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Which is more danger, AC or DC?
Engineering and workplace issues. topic
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Posted by Anonymous on 28 March, 2006 - 10:35 pm
Can any one tell me which is more danger: AC or DC?

Moderator's note: This topic is closed. I think all that needs to be said on either side of the argument has been said.


Posted by Curt Wuollet on 1 April, 2006 - 1:42 am
It all depends on the voltage. :^) But AC is held to be more likely to stop your heart and DC is held to give a stronger "can't let go" factor. Under the wrong circumstances, either will ruin your whole day.

Regards

cww


Posted by Dobrowolski, Jacek on 1 April, 2006 - 1:45 am
That's current flow what kills and if it's high enough it really doesn't matter if it's DC or AC. However, if one happen to survive the shock itself then DC is more dangerous. It's because DC current does elecrolysis of body fluids and products of it are toxic. So it may happen that few hours after shock one dies because of poisoning.

Regards,

Jacek Dobrowolski


Posted by Imran Ali on 1 April, 2006 - 10:15 am
DC is more dangerous than AC. Because, AC varies from zero to maximum and then again to zero..In this way, AC puts jerks to a person due to continuous variations. On the other hand, DC is smooth, unvariable and continuous.


Posted by Anonymous on 20 January, 2007 - 2:28 pm
DC is more dangerous than AC. Because, AC varies from zero to maximum and then again to zero..In this way, AC puts jerks to a person due to continuous variations. On the other hand, DC is smooth, unvariable and continuous.


Posted by Ahmed faraz on 21 September, 2010 - 11:19 am
As DC is steady current its voltage remains same i.e 220v. The AC is RMS. it increases from zero to maximum value. for example I = 220v so I=I under root 2 so I = 220 multiply 1.414 so I = 311.08v.

Therefore AC is more dangerous then DC


Posted by Anonymous on 1 April, 2006 - 10:15 am
Both are equally lethal, it is like asking what causes the worst death, a truck hitting you or a car, either way you die !

AC in theory would allow your muscles time to be able to move so that you could pull your hand / limb away from whatever it was that was giving you the shock. DC on the other hand is supposed to prevent this from happening.

I have had a few shocks in my time from both AC and DC and would strongly recommned NEVER getting them and designing systems to prevent them ever happening.

It has made me a super safety person and as a result i do not recieve shocks anymore.

Either way AC/DC are both more than capable of killing you.


Posted by Michael Griffin on 2 April, 2006 - 4:51 pm
There have been several suggestions that an AC shock will allow enough time for your muscles to relax to release the conductor. This of course is false, as the zero crossing time is only a few milli-seconds at most.

If you are receiving an AC shock, you might be able to pull your hand from the conductor (or pull the conductor from your hand) using muscles which are not in the current path. You will definitely not however be able to relax those muscles which are contracted by the electric current.

I was subjected to a non-job related accidental electric shock (someone had repaired an outdoor extension cord with electrical tape) which passed from my hand to my feet, and can assure you that you have no voluntary control over muscles which are subjected to an AC shock.


Posted by David on 10 August, 2011 - 12:25 am
Good answers. Dead is dead. I have been shocked by both and all is a bad experience. Building equipment that can electrocute someone is irresponsible and liable. Work on equipment with one hand in your pocket. Always, and very carefully, assess every situation, everytime, moment to moment before you touch anything that may kill you from high voltage. Electrocution is instantaneous with no warning and AC or DC, one is as deadly as the other -


Posted by David on 10 August, 2011 - 12:40 am
Real experience with750 VDC - When I was 20 years old (I'm 62 now) I was working on an old Heathkit Apache AM transmitter. I had recently changed out the modulation transformer with one from an ART-13 WWII transmitter. This (new) modulation transformer had the high voltage leads on the side through ceramic insulators. In the process of working on it, I had to set it up on its side. It was off but still plugged in to the wall. As I sat it up on its left side I accidentally flipped the unit on as it brushed by my belly and I sat the high voltage connections of the modulation transformer down on my left wrist just below my thumb. That was a really really bad experience. 42 years later I remember it well and still have the scar to remind me. Pain is horrible - the smell of my burning flesh was just as bad and my body was in a painful knot like I have never known before or since - Thank God. My mouth tasted like I had been chewing aluminum foil. It was truly a horrible experience. I am very lucky to be alive and not have suffered any permanent damage (although my wife may be able to point out some remaining anomalies in me…)


Posted by Phil C. Sr. on 11 August, 2011 - 12:38 am
David said:

> I had recently changed out the modulation transformer with one from
> an ART-13 WWII transmitter.

David....

