Which is the problem with electric shock?

  1. Which is the problem when a human being is electrocuted: the high voltage and/or the high current?

    What the high voltage make in the body human (such as brain, heart and other organs)?

    What the high current make in the body human (such as brain, heart and other organs)?
     
  2. jcsd
  3. mathman

    mathman 6,658
    Science Advisor
    Gold Member

    voltage = current times resistance. In order to get high current, high voltage is needed. Resistance is a property of the human body.
     
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  4. SteamKing

    SteamKing 9,939
    Staff Emeritus
    Science Advisor
    Homework Helper

    It's not the volts that kills you, it's the amps.
     
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  5. What differentiates a high shock of a low shock? For example, the shock that an outlet is perceptibly more intense than the shock by put a battery in the tongue. The intensity of the shock is the sensation of feel the amperage?
     
  6. SteamKing

    SteamKing 9,939
    Staff Emeritus
    Science Advisor
    Homework Helper

    It depends. The quality of the electrical contact between your body and the battery or the outlet has a great deal to do with whether you get a mild tingling, a nasty shock, or a trip to the hospital (or worse). If you wear shoes which insulate your feet so that your body doesn't provide a path for the current to flow, your chances of emerging without serious injury are greatly increased.
     
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  7. UltrafastPED

    UltrafastPED 1,916
    Science Advisor
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  8. Drakkith

    Staff: Mentor

    You cant have electric current without voltage, just like you cant have a current of water in your pipes without water pressure. The higher the voltage, the more current can potentially be pushed through your body. The key word there is "potentially". Even a low amount of volts can be more dangerous than a higher amount if people get lax with electrical safety around the lower voltage.
     
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  9. It's rather fortunate that the human body has quite a high resistance.

    I once had a shock from an electric cattle fence. Google suggests these range from 2000V to 10000V but I don't know if they can sustain that voltage with a human connecting the fence to ground! I had one hand on the wire and the other on wet ground and it was an experience I wouldn't want to repeat. Felt like I'd pulled every muscle in my body. Took about 20mins before I felt well enough to stand up and carry on walking.

    However most if us will have experienced much higher voltage shocks caused by static electricity. These can be as high as 50kV but because the source cannot deliver much energy it can't sustain that voltage or deliver significant current and they are relatively harmless (unless you happen to be filling your car with gas at the time).

    Here in the UK (I don't know about other countries) new houses are fitted with Residual Current Detectors (RCD) that monitor the electrical circuits supplying all sockets. RCD detect any mismatch between the current flowing in the live and neutral wires. A significant mismatch suggests some is electricity "escaping" to earth which could indicate a potential fault. Some slight mismatch can occur even in a perfectly normal circuit so a judgement has/had to be made as to what is an acceptable mismatch and what represents a potentially dangerous fault, otherwise you would get a lot of false alarms. Most RDC are designed to trip out if the mismatch exceeds about 30mA as that's about the safe maximum (for AC) that the human body can withstand. Any more (and sometimes less) and your heart can stop beating correctly.

    Google suggests the resistance of the human body varies from 1,000 to 100,000 Ohms. This suggests that in extreme cases around 30V AC could be enough to kill you. (V=I*R and if I=30mA and R=1000 Ohms then V=30V). However up to 42V is normally considered reasonably safe and that's the upper limit for SELV (safety extra-low voltage) appliances.

    I suppose I should insert a disclaimer at this point. Do not mess with electricity. If you mess with electricity and kill or injure yourself or someone else then it's your fault.
     
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  10. Hey guy, give me more analogies between electrical and others circuits (I'm speaking serious). Very interesting! Btw I remembered your analogy that answered me a question in my mind: "why the voltage is not divided when the circuit is divided in various path", answer: "because the voltage, like the pressure, is distributed uniformly in every possible directions". Therefore, how much more analogies better! But I can't think in the analogous for flux linkage... how can I understand the behavior of the flux linkage in the circuit?
     
  11. Drakkith

    Staff: Mentor

    Sorry, I'm all out of analogies. :tongue:
     
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  12. the electricity, whether high or low voltage must pass through your chest to be sure to kill you. I have sustained shock by 440 vac and simply had arm pain because I had grounded my elbow and touched toe wire accidentally with my hand. current passes shortest distance, lowest resistance. but a simple 120 volt across the chest stimulates Ventricular arrhythmias and death.
     
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