Human Electrocution: How is the resistance not ridiculously high?

[Tomás Ó hÉilidhe]

I've been doing electronics for three years now but I don't understand
how a person can be electrocuted by touching one part of the circuit
in a mains supply.

If I hold one lead of an ohmmeter in my left hand, and the other in my
right hand, it registers the resistance to be approximately 2
megaohms, which is ridiculously high.
Now if I hold one lead in my hand, and dig the other into the grass,
it doesn't even register -- I may as well be holding the leads apart
in thin air.

Current = Voltage divided by Resistance

Current = 230 volts divided by 2 megaohms = 115 microamperes

115 microamperes is nowhere near enough to electrocute someone.

So lets say I stick a metal rod into the socket on the wall. The
current has to flow thru my hand, down to my foot, thru my cotton
sock, thru my shoe, thru the wooden floorboards, thru the concrete,
thru the clay down to the metal rod we call ground. Now excuse me, but
is that not a RIDICULOUS amount of resistance, up in the gigohms
somewhere?

It may sound like I'm denying that people get electrocuted -- I'm not,
I realise that people do get electrocuted. But I can't for the life of
me understand how enough current can flow, given the massive
resistances that are involved.

Can anyone enlighten me?

 

[Jon Slaughter]

I've been doing electronics for three years now but I don't understand
how a person can be electrocuted by touching one part of the circuit
in a mains supply.

If I hold one lead of an ohmmeter in my left hand, and the other in my
right hand, it registers the resistance to be approximately 2
megaohms, which is ridiculously high.
Now if I hold one lead in my hand, and dig the other into the grass,
it doesn't even register -- I may as well be holding the leads apart
in thin air.

Current = Voltage divided by Resistance

Current = 230 volts divided by 2 megaohms = 115 microamperes

115 microamperes is nowhere near enough to electrocute someone.

So lets say I stick a metal rod into the socket on the wall. The
current has to flow thru my hand, down to my foot, thru my cotton
sock, thru my shoe, thru the wooden floorboards, thru the concrete,
thru the clay down to the metal rod we call ground. Now excuse me, but
is that not a RIDICULOUS amount of resistance, up in the gigohms
somewhere?

It may sound like I'm denying that people get electrocuted -- I'm not,
I realise that people do get electrocuted. But I can't for the life of
me understand how enough current can flow, given the massive
resistances that are involved.

Can anyone enlighten me?

Your not taking into account the blood stream. It offers a direct low
resistance path for current to get to the heart. All the current has to do
is break through the skin and not flow on it. If it flowed on it then you
wouldn't die even if it was 100A(although probably serious burns) because
your heart is not directly part of your skin.

Measure the resistance of your blood and then try measuring the resistance
between two points on your skin, first without pricking those points and
then pricking them. I bet you'll find a serious change in resistance.

 

[Tomás Ó hÉilidhe]

John Popelish:

Do the calculation again but with the other hand on the
water tap or the grounded case of an appliance.

2 megaohms in series with less than an ohm = 2 megaohms

Still 115 microamperes.

 

[Tomás Ó hÉilidhe]

Jon Slaughter:

Measure the resistance of your blood and then try measuring the resistance
between two points on your skin, first without pricking those points and
then pricking them. I bet you'll find a serious change in resistance.

Scenario 1: I have intact skin on my hand, and intact skin on my foot.
I put an ohm meter across my hand and foot and measure 2 megaohms.

Scenario 2: I have an open bloody wound on my hand, and an open bloody
wound on my foot. I put an ohm meter across my hand and foot and
measure 300 ohms.

It's rare that you'll find someone with exposed blood on both their
hand and foot at the exact time that they're electrocuted. Without
even taking that into account tho, take out an ohm meter and measure
the resistance thru your sock. Then measure the resistance thru your
shoe. Then measure the resistance of a wooden floor board.

Really I just don't understand how 230 V is enough to drive current
thru me, thru my sock, thru my shoes, thru the floor boards, thru the
concrete, thru the clay, to ground.

