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Posted by: Dave

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Topic: Dangers of electricity  (Read 6 times) previous topic - next topic
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Dangers of electricity
In this post I am going to outline exactly how dangerous electricity is


Current


Contrary to popular belief it is the current that will kill you.

10mA (0.01A) is enough to cause pain and depending on the location, a severe shock.

100-200mA (0.1-0.2 A) are fatal if across your heart or brain.

To put this in context your phone battery is typically capable of providing a sustained 2.5-3.5 amps.

So with that in mind you might wonder why you are not getting electrocuted any time you accidentally touch a battery terminal......


Skin


Your skin provides a huge amount of resistance, dry skin will cause a resistance of up to 100,000 ohms as a point contact. Large contact areas or AC electricity reduce this resistance quickly.
Wet or broken skin however can drop to about 1000 ohms.

It also needs to be noted that voltage below 10 V is quasilinear, in that it does not generally have the same interactive characteristics as higher voltages. 10-20V are nonlinear but symmetric and after 20V it tends to be both nonlinear and symmetric, at this point conductivity can increase in orders of magnitude in an extremely short period of time (milliseconds )
This means that current flow cannot be calculated using ohms law.


Shock location.


The area the electricity travels through your body dictates whether it causes serious injury or death.
If the current flows across your heart or through your brain, it's game over. Hip to leg, you may get away with burns as long as a part of the current doesn't find a way to your heart.


Voltage


Voltage × Amps = Watts.

Voltage on its own however can do nasty things to skin. High voltage (above around 600V) can cause Dielectric breakdown to occur within your skin cells, this in turn reduces the resistance of your skin, allowing more current to flow.
As stated above 100-200mA is fatal so it won't take much to cause a fatality.


TL:DR


There is a lot in the above to take in and that's a digest of several hours of revision for me as it's not something I've dealt with since college.
The long and short of it is, above 10 V you can get a shock, above 20V you can get badly injured very quickly and it is impossible to calculate how safe you really are.
Remember there have been recorded fatalities at just over 40v.
If you are not 100% sure about what you are doing with electricity then reconsider whether you should be doing it.

 

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