how much voltage to kill?

[Borkil]

So I had a power supply running at 1V but with 50 amps. Would it be dangerous to touch it? I know it doesn't take very much current to kill, something around .1 mA, but 1V is not enough to drive the current into someone right?

 

[lakedude]

So I had a power supply running at 1V but with 50 amps. Would it be dangerous to touch it? I know it doesn't take very much current to kill, something around .1 mA, but 1V is not enough to drive the current into someone right?

Oh boy, where to start...

What kills you is current across your heart. Zap your heart it messes with the normal beating and you are a goner.

Fortunately for you, your heart is deep inside your body.

Your skin provides most of the resistance to shock. If your skin is dry there is a high resistance so it takes a lot of voltage to push current into your body.

If you have been sweating your resistance is lower so it would be easier to push current into your body so it would take less voltage to be dangerous.

Voltage provides the push where current is the flow.

1v will never push enough current into your body to hurt anything. The PSU could be a million amps @ 1v and it would be perfectly safe, unless you ran the wires straight to your heart.

Generally speaking up to around 50 Volts is considered safe. The current path also matters a lot.

If the current goes from arm to arm straight across your heart you could die from a relatively small shock. While if the current went up one leg and down the other away from your heart you would be relatively safe.

Remember it is the current across the heart that does it. Unless you are talking about so much power you cook yourself...

 

[Borkil]

Oh boy, where to start...

What kills you is current across your heart. Zap your heart it messes with the normal beating and you are a goner.

Fortunately for you

yes i know, my question is about high currents but low voltage and how much voltage. i have 1v and 50 amps, so resistance of the circuit is .2 ohms. say my finger has a resistance of 10,000 ohms. so if i touch it, about .02 mA will go through me correct? i am just checking that even with high amperage, if the voltage is low enough it is not dangerous.

EDIT: lol i just wrote that and then saw your new edit

 

[PowerEngineer]

I think that the answer to your question depends on the nature of your power supply.

Is your power supply designed to act (more or less) as a voltage source or a current source. In other words, does the power supply hold the output voltage at 1 volt regardless of the level of output current, or does it hold the output current at 50 amps regardless of the level of output voltage. If it's the former, then the current through your body as a result of 1 volt is trivial (like handling a flashlight battery). However, if it's the latter, then you wouldn't want to insert yourself into the circuit (i.e. become part of the closed loop) because the power supply will raise its output voltage as much as it can to keep that 50 amps flowing -- through you.

Most power supplies I'm familiar with are (non-ideal) voltage sources.

 

[Paperdoc]

PowerEngineer is right. The specs on power supplies can be viewed as simultaneous maxima. In OP's case, the power supply is limited to a max output of 1 Volt no matter what the load (and thus current) is, AND to a max of 50 amps no matter what the load is (and hence, the voltage necessary to push that current through the load). In most cases, the limit imposed by the max voltage available becomes the actual factor limiting the current, because most loads have resistances over 0.1 ohms (which would allow a current of 10 amps driven by the 1.0 volts).

The most dangerous common problem for humans is current through the heart area - most specifically, through the nerves of the heart that control its muscle movements. A current of 10 to 20 mA may be sufficient to throw the heart into arrhythmia (did I spell that right?) and thus fail to keep blood supply flowing. That's one reason that GFCI devices typically trip at unbalanced currents of 5 mA or less. Because of resistance of the skin and the body interior, it seems that a voltage across two hands (and thus arms and chest) over about 30 volts may be felt, and as little as 50 volts may cause dangerously high current. BUT if the hands are really wet, the skin resistance drops a lot, and voltages as low as 25 to 30 volts MAY cause real problems for the heart in that path. Less voltage than that, however, is rarely a problem unless it is applied almost directly to the heart (thus skipping the resistance of the skin).

So, to answer OP's original question: no, it is not dangerous to touch that power supply's output. In fact, it is not dangerous to touch the output posts of a common automobile battery which has 12 VDC out, and CAN supply a few hundred amps to a low-impedance load like the starter motor. Even if you were to wet the fingers of one hand and place them across the battery's posts (thus producing a low skin resistance and short current path) you would not feel the small current travelling through your fingers, and they are loaded with sensitive nerves in the finger tips.

 

[Mark R]

The most dangerous common problem for humans is current through the heart area - most specifically, through the nerves of the heart that control its muscle movements. A current of 10 to 20 mA may be sufficient to throw the heart into arrhythmia (did I spell that right?) and thus fail to keep blood supply flowing.

Almost right.

The main cause of death in accidental electrocution is cardiac arrhythmia, where the heart beats in an unsynchronised or excessively fast way, such that no, or almost no, blood gets pumped.

