3 ms·

It is not the voltage that kills you. It is the current and a car battery can deliver quite the current.

aaronmdjones 4y ago
At such a low voltage, and a DC voltage nonetheless (so you're only dealing with resistance, and not impedance), you will never get enough current through you, even if you'd just waded out of the ocean.
upofadown 4y ago
Not through the resistance of a person. For electrocution, the voltage is the indicator of hazard. The current required is very small.
NovemberWhiskey 4y ago
V = IR. It's voltage that causes the current to flow. You can certainly get a lethal shock from a car battery if you pierce the skin with an electrode attached to one of the terminals, due to the reduced resistance through the body, but you're not going to get one through your skin. The amount of current required to stop you breathing is as low as a few hundred mA, and only 1A to stop your heart in v-fib. On the other hand, even wet or broken skin should offer about 1 kilohm; so your chances of being electrocuted by a car battery are slight.
- aaronmdjones 4y ago
  > and only 1A to stop your heart in v-fib Much less than that, depending on length of exposure. The AC death graph (probably not applicable to this DC scenario, but illustrative nonetheless): https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_60479-1_electric_shock_graph.svg https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_6... Red is fibrillation with increasing probability of occurrence. Yellow is injury, green is harmless, and blue is imperceptible.
  - jaclaz 4y ago
    I believe that AC is way more dangerous than DC, and particulary the low frequency (50-60 Hz) that are used on normal mains, once upon a time lighting in tunnels (during excavation) was through a frequency converter that elevated frequency (i.e. essentially making AC more similar to DC): https://news.ycombinator.com/item?id=20736124 https://news.ycombinator.com/item?id=20736124 According to: https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/physiological-effects-electricity/ https://www.allaboutcircuits.com/textbook/direct-current/chp... A DC shock may stop the heart (which once the contact is broken is easier to restart) whilst AC males it fibrillate, and there is the "tetanic" reaction induced by AC that in many case might make the contact last longer or be impossible to break. The old, basic rule is - in case of doubt if a wire is live - to touch it first with the back of a finger, and never with a fingertip, as the reaction to the shock would be to close the finger/hand around the wire in a very tight grip.
    - aaronmdjones 4y ago
      > I believe that AC is way more dangerous than DC Yes. I pointed this out myself several months ago: https://news.ycombinator.com/item?id=28682725 https://news.ycombinator.com/item?id=28682725
globular-toast 4y ago
It is usually voltage that kills you, but not all electric shocks are equal. The type that kills you quickly is one that goes through the heart, disrupting its rhythm. This happens, for example, if you use both hands to work on something electrical. It doesn't need much current at all. Electricians are trained to not use both hands. If you use only one hand the shock is more likely to be straight to ground. In that case a high current is going to do more damage to you, but might not actually kill you. But in any case you need enough voltage to overcome the resistance of the skin the first place.

At such a low voltage, and a DC voltage nonetheless (so you're only dealing with resistance, and not impedance), you will never get enough current through you, even if you'd just waded out of the ocean.

upofadown 4y ago

Not through the resistance of a person. For electrocution, the voltage is the indicator of hazard. The current required is very small.

NovemberWhiskey 4y ago

V = IR. It's voltage that causes the current to flow. You can certainly get a lethal shock from a car battery if you pierce the skin with an electrode attached to one of the terminals, due to the reduced resistance through the body, but you're not going to get one through your skin. The amount of current required to stop you breathing is as low as a few hundred mA, and only 1A to stop your heart in v-fib. On the other hand, even wet or broken skin should offer about 1 kilohm; so your chances of being electrocuted by a car battery are slight.

aaronmdjones 4y ago
> and only 1A to stop your heart in v-fib Much less than that, depending on length of exposure. The AC death graph (probably not applicable to this DC scenario, but illustrative nonetheless): https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_60479-1_electric_shock_graph.svg https://upload.wikimedia.org/wikipedia/commons/7/7f/IEC_TS_6... Red is fibrillation with increasing probability of occurrence. Yellow is injury, green is harmless, and blue is imperceptible.
- jaclaz 4y ago
  I believe that AC is way more dangerous than DC, and particulary the low frequency (50-60 Hz) that are used on normal mains, once upon a time lighting in tunnels (during excavation) was through a frequency converter that elevated frequency (i.e. essentially making AC more similar to DC): https://news.ycombinator.com/item?id=20736124 https://news.ycombinator.com/item?id=20736124 According to: https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/physiological-effects-electricity/ https://www.allaboutcircuits.com/textbook/direct-current/chp... A DC shock may stop the heart (which once the contact is broken is easier to restart) whilst AC males it fibrillate, and there is the "tetanic" reaction induced by AC that in many case might make the contact last longer or be impossible to break. The old, basic rule is - in case of doubt if a wire is live - to touch it first with the back of a finger, and never with a fingertip, as the reaction to the shock would be to close the finger/hand around the wire in a very tight grip.
  - aaronmdjones 4y ago
    > I believe that AC is way more dangerous than DC Yes. I pointed this out myself several months ago: https://news.ycombinator.com/item?id=28682725 https://news.ycombinator.com/item?id=28682725

globular-toast 4y ago

It is usually voltage that kills you, but not all electric shocks are equal. The type that kills you quickly is one that goes through the heart, disrupting its rhythm. This happens, for example, if you use both hands to work on something electrical. It doesn't need much current at all. Electricians are trained to not use both hands. If you use only one hand the shock is more likely to be straight to ground. In that case a high current is going to do more damage to you, but might not actually kill you. But in any case you need enough voltage to overcome the resistance of the skin the first place.