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Voltage and the Current Shocks

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purifier

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I was wondering if someone could give an explanation for the following:

1. How is a shock experienced?

2. I heard that when you touch a voltage source it pushes you off and when you touch a Current source it tries to pull you in.. Is this correct or merely some kind of a joke?

3. What is the ideal voltage that is fatal to a human?

4. What is the ideal current that is fatal to a human?

5. What do you think is the resistance offered by a human body?

6. I've been seeing in the news that a person survived a 20000V shock!!! How is it possible?
 

purifier

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Haha... Its not that i want to off someone... I've been hearing a lot of people saying the things about shocks and so i wanted to know it myself... The site was very useful thanks a lot....
 

epp

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1. AC
Because of 50/60 Hz your heart start to quickly ran according to frequency and your'e dead.
DC
Thermal effect. Water from your body's cell are disappeered and you're dead after some time.

2. You're pushed on or off depending of your mucules.
3. AC >50V, 50Hz
DC >100V
4. see 3.
5. 1000 ohm
6. His skin is like an insulator.
 

    purifier

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purifier

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But I think that the resistance offered by a human body is variable..and is not fixed at 1000 ohm... What do u say? And also how can that person's skin act as an insulator..?? Any explanations for this....
 

epp

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purifier said:
But I think that the resistance offered by a human body is variable..and is not fixed at 1000 ohm... What do u say? And also how can that person's skin act as an insulator..?? Any explanations for this....

You're right, but it is usually that you use 1000 ohms as body's resistance. In power dissipation it is about 100 W.

I do not know how in english to explain that his skin acts as insulator. E.G. Something is wrong with its skin so he has no water in some parts of a skin. His skin on a hand is pure electrical insulator (only electrical).
 

electronrancher

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neither push you in or pull you out - this is 100% bogus!

voltage is equivalent to the depth of some water (or the height of water in a tank), and current is equivalent to how much can flow at one time, such as the size of the pipe.

current is the real strength of electricity, and that is what will kill you. voltage only makes you feel it more - for example a stun gun can generate 100,000 volts but almost no current. a person is shocked severely, but not killed.

on the other hand, a car battery is only 12v, but it can supply several hundred amps. 12v may not conduct well with dry hands, but with wet hands you are dead. wall mains will easily kill you, industrial power will easily kill you, but a gas grill ignitor will NOT.

shocks are fatal when the cross the heart - arm to arm, head to crotch. a person may be anywhere between 10 kOhm when they are dry to 500-600Ohm when they are wet.

skin is not an insulator under any conditions. a person is like a bag of salt water to electricity, and only how wet/dry the skin is will affect how badly one is shocked.

last but not least - i hope you decide not to kill anyone or yourself. your questions are a little weird, and very targeted at lethal shocks. at least go look for a lightning storm so it looks like an accident and your friends can collect insurance on you - haha!
 

    purifier

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purifier

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electronrancher said:
neither push you in or pull you out - this is 100% bogus!

voltage is equivalent to the depth of some water (or the height of water in a tank), and current is equivalent to how much can flow at one time, such as the size of the pipe.

current is the real strength of electricity, and that is what will kill you. voltage only makes you feel it more - for example a stun gun can generate 100,000 volts but almost no current. a person is shocked severely, but not killed.

on the other hand, a car battery is only 12v, but it can supply several hundred amps. 12v may not conduct well with dry hands, but with wet hands you are dead. wall mains will easily kill you, industrial power will easily kill you, but a gas grill ignitor will NOT.

shocks are fatal when the cross the heart - arm to arm, head to crotch. a person may be anywhere between 10 kOhm when they are dry to 500-600Ohm when they are wet.

skin is not an insulator under any conditions. a person is like a bag of salt water to electricity, and only how wet/dry the skin is will affect how badly one is shocked.

last but not least - i hope you decide not to kill anyone or yourself. your questions are a little weird, and very targeted at lethal shocks. at least go look for a lightning storm so it looks like an accident and your friends can collect insurance on you - haha!

That's an outstanding reply!!! Thanks a lot...
So, if it gives out 10000V and low current everything is checked using the relation P=IV... So, does it mean the power remains constant or low?

I'm not getting exactly because when someone goes and touches a Home Power Supply(220V 50Hz) as he is on the ground, the current passes from the source through the body... and that gives the shock... Now, when someone says that the High Voltage gave a shock do you mean that the small current present gives us the shock?

And ok...many people are getting a doubt if i am planning to kill someone :) Come on buddies, i'm increasing EK(Electronics Knowledge) as I'm a student of ECE... And we are never taught the practical applications but only those complex ciruits... God, when will our education system change??
 

