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Getting shocked question

  1. Apr 24, 2009 #1
    My friend has been shocking me and friends with part of something (a lighter maybe) he found. We even got the shock to go through a ring of us. I'm sure that the thing produces a large voltage because it can spark.
    My question is why can a wall socket which has relatively low voltage (230 here) shock someone to death and the little thing cannot. My mind keeps on coming back to the V=IR relationship.
  2. jcsd
  3. Apr 24, 2009 #2
    Generally high voltage comes with quite a bit of current (but also used to circumvent this: the large power lines carry high voltage with low current to try to overcome resistance over vast distances). But the part of this equation that can kill you is the current. This is also why there's the famous picture of a volunteer (oops had Tesla apparently wrong) sitting and reading under the sparks of a massive Tesla coil with no ill harm. Its a high voltage low current environment. Or at least that's what I've gathered, I'm not too fond of electricity, both in equations and to my body lol.
    Last edited: Apr 24, 2009
  4. Apr 24, 2009 #3

    Andrew Mason

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    It is the voltage that shocks you. But it is the amount of energy dissipated in your body that kills you. The energy is a function of current and how long it is sustained for.

    If you are connected to the wall socket, a constant electric current passes through you because the voltage is sustained indefinitely. The shock from the device in question lasts for a tiny fraction of a second so there is not much energy dissipated in your body.

  5. Apr 24, 2009 #4
    it's the current that will harm,(kill) you not the voltage. Like the ''tazer'' the police have has high voltage, like, maybe 1,000, but it's produced by a small battery, so it'll shock you but not kill you, because there is very little current. Large current is produced at the electric plant by generators, be it coal, deisel gas, or water at the dam turning over the generators. There is a lot of energy behind the voltage, meaning lots of 'free electrons' will flow, this is called 'current'..The more electrons, the higher the current. It is said only 1/10 of 1 AMP(the measure of current) could kill you. Another twist is when there is lots of resistance to the current, then not many electrons will flow, hence low current. Your body is mostly liquid so it doesnt have much resistance to electron flow, (like rubber or wood or plastic or glass does), so when you put finger in socket you are gonna get shocked big time,( high current). WE humans' hearts dont like all those electrons charging thru it. IN theory, if you have rubber soles on or are standing on a wood floor, with ur finger in socket, you wont get shocked. BUT you better not be touching the wall with the other hand, cause the current/voltage will go in that direction, not to your feet. REMEMBER the current takes the path of least resistance,(meaning highest current), to "ground"., "ground" meaning something that (will allow the voltage to pass) is attached to the earth. The voltage always tries to go to "ground", to complete the path, and whatever/whoever it goes thru will get the shock.
  6. Apr 24, 2009 #5


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    That's 50,000 and the frequency is attuned to the human neural system to interrupt impulses.
  7. Apr 25, 2009 #6
    Yes, that is often the prevailing wisdom, but be careful. Even at low amperage, if your heart gets confused by the voltage and frequency, it will fibrillate. And that will kill you.

    I remember seeing a plot of the "lethality" of electric shocks years ago. Lower voltages are safer. And surprisingly, higher voltages (like 300) are safer also. This is because they "lock up" the heart in a contraction, so when the shock ends, the heart's muscles are still in sync.

    But right around 120, which is the voltage in US homes, the shocks are the most dangerous because they force the heart's muscles out of sync. That's a real bummer, but there's probably no hope of changing the standard now.

    Can't emphasize that bit about the frequency enough!
  8. May 15, 2009 #7
    well i have a question too. I was playing a trick on my brother, because he has a mini refridgerator, in his room that holds all of his pop, and when I unplugged it and when I unplugged it I got shocked and then like a week later I had a dream about a show called RESPECT to teach you about bullying at my school, and then, just today we had those same speakers in my dream, at our school. So I think i'm physic or maybe that just happens or something if you have any good information please write back. THANKS :)
  9. May 18, 2009 #8
    A lot depends on the route the electricity takes through your body. That's why a lot of TV repairers (in the good old days when TVs were actually repaired rather than just thrown away) used to work with one hand in their pocket.

    The reason is that if the other hand touches a high voltage the current should (in theory !) run down the side of the body to earth and miss the heart.

    If, however, one hand touched a high voltage and the other hand was in contact with something earthed, the current would flow across the chest where the heart is, potentially lethally.
  10. May 19, 2009 #9
    The Voltage of the piezoelectric lighters is quite high around 15000V. If we discard capacitive effects the current does indeed go quite high, but it does not have time to do much damage, the amount of power stored in one such pulse is limited by the energy that you put into the "snapper". This limits how long the current can flow.

    It is a similar thing with force or acceleration for that matter. Fighter planes can produce 9g and many people already go unconscious there. But there have been cases of people surviving more than 100g because it was for a very short time. If you remember how much work it is, to run something like a tiny light bulb of a bicycle by muscle power, you can imagine that the piezo cannot deliver much of "a punch" to your heart.
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