I am in the process of putting an ART-13 mod tranny in my Apache. Would you please e-mail me and tell me the results you obtained when you did this.

Thank you.

Phil C. Sr.
k4dpk e-mail k4dpk at comcast dot net


Posted by Anonymous on 1 April, 2006 - 10:15 am
dc is the most dangerous as it isn't alternating from positive to negative which gives you a release if you grip an AC POWER source. DC will grip you as your nerves clench and feel uncontrollable


Posted by awyoguy on 31 May, 2008 - 9:53 am
The cyclical rate that A/C operates at will not allow a "lax time" enough for you to let go. a 110 V household circuit will kill you deader than a doornail. A 220V will do it twice as fast.


Posted by Anonymous on 1 April, 2006 - 10:16 am
When electricity was in its infancy there was a battle between Edison and Westinghouse as to which would be the standard, AC-Edison or DC-Westinghouse. Since the electric chair was becoming the preferred method of executing people and the electric chair used AC, Westinghouse used that as a campaign against Edison to show people the killing power of AC. Of cousrse as we all know today, AC became the standard in all of our houses today. Hope that helps.


Posted by Curt Wuollet on 1 April, 2006 - 6:56 pm
Actually true, except AC Westinghouse and DC Edison. AC won out because of the ease of transmission whereas DC would have to be produced locally. Now they are figuring out the actual overall efficiency and it strongly favors local generation, though not DC.

Regards
cww


Posted by Walt Boyes on 1 April, 2006 - 6:59 pm
Actually you have it backwards...Edison was championing DC, Westinghouse AC, because he was unable to break Edison's patents.

Walt Boyes
Editor in Chief
CONTROL magazine
www.controlglobal.com

Blogging at Sound OFF! at controlglobal.com or direct at
http://waltboyes.livejournal.com

Putman Media
555 W. Pierce Rd #301
Itasca, IL 60143
+1-630-467-1301 x 368
wboyes@putman.net


Posted by Gustavo A. Valero P. on 4 April, 2006 - 1:28 am
Just to clarify the Edison-Westinghouse's tale:

1) Edison used and promoted the usage of DC and not AC. Even, the war against AC led Edison to development and promotion of the electric chair as a demonstration of lethal AC versus his "safer" DC.

As part of this promotion, Edison publicly electrocuted dogs, cats, and is considered the intellectual killer of Topsy, the Luna Park's elephant (have you ever seen that "ugly" movie?).

2) Edison and Westinghouse had a common friend called Telsa who worked for Edison first and later for Westinghouse when Edison did not understand/approve his improvements and investigations to improve electric power distribution (stuff that Westinghouse accepted with his arms wide open).

Also, Edison did not pay him the offer of $50,000 if Tesla was able to redesign of Edison's DC generators. Tesla did the task very well and Edison replied to him with the famous statement: "Tesla, you don't understand our American humor!"

The rest is history!

Best regards.

Saludos.

Gustavo A. Valero P.
BIConsulting C.A.
Valencia - Venezuela
gustavo.valero@biconsulting.com


Posted by Colm on 22 June, 2010 - 9:36 am
You've got that backwards mate, Edison was for DC and had the whole of New York wired up in DC. Of course it was a disaster because of the energy lost in resistance that could be avoided the most part by using transformers in AC, which are not available for DC as DC does not have a changing magnetic flux.


Posted by Mark Bayern on 1 April, 2006 - 10:16 am
Which is more useful -- sugar or salt?


Posted by DFL on 11 March, 2011 - 1:43 pm
>Which is more useful -- sugar or salt?

Salt was a primary food preservative throughout human history, and a ubiquitous reagent in many, many chemical processes.

Sugar gives you a a shallow burst of energy and tooth decay.


Posted by David Baird on 1 April, 2006 - 6:53 pm
Check:
http://www.epanorama.net/links/safety.html#safety


Posted by Anonymous on 1 April, 2006 - 6:54 pm
AC or DC?
It's depends on where it going to be used.

AC could be dangerous to human being, otherwise some devices more save if work with AC.

DC harmless and appropriate for small powered devices, but some devices could endanger overall system if using this DC.

So, word "Danger" is confusing . . . need some preparations and analysis for design.


Posted by raphael orimogunje on 25 May, 2010 - 9:07 am
>AC or DC?
DC is more powerful than AC current supply, because DC frequency is direct current of 50Hz,which moves in a direct straight line. While AC current moves alternatingly from zero to 220v. a life could still be rescued in such cases. This makes the DC more dangerous.


Posted by Adam on 8 August, 2010 - 6:45 am
DC stand for direct current. DC dos not alternate and therefore will always have a frequency of 0 hertz (cycles per second), unless you are pulsing it for radio transmissions or something but that is beside the point.


