Can everyone chill? I'm dead serious when I opened this thread. If my measurements are correct then it cannot kill you if Ohm's law is obeyed. So I was legitimately curious why I hear horror stories of people being blown across the room if they touch mains. I'm an electrical engineering student that wand to learn. Just answer the question or don't talk on this thread.

 

Don't forget, it takes very little current passing through your core (heart) to kill you. I'm thinking the number is 600µA but I'm too lazy to look it up.

 

Ther is no short yes or no answer to this question. It has too many unknowable variables in every situation.

The short answer is if you don't create a strong enough electrical connection then no it won't kill you. If it does then yes it will. The how's and why's vary between every person.

Personally, I have been exposed to enough shocks in my life I know how to react to a bad one and deal with it which means that hard shock that doesn't kill me could very well surprise an inexperienced person enough to kill them.

Hence the unknown variable of why something that just hurts one person a lot kills another.

 

My hand slipped forward and I contacted both prongs with a firm grip and wet fingers

Yeah, that was sort of my first experience with the buzz. I was a kid trying to plug something in and I was having a hard time. My fingers slipped forward and BUZZZZZ. I, too, have never forgotten that experience. And that was a good 50 plus years ago.

 

Yes 120 VAC can kill you and so can as little as 40~50 VDC by the way.

40-50VDC is not likely to harm you - at least electrocute you.

 

I worked on 600 VDC power in the transit industry and I managed to get by with only one shock in 32 years.

Someone put up the poles of an electric trolley bus with out notifying anyone and I touched both contacts of the line breaker that supplies power to the traction motor controller. The shock affected just my lower arm, but the emotional effect was very sobering.

That's why OSHA enacted the "LOTO" (Lock Out/Tag Out) rule and nothing can be energized without everyone removing their lock from the power disconnect switch.

 

There are many more that experience serious burns from flash over than injury or death by shock.
Max.

 

I di something stupid when I was younger. 15 ish. Sanding a car with an electric sander, so shirt, no shoes, no GFCI. Nobody home but me. Rib cage area in contact with the ground. Defective flat extension cord. I caught the defective cord between my toes.

Controlling the letting go muscle was not working, so I intentionally screamed. That actually let me control of the muscle I needed to move. Odd, but it worked. I don't remember the details.

There was a time when I started to slowly slide off the roof in a sitting position, I thought about what I learned in physics and layed down. I stopped sliding.

 

There are many more that experience serious burns from flash over than injury or death by shock.
Max.

When I was working on one of the trolley buses, another mechanic and I were troubleshooting the connections for the interior heater which was powered directly by 600 VDC from the overhead line. We were looking at a terminal block for the 600 VDC auxiliary loads when he noticed that a large wire that had come off its stud.

He said "Oh here's the problem" and touched the loose wire to the terminal. Then POW!!! a bright spark lit up the electrical compartment like a flash bulb. Luckily I wasn't blinded, but for the next hour I was having hallucinations of an orange triangle on a purple background.

The moral of the story, always remove the power before poking around for loose wires!!!

 

Out of curiosity I measured the resistance of my skin from one hand to the other. It measured about 4 MegOhms. So I wanted to see what kind of current would run through my body if I decided to jam my hands in the mains. Ohms law predicts I should have 60 microAmps running over my skin. (240/4,000,000) That sure doesn't seem like very much. What is the deal?

Disclaimer: I don't intend to jam my hands in the mains

It's entering the nerve lane what kills you. The skin thickness and salt/ PH is not constant over the body and is also a function of biological time and activities. However; voltages above the 60V, applied at the certain places, can kill you. The European standard declare 48V as save in an office environment.
Picbuster

 

I've been taking 120V shocks from hand to hand all my life since I was about 10. Sometimes with wet fingers (yes, much worse).

From cardiology rotations in medical school we were taught that 120V was VERY UNLIKELY to start a healthy heart fibrillating (spastic contractions where the muscle fibers aren't contracting in unison and blood doesn't pump).

If a heart has been ravaged by infarctions or cardiomyopathy, it is much more susceptible and any kind of cross-chest shocking should be avoided at all costs.

But again, with a healthy heart, 240V is a little more likely, but still pretty safe.

500-600V is the dangerous voltage threshold. Even a healthy heart will start to fibrillate at this voltage level.

Above 1000V, all the heart muscle fibers depolarize at the same time, so the heart should start beating again with the next pacemaker pulse. Again, with a healthy heart. But this is why defibrillators usually run at 1000V, with an energy of 100-200 joules delivered from a capacitor in 5ms.