An electrical current though the heart can trigger a dangerous cardiac rhythm disturbance (most commonly discussed in this context is ventricular fibrillation, which is fatal within a couple of minutes). The risk of developing VF is dependent on the current and the length of time that the current is applied. Most guidelines state that a current of 30 mA through an adult torso, will have a negligible risk of triggering VF, provided that the current flow lasts less than 1 second. Below about 10 mA, there is essentially no risk. Above 30 mA, the "safe" time rapidly declines.

Most residual current devices/GFCIs are set to trip within 10 ms at a current of 30 mA. This provides more than adequate protection against VF. The problem with using more sensitive breakers, is that there is an unavoidable current flow between hot and earth, caused by the inherent capacitance of a wire. A large home with a 10 mA breaker at the service is likely to suffer unacceptably frequent false tripping, because of capacitative currents, and that's even with no appliances connected. A lot of appliances are naturally "leaky" - e.g. water heaters, as the ceramic insulation eventually degrades due to the heat, but such leakage is not harmful, provided that the heater is earthed.

Note that the figures are based upon current flow through the torso of an adult. Children and infants are potentially at higher risk - but as the major risk of electrocution is from damaged cables, and as children and infants tend not to use power tools (which are the major hazard) this is considered acceptable. As it is, the "instant" trip of a GFCI provides sufficient safety margin that even an infant would be unlikely to be harmed.

If the current flow is directed through the heart itself, you need very much less current (and voltage). A typical medical pacemaker has an adjustable voltage, but if the heart is reasonably healthy, you may only need a pulse of 100 mV or less, to stimulate the heart muscle.

 

[donfm]

The generally accepted value of current that will kill you is somewhere between 100-200ma at 60Hz
which varies by the person and the age but 200ma will kill you for sure across your heart. At only 1v output I don't think you have anything to worry about. As has already been discussed the voltage doesn't kill you the current does. I once got 480v across my chest at work and I'm still here to tell about it. But it did burn the skin a bit. Thank god for skin resistance!!!

 

[john3850]

Many years ago I got bad shock while holding on to the side rails of a 440v heat conveyor and the handle of new faulty 220v air compressor.
It took over 3min. before I blacked out and let go.
For that 3 min I could hear the people talking about me but I could not talk back to them no matter how hard I tried.
Since then I melted a few screwdrivers but no more big shocks.

 

[Borkil]

I think that the answer to your question depends on the nature of your power supply.

Is your power supply designed to act (more or less) as a voltage source or a current source. In other words, does the power supply hold the output voltage at 1 volt regardless of the level of output current, or does it hold the output current at 50 amps regardless of the level of output voltage. If it's the former, then the current through your body as a result of 1 volt is trivial (like handling a flashlight battery). However, if it's the latter, then you wouldn't want to insert yourself into the circuit (i.e. become part of the closed loop) because the power supply will raise its output voltage as much as it can to keep that 50 amps flowing -- through you.

Most power supplies I'm familiar with are (non-ideal) voltage sources.

it's set to hold output at 50A lol, the 1V was the measurement of the circuit. but there is a vrm in circuit

 

[donfm]

Many years ago I got bad shock while holding on to the side rails of a 440v heat conveyor and the handle of new faulty 220v air compressor.
It took over 3min. before I blacked out and let go.
For that 3 min I could hear the people talking about me but I could not talk back to them no matter how hard I tried.
Since then I melted a few screwdrivers but no more big shocks.

My experience was similar....I was luckily working in a hospital at the time. I blacked out and next thing I remember is a staff member putting me in a wheelchair wheeling me to the Emergency Room. When you don't have any accidents for a very long time you get a bit too overconfident and lose your fear of working with electricity....and that is the result....glad you are ok. I have a great respect for it now.

 

[john3850]

I woke up on life support 2 days after a car accident.
I broke leg on chopper once and had a few minor dirt bike accidents but noting in my life came close to that 3min shock.
I get a little up tight when working with 440 volts and sweaty hands you can feel the voltage in your hand while your just holding meter probes.

 

[Modelworks]

The main cause of death from electricity isn't the electricity. The cause of most deaths from electric shock are from the reactions that people have when shocked, the normal reaction is to jerk back the arm, hand, leg. When a person jerks back a hand and works on a ladder they fall from the ladder. Imagine working in a busy factory with lots of machinery and getting shocked, or how about operating something like a table saw or an arc welder. While doing hobby electronics you have a very hot soldering iron, possibly chemicals like flux , the jerk of a hand knocking over flux could cause a fire.


I got shocked last week while moving something around in my aquarium. One of the powerhead pumps had a slight crack in the cord and when I went to move it, I got shocked, I jerked my hand back out of the water , dropping the pump, hitting the overhead light with my hand, and removing some skin from one finger that got scraped on the side of something. I did more damage to myself than the electricity.

Keep what I was told years ago in mind, work with electricity with the mindset that every wire can be live, and keep the left hand in your pocket.