Posted by Cybernaut on 1 April, 2006 - 6:54 pm
Danger is relative. Assuming you meant danger to human life, then both AC or DC currents are dangerous, provided that the magnitude of currents involved are deadly to humans. A DC current as low as 100 mA is capable of stopping the heart, if injected directly to the heart. That is why in instrumentation, 4-20 mA is the selected current range for analog signals, which means you can touch a live signal cable without danger. Of course, there are other instances when one is more dangerous than the other. For example, AC currents can induce voltages on dead adjacent cables, while a DC does not. You think that a circuit has been isolated already, but think again. To be on the safe side, consider them both as dangerous.

Cybernaut


Posted by W.L. Mostia on 1 April, 2006 - 6:58 pm
The below websites provides discussion AC/DC during shock and it can be seen that it takes on average a higher level of DC to provide the same effect as AC.

http://www.allaboutcircuits.com/vol_1/chpt_3/4.html<http://www.a llaboutcircuits.com/vol_1/chpt_3/4.html>
http://www.merck.com/mrkshared/mmanual/section20/chapter277/277a.js p<http://www.merck.com/mrkshared/mmanual/section20/chapter277/277a.jsp >

There is some good material on this subject in Appendix "B" of Lawrence Livermore National Laboratory EH&S manual at:
http://www.llnl.gov/es_and_h/hsm/doc_16.01/doc16-01.html<http:// www.llnl.gov/es_and_h/hsm/doc_16.01/doc16-01.html>

Some other web sites of interest on this subject:

http://www.ecmweb.com/ar/electric_basics_electric_shock/<http:// www.ecmweb.com/ar/electric_basics_electric_shock/>

http://www.eet.unsw.edu.au/staffweb/ohs/Safety%20Manual_UG-2005.pdf <http://www.eet.unsw.edu.au/staffweb/ohs/Safety%20Manual_UG-2005.pdf&g t;

A book which contains some good material on this subject:

"Electrical Instruments in Hazardous Areas, 4th Ed," Ernest Magison, ISA, ISBN: 1-55617-638-4

Several posters have correctly pointed out that both can seriously injure or kill you so if dangerous DC or AC voltage levels are present, it is doubtful that making engineering or administrative judgments on which is safer will result in safe practice.

Bill Mostia
WLM Engineering


Posted by Anonymous on 2 April, 2006 - 4:46 pm
Both are dangerous if they were high voltages, for example more than 12V.


Posted by pascal on 21 September, 2010 - 3:19 pm
>Both are dangerous if they were high
>voltages, for example more than 12V.

usually we used to say that the safe voltage is everything less than 50VDC or AC. this is why all equipment in 24 or 48 Vac/dc can be used in humid atmosphere or harsh environmental.

For example there is some actual talk and study to increase the battery voltage in cars as the electrical power used in vehicle is increasing drastically with all "automatic" equipment up to 5kw of electrical power in luxury vehicle is not rare. so to reduce Wiring size and weight manufacturers are thinking about increasing batteries voltage (and the whole electrical system of course) to 42Vdc!!! (less than 50Vdc)

Also, it is known that we need "high" voltage to "crack" the human skin and we need some current to maintain this crack. exactly the same as for electrical welding, High voltage to start the Arc, then a lot of current to maintain it.

But everything depending on the conditions, humidity, sensitivity of people, condition of electrification, etc


Posted by Anonymous on 20 November, 2007 - 11:59 am
AC is more dangerous since it deals with the amps. I've seen someone get hit by a 1000 Volts in a presentation. But only with 1mA a person can get killed.


Posted by VP on 15 May, 2008 - 1:12 am
It's good that people are showing they know the real facts about the history of Tesla and Edison. Edison was a monumental jerk and more businessman than a real scientist. Even today, his shotgun method of experimentation is called 'Edisonian' as a derogatory term by modern scientists.

Tesla was only one person whose ideas Edison robbed. Frankly it's appalling Edison has such a reputation as a 'great inventor'. It was the mobs of people working for Edison that gave him his success which he never shared.

But at least Tesla got the last laugh. And we're reminded of that every time we turn on a light.


Posted by Roy Matson on 16 May, 2008 - 2:35 am
You guys should read about Tesla first. Edison was promoting DC and made sure the electric chair was AC to scare people away from AC. He would electrocute animals on stage to demonstrate the danger of AC. "Tesla, a man out of time" is a must read for anyone working with electricity.

