I'm trying to make my workshop safer but I can't understand how electrocution happens.

For example, one hand is touching to live wire and neutral wire is not touched. If I know right, current flows from live wire to my body and to ground wire or earth but dry human hand's resistance is between 10-40k ohm so even my feet is touching directly to ground current is between 5.5-22mA and fatal dose is 30mA but how people get electrocuted from live wire without touching to ground or neutral wire?

Also can I measure resistance between live wire (or my hand) and ground? So I can get more accurate results.

I think I wasn't clear about my question : In my scenario neutral wire is insulated so current "have to" flow into ground , I understand my body's resistance not enough but floor or house have resistance too .

I made a small test for measuring resistance between my house and ground and I got three results :

1)One probe of multimeter connected to ground wire other probe connected to floor (I tried radiator too same result) multimeter showed more than 20M ohm resistance

2)One probe of multimeter connected to ground wire other probe connected my hand (feet touching to floor) multimeter showed 5M ohm resistance

3)One probe of multimeter connected to ground wire other probe connected to my left hand and my right hand touching to ground wire ,multimeter showed 200k ohm resistance

So only third scenario allows 1-2mA current other scenarios seem safe . if you see any mistakes in my tests please notify me so I can learn the truth. Also when I making these tests I used special extension plug which only conducts ground wire other wires isolated from plug

  • 2
    \$\begingroup\$ "Maybe most of people who got electrocuted is touching live wire and neutral wire at same time" I can tell you from experience that this statement isn't a correct assumption. I've been electrocuted by 440V and it was because somebody wired something wrong in both cases. All I did was touch the metal casing of the equipment and got zapped both times. Luckily all I got was a single phase... \$\endgroup\$ – Ron Beyer Sep 1 '19 at 20:21
  • 1
    \$\begingroup\$ Stop playing - you might get it wrong... \$\endgroup\$ – Solar Mike Sep 1 '19 at 20:22
  • 3
    \$\begingroup\$ Stop treating 30mA as a hard barrier between fatal and not fatal. That's like saying a bullet is only fatal when it becomes larger than X caliber. \$\endgroup\$ – DKNguyen Sep 1 '19 at 20:25
  • 2
    \$\begingroup\$ I'm voting to close this question as off-topic because it is not about making workshop safer rather than speculating under what conditions you can get an eletrical shock. The latter is NOT E.E. \$\endgroup\$ – Huisman Sep 1 '19 at 21:34
  • 2
    \$\begingroup\$ @RonBeyer If you lived to talk about it then you were not electrocuted. You were just shocked. The definition of electrocution requires that you were killed by an electric shock. \$\endgroup\$ – Elliot Alderson Sep 1 '19 at 22:48

The amount of current needed to kill is not some exact number. It is around 20mA. One person will die at 20mA, another lives despite more current flowing through his body.

Body resistance is not fixed, either. On a cool, dry day where you don't sweat your skin resistance will be higher than on a muggy day with the sweat pouring off your body.

220VAC can push enough current through your body and through the ground (the literal ground or floor under your feet) to kill you.

Never work on live 220V circuits.

Have all 220V circuits in a closed, insulated or grounded container when they are operating.

Have a ground fault interrupter installed in the house wiring or outlet you use when experimenting.

Your "theory" that people are only killed by touching live and neutral is wrong. If you rely on live to ground being safe, then it will kill you one day - and before that, you will experience painful shocks from the current that isn't quite high enough to kill you.

The ground wire in your house is connected to the ground (literal ground made of dirt outside your house.)

The ground wire is connected to the neutral wire in your house.

Your house and the floor are connected to the ground, and thus to the neutral.

Grabbing the live wire while standing in your house is therefore the same as touching live and neutral.

| improve this answer | |
  • \$\begingroup\$ I have differential relay in my workshop don't worry . Everyone saying body resistance changes but I'm asking how the current flow through ground or neutral wire ? Like everyone knows plastic boots prevent electrocution but floor have high resistance too , why it reacts differently ? \$\endgroup\$ – Mordecai Sep 1 '19 at 20:36
  • \$\begingroup\$ Wood and concrete aren't rubber. \$\endgroup\$ – JRE Sep 1 '19 at 20:39
  • 4
    \$\begingroup\$ Besides simple resistance, there is also a capacitor effect between your feet and the floor. Even if you have an insulator (rubber or plastic) between your feet and the floor, AC can still make it's way through you. \$\endgroup\$ – JRE Sep 1 '19 at 20:41
  • 1
    \$\begingroup\$ i read a post earlier from someone that said, that he has learned that a differential relay does not always prevent a shock \$\endgroup\$ – jsotola Sep 1 '19 at 21:17
  • 1
    \$\begingroup\$ @Mordecai: Houses have resistance. How much they have varies. If you depend on it having enough resistance then some day you will touch a live wire in a house where the resistance is lower than you expect - and it will kill you. So, act like houses are made of copper. It is safer. \$\endgroup\$ – JRE Sep 2 '19 at 5:38

First, dry hand resistance is 10-40k ohms, maybe. But it varies from person to person, and when you're stressed, it goes down.

People generally find it very stressful to be holding onto a live electrical wire, unable to let go because it's shocking the @#$% out of them. Think about that for a moment...

If it's hot and you're working anyway, you'll be sweaty. Sweat is mostly salt water. Think about that for a moment...

In addition, that 30mA figure is what is immediately fatal -- getting a lesser shock may not kill you immediately, but it can damage your heart. You may not care now, but future-you may not be happy with present-you, and your future-spouse will be really unhappy with present-you.

Yes, you can survive a few shocks -- more at 120V North American voltages than the 220V of most of the rest of the world, but even 220V. The last time I got zapped (with 120V), I felt it in my chest for most of the afternoon. I certainly thought about that, and how pissed my wife will be with me if I happen to keel over 20 years too early from congestive heart failure brought on by playing with live wires in my youth.

Read up on proper lab procedures, and follow them. Most really bad accidents happen because of a concatenation of errors. You don't stay safe by looking at the first possible error and saying "that won't hurt me". You stay safe by looking at the rare possibilities and keeping them from happening.

Because the first time you grab 600V because you were treating it as 60V? It'll be a once-in-a-lifetime event. Literally, and tragically (and your spouse will be pissed).

| improve this answer | |
  • \$\begingroup\$ Often it is because the shock time does not hit the heart cycle at the right, or wrong, time so you survive... \$\endgroup\$ – Solar Mike Sep 1 '19 at 20:29
  • \$\begingroup\$ But circuit supposed to be closed so for example my feet is touching to wooden floor , current has to flow through my body and floor ? I remember in the university my teacher said voltage isn't important , if you're touching metal surface even 5V can be deadly \$\endgroup\$ – Mordecai Sep 1 '19 at 20:29
  • 2
    \$\begingroup\$ @Mordecai Don't exaggerate, the 5v can't hurt nobody. What is below 48VDC or 34 VAC is safe. \$\endgroup\$ – Marko Buršič Sep 1 '19 at 20:33
  • \$\begingroup\$ @MarkoBuršič 20mA across the heart at the right time in the heart cycle can stop the heart... not something you want to test to prove it... \$\endgroup\$ – Solar Mike Sep 1 '19 at 20:41
  • 1
    \$\begingroup\$ @Mordecai I personally know somebody who was electrocuted to death on 4160V, I know 2 people who died (but were revived) working on 1KV transformers. I've been shocked more times than I like to admit on 120V and never died. I don't know where you're getting that information but it is dangerously incorrect. \$\endgroup\$ – Ron Beyer Sep 1 '19 at 21:13

Not the answer you're looking for? Browse other questions tagged or ask your own question.