 

[Tomás Ó hÉilidhe]

Stephen J. Rush:

The resistance of the human body varies widely, depending on the nature
of the contact. Dry skin does measure around some megohmes, but sweaty
skin conducts much better, and if the contacts abrade or penetrate the
skin, the internal resistance can be as low as 300 ohms, hand to foot.

A lecturer in my college posed this argument to me before. He said
that if you stabbed the ohm meter into your foot and also into your
hand, then you'd measure a hell of a lot lower than 2 megohms.

People are often very nonchalant about this idea of "getting past the
skin", but it's not meager feat at all.

I'm taking about simply touching the positive terminal of an
electrical socket, not about slicing your hand open, then slicing your
foot open, then touching the socket.

And, even if the resistance from hand to foot was extremely low, even
in the region of something like 4 ohms, then that still doesn't
explain how the current flows from my foot, thru my sock, thru my
shoe. I bet if I put one terminal of an ohmmeter inside my shoe, and
the other on the sole of my shoe, that the resistance will be too high
to measure. (If I had an ohmmeter I'd do it right now).

I'd love to do an experiment with one of those corpses that gets
donated to scientific research. I had considered using a dead mouse,
like the ones you get from the petshop for feeding snakes, but they're
far too small. A dead pig might do the trick.

 

[Tomás Ó hÉilidhe]

Michael A. Terrell:

Then stick your hands into a live AC power line, after making sure
your will is up to date, and your insurance is paid up. You know just
enough to be dangerous. The resistance also depends on contact area,
and what part of the body. Loose the attitude, or someone will find you
dead from your ignorance.

If you'll read my original post, I explicitly express that I _don't_
deny that people get electrocuted, so your accusations of ignorance
and "attitude" are illformed. What I'm questioning is the science of
it, as we understand it today. I've never, ever, not once, heard a
single valid explanation of how someone can get electrocuted by
touching a 230 V mains terminal.

I'm no denying that it happens. In fact I'm acknowledge that it
happens, and I also acknowledge that I don't understand how it
happens, and so I'm inviting people here to discuss the science of it.

I myself know about DC, AC, resistivity, resistance, capacitance,
inductance, impedance... but none of these things explain how 230 V is
enough to kill me if I grab the positive terminal.

Here's the path of the current:
1) From my hand to my foot: About 2 megohms.
2) From my foot thru to the other side of my sock: Probably in the
megohms, if not gigaohms.
3) From my sock to the inside of my shoe, to the sole of my shoe:
Probably in the megohms, if not gigaohms.

I just can't understand how 230 V is enough to push anything other
than a negligible current thru that gargantuan resistance.

 

[Yukio YANO]

Yes, its quite simple really, If you are like most people ,its "ouch
Shit its live !" But for a very few unlucky souls who might have wet
feet and or accidentally stepped on alive conductor, their friends will
say "hail mary". Any med-tech expects to find 50,000 OHMS or less,
between his electrodes ! In summary your resistance numbers are
optimistic to say the least, most people are very lucky, very few will
be found dead and I could electrocute someone in the middle of a desert
with only a nine volt transistor battery.

Yukio YANO

 

[stan]

Do the calculation again but with the other hand on the
water tap or the grounded case of an appliance.

How much current do you think it takes o cause death? Do you think it
matters if it's AC or DC?

Your model calculations treat the human body as if it were essentially a
lump of carbon with electrodes attached. While a typical resister is
largely considered as a fairly linear device at a constant temperature
the human body is generally not a linear resistance.

The path as well as the quantity of current matters a great deal when
trying to predict the effect on the human body. A human heart basically
operates as an electromechanical device and with typically very low
current. It really doesn't take much current to interfere with a normal
heart beat. In fact with 60 HZ AC it's very easy to cause the heart to
start something called ventricular fibrillation which is a particularly
dangerous condition. The heart becomes basically unable to effectively
circulate blood and that is a Bad Thing(TM).

The truth is that it's very complicated to determine an accurate
resistance that a human body will present to a difference in potential.
A simple multimeter will not give you a meaningful measure. The probes
and their point of contact will have a very large impact on your
multimeter reading. Not to mention with a nonlinear resistance like a
human body there's a difference between say a 9V DC multimeter and 115V
AC. Of couurse if you built a 115V AC multimeter you'd probably get a
very different reading even using the same ineficient probes from your
standard multimeter.