Pasted from a website about Tesla:
"Arriving in New York City with four cents in his pocket, Tesla found employment with Thomas Edison in New Jersey. Differences in style between the two men soon led to their separation. In 1885, George Westinghouse, founder of the Westinghouse Electric Company, bought patent rights to Tesla's system of alternating-current. The advantages of alternating-current over Edison's system of direct-current became apparent when Westinghouse successfully used Tesla's system to light the World Columbian Exposition at Chicago in 1893."

Westinghouse was also a prolific inventor, to this day most railways still use the Westinghouse brake system.

Roy


Posted by Hugo on 16 May, 2008 - 9:46 pm
Reading this I'm reminded of another danger: A hundered years after the Westinghouse company was founded it was run into the ground by top management handing the control to finacial managers who never learned what it was they were in business for. It was lost in half a decade...

Hugo


Posted by Roy Matson on 16 May, 2008 - 2:41 am
Don't you just hate it when those Amps sound off without any Volts to back them up?


Posted by dave on 22 May, 2008 - 1:48 am
The most dangerous is known as the COLUMB EFFECT. This is when the power passes between the two hands, across the chest and thru the heart. This is the real killer.


Posted by bubs on 25 January, 2011 - 11:40 pm
>AC is more dangerous since it deals
>with the amps. I've seen someone get hit
>by a 1000 Volts in a presentation. But
>only with 1mA a person can get killed.

you do not know what you are talking about....
AC deals with amps??? DC also deals with amps.


Posted by Basher on 3 June, 2008 - 12:45 am
You need to ask the question, "To current, are people more resistive or reactive?" The question will lead you to your answer.


Posted by Roy Matson on 4 June, 2008 - 12:35 am
"To current, are people more resistive or
reactive?"

Definitely more reactive. I remember as an apprentice giving one of the journeymen a shock with the 500 V megger. He "Reacted" by giving me a belt over the ear.

Roy


Posted by ieuan jones on 16 February, 2011 - 7:10 am
>Can any one tell me which is more
>danger: AC or DC?

defiantly DC o yes because DC is a direct current and will kill you if you have contact with it AC is safer because it is an alternating current so be careful if you are working with DC current


Posted by jlm on 19 February, 2011 - 12:25 pm
>Can any one tell me which is more danger: AC or DC?

The absolutely most dangerous voltage is the one you are working on.


Posted by curt wuollet on 19 February, 2011 - 5:38 pm
This has been argued about, but it is widely held that AC is more likely to stop your heart or push it into fibrillation. There is a difference in your ability to let go also, but I don't remember which way it goes. I try to avoid testing these theories.

Regards
cww


Posted by Process Value on 21 February, 2011 - 12:46 am
Danger factor : It is an accepted fact that for a given medium voltage DC is more dangerous.

AC has a definite frequency, thus skin effect kicks in and the current travels through the outer skin thus it does not damage your internal organs. Higher the frequency more pronounced the skin effect and greater the impedance it offers to the voltage. Ultimately what matters is the current flow which depends on the voltage. In ac because of the skin effect the impedance is more and thus lesser current flows, but in DC there is no skin effect and thus the current flows uni formally through the whole body smoking everything in its path. another advantage in ac (if you can call that) is that the current flow will cause a opposite force thus throwing you off.

but it all depends on the voltage level, it really does not matter if you go and touch a 400KV DC or AC (50/60Hz) line end result will be more or less the same.

so at a medium voltage level, say 110 V, 240 V, DC is more dangerous than AC.


Posted by Bob Peterson on 21 February, 2011 - 7:39 am
That is an interesting but completely wrong description of skin effect. There is very little skin effect at 50 or 60 Hz, and in any case, it has nothing to do with human skin.

It is true that there is a somewhat greater chance, at least theoretically, that one will be more likely to grip and hold on to a DC source over an AC one, but in practice, I suspect it really does not matter all that much.


Posted by Process Value on 11 March, 2011 - 7:22 am
AC/DC

well , i should get this off my mind, I was wrong to suggest that DC was more dangerous than AC. I spent a good part of the last 5 days on this and i got nothing substantial. It is quite a shame that i believed this myth for my 4 years of engineering education and two and a half years of power plant

comissioning and maintenence.

Bob, skin effect is the nature of AC current to have a greater density at the surface the conductor than at the middle. during the electic shock with AC it

was my belief that the current passes through the outer surface (the skin of the human body , which is primarly responsible for the body impedence). The fact was compounded by the fact that i have seen electrical injuries caused by shock and in two to threee patients , they all have one common malady ; burnt and peeled off skin. This compounded my faith in the fact that the bulk of the electricity passes through the skin. Now i came to know that ( from my friend doing Phd in biomedical) the skin has the highest impedance in the body and due to the higher resistance when exposed to electrical shock dissipates more heat thus causing desientegration of skin.

