AC or DC which is more dangerous - Page 1
Forum section: electronics / beginners

author: HobGoblyn
author_rank: Unknown
timestamp: March 11, 2020, 11:49:43 pm
content: Hi all, I’m sure this is often asked, I tried searching but even with search in quotes, it returned anything with “or” in, hence I got nowhere.Over the past couple of months I have watched a ton of Eevblog YouTube vids. In one (can’t remember which) Dave mentioned that DC was more dangerous than AC and his reasoning seemed to make sense.In my words, As AC alternates it contracts your muscles, then releases them whereas DC would keep your muscle contracted, hence you would be gripping what you touched, and your muscle wouldn’t let you let go.So today on a Facebook page, someone asked the same question I’m asking, and I replied“All things being equal ( enough current to contract muscles etc) DC is more dangerous. As AC alternates, it clamps then releases your muscles, in other words, while it can kill you, if you touch mains AC, your hand will be thrown away as your muscles contract then releases. Whereas DC, your muscles will grip what you touched and won’t let go.”The reply I got was“Nice opinion but wrong. Maybe you and everyone else who thinks it’s DC should go look it up. AC causes more sweating and lowers skin resistance . It also causes more muscles spasm which result in the inability to let go. Both AC and DC are bad if the currents high enough, but AC wins. Sorry guys lol”On googling, Wikipedia seems to back him up.Wondered what your opinions on this are?Edit: Someone else has replied“ BS 120 VAC causes muscle contraction and will kill you just fine. Higher voltage AC will throw you off but it can quickly get to the point where the puncture voltage of your skin gets reached and then the resistance drops and whammy you get enough current to kill you. So yes there is a range of ac voltage that will throw you off and not kill you a generic statement like that is just pure wrong since skin resistance is around 150K and it takes around 50 -100 ma to kill you so it would take very high DC volt to kill you “

author: JustMeHere
author_rank: Frequent Contributor
timestamp: March 12, 2020, 12:23:31 am
content: The electric chair uses AC.

author: SpecialK
author_rank: Regular Contributor
timestamp: March 12, 2020, 01:20:47 am
content: Yeah the peak voltage of 100VAC is 141V, and it's above the 100V RMS value for what looks like about 180 degrees of the cycle. The peak voltage of 100VDC is 100V. I think that's why AC is more dangerous.

author: Circlotron
author_rank: Super Contributor
timestamp: March 12, 2020, 01:48:32 am
content: Quote from: JustMeHere on March 12, 2020, 12:23:31 amInteresting bit of history ->https://www.smithsonianmag.com/history/edison-vs-westinghouse-a-shocking-rivalry-102146036/

author: digsys
author_rank: Unknown
timestamp: March 12, 2020, 02:00:23 am
content: Yeah, lots of opinions as usual, but I vote for DC !! by a long shot - and also when comparing, compare Peak AC with DC, not it's RMS.Having been shocked MANY dozens of times over the years - from AC 110-415V and from DC 60-4,000V (electric fences), I DEFINITELY vote for DC !! In fact, on MANY occasions, I've had 240VAC shocks and wasn't even sure I had been until I measured it. Even touching again with only minor tingles, IF THAT. NEVER had to question it with ANY DC above ~70V It's always beenmemorable!!!! :-)I even remember, back in the 70s, studies we did at Uni biology, testing this very same proposition, and DC won out every time, quite definitively.PS Back in the 60s / 70s, you were almostrequiredto accept HV shocks as part of the "work experience" :-) Never bothered me .. and NO, I avoid it these days !! age

author: David Hess
author_rank: Super Contributor
timestamp: March 12, 2020, 03:08:23 am
content: I would have to say DC because the muscle contraction is continuous which is more likely to lead to physical damage. I have been hurt much more by DC shocks than AC shocks.

