Electronic Engineering

[Andy]

Sorry to interrupt ...

I started a thread about electronics for fun. If anyone is interested, you can read/post here: http://webmasterjuice.com/thread-323.html

[Andy]

The shocking truth about Volts and Amps ...

I often hear in movies or TV the warning that an electrical connection contains deadly current. Well, the thing is, current is only deadly if it flows through your body in significant quantities and either burns you or stops your heart beating. This takes high Voltage! Check out Ohms law.

Without the high voltage, there can be no deadly current. Touch the + terminal on a car battery for proof. That battery can source 100+ amps of current. But the 12V won't be enough to cause deadly current to flow through your body to earth via your body and clothing.

You would have to pee yourself on grass, lick the terminal, and be hot and sweaty to get into any kind of trouble, and that may have nothing at all to do with the current.

OK, if you are creative enough, you could get a good current between the + and - terminals, so maybe don't try unless you are making a viral Youtube video.

[Andy]

This is truly electrifying information that should jolt your curiosity.

[Menard]

Oh...the PUNishment 

[donecweb]

Sorry, to disagree Andy but you can get a fatal shock without high voltage if you have the right conditions. It only (theoretically speaking) takes .1 amp to boil your blood or stop your heart. OHM's Law says .1 amp X (lowest body resistance) 300 ohms = 30 volts. This means that in theory if your body measured 300 ohms and you grounded your self to .1 amp source with 30 volts DC then you would have .1 amp flowing through your body. Of course your body usually is probably closer to 800 or 900 ohms so to get .1 amp current flow you would need 80 volts DC. That is not high voltage, even 110 v is not considered high voltage. I used to drive people crazy because I used my finger to trouble shoot a circuit that was fed by 280 amps while watching an "O" scope to see the effect my finger (using the skin resistance of my finger to short the pins of IC chips) had on a 1 microsecond pulse. I could do this because I was only working with 5 volts DC. If the voltage had jumped to 80 volts I could have been killed. Of course I was standing on a safety mat and had a grounding strap attached to my wrist for protection.

[Andy]

But the heart is inside of the body, so you have the paths of current to consider. To get a lethal potential difference across the heart takes some skill with low voltage application IMO   You probably have to wire up some needles and poke them into your chest.

Over a 3D area, the current will distribute itself between the source and sink points so it is a very difficult model to predict if the human body is the conductor. And I think, only the heart and brain are the organs that you could die from being electrocuted. But I may be wrong, DYOR before testing this theory out. I would start with battery clips on the ear lobes. But there is a balance between initial pain and overall conductivity.

[donecweb]

The current will not distribute it's self, but will follow the path of least resistance which will be the minerals in your blood like the iron. It does not take hardly any current to stop the heart or start it just voltage can do that. This is why the shock paddles used in many emergency vehicles run on 9 vdc batteries. In a circuit if the resistance drops the current will rise if the voltage stays the same. The greatest resistance in your body is your skin so once the resistance of the skin is overcome then you will have an increase of current flowing due to the drop in resistance. Since it only takes .1 amp to boil blood then as the current increases the blood will boil causing massive clotting which has killed more shock victim's than having their heart stopped and is why people do not have to receive an electrical shock that passes through their heart to be killed. Further should you touch a wire that has a small single strand that punctures your skin the a voltage as low as 30 volts with .1 amp can kill because the resistance of the skin has been bypassed.

[Menard]

The current will not distribute it's self, but will follow the path of least resistance which will be the minerals in your blood like the iron.

I would argue that once the skin is punctured that many parts of the body are good conductors unto themselves due to the large percentage of water composing our bodies. Iron, zinc, copper, and other conductive minerals do not exist in large enough of quantities in our bodies to be effective conductors; perhaps with the exception of magnesium which is second to calcium in its presence in the body.

(yes, anybody thinking we need hobbies or girlfriends is absolutely correct )

[Andy]

I don't think I am gonna die from 9 volts since I zapped myself a few times with mains voltage and lived. The worst that happened was that I got some holes burnt into my skin.

And I suspect that the pads of the emergency service gear are delivering much more punch than just 9 volts, more like 900V to get the body to jolt. They take time to build up the charge, so there is a charge pump cranking up the voltage and people need to stand clear of the pads. I know this since I saw it on TV dramas.

9V will do nothing unless you apply it to the tongue like we used to do at school.

Think about Tazers, they are non-lethal high-voltage units designed to bring down a rampaging DonEc (for example) with his revved up chainsaw or whatever without killing him. Rubber bullets are another option.

[donecweb]

I would argue that once the skin is punctured that many parts of the body are good conductors unto themselves due to the large percentage of water composing our bodies. Iron, zinc, copper, and other conductive minerals do not exist in large enough of quantities in our bodies to be effective conductors; perhaps with the exception of magnesium which is second to calcium in its presence in the body.