As the frequency increases the impedance of the skin increases but for a comparison between o hz DC and 50 Hz AC it is negligible and it is also dependent

on the path of the current.

My apologies to anyone who would have mislead by this post. Hope my other good posts will not be tarnished by this bad one. From now on i will post posts which are verifiable in their correctness.


Posted by James Ingraham on 21 February, 2011 - 2:48 pm
Process Value said, "It is an accepted fact that for a given medium voltage DC is more dangerous."

I disagree. I think it is a widely held belief with absolutely no hard data to back it up.

-James Ingraham
Sage Automation, Inc.


Posted by Zacharia, Tomy on 21 February, 2011 - 2:25 am
I simply loved the part about not personally testing the theory.

Sometimes, people 'better' qualified to 'test' the same should be allowed the 'opportunity'.

Regards,
Tomy Zacharia


Posted by numsi on 21 February, 2011 - 6:48 pm
It will kill you both, sooner or later.
Therefore I choose AC/DC & thunder :)
Guitar solo: dilidit, dilidit...
Sorry, could not resist.


Posted by curt wuollet on 22 February, 2011 - 2:34 am
I met a couple of candidates. When I was teaching electronics, there were a couple of err, students on the back bench amusing themselves by seeing who could hang on the longest while the other turned up the power supply. That was the last day in my class for both. I saw their future in the trade being quite limited anyway.

Regards
cww


Posted by CTTech on 11 March, 2011 - 8:15 pm
> Can any one tell me which is more danger: AC or DC?

Current kills and arc flash maims/kills more. Search for Professor C.F. Dalziel and find out what the research say.

In my opinion, 115, 220, 240 VAC home voltage is the most dangerous because too many unqualified people attempt to work with it. It is sort of like home water heaters or more dangerous than super critical boilers.


Posted by karim on 14 March, 2011 - 10:51 am
For me what is more danger and can kill with one touch 380 volt, means 2 phase line when you make contact between them with your finger 90 percent you will die if not you will loose it! so my answer is of course ALTERNATING CURRENT.


Posted by jayneu300 on 17 May, 2011 - 1:54 pm
>Can any one tell me which is more
>danger: AC or DC?

Lethality wise, they are equivalent. It is a factor of how much current is delivered through the body over a period of time.

A 100,000V shock delivering 1 mA of current for a brief period of time is most likely harmless (e.g. Van de Graaff generator). On the other hand, a 100V shock delivering 5 A would likely be fatal, causing burns and cardiac arrest.

Speaking purely of danger, AC is more likely to deliver a shock than DC because the alternating current causes dielectric breakdown of insulating material to occur at lower voltages than DC.

If you choose to work with power sources that are capable of supplying large amounts of current, even as low as 30V, make sure to use proper safety equipment. Voltages at this range and above have the potential to use the human body as a current path.


Posted by Jacob benson on 12 September, 2011 - 4:59 pm
> Can any one tell me which is more danger: AC or DC?

AC is more dangerous because your hand can get stuck to it because it cuts off the communication to your brain to tell your hand to let go of the wire. unlike DC were you touch it you will immediately let go. because of the alternating current that is why the AC is more deadly


Posted by James Ingraham on 13 September, 2011 - 4:06 pm
What worries me about Jacob's answer is that it doesn't seem to take in to account the 50 other replies. His response actually seems reversed from the conventional wisdom, but the conventional wisdom is wrong to begin with. I'm particularly fond of "Process Value's" mea culpa on March 11, 2011. It takes a big man to publicly admit that something you've taken for granted for years is wrong.

What the data shows me is that there is no "more dangerous" between the two. Both can kill you, even down to 50 volts. The 110V 60Hz / 220VAC 50Hz standard powers are more than enough to kill you. Since these are basically the minimums in the industrial world, assume any live circuit has the ability to kill you. Much like how you assume every gun is loaded, always assume a circuit is live. (It figures the Texan would bring a gun analogy into it.)

Stay safe out there, everyone.

-James Ingraham
Sage Automation, Inc.


Posted by Jerry Miille on 13 September, 2011 - 9:14 pm
Well said James and I fully agree with you: Depending on the conditions, almost anything above 50V can be lethal!

And you analogy is perfect: assume the gun is always loaded and assume that any electrical circuit is live!


Posted by Peg Ferraro on 18 September, 2011 - 8:16 pm
Hi,

Your friendly local moderator here.

I believe it is time to close this topic. I think all that needs to be said on either side of the argument has been said.

Regards,
Peg Ferraro, Control.com moderator

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