Title: What is the Smallest Current that Can Be Lethal? Exploring Electrical Safety in Workshops

Wiam, so let me tell you what I mean. I had fun today at the Workshop with a 30V 3A power supply and make it a "welder" "and I touched the cables, and more precisely the uninsulated crocodile clips, and the lady from the workshop saw it and said it is dangerous, after giving a short baptism, she gives me a homework penalty On the topic of what current can kill (she meant what the smallest current can kill, someone said from the 0.5A class and said that it was too much) and I have a question, is there someone about it or some pages with this topic
Greetings, Marek :?

It is assumed that the current of 20mA flowing through the body can kill. Assuming that in unfavorable conditions, the resistance of the body (e.g. from hand to hand) can be 1KOhm, it can occur even at a voltage of 20V. Usually, it is assumed that 24V is the safest voltage. It happens. There would have to be very unfavorable conditions for these 30V to kill you. And it is still constant .... The most dangerous is the variable from the network because 50Hz causes atrial fibrillation and stops the heart rate. These 24V refers to the variable. The constant can cause electrolysis blood, which produces some kind of poison and after such paralysis you can even die the next day.

look, was on the forum many times

Hello

1mA- feeling of current flow
over 30 mA paralysis of the respiratory tract
over 70 mA onset of ventricular fibrillation
over 250 mA heart block


these are approximate values. what is also important is the duration of the effect of the current and what the current is. the most tricky thing is direct current. the effects of an electric shock may take a few days to become apparent (kidney blockage).

First, don't write in bold letters or you'll get a warning from the moderator. Go to ise.pl and look there in topics related to electric shock protection.
From what I was taught, with a current of 30 mA flowing through the human body, you cannot free yourself (muscle contraction is so strong) and you get paralyzed. When it lasts long enough, it leads to fibrillation of the heart chambers (alternating current) or to electrolysis (and poisoning) of body fluids.
You can release yourself at a current of approx. 10 mA.

I greet everyone

jjanek

oki thx for the replies so when I was holding 3A it could have killed me hehe cool

the fact that you held 3a does not mean that 3a flowed through you, the tension and resistance of your body depends on it, more likely the resistance of the hand skin. calculate the current with the law of ohma measure yourself the resistance between your hands hehe. I wonder how much will come out ?? I = U / R

Oh, buddy, you do not know Ohm's law, if you knew, you would know that the condition for the current flow is voltage, in other words, for the mentioned 20-30mA to kill you, the epidermal resistance and voltage are important.

if we are talking about flowing current, the circuit must be closed.

The circuit will be closed when you take a different pole for each hand (eg left + right - or left - phase right - neutral), then the circuit will close by the resistance of the body (assumed 1000 ohms). Know the voltage, you can count the current that will flow through the "electric circuit".

I greet everyone

jjanek

I had a pole in one hand and the other in the other and by the way I also shorted them and the maximum current flows in the event of a short circuit

Yes. But it flows through the short circuit, not through you. Shorted wires will have a negligible impedance compared to yours, in addition, the voltage at the output of the power supply will drop, you may feel like an insulator in this situation.

I witnessed my dad running up an electric motor in his hand with a 4.5 V battery and the induced current burned him.

The body resistance in not very comfortable wet conditions is CIRCA 600 Ohm, which at 24V should be safe.

But there are people and folks, some have thick paws from loading coal, others have thin skin.

Well, how many times has it happened that some robots have pierced their skin and landed it is known where.

Willing to give tutoring in physics or electrical engineering ...

And as for the comment "the circuit must be closed" ... not at all - grab a bare high voltage wire and check ... a closed circuit does not have to be because some objects may indicate capacitance ...

DetoXX wrote:

And as for the comment "the circuit must be closed" ... not at all - grab a bare high voltage wire and check ... a closed circuit does not have to be because some objects may indicate capacitance ...

that is, the circuit must be closed - after all, the compensator also closes the circuit (admittedly only for alternating currents, but always)

As for the closing of the circuit, it can also be closed by the ground and an electric shock will also occur (with sufficiently high voltages of course)

Regarding the "killing current". If you touch 2 non-insulated wires through which 1kA flows, you will not get shocked (depending on the wire, you may get shocked, but not necessarily either). If you catch 2 wires, one for 15V and the other for -15V, it might flap you.