author: Zero999
author_rank: Super Contributor
timestamp: March 12, 2020, 09:29:12 am
content: Quote from: digsys on March 12, 2020, 02:00:23 amQuote from: David Hess on March 12, 2020, 03:08:23 amIt depends on the definition of AC. If you're talking about mains frequency, then you're mistaken, it's far more dangerous than DC. This isn't about opinion. It's a fact and was proven over a hundred years ago. High frequency AC, i.e. above the audio band, is less dangerous than DC, because it doesn't stimulate the nerves.The most dangerous myth is with AC, the zero crossing point enables the muscles to relax, thus allowing one to let go, but this not true at all. The zero crossing point is too shorter period for the muscles and nervous system to recover and regularly interrupting the current seems to promote loss of muscle control and ventricular fibrillation. I still can't believe many otherwise educated people believe this myth today. Finally the peak voltage of AC is higher, than DC, so a 50VAC shock has a peak voltage of over 70V, although it's likely to be more painful than a 70VDC shock, for the reasons describe above and by the studies linked to below.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730001338.pdfhttp://www.wright.edu/~guy.vandegrift/wikifiles/Electric%20shock%20voltages%20Dalziel.pdfAnd if you look at the safety standards, you'll find the limits for "safe" voltages are much higher for DC, than AC.https://en.wikipedia.org/wiki/Extra-low_voltage

author: JohnPen
author_rank: Regular Contributor
timestamp: March 12, 2020, 11:54:00 am
content: This topic reminds me of the way some of us used to do a quick check of the performance of TV EHT supplies (approx 25Kv for colour ones) by drawing an arc from the line output valve anode with an insulated screwdriver. If the arc length was very short the EHT was low. If the arc was over approx 1.5cm it was likely OK. It relied on skin effect and the line frequency rate as you didn't feel anything unless you allowed the arc to directly reach your skin then you would get a small electric burn hence the insulated screwdriver. Be warned however never touch the valve anode directly as that could give you a very severe shock because of the high DC volts also present on line output stage anode.

author: Zero999
author_rank: Super Contributor
timestamp: March 12, 2020, 12:17:54 pm
content: Quote from: JohnPen on March 12, 2020, 11:54:00 amYou have a point about the frequency, as the nervous system doesn't respond to such high frequencies, but the skin effect is another myth. The skin depth in human flesh, at the tens of kHz a TV flyback operated at, is in the order of metres. If the skin effect was a factor, then microwave ovens would only warm the surface of meet, but they penetrate a good few cm.

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 12, 2020, 03:13:58 pm
content: Quote from: blueskull on March 12, 2020, 04:20:34 amThen we can move on to point 2: Is it voltage or current that kills?

author: atmfjstc
author_rank: Regular Contributor
timestamp: March 12, 2020, 07:10:41 pm
content: Short answer, current. Whether it's by disrupting the heart rhythm, causing burns or jolting your body and causing a fatal fall, the current seems to be the most important variable in fatalities. Of course, even for the same current, voltage is not entirely irrelevant, as high voltage can strike you down from a distance, and there is, of course, a minimum voltage necessary to produce a fatal current given that the body exhibits some electrical resistance.I vaguely recall reading somewhere that, in principle, there are cellular structures that can be disrupted by voltage alone. But since the body is built so differently from an electronic circuit, it is practically impossible to generate a significant voltage inside it without also generating current.

author: twospoons
author_rank: Frequent Contributor
timestamp: March 12, 2020, 09:19:11 pm
content: Having worked designing electric fence energisers, I would say its the combination of current and time. We designed around something called the "C2 line", which related the pulse duration to the peak allowable current. Can't find a reference to it now. But basically the line represented a 1 in 140,000 chance of causing fibrillation. Shorter pulses were safer, lower currents were safer. One figure I recall was that for a pulse duration of 100uS you could have a current of 15A! The load model assumed a resistance of 500 ohms when calculating peak current.By far the nastiest shock I've ever had was from a 900VDC capacitor bank, with 25J stored in it. Arm to arm. Burnt holes in my fingers. I think I was rather lucky to survive that one. And yes, it was from a prototype fence energiser I was working on. It got a bleed resistor and a neon telltale after that.

