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Whats the real killer, voltage or amperage?

M

Mr. J D

Jan 1, 1970
0
I have always heard that the amount of amperage that a power supply
could provide to a load, your body, was the real killer. But people on
here are saying that under 50 volts is non-lethal.I have heard a story
about a navy electrician who poked himself, under the skin, with a
probe of a multimeter, to both of his thumbs on his hands, having them
come in contact with his blood. When he turned it on to find the
ohmage, the 9V Multimiter, fibrillated his heart, killing him.
CNN reported that a milionth of an amp can kill you, 1 micro amp. If
this is true, than why doesnt a tazer kill you? The barbs on a tazer
rip in to the skin, making a complete circuit, just as the 9V
Multimeter case.
Whats the real deal here?
 
M

Mr. J D

Jan 1, 1970
0
I have been shocked by an Strobe ECAP that discharged 300 volts to me,
the sensation I could describe as a thousand pins poking at me. If
voltage was the real killer, than I should have been killed.

However, because of the resistance of my skin, my body did not assume
much amperage. Doesnt thisd support the fact, that amperage is the
killer and not voltage?
 
A

Al

Jan 1, 1970
0
Mr. J D said:
I have been shocked by an Strobe ECAP that discharged 300 volts to me,
the sensation I could describe as a thousand pins poking at me. If
voltage was the real killer, than I should have been killed.

However, because of the resistance of my skin, my body did not assume
much amperage. Doesnt thisd support the fact, that amperage is the
killer and not voltage?

It depends on the path. If it's through your heart, 5 ma is enough.

Al
 
M

martin.shoebridge

Jan 1, 1970
0
It is the current that can be delivered, not the voltage, that kills. The
current will depend entirely on the conductivity/resistivity of your body.
Your tongue is particularly conductive, hence the 'interesting' tingle on
your tongue when you lick a 9V battery. For most people, voltages above 80
or so can become lethal if the source can supply 'unlimited' current.
 
M

martin.shoebridge

Jan 1, 1970
0
Al said:
It depends on the path. If it's through your heart, 5 ma is enough.

Al
And that's why smart guys keep one hand in their pocket when working with
potentially lethal voltages.( TV's especially!)
 
M

Mr. J D

Jan 1, 1970
0
martin.shoebridge said:
And that's why smart guys keep one hand in their pocket when working with
potentially lethal voltages.( TV's especially!)

Yes. not only that, but if to never touch a pontential voltage source
with your palm. It is always best to touch with the nuckle side of the
hand. By doing this, your hand wont contract and grip the wire.
 
H

Homer J Simpson

Jan 1, 1970
0
Mr. J D said:
I have been shocked by an Strobe ECAP that discharged 300 volts to me,
the sensation I could describe as a thousand pins poking at me. If
voltage was the real killer, than I should have been killed.

However, because of the resistance of my skin, my body did not assume
much amperage. Doesnt thisd support the fact, that amperage is the
killer and not voltage?

Duh.
 
J

John Larkin

Jan 1, 1970
0
I have always heard that the amount of amperage that a power supply
could provide to a load, your body, was the real killer. But people on
here are saying that under 50 volts is non-lethal.I have heard a story
about a navy electrician who poked himself, under the skin, with a
probe of a multimeter, to both of his thumbs on his hands, having them
come in contact with his blood. When he turned it on to find the
ohmage, the 9V Multimiter, fibrillated his heart, killing him.

Urban legend. It didn't happen.
CNN reported that a milionth of an amp can kill you, 1 micro amp. If
this is true, than why doesnt a tazer kill you?

You believe CNN?

John
 
M

Mr. J D

Jan 1, 1970
0
John said:
Urban legend. It didn't happen.


You believe CNN?

John

I believe CNN more than Fox news. Now that is not to say that I found
their story that mention 1 micro amp could kill you a little
misleading.
 
J

John Larkin

Jan 1, 1970
0
I believe CNN more than Fox news. Now that is not to say that I found
their story that mention 1 micro amp could kill you a little
misleading.

CNN doesn't know a milliampere from a microampere, or a kilowatt from
a kilowatt-hour.

John
 
M

mc

Jan 1, 1970
0
The question is misconceived -- sort of like "What do you need to breathe,
air pressure or air flow?"

Voltage is a force, like pressure. It is the force that makes current flow.
It can be present even when no current is flowing (like the pressure of
compressed air in a tank when none of it is leaking out).

Voltage, when it meets conductance, causes current to flow. Current =
amperage = zillions of electrons per second. (An amp is some huge, fixed
number of electrons per second.)

We normally express conductance as resistance, which is its reciprocal:

Zero conductance = infinite resistance

Zero resistance = infinite conductance

In between, resistance is measured in ohms.

The human body has a certain resistance. Electric current flows through it
in proportion to the voltage applied.

Current is the killer, *but* this current is *caused* by voltage.

That is:

Nothing happens to you if no current flows through your body.

Current cannot flow without a voltage to cause it.

