I have had plenty of 'belts' in my time, including 240VAC, 25000V off the EHT in the back of a TV and 110VDC. The DC shock is the one I don't want to feel again. My hand was on an earthed roller the the DC supply touched my elbow and I couldn't let go until someone turned the power off. My colleague said I was dancing like Michael Jackson.

That said you're better off not getting either as they can both kill

Al

I think this has been covered in a previous post but I haven't looked it up.

An electric current makes your muscles contract. If you grab a hold of a wire which is carrying an electric current be it AC or DC the muscles in your hand will contract making it hard or impossible to let go. When you the fuse blows and you can let go you will probably let go pretty damn quick and jump back in shock, and probably be shouting some profanities too.

I've seen guys getting mains shocks and jumping back of their own accord because of the fright they got only to tell others that they recieved a shock which threw them across the room.

You can let go of an AC shock as the voltage is 0 twice in every cycle

Al

With a 50 Hz supply the zero voltage part of the wave comes around every 40ms. Sure you can anticipate to pull your hand away at the next zero volt interval but you wont be thinking that quick will you.

As I have seen and felt myself, when you get an AC shock you are a little suprised. By the time you have registered what is happening it feels like you cannot let go of the wire because the muscles in your hand are contracting (50 times a second) with the current passing through them.

If MCB's or fuses are in place they can easily trip before you can pull your hand away.

Finally it would be interesting to hear from anyone who has taken a three phase shock. Bet you can't pull your hand off of that baby!

Sorry that should have been 10 ms not 40ms.

Now you have me thinking...

60 cycles (for us on this side of the pond), two zero crossings per cycle, 60 x 2 = 120 "zeros", or 1000ms / 120 = 8.333333ms.

Maca,

When I get a 240 VAC belt I seem to want to pull my hand off the instant I feel it. Its not a case of 'Oh damn missed that one not to worry I can try again in 10mS'

Al

I agree 100% mate. When I've accidentially brushed a live 240VAC wire with the back of my hand I've done the same ( pull away my hand). The one time I mistakenly thought a wire was dead and it wasn't and I grabbed hold of it, it felt like I couldn't let go.

Anyway this isn't important. As I've been informed by my good friends at health and safety, neither AC or DC are dangerous. The only danger is the fool adding parts of his body to the circuit. I'm afraid that has included me on more than one occasion :)

maca; that would be cool! left foot on A phase, right foot on C phase & your head on B phase, wow like meth ?

I'll have to trust you on the meth thing!

I thought that a defibrillator was a devise that stopped your heart using electicity. Then the heart can restart itself, hopefully in the correct ryhthem.

I once pulled some automobile jumper cables off a spark plug that was hooked up to a fuel oil furnace transformer. I found out the plastic on the clamps didn't help me much and I couldn't let go. I should have done one clamp at a time. Afterwards I felt like I had a great workout and considered doing it again for the exercise.

That is correct.

The fact is that both are dangerous. However all things considered DC is more dangerous. This is because, as stated above, when you come into contact with a DC power source you cannot let go. Granted as was stated previous it may not kill you. But the longer you remain in contact, the greater the damage. Burns are a very painful injury, and electrical burns don't only cause damage to surface tissue. As to one throwing away, AC is used in electrical fencing to allow those that come into contact to survive the experience. My father was a residential electrician, and I worked for him through my teenage years. While I've been "bit" several times, generally through my own carelessness, I've never been thrown. However my sampling has been in lower voltages and may not hold true for high voltage AC.

"AC voltage or DC if considered both are at same magnitude."

The potential voltage is going to be what is the danger. The effect of being held or thrown away is your bodys reaction to the current as it force muscles to contract.

Treat all DC and AC voltages above 36 volts as hazardous and take steps to avoid contact.

Snapper,

You make a good point, actually several good points. Let me add that a few years ago a worker in the plant was unware that the circut he had in his hands were 'live'. As a result, when they came in contact, "BOOM"!!

I was nearby. When I got there he was sitting down, someone said he was thrown back. There were about 9 people standing around and no one was talking to him at all. So I did. I went up took his hands and started to ask him questions. I got him talking, he told me he was blinded by the flash, I asked if he was hurt, he said he couldn't see but his hands felt burned.

I reassured him his hands looked fine, maybe had the hair burned off but nothing more.

Later I found out that I kept him from going into shock. I was glad to help, but this was a case where 'Shock' was worse then the electrical shock he had just done through. he thanked me a few days later.... glad he was all right.

Very good and accurate answers all round. The following just 4 interest. There is usually a degree of embarrassment following an electrical shock, like the time i had just told my staff to stay away from the installation I was doing only to then walk backward into it and get hammered by 380v 3 Ph. Another classic moment was in the crowded open plan office of the banks mainframe room. I removed a faulty psu from a financial teller only to forget to remove the power first. Some uncontrolled audible words came out of me which I decline to repeat. But by far the cherry on the top was waking up 20 feet from where i was standing, shaking with severe abdominal pain and contraction. Those standing in view of me could not believe it either, I had just being hit by a bolt of lightning. Which is dc The magnitude I gauge as 20 feet

Yes, left permanent markings and I'm sure it fried a few brain cells....now madness has toys in the attic.