There are a lot of variables involved and it's not likely you will get a
meaningful resistance from a multimeter. I also think you would be
surprised how little current it can take to upset a normal heart rhythm
and cause reduced or complete loss of normal blood circulation.

There are also other impacts from current flowing through the body. It
can easily disturb the ions in the blood and cells die quickly when
required ions aren't present is correct quantity. Cells count on some
ons for proper hydration and it's not hard to over/under hydrate to the
point of permanent damage. While some cells can divide and replace the
damaged cells, the process isn't instantaneous.

Electrocution is complicated. Consider that some people survive being
hit by lightening and some die from simple contact with a wall outlet.

 

[David L. Jones]

I've been doing electronics for three years now but I don't understand
how a person can be electrocuted by touching one part of the circuit
in a mains supply.

If I hold one lead of an ohmmeter in my left hand, and the other in my
right hand, it registers the resistance to be approximately 2
megaohms, which is ridiculously high.
Now if I hold one lead in my hand, and dig the other into the grass,
it doesn't even register -- I may as well be holding the leads apart
in thin air.

Current = Voltage divided by Resistance

Current = 230 volts divided by 2 megaohms = 115 microamperes

115 microamperes is nowhere near enough to electrocute someone.

So lets say I stick a metal rod into the socket on the wall. The
current has to flow thru my hand, down to my foot, thru my cotton
sock, thru my shoe, thru the wooden floorboards, thru the concrete,
thru the clay down to the metal rod we call ground. Now excuse me, but
is that not a RIDICULOUS amount of resistance, up in the gigohms
somewhere?

Not at several hundred volts.

It may sound like I'm denying that people get electrocuted -- I'm not,
I realise that people do get electrocuted. But I can't for the life of
me understand how enough current can flow, given the massive
resistances that are involved.

Can anyone enlighten me?

As others have said, the body (and your clothing and footwear etc) and
the path taken is not just a simple resistor model, it is a very
complex model with dynamic impedance that changes with voltage. A
simple multimeter which tests at say 1V DC is not representative. If
you tried it with a "megger" resistance meter (and you shouldn't, it's
DANGEROUS!) at a few hundreds volts and it'll be a different story.
Take into account capacitive issues and it's a different story again.
And the list goes on.
Even a simplistic model is very difficult to construct.

Dave.

 

[Jon Slaughter]

Jon Slaughter:


Scenario 1: I have intact skin on my hand, and intact skin on my foot.
I put an ohm meter across my hand and foot and measure 2 megaohms.

Scenario 2: I have an open bloody wound on my hand, and an open bloody
wound on my foot. I put an ohm meter across my hand and foot and
measure 300 ohms.

It's rare that you'll find someone with exposed blood on both their
hand and foot at the exact time that they're electrocuted. Without
even taking that into account tho, take out an ohm meter and measure
the resistance thru your sock. Then measure the resistance thru your
shoe. Then measure the resistance of a wooden floor board.

Really I just don't understand how 230 V is enough to drive current
thru me, thru my sock, thru my shoes, thru the floor boards, thru the
concrete, thru the clay, to ground.

Um... your measuring the skin restance from your foot to your arm. Once the
electricity gets through your skin to your blood its much smaller. That is
the point. You think that the current must travel along the skin? The blood
is right below the skin.

Think of a wire with insulation. The insulation is your skin. The wire is
your blood. If you put a multimeter or low voltage on the insulation you
don't get squat. Your ohmmeter might read 100000MOhms or something... But
put a high enough voltage on it and it will get through the insulation to
the copper and it doesn't matter how long the wire is.

You are using a multimeter to test something and then assuming that the real
situation is like the multimeter.

If your multimeter uses 200V then its a much better test... Although your
still not taking into account other issues.

Who said it will drive current through you with all that stuff? Why do
people where protective equipment when working with HV? ITS NOT THAT IT
WILL!!! ITS THAT IT CAN!! THERES A BIG DIFFERENCE.

