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01-19-2010, 10:17 PM   #1
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## shocking amp question

No really, it's a question about shocks and amps.

Ok so from my understanding it takes about 1 amp, maybe even less to kill. So say you get a shock between the two terminals of a socket since you touched both screws or something, what exactly determines how many amps will go through you?

Now whether said socket is rated at 15, 20 or even 50 amps, I can't see that making any difference, since the rating just means that if an appliance draws that amount, it trips the breaker. Voltage is what is pushed out, amps are just what are "taken" if that makes sense. I've seen people think that you can "blow" an appliance if you give it too much amps, but, appliances are not given amps, they're given voltage, then they draw whatever amps they need. At least that's my understanding of it.

Now in the case of a series shock, such as turning off a light switch and touching the two terminals, then you would complete the circuit and get more amps through you right? So is this a more dangerous type of shock? Guess this depends on the load too, like a incad light vs a motor, might be different.

The only thing I can think of is that skin creates a resistance, then it increases the amperage so like depending on where you are shocked the resistance is greater, thus more voltage. So from finger to finger = less amps then from one arm to the leg. Water seems to give a better shock too. I noticed this when playing with about 13 9 volt batteries to see how many it takes to get a shock.

01-19-2010, 10:40 PM   #2
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The basic equation is I = V/R where I is the current in amps, V is the voltage in volts, and R is the resistance in ohms. This equation is correct for direct current, and for purposes of your question is correct for alternating current as well. So if your finger has a resistance of say 1000 ohms, and the voltage is 120 volts, and you dead short across the hots of an outlet, you will draw about 0.125 amps. A potentially lethal amperage at 120 volts AC is somewhere around 100 milliamps (that is one tenth of an amp)

However, that will only kill you if the circuit is connected across your heart, causing an arythmia. This could occur if one hand is touching a hot wire, and the other hand is grounded. The current that would flow would then be determined by the effective resistance of your body, which varies from somewhere around 1000 ohms if you are sweating to 100,000 ohms if you have dry skin. Note that the lethal ampacity varies depending on the frequency of the source, and whether it is AC or DC.

 01-19-2010, 10:49 PM #3 Wire Chewer     Join Date: Jun 2009 Location: Ontario, Canada Posts: 3,309 Rewards Points: 46 Ah ok makes sense. I'm guessing how long you are exposed makes a difference too. I'm sure if I hold on to 120 long enough it will be harmful evne if I'm drawing few miliamps. Guess the I = V/R explains why you don't feel a shock with very low voltage. For example a computer power supply gives out 12 volts, but it has a potential to give quite a few amps. I remember getting a shock from arm to arm once and it was quite the kick compared to just a finger shock. Silly person wired the ground into the hot and I was holding the "grounded" wire box and reached for something that was grounded. Never trust other people's electrical since for them a bare copper wire may not mean the same as you.

 01-19-2010, 10:49 PM #4 Member   Join Date: Sep 2008 Location: Oregon Posts: 1,497 Rewards Points: 500 Shock current path... http://vias.org/feee/safety_04.html
 01-19-2010, 10:56 PM #5 Inspector/Instructor     Join Date: Dec 2009 Location: NC Posts: 369 Rewards Points: 250 Heres a chart that may help. Courtsey of IAEI. Attached Images
 01-20-2010, 08:32 AM #6 Member   Join Date: Nov 2007 Location: Nashua, NH, USA Posts: 7,906 Rewards Points: 1,418 You are most likely to get electrocuted if the path of the electricity goes past your heart or past your spinal column (nerve trunk), such as from the finger in one hand to the sole of your foot. While dry skin has considerable resistance, salt water moisture including that in the sweat glands may result in a minute current flow starting and the skin and tissues in that vicinity get burned with more liquid (means of conduction) exposed which in turn lets the current flow increase. __________________ The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.
 01-20-2010, 08:42 PM #7 Newbie   Join Date: Jan 2010 Location: Pittsburgh Posts: 8 Rewards Points: 10 Also remember that any shock could be dangerous, regardless of how many milliamps are delivered. A relatively small shock could cause you you to flinch or move unexpectedly. Considering that most people working with electricity at some point find themselves on a ladder, a small shock could cause a fall. Anyone working with electricity, especially the DIYer, should work with the circuit de-energized! A friend of mine was changing a light switch in his kitchen. He got shocked which caused him to drop a set of pliers...of course they cracked his floor tile. A small price to pay, but a lesson learned. Turn the circuit off! http://www.electriciansgangbox.com/blog Last edited by Scuba_Dave; 01-20-2010 at 09:29 PM. Reason: nevermind
01-20-2010, 10:04 PM   #8
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Quote:
 Originally Posted by ElectGangBox Also remember that any shock could be dangerous, regardless of how many milliamps are delivered. A relatively small shock could cause you you to flinch or move unexpectedly. Considering that most people working with electricity at some point find themselves on a ladder, a small shock could cause a fall. Anyone working with electricity, especially the DIYer, should work with the circuit de-energized! A friend of mine was changing a light switch in his kitchen. He got shocked which caused him to drop a set of pliers...of course they cracked his floor tile. A small price to pay, but a lesson learned. Turn the circuit off! http://www.electriciansgangbox.com/blog
This is true, any time I've been shocked I've flinched and dropped anything I was holding. When I got my shock from arm to arm due to a badly "grounded" item (was hot!) I actually "jumped" back like 3 feet and dropped everything. It happened so fast, was like a flash. I was actually laughing for the next 15 minutes and it took at least half an hour for the sensation to go away. Had I been on a ladder I probably would not have been laughing!

I also noticed water makes the shock hurt way more.. I can't speak for 120vac as I've only gotten "Dry" shocks but at work we were messing around with lot of 9 volt batteries to see how many it takes to feel a shock. We were at 13 and I could only feel a sensation. I decided to see what happens if I lick my fingers. OUCH!

01-20-2010, 10:10 PM   #9
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Quote:
 Originally Posted by Red Squirrel This is true, any time I've been shocked I've flinched and dropped anything I was holding. When I got my shock from arm to arm due to a badly "grounded" item (was hot!) I actually "jumped" back like 3 feet and dropped everything. It happened so fast, was like a flash. I was actually laughing for the next 15 minutes and it took at least half an hour for the sensation to go away. Had I been on a ladder I probably would not have been laughing!
Yeah, I still do not follow my own advice sometimes and it ends up biting me sometimes also! If you do get shocked with enough milliamps, your body actually burns from the inside out. Google "electrical burns" and look at some pics and vids. Pretty nasty stuff! Here is a good example...
http://www.osha.gov/SLTC/etools/cons...nts/burns.html

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