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Electrocution Question

  1. May 8, 2003 #1
    I am new here (my first post) but I am an atty in Texas and have a claim which deals with a person who was "stuck" to a sumppump that shocked him. I have a few years of college physics, but that was 15 years ago.

    I am preparing questions for the Chiropractor who is treating an electric shock patient (don't ask). The Chiro has made several statment that, based on my (albeit) limited knowledge, do not appear to make sense. Here's what she says (then I have some questions):

    "Mr S's right hand and wrist first touched the pump, followed by his forearm and elbow. He then experienced a strong electric shock. His arm was stuck to the pump by the electric current. He reached over with his left hand and was able to push himself off the pump."

    My Q's:
    I am familiar with the "can't let go" phenomena, but isn't it due to the contraction of the muscles in the hand. A person cannot release the grasp and are thus "stuck." Is there also some kind of "magnetic" effect that would make your elbow stick? If so, how could a person push themself off an electric force with their other hand?

    It is my understanding (correct me if I am wrong - Please) that an electric shock could incapacitate someone and they would be unable to step away from a shocking current, but under that circumstance would they be able to push themself off with there other hand?

    TIA for any info.
  2. jcsd
  3. May 8, 2003 #2
    His arm wouldn't just magically stick to the pump. There would be a contraction of the muscles that occurred which might cause his hand to clamp down on something, but if the pump was too big to grab then it still couldn’t happen. I am reasonably certain that 660 volts will do this, I think that 440 doesn’t do it, and if the pump was running on 110 volts or even 220 then I don’t think there would have been any clamping going on, at least 220 never did this to me.
    I think the comments of the Chiropractor are at best, not well written.
  4. May 8, 2003 #3
    Welcome, bienvenue, Abbington.

    No, there is certainly no type of magnetic force that would cause their arm to stick -- it is all muscle/nerve stuff, like you said. However, if his right arm touched the live part of the part, it is possible that the current (which would flow through that arm and take the most direct path to the ground) would freeze the muscles in that arm and so make him feel like it was stuck, while leaving his other arm working. Then he could have pushd himself away with his other arm, or probably have just stepped away, if he still had control of his leg muscles.

    If he touched an electrically live part of the pump with his other hand, that arm would have conducted current and probably frozen too -- but it seems like the whole pump wasn't live, just part of it, right?
  5. May 8, 2003 #4


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    From the inadequate description, I have to make many assumptions.

    To have current flow, the current must flow from the source (pump) to a grounded conductor, either the neutral wire (unlikely) or nearby metal, wire, or wet surface that is earthed (grounded).

    As only the person’s arm seemed to be affected, I assume the likely ground path was through a bare elbow or a bared shoulder. I further assume that the person was supporting himself by leaning on the shoulder or elbow, else he could have pulled away using the stronger leg muscles aided by body weight.

    Using the other arm was possible as current through that arm would have been much lower as it was a less direct path to ground, or it contacted a part of the motor that was not conductive.

    The motor was either not wired correctly or had a fault, and was not grounded. A motor may not be required to be grounded if it was “double insulated”. If so, barring insulation failure, the person would have had to contact the power wire entering the motor.

    That’s about as far I can take it without more information. My best guess is that the motor was improperly installed, or poorly maintained.

    There are to many variables to “guesstimate” the voltage required to exceed the “let go” threshold, but it could be as low as 30-40vac in laboratory conditions, and would vary among individuals.
  6. May 9, 2003 #5
    I was just thinking about something. I have heard stories of power-line workers being electrocuted and falling to the ground. The details involved the statement that the man's heart stopped, but hitting the ground got it started again and saved his life.

    I'm wondering how anyone could claim to know the man's heart actually stopped since nobody was up there listening with a stethoscope.
  7. May 9, 2003 #6


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    It is posible for a shock victim to experience the illusion of being "magnetically stuck" to an object. If the victim's hand had something to grasp (some protrusion from the pump), then the shock could cause the to fingers convulse and make release impossible. If the person's arm was then convulsed, attempting to flex at the elbow, the elbow would be brought into contact with the side of the pump and press hard against it. To the person, who is unable to pull his arm away (and who's recolections are bound to be confused by the fact that he was undergoing electro-shock therapy during the incident he is now trying to recall!), this might seem very much like being stuck to the object.

    However, it is important to determine what the party in question was doing with/holding in his right hand. If the hand was not gripping something that was affixed to the pump, you're being fed a load of fertalizer!
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