Do you want to take a chance of killing yourself when working with 10kV
because you accidently stepped in some wet dog poo and had nail through the
soul of your foot that was ever so slightly piercing your skin... and then
accidently stuck yourself with a HV wire? (In fac the nail doesn't even need
to pierce your skin at that voltage)

What you don't get is that accidents can happen. Chances are if you go grab
the two ends of the mains you will not get electrocuted(you probably will
get shocked)... but if you do that 100 times there is a much larger chance.

If you are cautious then you can reduce your chances significantly but that
chance always remains.

Do you realize that you can easily die from 500kV high power line just by
standing a few feet away? (In fact the chances are close to 1 that you will)

Whats the difference between 200V and 500kV? Not that much if your stupid
cause even 10V can kill. Ok, maybe not 10V as it depends on a lot of factors
but your chances of dieing go up dastically with voltage... although you can
mitagate to some degree that with a little common sense.

I think your problem is that you seem to believe because it won't kill you
in one circumstance that it will never kill you in any other circumstance.
(and you happen to be taking the best case scenario instead of the worse
case)

 

[David L. Jones]

Michael A. Terrell:


If you'll read my original post, I explicitly express that I _don't_
deny that people get electrocuted, so your accusations of ignorance
and "attitude" are illformed. What I'm questioning is the science of
it, as we understand it today. I've never, ever, not once, heard a
single valid explanation of how someone can get electrocuted by
touching a 230 V mains terminal.

I'm no denying that it happens. In fact I'm acknowledge that it
happens, and I also acknowledge that I don't understand how it
happens, and so I'm inviting people here to discuss the science of it.

I myself know about DC, AC, resistivity, resistance, capacitance,
inductance, impedance... but none of these things explain how 230 V is
enough to kill me if I grab the positive terminal.

Here's the path of the current:
1) From my hand to my foot: About 2 megohms.

On your multimeter at 1V. It will vary a LOT under all sorts of
conditions.
That has very little correlation to the "resistance" at much higher
voltages.

2) From my foot thru to the other side of my sock: Probably in the
megohms, if not gigaohms.

Same as above.

3) From my sock to the inside of my shoe, to the sole of my shoe:
Probably in the megohms, if not gigaohms.

Same as above.

I just can't understand how 230 V is enough to push anything other
than a negligible current thru that gargantuan resistance.

You just don't get it.
The "resistance" varies a LOT based on all sorts of factors, not least
of which is voltage.
The figures you have measured on your multimeter are of very little
indication at all.
That is why "high voltage" resistance meters ("meggers") are available
and commonly used to test insulation resistance at mains voltages.

Dave.

 

[stan]

Several people have tried to explain that a human body is not very much
like a typical carbon resistor. I suggest that you start by trying to
wrap your mind around that concept. Think of a cap for a second.
Frequency is one factor that impacts the impedance. In a somewhat
similar way there are many factors that affect the resistance of a human
body. Your trusty multimeter is incapable of giving you meaningful
information about a capacitor. Likewise it's incapable of giving you any
real info about the human body. Life is more complicated than we like
sometimes.

On your multimeter at 1V. It will vary a LOT under all sorts of
conditions.
That has very little correlation to the "resistance" at much higher
voltages.

I'd be very surprised if your feet don't sweat at least a tiny bit. I'm
sure you know that salt waater conducts pretty well.

Same as above.

Would depend a lot on the shoe. For a street shoe and some boots which
use nails or tacks to help hold the sole on I think you might be way
off.

Same as above.

On a good day it won't. The problem is that other day when a shoe
becomes compromised. Even when the shoe isn't the path all it takes is
an entry and an exit. Techs are taught habits that reduce the chances
you will get into a bad situation. Removing watches and rings, keeping
one hand in a pocket when reaching into a live circuit, and others. At
really high power at rf frequencies even providing a sharp point can be
a bad thing. Techs are taught not to point at anything while in the
transmitter room at LORAN stations. Pointing with a single finger can
privide an opportunity for an arc that won't be any fun.

