Can touching 120VAC kill you?

Discussion in 'General Electronics Chat' started by rlm0360, Apr 1, 2016.

  1. rlm0360

    Thread Starter New Member

    Mar 13, 2016
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    Out of curiosity I measured the resistance of my skin from one hand to the other. It measured about 4 MegOhms. So I wanted to see what kind of current would run through my body if I decided to jam my hands in the mains. Ohms law predicts I should have 60 microAmps running over my skin. (240/4,000,000) That sure doesn't seem like very much. What is the deal?

    Disclaimer: I don't intend to jam my hands in the mains
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    Depends on skin moisture,is skin intact and for how long are you in contact with the mains.
     
  3. crutschow

    Expert

    Mar 14, 2008
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    Add a little moisture to the skin at the contact points and then measure it.
     
  4. #12

    Expert

    Nov 30, 2010
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    Think about what might happen if you touch the mains and you will start sweating immediately.:D
    That will reduce your resistance in about one second.
    ps, the peak voltage of 240 VAC is 339.4V

    There is also the chance of a burr on the metal penetrating you skin just a little, but just a little is all it takes to change your resistance drastically.
     
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  5. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Just measured across my body via the hands and got 400K and slightly moistened not much difference?

    It's measured at just a few volts but I imagine at 120VAC things behave differently because the body isn't a perfect resistor and capacitive effects start to happen?

    If I remember rightly a current as low as 30mA AC across the heart can cause fibrillation.
     
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  6. SLK001

    Well-Known Member

    Nov 29, 2011
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    At low frequencies (50-60Hz), the current travels THRU the body, so grabbing 120V mains with both hands CAN be fatal.
     
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  7. #12

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    Nov 30, 2010
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    Today I'm 6 meg, thumb to thumb, 1 meg wet.
    The capacitance idea is valid because skin is only a millimeter or two thick before it gets really wet.
    I work with my hands, so my thumb skin is thicker than the skin in the middle of my hands.
     
  8. ISB123

    Well-Known Member

    May 21, 2014
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    180k Here:eek:
     
  9. rlm0360

    Thread Starter New Member

    Mar 13, 2016
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    I just assumed that since 120VAC has a voltage range of +- 120v then it would be 240V overall
     
  10. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Locked and then unlocked?

    Thought it was a little harsh!
     
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  11. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Dying is worse. The answer is to the TS's question is "yes." What more is there to discuss?

    Advice to the TS without data, and there are lots of data on electrocution, is irresponsible, if not being an accessory. That is, assuming the TS is actually serious about performing the experiment.

    John
     
  12. #12

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    Nov 30, 2010
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    Read the first post.
     
  13. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    It's a hypothetical question at its best and stupid in fact.

    We do not allow discussion, even at a hypothetical level, of transformerless power supplies from 120 VAC. Shock from that voltage is the predictable outcome and is well known to be potentially fatal. Why would AAC then allow discussion, hypotheitically of course, whether that shock is bad (i.e., fatal)?

    The answer is yes. This discussion is illogical with respect to the strict prohibition by AAC against discussion of circuits that can produce such shock. What possible good can come from it? In contrast, contributors may imply it is not really dangerous,"if you have dry hands, " or other foolish and debunked legends (like not touching with both hands will keep you from being killed).

    John
     
  14. tcmtech

    Well-Known Member

    Nov 4, 2013
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    If you don't complete a circuit well enough pass enough current to cause problems with your body functions then no it won't kill you.

    I just did a live 120 VAC connection bare handed yesterday and didn't feel a thing being my hands and shoes were dry and I was on dry concrete thus did not complete a current carrying circuit to any significant effect.
     
  15. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    OK, that's good for you. But how does that address the titular question,
    As I recall, there are documented examples of people falling from airplanes and surviving. That does not prove you can't be killed by falling from an airplane.
    John
     
  16. profbuxton

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    Feb 21, 2014
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    You'll die!
     
  17. Tonyr1084

    Active Member

    Sep 24, 2015
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    Enough people have already said yes, it can kill you. And I can't deny that answer.

    I've been hit with 120 VAC several times. Some people just NEVER learn the lesson. I've shocked across finger to finger (one hand) (hurts), Palm to elbow - (really hurts), and yes, from hand to hand a couple times - directly through the chest. I'm lucky it didn't stop my heart. But don't try this at home - or anywhere else for that fact.