With less energy, as in current limiting, one can tolerate higher voltages. My son and I like to make shocker toys that use inductor pulsers with transistor-radio type audio transformers to generate around 300V but with very little current. It does give our victims a nasty jolt in the arms.

 

Hello,

It is all about electrical safety.
Touching the mains can be lethal.
For electrical safety read the following handbook:
http://www.lanl.gov/safety/electrical/docs/09_doe_electrical_safety_handbook_rd.pdf

Bertus

 

Your body is not resistive or reactive. It's a bipolar active device.

Think of a balloon of saltwater. If you put a voltage across it, internal ions will separate, causing an increase in potential across boundary skin. Squeeze a little saltwater thru the skin(sweat) and you have a ready made circuit with potential. Current will flow.

 

@InspectorGadget

From cardiology rotations in medical school we were taught that 120V was VERY UNLIKELY to start a healthy heart fibrillating (spastic contractions where the muscle fibers aren't contracting in unison and blood doesn't pump).

Unfortunately, we really don't know the context of what was said and what was remembered. If your professors thought that cardiac fibrillation from shock is the only cause of death, that was wrong. Respiratory arrest is also a major cause. Moreover, there is no doubt that a 120-V shock not only can cause death, it is a significant cause of electrocution deaths. THAT answers the TS's question.

First, what do you mean by "very unlikely?" I could not find statistics from the CDC quickly, but I did find a report from NIOSH (http://www.cdc.gov/niosh/docs/98-131/pdfs/98-131.pdf ). Of course, that report only includes occupational electrocutions. Accidental electrocutions in residential settings probably show a much higher percentage for deaths from "low voltage," since residences rarely have access to voltages greater than 600 VAC. Nevertheless, 25 of the 221 deaths (11%) regardless of voltage were due to household voltage of 110 to 120 V. Of the 84 deaths due to low voltage (<600 V), household voltage accounted for 25 (34%).

Second, it is well known that voltage with negligible current through the body rarely causes death directly (e.g., all of the neat experiments with static electricity and shocks after walking across carpet). However, a jerk or fall secondary to a low-current shock can cause death and would be attributable to the electric shock as causation on a death certificate.

More directly related to the question of electrocution per se, so-called threshold currents are better associated with electrocution death than voltage, but are difficult to determine in cases of accidental death. Many factors contribute to the current, including characteristics of the source, resistance of the skin, whether the contact was through intact skin, duration of contact, and area of contact. Here are some sources for additional reading on that subject:

http://bme.ccny.cuny.edu/faculty/mbikson/BiksonMSafeVoltageReview.pdf
http://www.ncbi.nlm.nih.gov/pubmed/8566912
http://www.ncbi.nlm.nih.gov/pubmed/9662120

Regards, John

 

Apparently more people die each year from sticking a 9volt battery on their tongue than being eaten by a crocodile.

 

These are actually educational, as well as entertaining:

 

it cannot kill you if Ohm's law is obeyed.

That's assuming that a few ma cannot kill you - i don't think that's established. 36Vac is typically considered the upper end of safety for most people, higher for DC. and I can tell you from personal experience that it is not comfortable to touch 36Vac with your hands.

Having said that, what kills is the potential ***difference***. You can actually touch 100KV+ lines without being harmed, as long as your body doesn't form a loop. but that's not without risk either.

 

A finger slip across a live line will leave you shaking a bit.

The movies make it seem like a good torture idea but it is really a good way to kill a person by causing heart fibrillation.

Every time you get a shock strong enough to hurt, there is a chance it could cause a heartbeat abnormality.
Even current limited devices labeled non-lethal can be dangerous if someone already has heart issues (taser)

 

The worst one I ever had was during my training years and I needed to pull a pair of 240v ac conductors through a small hole, I assumed the power was off!
Grasping one Cond. in each hand I felt as though someone had hit me with a bat, fortunately it threw me backwards, releasing my grip.
It was even worse that the CRT HV one I had later on.
Max.

 

@InspectorGadget

Unfortunately, we really don't know the context of what was said and what was remembered. If your professors thought that cardiac fibrillation from shock is the only cause of death, that was wrong. Respiratory arrest is also a major cause. Moreover, there is no doubt that a 120-V shock not only can cause death, it is a significant cause of electrocution deaths. THAT answers the TS's question.