Anyway, the resistance of a human body is very complex and bears almost
no relation to the common and much simpler carbon resistor. You're going
to have to shift your thinking here.

You just don't get it.
The "resistance" varies a LOT based on all sorts of factors, not least
of which is voltage.
The figures you have measured on your multimeter are of very little
indication at all.
That is why "high voltage" resistance meters ("meggers") are available
and commonly used to test insulation resistance at mains voltages.

Being retired military we always had a lot of meggars around. Guys would
play around with them once in awhile. It was always amazing how heavy
those test leads got so fast. I was also surprised that apparently
meggars seem to turn people into geneologists. Soon after dropping the
heavy leads they would start questioning ancestry almost without
exception. I can't explain the brain chemistry behind it, but but it was
clearly a statistically significant observation.

 

[John G]

Michael A. Terrell:



If you'll read my original post, I explicitly express that I _don't_
deny that people get electrocuted, so your accusations of ignorance
and "attitude" are illformed. What I'm questioning is the science of
it, as we understand it today. I've never, ever, not once, heard a
single valid explanation of how someone can get electrocuted by
touching a 230 V mains terminal.

I'm no denying that it happens. In fact I'm acknowledge that it
happens, and I also acknowledge that I don't understand how it
happens, and so I'm inviting people here to discuss the science of it.

I myself know about DC, AC, resistivity, resistance, capacitance,
inductance, impedance... but none of these things explain how 230 V is
enough to kill me if I grab the positive terminal.

Here's the path of the current:
1) From my hand to my foot: About 2 megohms.
2) From my foot thru to the other side of my sock: Probably in the
megohms, if not gigaohms.
3) From my sock to the inside of my shoe, to the sole of my shoe:
Probably in the megohms, if not gigaohms.

I just can't understand how 230 V is enough to push anything other
than a negligible current thru that gargantuan resistance.

No body has said much about AC and Ground.

Most everything that is not a live wire is connected to GROUND in one way or
another and so the whole environment you are in is one side of a capacitor
and so if you touch a live wire then you are the other side of this
capacitor and some current will flow because the power system is Alternating
Current.

No measurements with your punny little multimeter will mean anything in this
case and depending on a myriad of facts already discussed you could be dead.

John G.

 

[Paul E. Schoen]

No body has said much about AC and Ground.

Most everything that is not a live wire is connected to GROUND in one way
or another and so the whole environment you are in is one side of a
capacitor and so if you touch a live wire then you are the other side of
this capacitor and some current will flow because the power system is
Alternating Current.

No measurements with your punny little multimeter will mean anything in
this case and depending on a myriad of facts already discussed you could
be dead.

John G.

There is some more information at
http://van.physics.uiuc.edu/qa/listing.php?id=6793, where it states that
the external human body reistance is about 1k to 100k Ohms, and the
internal resistance is 300 to 1000 ohms. Only a thin layer of dry skin
separates the internal resistance from an external object.

The human body capacitance to a far ground is 100-200 pF, which is really a
minimum value. This correlates to an impedance of about 13 MegOhms at 60
Hz, which corresponds to a minimum of 9 uA at 120 VAC to ground. This is
enough to be sensed and used for capacitively operated light dimmers.

Here is a way to measure your body capacitance:
http://web.mit.edu/Edgerton/www/Capacitance.html

The inside of your body can be considered a conductor, and thus if you
place your hand flat on a metal plate, you will form a capacitor with an
area of perhaps 15 square inches, with a thin (maybe 0.005") insulating
layer of dry skin, which will form a capacitor much higher in value than
the 200 pF stated above. According to a formula in
http://www.sayedsaad.com/fundmental/11_Capacitance.htm, this would be C =
0.2249 * k * A / d = 1350 pF, (assuming k for skin is 2, about like dry
paper). This will be an impedance of about 2 MegOhms, and current of 60 uA.
This is still below the normal threshold of sensation, and still far below
the usual safe current levels of 1 to 5 mA.