(yes, anybody thinking we need hobbies or girlfriends is absolutely correct )

Water will not conduct it is the surface of water that conducts and the minerals within the water that conducts. While it is true that electricity will follow multiple paths it will not disperse.

[donecweb]

I don't think I am gonna die from 9 volts since I zapped myself a few times with mains voltage and lived. The worst that happened was that I got some holes burnt into my skin.

That's the point I am trying to make. The 9 vdc is harmless but by using special circuits they can make a heart start and stop using just a 9 vdc batter due to the fact they are increasing the voltages to high voltage with out hardly any current.

And I suspect that the pads of the emergency service gear are delivering much more punch than just 9 volts, more like 900V to get the body to jolt. They take time to build up the charge, so there is a charge pump cranking up the voltage and people need to stand clear of the pads. I know this since I saw it on TV dramas.

9V will do nothing unless you apply it to the tongue like we used to do at school.

Think about Tazers, they are non-lethal high-voltage units designed to bring down a rampaging DonEc (for example) with his revved up chainsaw or whatever without killing him. Rubber bullets are another option.

Tazers operate in the kv range and produce almost no current but they can change the rhythm of the heart and the stronger ones if used excessively can kill by stopping the heart, again this is done with voltage alone no real use of current and no boiling of blood just burn marks on the skin.

[Menard]

Water will not conduct it is the surface of water that conducts and the minerals within the water that conducts. While it is true that electricity will follow multiple paths it will not disperse.

Water will conduct, especially depending on the ion density of the water. True, purified water is not a good conductor compared to metals, but we don't have purified water in our bodies.

A material which does not conduct, or is a better insulator than conductor, but will conduct electricity on the surface is glass; which, btw, is a liquid.

[Andy]

Trying to claim that low voltage and high current is lethal, is misleading, for example, a NiCad battery may be capable of high currents such as 100 Amps at 9.6 V or whatever as used for model car racing, but if one falls in your bath I would not expect to die any time soon. But throw in a hair drier or bar fire, then I would get worried even though they may only be able to source 1/10th of the current.

Faced with volts, I am a running man, but amps, I laugh and pull out my bazooka to blow you away sucker!

And in regard to water conduction, this smacks of somebody that did too much reading and not enough experimentation. Dip nails wired up to a battery into some tap water and you will see bubbles appearing on the nails UNDER the water. Throw in some salt to make it better.

[donecweb]

Trying to claim that low voltage and high current is lethal, is misleading,

What do you consider high voltage and low voltage?

for example, a NiCad battery may be capable of high currents such as 100 Amps at 9.6 V or whatever as used for model car racing, but if one falls in your bath I would not expect to die any time soon. But throw in a hair drier or bar fire, then I would get worried even though they may only be able to source 1/10th of the current.

At that low of a voltage you do not have enough voltage to overcome the resistance of the skin so the amps do not matter. The voltage required to overcome the resistance of the skin varies since the resistance of the skin varies. However! in some people the resistance of the skin is low enough that 27 v can pass through. This is not the common situation but it is possible. For these people high amps and 27 v can be fatal. More commonly it would take more in the line of over 80 v to overcome the resistance of the skin but 80 v is not high voltage.

Faced with volts, I am a running man, but amps, I laugh and pull out my bazooka to blow you away sucker!

Quite simply don't work on electricity or in electronics then, as with that opinion you would not be safe.

And in regard to water conduction, this smacks of somebody that did too much reading and not enough experimentation.

You are free to think what ever you want but this information is from 38 years of hobby, experimentation, practical everyday work, specialized training and teaching in the field of electronics covering all levels of electronics including true high voltage of circuits of over 35 KW of power and working with 35 Kvdc with over 500 amps all the way down to 5 vdc and a few milliamps of current. So lets not take this to a personal level. This is one area that I am qualified to discuss and teach.

Dip nails wired up to a battery into some tap water and you will see bubbles appearing on the nails UNDER the water. Throw in some salt to make it better.

Your not talking about a proper controlled experiment and so you can not qualify your results or know why you got those results. In the given situation the surface of the water along the surface of the nails and across the top surface of the water creates a great path for the conduction of current and so you could get the results you describe. Now place a meter in completely demineralized water (like they used to use in high powered radio amplifiers for coolant) with the negative probe touching ground but not the surface of the water and the other probe just floating in the water and the place a live wire into the water. You may get sparks and other indications but the meter will not read any current flow through the water because the water will not conduct. Now add some minerals like dissolving salt in the water and you may at some point see the meter start reading current flow as the minerals conduct current.

[Andy]

Good response, sorry about the getting personal  

I am a bit reckless when it comes to electricity and other things at times.

As a boy, I nearly killed myself a few times playing with electricity, and my mom was afraid to enter my room due to all the wires.

At an early age I connected my toy car to the household mains and blew up the fuse box.

I'm trying to remember what sparked my interest in the subject.