Question about shock

[blva888]

If you take a 3volt battery add a 3ohm resister to it you get 1amp. My question is this. If you touched the ciruit would you die or get shocked from it? I dont think i'm understanding electronics as i should understand it. I hope you all can help.

 

[akg]

If you take a 3volt battery add a 3ohm resister to it you get 1amp. My question is this. If you touched the ciruit would you die or get shocked from it? I dont think i'm understanding electronics as i should understand it. I hope you all can help.

no u wont.
u will die IF 1A current flows thru ur body.remember ur body has many K ohm resistance.

 

[blva888]

So then if you touched that circuit you would not get shocked because of your body resistance? I know that one amp will kill you.

Thank you for your reply by the way.

 

[Nigel Goodwin]

So then if you touched that circuit you would not get shocked because of your body resistance? I know that one amp will kill you.

3V is far too low to be dangerous, current is only dangerous if it's passing through you.

As to how high a voltage can be without being dangerous?, it varies massively - if you've ever watched films (like The Green Mile) which feature the electric chair, you will see how hard it is to kill someone by electrocution. But people every year manage to kill themselves on the UK 230V mains, and even on the 110V mains in the USA - I think you have to be really unlucky to do so?.

 

[blva888]

The thing i am trying to understand is that if 3v and 3ohms make one amp and then you place each of your hands in the circuit you should die from it because it is one amp of current.

 

[Nigel Goodwin]

The thing i am trying to understand is that if 3v and 3ohms make one amp and then you place each of your hands in the circuit you should die from it because it is one amp of current.

No, there won't be 1A - 1A will only flow though 3 ohms, inserting your body in the circuit makes the resistance greatly higher, probably in the tens or hundreds of thousands of ohms. Although being wet, or very sweaty, could bring it down to just thousands.

 

[blva888]

Ok now its makeing a bit more sense. That is what i thought.

Lets take say 1,000 volts and 1,000 ohms which would make 1 amp. now lets add me into the picture. Does that make the 1amp lower like it did before?

 

[Nigel Goodwin]

Ok now its makeing a bit more sense. That is what i thought.

Lets take say 1,000 volts and 1,000 ohms which would make 1 amp. now lets add me into the picture. Does that make the 1amp lower like it did before?

Yes, but probably NOT low enough :lol:

 

[blva888]

Ok so the reason why it wont be low enough is because of the voltage pushing the current threw the circuit? Did i get and understand this right?

 

[Nigel Goodwin]

Ok so the reason why it wont be low enough is because of the voltage pushing the current threw the circuit? Did i get and understand this right?

Yes, the higher voltage will push more current through the high resistance of your body - simple ohms law.

 

[blva888]

Thanks for your continued help.

If you take the 1,000volts and then increase the resistance to something like 200,000ohms and then add you in the picture the current will be low enough to get a jolt and live?

 

[Nigel Goodwin]

Thanks for your continued help.

If you take the 1,000volts and then increase the resistance to something like 200,000ohms and then add you in the picture the current will be low enough to get a jolt and live?

It's a VERY inexact thing, what might kill one person under certain circumstances might do no harm whatsoever to another, or even the same person under different circumstances.

However, as long as you have a high enough resistance in series with the voltage (NOT your bodies resistance) then current through your body 'should' be low enough to be harmless.

However, I understand that the Tazers used by American police kill a number of people every year? - 'safe' is a very relative term!.

 

[blva888]

I was using it as an example is all. but now i understand about voltage and current better, and why a stun gun with a nine volt battery can make a person fall to the ground. There is high voltage and low enough current to most likely not kill him. I understand that transformers step the voltage higher and the capaciters in the circuit can compound the current to get that higher. Am i right?

 

[Nigel Goodwin]

I was using it as an example is all. but now i understand about voltage and current better, and why a stun gun with a nine volt battery can make a person fall to the ground. There is high voltage and low enough current to most likely not kill him. I understand that transformers step the voltage higher and the capaciters in the circuit can compound the current to get that higher. Am i right?