The actual thickness of the epidermis (per
http://dermatology.about.com/cs/skinanatomy/a/anatomy.htm) varies from 0.05
mm (0,002") for eyelids to 1.5 mm (0.06") for palms and soles, but the
actual outer layer of the epidermis that is a good insulator is composed of
flat, dead cells, which is much thinner. So the capacitance could be much
higher than the quick estimate above.

Probably the main reason for electrical current to reach levels high enough
for electrocution to occur (6 to 200 mA for 3 seconds, according to
http://www.codecheck.com/ecution.htm), is when skin becomes sweaty or
otherwise loses its dry protective layer, which quickly exposes the
underlying 1000 ohms or less, which will conduct 120 mA at 120 VAC.

There are safe ways to measure the body's resistance and capacitance using
realistic higher voltages, skin conditions, and contact surfaces, but I'm
not going to suggest anyone try it. Suffice it to say that ohmmeter
readings are misleading, and any carelessness around any kind of voltage
source can be dangerous.

For very high voltages, there are standard minimum distances that must be
maintained between a worker and an energized line:
http://www.dir.ca.gov/oshsb/rubberglove.html. I found this on a search for
rubber glove testing. My previous company manufactured oil and glove
insulation breakdown testers.

The field intensity near high voltage lines is so great that it might be
fatal to touch them even if you were suspended in free air. You may notice
that birds can sit on lower voltage transmission lines which are 5kV to 50
kV or so, but not on 200kV+ lines.

Paul

 

[Teodor Väänänen]

Chuck skrev:

Probably not I.

But have you considered the difference in potential between your head
and your feet when you stand outside? A somewhat different situation
that may cause you to pose the same questions.

Another thing that occured to me while reading this thread is the
question of what kind of ohmmeter the OP used to get 2 Megohms...
My interests apart from electronics have occationally caused me to
experiment with skin galvanic response (the resistance of the skin and
how it drops and rises under certain circumstances (wikipedia it)).

One thing I noticed during those experiments is that I get a much higher
reading with Digital Multimeters than with old-school Analog ones. IIRC,
the main difference between the two types of meter is that the digital
ones tend to measure the voltage drop over the resistor when connected
to a constant current source, while analog ones tend to to be a battery
connected in seriers with the meter (through a variable resistor to be
able to null the meter).

I do not claim to know the cause of this, but my hunch is that the
amplifier (OP or Transistor) picks up hum from the body, making the
reading be a little off. I do not know if making the amplifier
insensitive to AC voltages is a priortiy for the designers, but it
wouldn't surprise me if they save money on not making it so.

Oh, BTW, the readings I've got with my analog meter have been 50k to
150k -ish, which puts it near the area of being dangerous with regards
to current passing through your body. Factors I've noted that affect
skin resistance is your emotional state, area of contact (2 leads when
compared to, say, two washer with leads soldered to them), to name a few...

And the traditional "my worst zap story":
I've accindentally connected myself to a 235VAC/50Hz power grid, phase
in on hand, neutral in the other (don't ask). I actually heard the 50Hz
hum in my ears, and my ticker occationally still bitches about it, a
whole 14 (sic!) years later... Yes, I do respect the national power grid
a lot more these days

Just my $.02 worth,

/Teo.

 

[Don Klipstein]

I've been doing electronics for three years now but I don't understand
how a person can be electrocuted by touching one part of the circuit
in a mains supply.

If I hold one lead of an ohmmeter in my left hand, and the other in my
right hand, it registers the resistance to be approximately 2
megaohms, which is ridiculously high.

I do find readings like this for this situation to be common.

Now, for some factors to complicate this:

1. Skin being just a little on the moist side - due to body chemistry,
mood, recent past activity, body response to ambient temperature and
humidity - it's a little common for this to be a few hundred K-ohms rather
than a couple megohms. Occaisionally this kind of reading can get down to
50K ohms or so.

2. Current in the roughly-1-milliamp range or more can do a few things
to make the resistance decrease:

a) Stimulate sweat glands - especially if the current is AC or
pulsating DC of frequency probably anywhere in/near the lower half of the
audio range, especially 50/60/100/120 Hz

b) Cause electrolysis that results in a decrease in contact resistance
over time.