author: james_s
author_rank: Super Contributor
timestamp: March 12, 2020, 09:28:47 pm
content: It depends on the circumstances, there are numerous factors that have a much larger impact on the danger than whether it's AC or DC, either one can kill you if the voltage is high enough and conditions are right. I treat voltages above about 50V as dangerous no matter what and handle them accordingly. High frequency AC is probably less likely to electrocute you due to the skin effect but it will cause extremely painful RF burns so I'm not sure I'd call it safer.

author: Zero999
author_rank: Super Contributor
timestamp: March 12, 2020, 10:53:01 pm
content: Quote from: james_s on March 12, 2020, 09:28:47 pmWhat do you mean by high frequency? If it's tens of GHz, then you might have a point, but 3MHz to 30MHz will pass through your heart, just the same as DC will. It's just less dangerous because it's way above the frequency the nerves are sensitive to.The human body is less conductive than metals, so the skin effect is much less and is not why higher frequencies are less dangerous than mains. The myth probabably stems from people calculating the skin depth of copper wire and mistakenly believing human flesh is the same.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763825/https://electronics.stackexchange.com/questions/171023/is-this-true-at-over-700-hz-current-simply-flows-over-your-body/171025

author: james_s
author_rank: Super Contributor
timestamp: March 12, 2020, 11:23:52 pm
content: Quote from: Zero999 on March 12, 2020, 10:53:01 pmWell I've had the output of Tesla coils in the 300kHz range arc to my fingers many times without receiving a shock. It's not something I'd generally consider advisable though. I got an RF burn once when I touched a grounded object while I was standing a couple feet from a coil.

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 12, 2020, 11:29:44 pm
content: Search YouTube “electrocuting an elephant”, for a demonstration of the Edison vs Westinghouse’s War of Currents

author: Electro Detective
author_rank: Super Contributor
timestamp: March 12, 2020, 11:51:03 pm
content: I reckon AC with the local street power transformer backing it, should give unfortunate punters good value zappageversus a 200 amp belt from a car battery or PSUTBH, I don't want to know.. againor consider comparing..BTW, was it always AC used in electric chairs ? maybe some stashed rectifiers and capacitor banks fitted too, for a smoother consistent ride to the 'other side'and is it a DC, or modified AC/DC pulse they use in hospitals to zap ones heart or respiratory system back into gear?Apparently a diet high in salt and or sweaty hands won't do zap candidates any favors either

author: AVGresponding
author_rank: Super Contributor
timestamp: March 13, 2020, 01:24:04 pm
content: Quote from: Electro Detective on March 12, 2020, 11:51:03 pmYou're only likely to get a belt from a car battery if you lick the terminals... unless we're talking EV batteries like Tesla which is several hundred volts, 600 or so iirc.The sweaty hands thing is the most ironic, since if you're working on such equipment, the likelihood of sweaty hands increases proportionally to the available energy of the system, in my experience!

author: Zero999
author_rank: Super Contributor
timestamp: March 13, 2020, 03:11:43 pm
content: Quote from: james_s on March 12, 2020, 11:23:52 pmYes, higher frequencies cause burns, rather than shock and because the skin depth in human flesh is so great, the burns can be very deep, causing damage to internal organs.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: March 13, 2020, 03:26:32 pm
content: My personal experience with this is being stuck for a long time gripping a metal garden tap which was live due to an electrical fault. 50Hz AC. 0/10 would not recommend under any circumstances.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: March 13, 2020, 04:08:27 pm
content: Obviously, it’s the current thatkillshurts you, not the voltage. Try touching the two terminals of a 9V battery with your fingers, then with your tongue and see if it feels differently. If yes, why would that be? The voltage is the same in both cases.Also unless the AC frequency is very low (say, 0.1Hz or maybe even lower), your muscles would not be able to keep up with it, their relaxation time is much longer than the period of most AC voltages we might encounter. As already pointed above, it would impossible to relax your muscles (and release the live wire) in between two alternances of a 50 or 60 Hz AC sine wave.On top of that AC (unlike DC) can pass through dielectrics (lipids, cell membranes), so you might expect a higher total current for the same applied voltage in case of AC.But, of course, both high AC and DC voltages are dangerous and can seriously hurt or kill you.