I don't appreciate half-truths for the purpose of inspiring fear. First of all, 120V shock is a significant percentage of electrocution deaths because the vast majority of people never have the opportunity to contact anything other than 120V. But that doesn't mean that death is a significant result of 120V contact. And I have numbers to support that further down when I discuss your half-truth numbers.

But before that you took a cheap shot with a "straw man" argument: I never said fibrillation was the "only" cause of death. But it's the most common cause of death. Respiratory arrest only happens when the muscle clonus is prolonged from the hands clamping down on the source of the current and not being able to let go. In that case you also have severe burns both internally and externally (think electric hot dog roaster) and it's often a tossup whether it's the heart stopping or the lungs stopping or cauterized blood vessels that killed you.

First, what do you mean by "very unlikely?" I could not find statistics from the CDC quickly, but I did find a report from NIOSH (http://www.cdc.gov/niosh/docs/98-131/pdfs/98-131.pdf ). Of course, that report only includes occupational electrocutions. Accidental electrocutions in residential settings probably show a much higher percentage for deaths from "low voltage," since residences rarely have access to voltages greater than 600 VAC. Nevertheless, 25 of the 221 deaths (11%) regardless of voltage were due to household voltage of 110 to 120 V. Of the 84 deaths due to low voltage (<600 V), household voltage accounted for 25 (34%).

Now you're pulling numbers out of context to create misleadingly high percentages. That's 25 deaths out of tens or hundreds of thousands of household electrocutions. And many of those electrocutions are in children, who don't have as large or strong a heart or as much internal resistance as adults. Here is a reference from the Electrical Safety Foundation International that says alongside 30,000 non-fatal electrocutions a year there were 60 deaths. That's 0.2%. And those 30,000 non-fatal electrocutions were only the REPORTED ones, out of probably 100,000 - 200,000 actual brushes with 120VAC, which would make it more like 0.05% of shocks with household electricity result in death.

Second, it is well known that voltage with negligible current through the body rarely causes death directly (e.g., all of the neat experiments with static electricity and shocks after walking across carpet). However, a jerk or fall secondary to a low-current shock can cause death and would be attributable to the electric shock as causation on a death certificate.

This is called a "red herring." It's just a distraction. Death due to falling after being electrocuted is going to be reported as an electrocution-related death.

More directly related to the question of electrocution per se, so-called threshold currents are better associated with electrocution death than voltage, but are difficult to determine in cases of accidental death. Many factors contribute to the current, including characteristics of the source, resistance of the skin, whether the contact was through intact skin, duration of contact, and area of contact.

Yes, there are many factors. But no, you can't say necessarily that "currents are better associated" because it's always both voltage and current. And in cases of household and municipal electrocution where the current supply is essentially unlimited, morbidity and mortality are absolutely dependent on the voltage level present. And that's where my guidelines of <500V, 500-100V, and >1000V came from.

In addition, there is skin breakdown at higher voltages that leads to lower resistance and more current flow. An NIH article states, "At 500 V or more, high resistance in the outer layer of the skin breaks down. This lowers the body's resistance to current flow greatly." This also contributes to my 500V threshold of danger in electrocution.

Another direct relation of voltage to heart morbidity can be found in defibrillator technology. It's known from defibrillation tests that "a gradient of three to five volts per centimeter" is needed to depolarize heart muscles in an adult. Out of the ~200 centimeters from hand to hand, you need a total of 600-1000V to induce heart muscle depolarization. At lower levels of voltage, in a healthy adult, you just won't be depolarizing muscle, and you'd have neither asystole, nor fibrillation, nor respiratory arrest.

Here are some sources for additional reading on that subject:

http://bme.ccny.cuny.edu/faculty/mbikson/BiksonMSafeVoltageReview.pdf
http://www.ncbi.nlm.nih.gov/pubmed/8566912
http://www.ncbi.nlm.nih.gov/pubmed/9662120

Regards, John

OK, I'll hand you one point in those articles. Anal electrodes are dangerous at any voltage.

But my earlier point stands, that touching 120V "very unlikely" to kill you if you're a healthy adult. Doesn't mean it can't happen. But the statistics are down below 0.1%, and most of those deaths were probably not from just "touching" 120V, but from some more robust and sustained contact, with physiological conditions contributing (youth, old age, cardiac disease, etc).

Bottom line is, if you want to be absolutely safe, never touch 120V. But will "touching" 120V kill you? No, not for the vast, vast majority of healthy adults, which I assume the TS is. And I present myself as an (albeit anecdotal) example. I've "touched" 120V a lot and I'm not writing this from beyond the grave.