You can charge a capacitor up over a long time, and then discharge it in a short time to get a much shorter higher current pulse - but you only get out what you put in! (in fact less than you put in!).

Consider a camera flash, it takes 10-30 seconds to charge it's capacitor, then discharges it in a fraction of a second.

 

[Oznog]

I most often see like 3 megaohms going from hand-to-hand on a multimeter. It varies a lot depending on how thick/moist the skin is and how far apart on the body it is. Just get a multimeter and test it with the high ohms scale, it's harmless.

When working on 12v, if the more tender underside of my forearm presses on a metal edge and I touch a live +12v post I can get a slight tingle.

If you put a 9v battery on your wet tongue you can get significant current, probably several mA. Stings awful, it makes your tastebud nerves go wild. Try it, it won't actually harm you. But cover both terminals with your thumb (no 1 ohm resistor necessary) there won't be enough current to feel. Push it into your forearm, might feel it. Actually try it after a shower with your skin damp and it may be much more feelable.

 

[Nigel Goodwin]

I most often see like 3 megaohms going from hand-to-hand on a multimeter. It varies a lot depending on how thick/moist the skin is and how far apart on the body it is. Just get a multimeter and test it with the high ohms scale, it's harmless.

It varies widely from person to person, one of our favourite tricks with work experience kids is measuring their resistance (with a Megger :lol: ). It's an old (ex WW2) hand cranked Megger, not one of the new battery ones - so it only puts out a VERY low current. It works best with kids who have very dry skin, and who hold the leads loosely - with damp skin and a tight grip the voltage falls so low you don't even feel it.

If you put a 9v battery on your wet tongue you can get significant current, probably several mA. Stings awful, it makes your tastebud nerves go wild.

Common practice for testing batteries out of guitar pedals :lol:
I believe part of the 'taste' on your tongue is salt from electrolysis of the saliva on your tongue?.

 

[Peepsalot]

Yep dry human skin is a decent insulator. Now on the other hand, if you had open wounds, or a a metal pin sticking under the skin of each hand, I would imagine the resistance could be greatly reduced, since blood is an electrolyte. In a case like that, I imagine it wouldn't take much voltage to kill you. I never tried measuring the resistance like that though, hah.

I'm not sure exactly, but I think I remember hearing that 30ma can be enough to kill. I might be way off here, it was many beers ago.

Also, a good safety precaution is to keep one hand in your pocket or behind your back if you are working around high voltage. This is so that in the event of a shock, you are not creating a circuit path that goes from one hand to the other, passing directly through your heart on the way. Of course you could still die depending on the circumstances, but it keeps the odds slightly more in your favor.

Ohm's law by the way, since you don't seem too familiar with it:
I = V / R
V = I * R
R = V / I
Depending on what you are solving for. Where V = Voltage, I = current in Amps, and R is resisitance in Ohms.

 

[Electrostatic]

I'm not sure exactly, but I think I remember hearing that 30ma can be enough to kill. I might be way off here, it was many beers ago.

Actually 10mA makes a person say "F@$K that hurt" and 50mA can actually kill a person.

 

[ZIGGY_DAN]

i keep one hand in my pocket when working with high voltage, i also have been told that 6ma across the heart will kill, because it will cause you to skip a beat!

 

[mramos1]

Also note, the nine volt on the tongue sends the current point to point across your tongue not to your heart (but you will feel it on your tongue with the close distance and it is wet). If you have power running to each hand, the path can go thru your heart as it is a path for the current, though your body is generally high resistance.

Like Nigel said, it is an unlucky thing in most cases, but I would not play with it either way. A lot of people get hit and can get away, sometime based on current type your muscle will contract and you cannot let go or escape it. They are the unlucky ones. The heart can explode (or stop) depending on the current type.

Also, you can touch one side of 110AC main and as long as you to not give it a path, you will not feel a thing. Make sure you have shoes on (insultation from ground) as you can ground your feet and it will flow that direction. Also, that you are not touching anything grounded with the rest of your body..