surfed the net for clues but I just cannot grasp it!! any help appreciated.

    Regards,

    Peter.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    951
    Voltage divided by resistance equals current.

    The larger the voltage, with a constant resistance, the larger the current.
     
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  3. victorhugo289

    Member

    Aug 24, 2010
    49
    3
    In the first case 60 milli-amps would flow through the person, in the second case 27.5 milli-amps.
    Either case, he would be dead, or almost!
    According to the shock hazard table 23mA of Alternating current will be enough to cause severe pain and difficulty breathing.

    Resistance in the body is highly changing, if you press your finger against a live wire you get shocked more, if you don't press it too hard you don't.

    Having 1 mega-ohm of resistance (hopefully)in your body would probably give you time to react and pull your finger out of the source with a slight pain, but electricity could push you and make you stuck to the source, that's dangerous.

    Anyway, that's how I see it.
     
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  4. WellGrounded

    Member

    Jun 19, 2011
    32
    2
    vol2011,

    The replies are partially correct.

    When dealing with higher voltages there is another factor that comes into effect. When shocked by a high voltage the initial contact voltage can cause the person to rapidly disconnect from the high voltage source by jerking the hand(or aqrm) backwards. The aftereffect of even a short contact(less than 1/10 of a second) can be intermittent muscle twitching afterward. I don't have the electrical chart in front of me but the critical voltage seems to be 600 Volts where the muscle seems to spasm and "lock" the person to the voltage source, then eventually kill(maim) them them through continuous milliamperes being conducted through the body and disrupting the heart rhythm. Super high voltages (1,000s) repel the person from the contact point, but not without the after efffects.

    Please note that electroacupuncture(which I have had) deals with microampereres to trigger body responses. (An aside - Yes it works!)

    The initial current flow into the body will be based on the "skin resistance" which is a combination of dry skin resistance and "wet"(perspiration) contact and the contact surface area.

    I hope this helps.

    Danny
     
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  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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  6. vol2011

    Thread Starter New Member

    Jun 24, 2011
    2
    0
    Electrics / Electronics not my back ground, but never too old to learn mi thinks, thank you to all for your time and efforts, by jove I think I've got it!!

    Regards,
     
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