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i touch the PSU|(power supply) bare wires 12v with my hands but nothing happens when power supply is on its harmless or not? please someone reply me i want to know,thanks in advance,i use the power supply in a socket and for beacons 12v

Trevor_G
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    Try putting the bare wires on either side of your tongue (NOTE: DON'T ACTUALLY DO THIS.) – Ignacio Vazquez-Abrams Oct 07 '17 at 19:14
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    You're still alive, right? – Finbarr Oct 07 '17 at 19:14
  • this is bad please tell me – info Oct 07 '17 at 19:16
  • someone tell me i need to know – info Oct 07 '17 at 19:21
  • "nothing happens" is your answer. – Finbarr Oct 07 '17 at 19:23
  • i dont know i just told you to understand but this is bad for health? i need to know that,what happens then please explain me – info Oct 07 '17 at 19:28
  • Harmless? If you drop it on your foot it might hurt a bit. REally, though harmless is a bit of a relative term.As @IgnacioVazquez-Abrams states, hooking it up to your tongue or sweaty salty skin you will get quite the buzz. Then there is the possibilities of shorts in the PSU. – Trevor_G Oct 07 '17 at 19:29
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    You really ought to indicate harmless for such and such a situation. Generally we consider 12V to not be a dangerous voltage. But there are a lot of provisos in there, for example how much current it can source.... (Car batteries can be mean son of a ...) Other thing you need to consider is if it can get hot/overheat/start a fire. – Trevor_G Oct 07 '17 at 19:37
  • 12 V is near the threshold where I go from "sure, no problem" to "maybe not" with regard to placing a pair of copper wires on my tongue to see if it is "active" or not. I can and do use my tongue to tell me how charged a 9 V battery is, if I don't have a better method handy at the time. 12 V bites more. But I'm still okay there. That said, I would under NO circumstances consider placing my hand anywhere NEAR a bar of copper placed across the 12 V of a car battery. Voltage is one thing; molten metal is another. – jonk Oct 07 '17 at 19:51
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    @jonk I do too. And yes.. car batteries scare the willies out of me. Was in a cargo van once and someone dropped a roll of wire (steel) wool on the battery... Nice little explosion/fire and van filled with smoke. WHo knew steel could burn... – Trevor_G Oct 07 '17 at 19:54
  • Harmless to dry skin. If you wear jewelry (rings, metal bracelets, watch with metal band), these combined with a little sweat might allow more current to flow through you - enough that you could feel it. My watch (when I wear it) has a leather strap. A general rule I follow: no metal on dry hands when working with electrical stuff. – glen_geek Oct 07 '17 at 19:54
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    @Trevor These newer lithium batteries used often for quadcopters and the like are truly awesome and scary. I've watched a few videos where someone takes one out into a field and either drops a heavy rock on it or else shoots it using a gun. Either way, huge fireball results. You don't see that with a car battery. This scares the willies out of me, thinking about a new world with EV cars -- every one of which has enough energy to move that car and people hundreds of miles. Accident? I don't want to be anywhere near it. Even spilled gasoline is safe, by comparison. – jonk Oct 07 '17 at 19:59
  • @glen_geek Now you just reminded me of a watch I really loved and... sadly lost. It had a beautiful radium dial that I used to read books by, when I went to sleep. It was like a flashlight, almost! Nice green color, too. – jonk Oct 07 '17 at 20:01
  • @Jonk Yup and they want to make them autonomous too... – Trevor_G Oct 07 '17 at 20:01
  • In the 90's I would touch the -48V phone line to see why my modem was not connecting with wet fingers until I was able to get idle detect to work. Safe Low Voltage or SLV means < 50V. – Tony Stewart EE75 Oct 07 '17 at 20:14
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    A 12V car battery can supply significant current- which under the right conditions can cause a lot of heating. Check this out (warning graphic images), from this paper to see what contact with a metal ring (eg. via a wrench) can do to a human finger. – Spehro Pefhany Oct 07 '17 at 20:38
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    It's all about your impedance. I remember as a child playing with my 12V DC train set (um, "model railroad" in the USA) that if I accidentally leaned my hand on the tracks, the tingle was quite upsettingly powerful. – Ian Bland Oct 07 '17 at 21:52
  • Short term exposure to 12V won't hurt you, but you might not want to hook yourself up to a 12V battery over night. Any time you've got DC flowing through an aqueous solution (e.g., your wet, blobby, body), you've got electrochemistry happening. Even a current that is too weak for you to feel can cause chemical changes that build up over time---build up enough to cause tissue damage, especially at the contact points because that's where the current is most concentrated. (Note: the same thing does not happen with AC because each reversal of the current also reverses the chemical reactions.) – Solomon Slow Oct 29 '17 at 23:57

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12V is so low voltage that it cannot generate harmful currents through the hands that touch the wires. The situation is another, if you poke sharpened wires through your skin. Then some harmful local effects can occur, for example electrolysis. Some nerves can get so much disturbing current that you feel bad or even your muscles can do some unexpected movements.

The resistance of human skin is so high that it prevents harmfully high currents at 12V. Learn Ohm's Law about how voltage, current and resistance are related.

12V connected to opposite sides of your tongue will cause unforgettable effect because no high-resistance skin are protecting you. It's told that Napoleon Bonaparte tasted five times higher voltage once, when inspecting the electric lab in a local university. But despots usually demand more than the ordinaries. He survived and conducted several wars and battles. The death toll was millions, altough it could have been =1, if the battery had been a normal AC outlet of today.

If you happen to get 12V from a high capacity battery onto your hands - not onto the skin, but onto a ring or other metallic part, that part can get red hot within a second and burn itself into your flesh with some never forgetting hiss and smoke.

  • +1 for better than mine :) I guess the high capacity bit really applies to any voltage source though.. we both went there. – Trevor_G Oct 07 '17 at 19:48
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Power Supplies are all factory tested to pass HiPot and leakage current to not exceed 250uA for safety. So touching the DC will not conduct more than 250uA of noise current if you touch earth ground.

Tony Stewart EE75
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  • Unfortunately is you have a cuts or skin damage down to lower epidermal layers 12 V can give you a nasty tingle and cause heart arrhythmia. There is virtually no safe voltage for all conditions. http://drwes.blogspot.com/2009/10/electricity-and-heart.html As a professional you should always tell forks there is risk when handling electric circuits. – Jack Creasey Oct 07 '17 at 22:18
  • I suppose it is wise to be safe if you have a condition to be prone to this condition easily, yet healthy people can withstand 30kV jolts with some pain and no heart issues. – Tony Stewart EE75 Oct 07 '17 at 22:34
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Harmless? If you drop it on your foot it might hurt a bit.

But seriously though, harmless is a bit of a relative term. As @IgnacioVazquez-Abrams states, hooking it up to your tongue or sweaty salty skin you will get quite the buzz. Then there is the possibilities of shorts in the PSU.

You really ought to indicate harmless for such and such a situation.

Generally we consider 12V to not be a dangerous voltage. But there are a lot of provisos in there. For example, with any voltage source, how much current it can source can be dangerous when shorted.

Another thing you need to consider is if it can get hot/overheat/start a fire.

Trevor_G
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