Electrical Shock!!!!!

[Badar]

hi.
I've seen different boards near poles having a danger symbol with printed DANGER 11KV,DANGER 440VOLTS,DANGER blah blah.
My question is that why we are shocked,Is it volts , ampere , or both(i.e. power)that make us feel shocked.what is the relation of any of these with shock.

 

[dknguyen]

What makes you feel a shock is the voltage (like static electricity). What kills you is the current (which static electricity does not have a lot of). But in order to get that current to flow through you, you need to have a high enough voltage. So they are related.

 

[Papabravo]

If we go back to basic units.
Amperes is actually coulombs/sec it is the flow rate of electrical charge
Volts has units of joules/coulomb and represents the driving force.

https://en.wikipedia.org/wiki/Amperehttps://en.wikipedia.org/wiki/Amperehttps://en.wikipedia.org/wiki/Ampere
https://en.wikipedia.org/wiki/Volts

It is the current measured in amps that creates the shock, and it is the volts that overcomes the resistance of the load. Using ohms law you can calculate how much voltage is required to deliver a fatal shock.
https://en.wikipedia.org/wiki/Electric_shock

 

[Andy1845c]

Its the amps(current) that will kill you and the volts that allow the current to move though the body. The higher the voltage, the more current that will flow through the resistance of the human body.

 

[jbelectric777]

Use a GFCI

GFCI's trip between 4-6 ma , in 25 ms or less. It is my belief that 5ma is the amount of current to stop the human heart at 60 HZ. DC on the other hand is extremely dangerous because it does not cycle like AC. Naturally low voltage cant create that kind of current just through the bodies resistance but it can hurt you pretty good if you get between another load such as a light bulb, then you feel not only your bodies resistance current but now add the current in line from the light bulb (which I did on an old knob & tube circuit) Best advice, always respect electrical current in any shape or form and always assume it's hot, work carefully and use hot sticks over 600 VAC as well as tested lineman gloves rated to 20K VAC or higher depending on your work. I have to ask; From your questions you dont seem confident around electricity (line voltage) did you recently start a new job at a plant or other facility ? Just wondering..... jb

 

[Hank Fletcher]

You can't be shocked from a car battery because the voltage is too low to allow enough current to flow...

I have some wet sponges and a car battery. Come over and take your shirt off and we'll see if you're right. Maybe you meant lethal shock, but even then, I hope you don't have a pacemaker.

 

[dknguyen]

I have some wet sponges and a car battery. Come over and take your shirt off and we'll see if you're right. Maybe you meant lethal shock, but even then, I hope you don't have a pacemaker.

Why is that anyways? It isn't high enough voltage to push enough current pass through the resistance of the skin but you can still get shocked with wet sponges. Does it have something to do with the sponge acting like a large conducting electrode and the the increased surface area that is in contact with the skin lowers resistance?

 

[Hank Fletcher]

Why is that anyways?

Ever try to short a 9V battery with your finger? Can't be done. Ever try using your tongue? Trust me, you don't want to. But I know you want to. Go on. Come on. It'll be fun.

Water's a better conductor than dry skin. There's a lot of water inside people. Try to keep the water on the inside of your body, and the electricity on the outside. So don't:
- lick batteries
- try to imitate Mel Gibson's torture scene in Lethal Weapon
- golf in the rain
- pee on an electric fence

Ever get a rug burn? Not a serious injury, but it stings like anything! That's because a rug burn causes a great surface area just below the outside of your skin to be exposed, which in turn makes a lot of nerves say, "Hey brain, something's going wrong here, check it out!" Too much trauma/pain will cause your body to go into shock, i.e., you will be beyond voluntarily reasoning a solution to ending your own pain. It's a catastrophic failure of your body's nervous system.

Imagine the water in your body as if it is copper leads on a PCB, and the nerves in your body are like LEDs, and then imagine there are no resistors on your PCB. Sending enough voltage and even a little current (combined for a POWERful experience of some kind or another) through your PCB leads will make your LEDs light up like crazy. A little too much, and the LEDs start to pop out. A bit more and you get that familiar smell of an electronics project gone wrong.

 

[Nigel Goodwin]

Ever try to short a 9V battery with your finger? Can't be done. Ever try using your tongue? Trust me, you don't want to. But I know you want to. Go on. Come on. It'll be fun.

It's not just because your tongue is wet, it's because it's VERY sensitive - try pouring water on your hand and applying a 9V battery!.

Presumably EVERYONE on these forums has tested a 9V battery with their tongue?, and will continue to do so.

 

[jbelectric777]

ok , someone hook me up to an ohm meter and we'll just find out.... hanks right , the body fluid amounts differ from person to person... maybe i could withstand 277 through my hand down out my foot and another person can't... i guess it's how and where your body takes the fault and the condition of your heart... i've taken hits from just my hand and through my chest and one thing is darn sure.... THE CHEST IS WORSE ! you get a taste of metal in your mouth and a few mins to compose yourself and say " what happened " ......... i try to avoid that these days......

 

[Hank Fletcher]

maybe i could withstand 277 through my hand down out my foot and another person can't... i guess it's how and where your body takes the fault and the condition of your heart... i've taken hits from just my hand and through my chest and one thing is darn sure....