This is so because in the first case we can deal with a cable powered by a voltage of 1V and a resistance of 1mOhm. As you know, a tension comparable to a finger will not kill anyone :)

To better understand why this is happening, you can draw both situations as a circuit in which a human will be a resistor. From Ohm's law and Kirchoff's laws, calculate the voltages on individual elements and what currents will flow through the individual branches.

From what I remember, the human endurance threshold for the value of the current intensity is 25mA. One of the factors affecting the severity of an electric shock is the voltage value. The safe value of alternating voltage for humans is 50V for normal environmental conditions, 25V for special conditions, i.e. in rooms with high air humidity, etc., and 12V in very special conditions, e.g. under water. For a fixed one, however, 120V, 60V and 30V, respectively.

Marro8 you were only in danger when you played with the "welder" in the rain or in the swimming pool. Ha ha. And Lady from the workshop, try a 9V battery.

Hi!
Nobody has explained yet how it could happen that the current "burned" someone who started the electric motor from a 4.5 V battery. A motor is an inductance. As soon as it is connected to the current, a self-induction EMF (electromotive force) or voltage is produced (in the coil). this voltage is very high, but it is very short-lived. Therefore, we can read its "kick" even when powered by a few volts. The ignition coil in motor vehicles works in a similar way.
Greetings!

it also depends on the person. one is enough 15mA and the other 30mA will be low. But theoretically, we assume that 20mA can cause human death.

As for the motor, I think it was like this:

the engine was powered not by a battery, but by a well-charged battery. Instead of starting the "dad" engine, the akku shorted and the wire got hot, burning it. If someone does not tower, let him make a short circuit on the AA 1.2V - 1.25V battery with a telephone conductor (it happens in different ways) I guarantee that it will light up in red

But you wrote it down ... The basic thing is that the human body is not a homogeneous object and neither the different components have the same resistance, nor are they equally resistant to the effects of flowing current. Dry skin is a relatively good insulator, but it is enough to have sweaty palms to reduce the resistance of the "body" by 20 times. I suspect that two needles-electrodes stuck in the vicinity of the heart will kill a man much more ecologically (more sparingly) than if he were to connect the electrodes to the adjacent toes of the right leg ...

as for the motor, it could not have been a "shock" but a "burn". when I was a kid, I played with a wire and a battery. at some point I shorted + to the housing and a current of several amps began to flow through the wire. Then I had a few millimeter holes in my finger but it didn't bleed because it stung. the same experiment can be performed using scissors, including a regular battery. rather, you won't get burned with them, but you will feel like it's warm.

Someone wrote in an earlier post that the limit for direct current was 120V. as far as I remember it was a specially prepared work station with an insulated floor and so on. I do not advise anyone to check their strength at this voltage at home ;)

As for the value of electricity - in Stanisław Bolkowski's book "Elektrotechnika" from the series "Electric Library" he writes:
"The values of the" breakaway "current (self-liberation) are: for men - 16mA, for women - 10.5mA. So the upper limit of the breakaway current was assumed to be 10-12mA at alternating current 50-60Hz" (this would explain why women are less interested in electronics )

Thanks for the posts so far that is, grandmother, it is a pity to talk about this stupid task through her. Regards, Marek

Maybe a stupid task, but you already know what is threatening you and what is not. It has a good side because you did not know what kills and what does not. Because it is not true that the electrician does not tick, but how does it tick? this electrician is fictional.

Hello

See www.republika.pl/murysz/
OHS department

Stupid or not dumb, that is the question. If someone asks on mathematics "why do I need the Pythagorean theorem", it is often the answer "to die wiser". If you ask "why do I need to know what current is killing", he will answer you "lest you die" . If you are going to "play with the current" you better know what you can touch and what better not. By the way, they should tell you such things in the studio during the first class ...

Hello!
Do you know what voltage flows in electric shepherds?
because I used to walk under one and I got hit on the ridge
and I have one more question
I want to make a ball mill and I have an old laptop power supply
it writes on the housing:
input: 230 ~, 50Hz, 100mA, 23VA
output: 30v, 400mA, 12w
can the current and / or voltage of the output do something to me?
because I want to smudge something that will allow you to adjust the speed (smooth potentiometer adjustment?) of the motor that will be powered from it (if I find a suitable one)
greetings!