I'm not an electrophysiologist, or even a doctor. But I do teach CPR, and I have a great interest in the proper operation of the heart.
If we restrict this discussion to death due to heart disruptions, it's slightly easier to comprehend.
However, the simplistic ohm's law calculations for metallic conductors are not going to provide good answers, given that the electrical system of the heart is based on the movement of ions through cell membranes.
I'm also not a biologist, but my understanding of the very basics of the heartbeat is that the cells use energy to put themselves in a polarized state, and then an electrical wave travels along those cells to trigger the depolarization, and the muscle contraction that pumps the blood to your body. The cells then repolarize, and the cycle repeats until that day when it doesn't anymore.
Anything that interferes with that wave can put you into an arrhythmia, some of which are incompatible with life. (That's what medical people say instead of saying that you die.)
You can apply good electricity to the heart, as in a pacemaker, or you can apply bad electricity to the heart, as in you stuck a paper clip into an outlet.
A defibrillator stops the heart, at which point you hope that its natural rhythm will return. A defibrillator won't shock a stopped heart (flat line).
References: https://opentextbc.ca/anatomyandphysiology/chapter/19-2-cardiac-muscle-and-electrical-activity/
Message: 5
Date: Tue, 18 Dec 2018 08:27:02 -0500
From: Peter Schoch <pschoch@fandm.edu>
To: Forum for Physics Educators Physics Educators <Phys-L@phys-l.org>
Subject: [Phys-L] Current or Voltage is the thing that kills?
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that contradicts it. In response to this video, a thoughtful student wrote
me the following:
"...here are my calculations and conclusions: ohms law: [image: I={\frac
{V}{R}},] states that current is equal to voltage divided by resistance.
This means that current is limited by by the voltage of the circuit and the
inverse of the resistance of the circuit. That being said, humans are not
good conductors, relative to metal such as in wires. In fact, a typical
resistance for 'human' is anywhere from 500(very wet skin)- 100,000(dry
skin) Ohms. For comparison, a typical wire is usually around the .1 - .01
ohm range, meaning that there is a minimum of 3 orders of magnitude
difference between the resistance of wet skin (e.g. your tongue) and even a
bad wire. Thus, if you have a power supply producing 10 volts, even if the
current it can produce is infinite, the maximum that could run through your
tongue is given by: [image: LaTeX:
I=\frac{10}{500}=.02\:amps\:=\:20\:miliAmps]I=10500=.02amps=20miliAmps This
is enough to hurt and even cause strong muscle contractions, but it isn't
enough to kill, which is 60 miliAmps (for DC it is actually higher than
this), and this is on your tongue. In fact, in the video, this is exactly
what Mehdi Sadaghar does to himself. However, for dry or even mildly damp
skin, this value would be < 1 miliAmp, which would not even be felt. So
while it is in fact the current that kills you, saying only that "current
kills, not voltage" is similar to saying that cancer doesn't kill people,
organ failure does. While this isn't strictly wrong, it isn't completely
true either, and it can give people the wrong impression. This would also
explain why warning signs say 'High voltage' not 'High Current'."
While I agree that you can't have a current without a sufficient voltage to
move it, they don't 'discover' that in lab until the second or third week
(the first week or two being spent on just familiarizing themselves with
the various peices of equipment and what they do).
Ultimately, my question is -- Should I stay with my simple "current kills"
message to drive home the necessity for safety; or, should I ammend it in
some way?