Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Electric shock?

Status
Not open for further replies.

chris414

New Member
I'm trying to find out when exactly an electric shock becomes lethal. I've heard that you need a certain current to flow across your heart (the number i've heard is 9mA), which is obviously dependent on the voltage source and the resistance of your body and the path the electricity takes when travelling through your body. Where does the length of time you are shocked come into the equation? I know that the power dissipated by your body = I²rt, but surely that's only referring to how badly your body gets burnt by the shock and not what's going to make your heart stop?

On a similar note, how do electric fences and tazers ensure that the person is only shocked and not killed? Simple current limiting like one would use in a lab power supply...?
 
From past experience with this question, you are going to get about 10 different answers. May I inquire the purpose of your query?
In the mean time check this link.
http://vias.org/feee/safety_04.html
 
Last edited:
Fatal depends entirely upon the person.
If they are old frail weak and sickly then a few Ma could be enough.
If they are strong and healthy a few tens of ma can still be taken and lived through.
 
Here is an interesting site on this subject. They say that the danger zone is in the range of 100mA to 200mA.
Here is another site that says the same thing.

Don't shoot the messenger.:eek:
 
As far as the heart goes even a healthy person can't sustain more than a few mas of current for even short period of time, it has absolutely nothing to do with the health of the person it has everything to do with the nerves that transmit the hearts pacemaker signal from the brain being stunned into fibrillation or damaged to the point where a normal rhythm can't be restored in time due to nerve damage. No physical damage to the heart needs to occur for it to be lethal. This same thing can happen to breathing regulation.

As far as I²R heating goes this is NEVER good as body tissues don't generally like to be cooked =) However it is a separate issue from possible heart or breathing stoppage. Which is why even current limited high voltage electricty can be dangerous.

As far as tasers go they are VERY carefully current controlled. The intial voltage on them is incredibly high, something like 50-100kv's but current limited to prevent instant death, once the probes hit and intial high voltage starts conduction the taser automatically goes into lower voltage (few thousand volts) mode that is very low current designed (and quiet effective) at causing uncontrolled muscle contractions. The heart being in the center of the body is seldom in the direct path of the electricity so the danger to the important parts of the nervous system tend to be limited, however even a very safe taser can overwhelm someone with a weak heart or an otherwise compromised nervous system. There have been several reported deaths of people that were tased, sometimes long after the tasing actually occurred from nervous system shock.
 
Electric shock CAN be lethal at anything over 50mA or so. But it's a lot like rolling a dice.

Electricity is a very poor way to kill, even electric chairs with massive currents, shaved body parts and clamped electrodes kill poorly and have had some gruesome failures to kill in history. Even with modern technology the electric chair is not considered a good killing machine and is way behind lethal injection and gas.
 
As far as the heart goes even a healthy person can't sustain more than a few mas of current for even short period of time, it has absolutely nothing to do with the health of the person it has everything to do with the nerves that transmit the hearts pacemaker signal from the brain being stunned into fibrillation or damaged to the point where a normal rhythm can't be restored in time due to nerve damage.

Sorry Sced, I have to disagree with you here. Indeed the health of a person is a factor in the fatality due to electric shock. Contrary to your statement that "it has everything to do with the nerves that transmit the hearts pacemaker signal", there are many physiological effects that occur in the body that leads to the eventual demise.

During an electric shock the human cells are exposed to elevated temperatures and many are damaged, cell membranes burst, and many enzymatic processes fail to function. In addition, many bodily functions are bio-electric such as muscle function and during an electric shock the bio electric functions can be disrupted in turn causing uncontrollable muscle control. One such outcome is the fibrillation of the heart muscle, and back to your statement; age has a good deal to do with it as a weakened muscle and overall unhealthy body will fail with much less stress than a healthy body.

Also the vagus nerve (Pacemaker) controls heart rate, not heart beat, other nerves serve that function, so the pacemaker does not have everything to do with it.
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top