    When working on aircraft I managed to accidentally touch the live terminal of a switch with my right hand while my left hand was locked onto another grounded metal surface. THAT HAD THE POTENTIAL TO BE DEADLY. Fortunately it just simply knocked me on my butt. It would seem that momentary contact is somewhat less dangerous - I still say don't try this at home or anywhere else - it would seem that the more dangerous situation is if you're using a power tool, one with a hand grip, and with the other hand you grab a grounded metal pole. Your muscles will contract, tightening your grip on the tool and on the pole. It's the not letting go part that is the worst. Even still, the briefest contact with current flowing across the heart muscle CAN end your life for good.

    Someone said to me "You must have high internal resistance." Then someone else said "Yeah, chit don't conduct." Maybe being full of chit has saved my foolish life on a number of occasions. Still, 6 milliamps has been proven to be able to end your life.

    Wanna try a real world experiment? Get a sheet of aluminum foil and lay it on a table. Lay your left arm on the sheet and take another strip of aluminum and make an arm band out of it. Grab an old transformer (smaller would be less uncomfortable) then take the primary and connect one wire to the sheet on the table and the other to your arm band. Then take the secondary and connect it to a D cell battery. Give it a brief moment to charge the magnetic core then disconnect the battery. The resulting shock will suddenly contract your arm muscle causing your arm to jump off the sheet.

    Now: Consider that your heart is just a muscle. So is your arm. If an electrical impulse can lift your arm off the table imagine what 120 VAC can do to your heart muscle. And it doesn't take much current. As little as 6 milliamps CAN kill you. This is not something you want coursing through your chest. But the left arm thing will demonstrate a very powerful jolt just from a 1.5 volt D Cell battery. And that's merely 1.5 volts.

    OK, the resulting voltage from the transformer - depending on the size WILL amplify the jolt quite a bit. Maybe 40 to 80 volts. You'll learn something from the aluminum experiment. But if you try with the 120 VAC - could very well be the last experiment you ever perform. Unless you believe in god and hope he'll resurrect your dumb butt.
     
  18. paulktreg

    Distinguished Member

    Jun 2, 2008
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    OK 120 VAC was mentioned and transformer wasn't so end of discussion?

    Yes 120 VAC can kill you and so can as little as 40~50 VDC by the way.

    Let's end the thread now in case it starts talking about ways on not how to kill yourself.
     
  19. Tonyr1084

    Active Member

    Sep 24, 2015
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    You CAN touch a 120 volt line and not die. In fact, birds land on wires that are powered with 25,000 volts or more with no ill effects. Why? Because no circuit is being completed. I believe TCMTECH is saying this exact thing.

    I've wired plenty of live circuits without getting a shock BECAUSE I did not touch ground at the same time. It's when current has a path to flow that you run the risk of serious injury or death. I didn't see it but a technician working on the generator on a commercial jet liner mistakenly grabbed a hot line with his left hand. His ring (reportedly - I don't know how true this is - I'm always skeptical about repeating a story I heard but have no proof of), but reportedly his ring welded to the terminal while his arm - pressed against the aircraft frame - completed a circuit and fried his arm to a crisp.

    In high school we DID take nails on a board, put wires on one half of a 120 volt circuit to half the nails and to the other half of the nails on a different board we hooked the neutral. We then took hotdogs and stuck them from the live wire to the neutral wire and then plugged it in. The hotdogs cooked from the electrical current passing through them. If the hotdogs were once alive - I'd say that pretty much guaranteed they were dead by the end of the lesson.

    We weren't learning how to cook hotdogs we were learning how a completed circuit can harm you.

    Yes, you CAN touch a live wire and not die. But if you complete a circuit from hot to ground then your chances of injury or death go way up.
     
  20. wayneh

    Expert

    Sep 9, 2010
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    Short answer: Hell yes it can kill you.

    Ever stick a 9V battery on your tongue? It's unpleasant. Anyone that has ever touched the mains knows how much MORE unpleasant that is, or they didn't survive to tell us.

    I've felt the 60Hz buzz many times. It's usually only from a glancing touch to a hot conductor (a stage microphone, for instance, or some house wiring), without a good path to ground or the neutral wire. You'll still feel it. It doesn't really hurt all that much but sure gets your attention and will make you jump.

    Once I was plugging a string of lights into an extension cord, with wet hands from the snow. My hand slipped forward and I contacted both prongs with a firm grip and wet fingers. That was 50 years and and I remember it better than today's lunch.
     
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