Low Current High Voltage

beenthere

Joined Apr 20, 2004
15,819
I believe that confining conduction to the skin layers is a function of high frequency.

But, if you're really wet with sweat, the best conduction path may not be under the skin for AC or DC. Electric shock is always somewhat unpredictable.
 

b.shahvir

Joined Jan 6, 2009
457
But, if you're really wet with sweat, the best conduction path may not be under the skin for AC or DC. Electric shock is always somewhat unpredictable.
Normally Electrical Engineers claim that AC conducts more easily thru the human body as compared to DC, whatever the skin condition.

This claim gave rise to the historical debate between Edison (all for DC supply) and George Westinghouse (all for AC supply). Edison claimed that AC supply is more dangerous as it could conduct easily thru human body and hence can be used for execution purposes giving rise to the idea of the electric chair! :eek: Hence, I want to understand as to what factor makes AC supply (at fundamental frequencies) more dangerous than DC supply. :confused:

Thanks & Regards,
Shahvir
 
is it also true that some freqensies push you and some pull you i'm a elctritian and have a bit of personal experiance with shocks 220v50hz tend to be shocking(pun intended) on a more mental note were as electrick vence had a more of a devestating evect it felt as if i got kicked by a horse
 

steinar96

Joined Apr 18, 2009
239
You can think of the volt count as the energy that every electron has when it moves trough you. A single electron with an energy of 20kV is pretty much just beta radiation (aproximation) and in large numbers is quite hazardous.

So no matter how "few" electrons or small current. With this energy it will always do you harm as it will transfer its energy to you once it's inside your body.
 

b.shahvir

Joined Jan 6, 2009
457
on a more mental note were as electrick vence had a more of a devestating evect it felt as if i got kicked by a horse
I too have experienced this 'kick by a horse effect' when I was once electrocuted while working on a blender motor rated at 220VAC, 50Hz. :eek:

But it doesn't recur always!
 

thingmaker3

Joined May 16, 2005
5,083
is it also true that some freqensies push you and some pull you
This is true of different AC voltage ranges as well. Some cause a spasm which will cause the victim to sometimes throw theirself clear, others will lock up the muslces & keep the victim from letting go.

Safety protocols should always be adhered to!
 

b.shahvir

Joined Jan 6, 2009
457
This is true of different AC voltage ranges as well. Some cause a spasm which will cause the victim to sometimes throw theirself clear, others will lock up the muslces & keep the victim from letting go.
This seems to be quite interesting! is there an online link or paper which represents the effects of different AC frequencies or voltages on the human body? Also the effect when the supply is DC?

Thanx. :)
 

Truchaos

Joined Oct 29, 2009
1
Ive read a quite a few bits of incorrect information in this forum. Ive managed a series of electrical engineering laboratories for over two decades and have spent a good bit of time learning about electrical safety and Id like to share with you some of the things Ive learned.

First, human skin resistance varies greatly. In fact, the measurement of the skin resistance change is used in polygraph machines (lie detectors) and is called galvanic skin response. As you perspire your skin resistance lowers. One day you can touch a 115 volt line and receive a mild buzz because your skin is dry, another day it could be a fatal shock because your skin is more conductive. I worked with a man whose hands were very calloused and dry, as a result he could handle live 115V wiring without any sensation of a shock. DO NOT TRY THIS!

Sources of electrical shock are not created equate. For example, a 50,000 volt (50KV) stun gun can use a 9 volt transistor radio battery to generate its voltage. However, the current is very small, so the peak power is also small hence the ability to generate 50KV from a small 9 volt battery (a 9volt battery has a low power density). On the other hand, a 50,000 volt transmission line has currents in the 100s or 1000s of amps. The peak power is very high. So, to be shocked by a 50KV stun gun is painful but survivable due to its very low current capacity (low peak power). A shock from a 50KV transmission line is almost always fatal because of the current capacity (very high peak power).

I was once struck in the chest by the discharge of a 500,000 volt Tesla Coil. While the coil was a 400 watt coil, I survived. I was sick for three days but I didnt suffer permanent damage. Had that been a 500,000 volt transmission line I would have burst into flames and would have been dead before my body hit the floor.

A very common misconception about electrical shocks is that the lower the current the safer the shock. Years ago I had a very good chart (which Ive since lost) that plotted the death rate versus shock current. At the very lowest end of the current scale the death rate was higher, then as the current increased the death rate lowered then it increased again. The plot resembled a U. The death rate is higher at the lower end of the scale because low current shocks can throw the heart into fibrillation. Which is a dangerous arrhythmic condition of the heart. Unfortunately the heart often does not self correct this arrhythmia and death can occur. Oddly, the medical treatment for this condition is to shock the heart at a higher current. As the shock current increases, the heart will stop completely then when the current flow stops the heart starts again so the death rate drops. This is exactly what happens with a defibrillator machine (the paddles used to jump start hearts on the TV shows). As the shock currents continue increase, the fatality rate increases with tissue / nerve damage.

hope this helps.
 
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