If you connect your body to something with a high enough voltage, a
significant current will flow. "High enough voltage" is usually reckoned as
about 30 to 200 volts depending on how you make contact (e.g., dry skin vs.
broken skin).

See? All this physics stuff (Ohm's Law) isn't just a dry abstraction. It
is a vitally important description of how something works.
 
M

mc

Jan 1, 1970
0
Now in more detail...

Mr. J D said:
I have always heard that the amount of amperage that a power supply
could provide to a load, your body, was the real killer.

No. The amount of amperage that it CAN provide has NO effect unless it is
actually providing it!

A power supply normally tries to put out a constant voltage, delivering as
many amps as will flow through the load resistance.

Most power supplies will be damaged if the load has very low resistance and
the power supply tries to deliver more amps than it safely can. That's what
the "amperage it can provide" means.

Some power supplies have current limits and will simply decrease the voltage
if they cannot maintain the normal voltage while delivering the amps
demanded by Ohm's Law.

A few power supplies, such as neon sign transformers, have a high resistance
built into the power supply to limit the current that will flow to a very
small amount.
But people on
here are saying that under 50 volts is non-lethal.I have heard a story
about a navy electrician who poked himself, under the skin, with a
probe of a multimeter, to both of his thumbs on his hands, having them
come in contact with his blood. When he turned it on to find the
ohmage, the 9V Multimiter, fibrillated his heart, killing him.
CNN reported that a milionth of an amp can kill you, 1 micro amp. If
this is true, than why doesnt a tazer kill you? The barbs on a tazer
rip in to the skin, making a complete circuit, just as the 9V
Multimeter case.

1 microamp can kill you if it flows directly through the heart muscle.
Normally, lethal current is much larger, some tens of milliamps. The
current from the Taser is limited to a very small amount.
Whats the real deal here?

Well, as I sometimes say to people I'm tutoring, "You can't understand it
without understanding it." You can't think about volts and amps without
knowing what they *are* and how they *work*. That's what the physics of
Ohm's Law is all about. "Volt" and "amp" need to become more than just
words to you.
 
J

James Thompson

Jan 1, 1970
0
Mr. J D said:
Yes. not only that, but if to never touch a pontential voltage source
with your palm. It is always best to touch with the nuckle side of the
hand. By doing this, your hand wont contract and grip the wire.
If you test for voltage that way, My condolences - RIP.
 
E

Eeyore

Jan 1, 1970
0
Mr. J D said:
I have always heard that the amount of amperage that a power supply
could provide to a load, your body, was the real killer. But people on
here are saying that under 50 volts is non-lethal.

Typically. It's not voltage that's the killer though, it is indeed current.

I have heard a story
about a navy electrician who poked himself, under the skin, with a
probe of a multimeter, to both of his thumbs on his hands, having them
come in contact with his blood. When he turned it on to find the
ohmage, the 9V Multimiter, fibrillated his heart, killing him.

That's why I included a caveat in my reply stating caution about contacting
*bare flesh* as opposed to skin. The resisitivity is very different.

Graham
 
E

Eeyore

Jan 1, 1970
0
Mr. J D said:
I have been shocked by an Strobe ECAP that discharged 300 volts to me,
the sensation I could describe as a thousand pins poking at me. If
voltage was the real killer, than I should have been killed.

However, because of the resistance of my skin, my body did not assume
much amperage. Doesnt thisd support the fact, that amperage is the
killer and not voltage?

Would you mind asking your silly questions elsewhere ?

Graham
 
E

Eeyore

Jan 1, 1970
0
Mr. J D said:
Yes. not only that, but if to never touch a pontential voltage source
with your palm. It is always best to touch with the nuckle side of the
hand. By doing this, your hand wont contract and grip the wire.

Also don't wear rings.

Graham
 
E

Eeyore

Jan 1, 1970
0
Mr. J D said:
I believe CNN more than Fox news. Now that is not to say that I found
their story that mention 1 micro amp could kill you a little
misleading.

40 mA is where it starts getting dodgy.

Graham
 
S

Stanislaw Flatto

Jan 1, 1970
0
Mr. J D said:
I have been shocked by an Strobe ECAP that discharged 300 volts to me,
the sensation I could describe as a thousand pins poking at me. If
voltage was the real killer, than I should have been killed.

However, because of the resistance of my skin, my body did not assume
much amperage. Doesnt thisd support the fact, that amperage is the
killer and not voltage?
"There is more than one way to skin a cat!"
a) To get your heart into fibrillation you need through it ~9V at about
=50uA and in such timing that it confuses the timing of nervous system.
That's why you work with one hand in your pocket when near such systems.
b) To "cook" you to crisp you need energy. As your body resistance
decreases under the influence of voltage more and more current flows
through it, so if the source can supply enough you become "well done" in
few seconds.

Have fun

Stanislaw
Slack user from Ulladulla.
 
M

mc

Jan 1, 1970
0
Summing this up even more pointedly:

Volts and amps do not go around separately from each other. They are not
two independent variables. One of them, along with resistance, is the cause
of the other.
 
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