Try holding tightly two bare wires coming from a DC power supply of
voltage of whatever voltage is low enough for you to assume is safe and
not have yourself or next of kin sue me over if things go wrong in any
way, with a milliammeter or microammeter in series with the current path.
If that voltage is around/above 12 volts, see if that current stays
steadily low or starts increasing.
Imagine what could happen at 120 volts.

c) At/near 120 volts or more, localized heating could occur at skin
contact points. Skin and body fluids generally have negative
temperature coefficients for their resistance, especially skin.

===========================

Other things to consider:

1. You may get accidentally shocked or shocked by malfunctioning
equipment with skin contact area larger than that typical with handling of
ohmmeter leads.

2. You could get such a shock if sweaty or otherwise wet.

3. The most-widely-mentioned "fatal range" of current, for causing
ventricular fibrillation, is 100 mA to 1 amp for an arm-to-arm or
arm-to-leg shock with 50-60 Hz AC. (Increase of current past 1 amp has
fatality rate less than that of .1-1 amp, in case of arm-to-arm shock with
"power line frequency AC", but there is still some fatality rate from
outright cardiac arrest - plus risk of vital organs getting outright
cooked.)

This is merely a "most deadly range", with the "deadliness" not dropping
to zero at 99 or 90 mA. Some sources say 50 mA is the lower end of the
range of having a fairly significant chance of causing ventricular
fibrillation from an arm-to-arm shock, and a small number of sources say
that 30 milliamp neon sign transformers (which have current-limiting
means, unlike most transformers that are not "lamp ballasts") have a bit
of a body count!

For that matter, I have seen one bit saying that there is some chance of
fatality at currents as low as around 5 mA - from someone being paralyzed
by the shock, with paralysis including paralysis of breathing muscles.

Keep in mind that shock causing someone to involuntarily maintaining a
position that maintains exposure to the shock is widely said to be worse
with DC, but is actually worse with AC (or pulsating DC as opposed to
steady DC). Steady DC is "less-shocking", since most effects of electric
shock result from variation of current.
The horror stories from people receiving severe electrical burns on (and
also inside) their bodies mostly involve those zapped with either DC or
radio frequencies - so that they survive to tell the horrors!

======================

Keep in mind that electrocution can get unreliable. The "Electric
Chair" appears to me designed to rely on the jolt either cooking vital
organs, and/or paralyzing breathing muscles (and preferably also the
heart) long enough to have the brain deprived of oxygen severely enough to
be unable to restart breathing when the jolt stops.
Sometimes the condemned is subjected to more than one jolt.

As unreliable as electrocution is, lack of fatality from electric shock
is similarly unreliable.

======================

The human body is a 470K-ohm 1/4 watt resistor with tolerance of
+5000/-98 % and a negative temperature coefficient!

(I don't know who started this, and I could easily be "off" with the
numbers somewhat for that one)

- Don Klipstein ([email protected])

 

[Don Klipstein]

How much current do you think it takes o cause death? Do you think it
matters if it's AC or DC?

AC is worse. Pulsating DC is worse than steady DC.

DC gets some worse reputation due to higher survival rate of those
getting zapped with current that causes horrific burns, especially to
internal tissue that heals slowly or never heals right.
Being jolted into maintaining body position that has you getting zapped
is often said to be worse with DC, but that is actually worse with AC (or
pulsating DC). The horror stories come more from survivors than from
those who don't live to tell horror stories.

- Don Klipstein ([email protected])

 

[[email protected]]

On Apr 4, 10:47 pm, [email protected] (Don Klipstein) wrote:

  AC is worse.  Pulsating DC is worse than steady DC.

  DC gets some worse reputation due to higher survival rate of those
getting zapped with current that causes horrific burns, especially to
internal tissue that heals slowly or never heals right.
  Being jolted into maintaining body position that has you getting zapped
is often said to be worse with DC, but that is actually worse with AC (or
pulsating DC).  The horror stories come more from survivors than from
those who don't live to tell horror stories.

 - Don Klipstein ([email protected])

Has Tomás Ó hÉilidhe stopped responding because he offed himself ?

GG