3 ms·

You can also get burned without current flowing through your body, e.g. by accidentally shorting the circuit through some sweat on your skin.

H8crilA 7y ago
Uh right. But still - my skin sweat having less than 10 ohm resistance sounds like a stretch. It is more salty than blood though (because of evaporation).
- zaarn 7y ago
  If the droplet of sweat has a resistance of 10 Ohms, 1.2 Amps will be flowing at 12V. The droplet will be heated by 14 Watts of energy. Doesn't sound much. But it's enough to bring a droplet of sweat to the boiling point within 10 seconds. Your sweat starting to boil of your skin doesn't sound like a very pleasant way to pass the time.
  - H8crilA 7y ago
    I was thinking on a longer distance, like between left and right hand, or between a hand and a leg (which I still think is near impossible to cause any harm with 12 volts). But surely it can happen on a distance of less than few cm, when the + is in a very close proximity to the - (touch here to get your fingertip heated!).
    - zaarn 7y ago
      Doesn't need to be a terminal, touching a broken wire with sweaty hands would be enough to induce flash evaporation of fluids on your skin.
      - rlonn 7y ago
        not with 12V. 12V batteries are pretty safe for human skin contact. If you put your wet tongue across a 12V battery it will hurt, but not more than that (it's a good way to test 9V batteries actually)
        867-5309 7y ago
        only on HN..
        zaarn 7y ago
        Well, if you put your tongue on it, you'll obviously have a lot more distance to cover and a lot more fluid to handle the current. Batteries in general are fairly safe because their voltage breaks down at high loads. The chemistry can only react so fast internally and is controlled by various factors. Contrast this with capacitors, where there is always a general safety warning when handling them in live circuits. They have no limit based on chemistry. You don't want to test a capacitor with your tongue. A capacitor has no other current limit than it's internal resistance, with a modern sub10mOhm ISR a capacitor can, for the briefest of moments, discharge at up to 14 Kilowatts, quite the upgrade from the 14 measly watts that your spit will handle. A 100 Millifarad Low ISR Cap can sustain a kilowatt of output for almost 0.1 milliseconds, at which point you'll likely regret the choice of mishandling a cap. (It's only 14 Joules but these 14 Joules will be moving very fast)
  - colechristensen 7y ago
    When I was young I got a good burn on my skin pinching a tiny bit of my finger between wires hooked up to a 6v remote control car battery. Smelled awful and had a brown patch a few mm wide on my finger for a while. This happened more or less instantaneously.
    - madengr 7y ago
      When I was a kid, I stuck a 9V battery across my braces (top to bottom teeth). Just about knocked me out.

H8crilA 7y ago

Uh right. But still - my skin sweat having less than 10 ohm resistance sounds like a stretch. It is more salty than blood though (because of evaporation).

zaarn 7y ago
If the droplet of sweat has a resistance of 10 Ohms, 1.2 Amps will be flowing at 12V. The droplet will be heated by 14 Watts of energy. Doesn't sound much. But it's enough to bring a droplet of sweat to the boiling point within 10 seconds. Your sweat starting to boil of your skin doesn't sound like a very pleasant way to pass the time.
- H8crilA 7y ago
  I was thinking on a longer distance, like between left and right hand, or between a hand and a leg (which I still think is near impossible to cause any harm with 12 volts). But surely it can happen on a distance of less than few cm, when the + is in a very close proximity to the - (touch here to get your fingertip heated!).
  - zaarn 7y ago
    Doesn't need to be a terminal, touching a broken wire with sweaty hands would be enough to induce flash evaporation of fluids on your skin.
    - rlonn 7y ago
      not with 12V. 12V batteries are pretty safe for human skin contact. If you put your wet tongue across a 12V battery it will hurt, but not more than that (it's a good way to test 9V batteries actually)
      - 867-5309 7y ago
        only on HN..
      - zaarn 7y ago
        Well, if you put your tongue on it, you'll obviously have a lot more distance to cover and a lot more fluid to handle the current. Batteries in general are fairly safe because their voltage breaks down at high loads. The chemistry can only react so fast internally and is controlled by various factors. Contrast this with capacitors, where there is always a general safety warning when handling them in live circuits. They have no limit based on chemistry. You don't want to test a capacitor with your tongue. A capacitor has no other current limit than it's internal resistance, with a modern sub10mOhm ISR a capacitor can, for the briefest of moments, discharge at up to 14 Kilowatts, quite the upgrade from the 14 measly watts that your spit will handle. A 100 Millifarad Low ISR Cap can sustain a kilowatt of output for almost 0.1 milliseconds, at which point you'll likely regret the choice of mishandling a cap. (It's only 14 Joules but these 14 Joules will be moving very fast)
- colechristensen 7y ago
  When I was young I got a good burn on my skin pinching a tiny bit of my finger between wires hooked up to a 6v remote control car battery. Smelled awful and had a brown patch a few mm wide on my finger for a while. This happened more or less instantaneously.
  - madengr 7y ago
    When I was a kid, I stuck a 9V battery across my braces (top to bottom teeth). Just about knocked me out.