IanP

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a car battery is only 12v, but it can supply several hundred amps. 12v may not conduct well with dry hands, but with wet hands you are dead

I don't think a car battery can kill you.
According to Guid-lins for the saf use of electricity underwater, issued by A.O.D.C (The Association of Offshore Diving Contractors maximum unprotected dc voltage in underwater operation (salt ocean water) is 24Vdc.
 

sefton

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Its not about current OR voltage - it's about power - ie a combination of the 2. Take an electric fence for example which is about 10 000 volts. The output energy (joules) are limited (by law) so that only a very small current will pass through you - you still get a good kick, but do not die.
Also ohms law applies, so if your body resistance limits the current say with 100 volts, it wont be so bad, but if your hands are wet, it will be much worse.
Also remember that the nuetral of the mains supply is earthed at the power station, so you can get a shock by touching just 1 wire (live) because the return path flows through earth. DC is worse than ac (same voltage) because with ac the voltage and current pass through zeroevery half cycle, and so with dc it is difficult to let go.
 

FANT

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Usually is the current that gives you the shock sensation.
These are the standard currents and their effects ( based on 50 Hz frequency ):

0 - 3 mA = no effect, small sensation of discharge

3 - 10 ma = strong sensation of electric shock, but is possible to disconnect from mains and no permanent damage.

10 - 30 mA = if the contact remains for some seconds, risk of heart stop, your muscles react with contaptions and you nave no more the control over them.

30 - 100 mA = Bigt risk of heart stop, contraption of the thorax muscles and then asphyxia.

> 100 mA = reduces the risk of heart stop, but increase the damage due to the thermal effect of the current and the risk of internal hemorrhages due the vaporization of the blood inside the veins and subsequent rupture of the vein.

Mandi
 

purifier

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Can someone summarize the whole thing please... Because we have been getting three different views... current, voltage, power...
 

usernam

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The severity of electric shock depends on the current flowing through the body.
The effects of different values of current is
1 mA
Threshold of feeling, tingling sensation.

10-20 mA
Let-go Threshold current - onset of sustained muscular contraction.

100-200 mA
Ventricular fibrillation, fatal if continued.

As to how long you can receive a shock and still survive it depends on your heart. During a severe shock it suffers from ventricular fibrillation which is the disorganized pumping of the heart.
According to IEEE Std. 80, you can determine the maximum safe shock duration by the formula, t=0.116÷I. Where I is the current in amps and t the time in sec.
 

electronics_kumar

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I ACCEPT WITH SMALL CHANGE

a person may be anywhere between (10-50) kOhm when they are dry to (500-600)Ohm when they are wet.
 

masai_mara

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Hi,
All of them are correct in a way. But as mentioned previously the amount of flow of current is what determines whether the shock is fatal or not. And you have to remember the amount of current that flows depends on the voltage driving it and the resistance of the path of current flow. yes as given before roughly a current of 15ma or more sustained for a peiod of time (say a few tens of seconds) is going to be fatal.
So this being the case now the amount of current that flows depends on the body's resistance, particularly skin. but as noted earlier the skin generally dosent offer more than a few kohms of resistance at most, which we can take to be fairly constant with some exceptions. so it all comes down to what is the voltage supply driving it. but a high voltage dosent necessarily imply a big shock as the voltage has to sustain throughout its current delivery. that is the reason that static electricity which can build upto more than 1000v dosent bother us other than a mild prick because its voltage immediately drops to around zero the moment it is shorted(but it can be lethal to IC's). this is same with many small portable batteries also(there are exceptions!!l)
hence a source of voltage which is sufficiently high to pump in the threshold current and also can maintain its voltage during that time is defenitely a killer apparatus to beware. So => donot be careless with the electricity supply from the grid, even if its 110v, its got huge capacity generators feeding it to push these currents for any duration of time.

hope this is clear.
 

checkmate

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Just some deeper thought. Burns from current is not necessarily the most fatal cause of death. Severe muscular contraction (especially the heart) may just as likely kill you, and it has found that 50-60Hz AC has a resonant effect with nerve impulses to give the maximum damage compared to DC. One danger point about DC is that the contraction is sustained. A person shocked with AC would probably let go of the line like a hot potato. But one shocked by DC may grip on to the line even more tightly, allowing current to finish the job.

Some ref : https://www.meralco.com.ph/Consumer/didyouknow/electrical_hazard2.htm

No matter what, electricity is dangerous and precautions should always be made.
 

DrDolittle

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Even i have seen in some shows in which a person surviving high voltage across his body. That's because there is no completion of current loop in his body. Formation of even a small loop will cause a detrimental effect.
Regarding the body resistance, it has a different value when in dried state compared to wet state.
Pushing ypu out and pulling you in is medacious. There is no such thing.

Regards
drdolittle :)
 

usernam

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DrDolittle said:
Even i have seen in some shows in which a person surviving high voltage across his body. That's because there is no completion of current loop in his body. Formation of even a small loop will cause a detrimental effect.

How do maintain an incomplete loop? After all, the equipment delivering the current is connected to the earth and you are probably standing on the earth too. Or do they stand on some huge rubber block or somehing?
 

DrDolittle

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The current just passes through the body and gets earthed. By completion of loop i mean a mesh like structure or likewise gettting formed in the body.

Regards
drdolittle :)
 

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