Geezus, man, be careful. It also depends on your "extra skin" you're wearing at any given time, e.g., your clothing and shoes. Remember, conductor and insulator are relative terms, and with enough voltage and current everything eventually becomes a conductor. Like this pickle:
https://www.youtube.com/watch?v=tMhXCG6k6oA
Think it'd work with a rubber on the pickle? Eventually, if you kept turning up the juice.

 

[Hank Fletcher]

It's not just because your tongue is wet, it's because it's VERY sensitive - try pouring water on your hand and applying a 9V battery!

I gather your argument is that with water on your hand, you won't feel the shock of the battery? Maybe so, but that's because there's still the resistor of your nerveless, waterless outerskin protecting you. It's gotta be there - can you imagine if everytime you felt something, you felt pain?

Go for a long bath. Saturate your outer layer of skin till you have prune hands. The nerves in your hands are quite tough and are under a lot of nerveless, dry skin, so even with prune hands you might have a hard time getting a shock from a 9V, so explore your body for the most nervy part. I'll leave that to your imagination, but by the way, pinch your dry, nerveless elbows as hard as you can (on the far side of your arm) - you just can't hurt yourself at all that way no matter how much damage you do, which explains why the body has to feel pain.


Since Luigi Galvini and his frog, and the days of Frankenstein, there's been a notion that the body uses electricity to transmit nerve information (sensor feedback data) and control muscles (motor control), and in a lot of situations that model's quite useful. But just FYI: modern medical thinking is to view this interaction in the human body as part of a chemical process, and this thinking stems from a holistic philosophy to approaching the understanding of living things, as opposed to the largely atomistic philosophy of the 18th and 19th centuries. There's a show somewhere on PBS just waiting for a guy like me...

 

[jbelectric777]

i'm always careful , someone manually closed a lighting contactor on me when i was working on some lighting poles in a hotel parking lot.... i tell ya what ,,,, i flipped backwards and never found my wire strippers... lesson learned.... never trust your co-worker, experienced or not, always open the breaker, use lock-out/tag out and don't assume anything.....

 

[Hank Fletcher]

<<shiver>>

 

[Sceadwian]

I have a stepper driver setup on my breadboard right now and I was testing it with 12 volts, the tabs aren't issolated and since I know the circuit was safe I was using my fingers to see how warm the part was getting. Even with dry fingers I was getting enough current to my fingers to feel a tingle, those were my finger tips though.

 

[Pax Writer]

Hey Hank, I gotta give it to you: You're a really funny and imaginative person. I read your PCB/body-analogy, and while I found it pretty good, I also smiled at your efforts to go to such details to describe the physiological effects of shock.
Nice writing, although a tad sinister.

 

[Roff]

I just got around to reviewing this thread. I couldn't pass this up.

<snip> pinch your dry, nerveless elbows as hard as you can (on the far side of your arm) - you just can't hurt yourself at all that way no matter how much damage you do, which explains why the body has to feel pain.

Don't try this when you're drunk. You might confuse your wenis with another, more sensitive part of your body.

 

[Hank Fletcher]

Hey Hank, I gotta give it to you: You're a really funny and imaginative person.

Hey, thanks! This was one of my better moments - I've written some quite critical things lately on this site, especially in the ****-Chat forum. I stand by everything I've written, but every now and then I forget to keep things light. Truth is, I'm an extremely self-critical person, and until people know me, my characteristic criticism to them comes across as a personal attack (which I don't do, except in very, very rare cases).

That said, there are a few members of this forum who I've, let's say, "shared my piece (peace?) of mind with." In the off-chance any of those folks (and I think they know who they are) read this, I hope they understand that my criticism is mostly vicarious. What I mean is, I have a strong connection, be it through gender, geography, nationality, politics, generation, ethnicity, or personality, to the people I criticize most.

The reasoning behind my criticism is two-fold. First, what most draws me to criticize a person is when I see them making the same mistakes I made. Knowing that might help people get past the idea that I write the things I write in order to fuel my own ego, or whatever. Second, I feel compelled to direct my criticism at people most like me due to my sense of a kind of communal self-consciousness, or call it guilt by association. I think this sense is compounded given the nature of the medium (international forum), that is, knowing that what's read is mostly being read by people very much unlike me, and hoping that they get a good impression of me and my type of people.

wenis

That's a new one! Looks like something right out of the Douglas Adams dictionary. For the record, I don't suggest anyone does anything that they know will harm their wenis, themselves or others. There's no Hippocratic Oath for electical engineers, but I see no reason to expect it to be exclusive to doctors.

 

[ncd59]

"Volts Jolt, Mills Kill" :-o

 

[Optikon]

I have a stepper driver setup on my breadboard right now and I was testing it with 12 volts, the tabs aren't issolated and since I know the circuit was safe I was using my fingers to see how warm the part was getting. Even with dry fingers I was getting enough current to my fingers to feel a tingle, those were my finger tips though.

I feel minor shocks all the time when I probe around my low voltage circuits with my hands. Usually somewhere around 30VDC (+/-15V supplies) I've managed to keep the drainbamage to a minimum.