Sirs ,

Rare collections are come in link . Good to have these in Mind . Thanks .

dc

From a medical perspective, AC is much more dangerous.

A DC shock will overload the heart's control nerves and simply stop the heart. If the nervous system is not damaged, the heart may restart on its own, or it can be restarted with basic CPR.

AN AC shock, because of the alternating polarity, will often send the heart into fibrillation, where the the various muscles that operate the heart lose coordination. The muscles will still squeeze and relax, but not in the proper sequence, so no blood will flow. Fibrillation is much more difficult for the nervous system to fix because the nerves are still firing, just not in the proper order.

The shock device used by emergency medical crews is called a de-fibrillator. It actually applies a DC shock to stop the heart completely. Once the heart is completely stopped, it often restarts on its own, or it can be restarted with CPR.

With DC the arch is dangerous and if voltgage is high enough and air is very moist it can bounce across many meters and hit you. There is a few stories about marine engineers being killed walking into steam filled generator rooms when ships ran DC generators and being hit by an arch from the generator. This is why AC was choosen over DC for residential power, AC does not maintain an arch the potenial is still there but switch gear is cheaper. AC switch contacts can be copper DC contacts need to be platinum to stand the heat of the arch. Both AC and DC are dangerous but you stand more chance of escaping an AC arch, DC you are fried

"This is why AC was choosen over DC for residential power, AC does not maintain an arch the potenial is still there but switch gear is cheaper. AC switch contacts can be copper DC contacts need to be platinum to stand the heat of the arch."

This statement is either due to misinformation of fantasy.

FACTS:

AC was chosen because it can be transmitted over long distances in three phases and voltages then changed at points of use to meet the needs of usage.

DC can not be changed in voltage effeciently nor transmitted long distances.

Tesla and Stienmetz both sustained and supported these conclusions.

Legacy of Edisons smear campaign?

"Legacy of Edisons smear campaign?"

Just the facts, Ma'm. Just the facts.

Sorry sterling stan but DC can, and is, transmitted over long distances. On the low power scale, every telephone uses dc and on the high power side how about the UK and france who share power but to avoid phasing problems send the power by dc and convert at each end.

capblanc: First off it is Stirling as in Stirling engine. Sterling is as in silver vs. coin silver.

Telephone lines do NOT transmit power but low voltage signals and pulsating ringing voltage on the order of 24 volt IIRC.

The trans-channel lines are special purpose and of limited distance.

To the best of my knowledge there are NO long distance d.c. power transmission lines.

Cryogenically cooled d.c. lines may become practical in the future.

World wide electrical power is transmitted via 3 phase lines.

Sorry for getting the name wrong Stirling, just a typo, I recognised the significance of your avatar. (see off topic comment).

However to the point. If telephone lines do not transmit dc power then try to cut your line and insert a capacitor in series. You will find that your telephone will not work as it is powered by 50V dc (or thereabouts) from batteries back at the exchange. this is the reason that your phone works when the power is out. Your internet connection will work however as it is powered from your 110Vac system and the signals will pass through the capacitor.

regards

Chas

yes i want to know

I was in the RN between 1963 and 1973. It was most interesting as we had ships still in use that were built before the NATA set the standards of 415 Volts AC, 3 phase for all new builds (sometime in the 50s!)

RN ships up to this time were 220 Volts DC.

DC ships were constructed with switchboards that were entirely open, you could (if you were daft enough!) touch 220 Volts DC all over the place.....very few people were ever killed.

The first AC ship, a Daring class destroyer (Darings were built in both DC and AC models), also had open plan switchboards. This killed a large number of ratings in quite a short time and not only was the destroyer refitted with closed front switchboards at great cost, but all subsequent AC ships also had closed front switchboards....

I worked on both styles of mains voltage.

I have experienced thousands of 220 volt DC shocks, we searched for earths with our fingers!!!

I only had one AC belt, it was awful, never, ever again......you do not live through such things twice!!!

We were all warned (many, many times) in our training, that AC was far more dangerous to life and limb than DC, my personal experiences support this completely.

I have had 230 volt AC shocks since, they are also not to be taken lightly.....so I do not attribute the difference to the difference in voltage either......

Depend upom current

example

1. 220v 1A Ac is more denger than that of 220v 1A DC Beacause peak value Of AC=rsm ×√2 if rms voltage of Ac is 220Volt than Ac pick Voltage =220 ×√2 = 311.12V
2. 220v 10A Dc is mare denger than that of 220v 1A Ac
3. Even low voltage Dc is genger if current is high

The thinking is flawed.

You only need milliamps to kill someone........

Furthermore, AC causes the muscles to lock, where as DC causes them to contract, more than likely pulling your fingers away from the power, with AC you lock on!!!

I have experience both, I am not talking theory from books from people who have never ever experienced both, I am talking from first hand practical experience......that should count for something here.....

I saw a film recently on underwater welding, they mentioned that they ONLY use DC as AC would kill too many divers. DC not being dangerous at all.....

My own viewpoint exactly, but it was interesting to hear it from another source.....

Ac is dangerous then dc. because dc is steady current and ac is RMS. for example I=220v then I.=Iunder root2 then I.=220multiply1.414 so I.=311.08v. it is prove that ac is more dangerous then dc