author: magic
author_rank: Super Contributor
timestamp: March 13, 2020, 07:18:03 pm
content: Quote from: Caliaxy on March 13, 2020, 04:08:27 pmYou aren't man if you haven't done it with a 19V laptop brick next

author: Electro Detective
author_rank: Super Contributor
timestamp: March 14, 2020, 12:01:21 am
content: Quote from: magic on March 13, 2020, 07:18:03 pmGuys, invest in a Low-Z equipped multimeter! The tongue it saves may be your own !

author: SL4P
author_rank: Super Contributor
timestamp: March 14, 2020, 08:58:24 pm
content: For some reason, comparing apples with apples, I’d think the charring effect of a DC burn may help insulate the contact points.AC less so, along with the oscillating change of current flow/direction. would ensure your organs get well shook up.I don’t like the idea of either, because you can’t choose the parameters.

author: David Hess
author_rank: Super Contributor
timestamp: March 15, 2020, 01:30:16 am
content: Quote from: Zero999 on March 12, 2020, 09:29:12 amI am sure I have more personal experience with this than most or everybody here, and I'm only referring to 60 Hz AC versus DC although I have experience with RF also.Shocking myself on a 1000 volt DC power supply was much more damaging, both from the muscle contraction through my arm and flying across the room, then holding a current limited 25 kilovolt 60 Hz AC source. In the former case, there was no question of control as I just flew across the room and I was sore for days both from the impact and from the muscle contraction. In the later case, I set the neon sign transformer down consciously instead of dropping or throwing it.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: March 15, 2020, 05:38:14 am
content: As to your first question, both are just as dangerous, however I agree that the peaks of a given AC voltage are much higher for the equivilant AC RMS voltage. This is the story of Edison and Tesla, back in the late 19th and early 20th century. Tesla wanted to use AC power and Edison was committed to DC power. The antics that Edison pulled to discredit AC was things like electrocuting a live elephant in a public place with AC to show how "Dangerous" it was, but the efficiencies of AC over long distances won out. I suggest that you do a google search on Edison, Tesla and AC electricity to find out about that story. As for my opinion, it just depends on circumstance.As for your second question about current, the physics are quite clear, it is the entire electrical triangle relationship that determines the dose of current that you will get in the wrong place that will kill you. That triangle relationship is Voltage, Current and Resistance. The fact is, you can't have current unless you have voltage. So the answer is both.Just my 2 cents... Hope this helps.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 15, 2020, 07:52:29 am
content: It's pretty much like asking if you would prefer to be eaten by a shark or a crocodile!

author: Electro Detective
author_rank: Super Contributor
timestamp: March 15, 2020, 09:01:46 am
content: Elephants are rumored to have good memories, especially for cruelty payback on idiotsI wouldn't want to be in Edison's shoes on the other side.. with a zapped elephant waiting to stomp on his DC loving ass

author: Zero999
author_rank: Super Contributor
timestamp: March 15, 2020, 09:17:29 pm
content: Quote from: David Hess on March 15, 2020, 01:30:16 amThat's hardly a scientific test. You're not comparing like with like. The 25kVAC neon lamp transformer was obviously current limited to a relatively safe level, whilst the 1000VDC PSU was not and no doubt had a relatively large capacitance across the output. Experiences like that can easily cloud one's judgement. Numerous scientific studies have shown mains frequency AC to be much more dangerous than DC, given the same current and volt.

author: exe
author_rank: Unknown
timestamp: March 16, 2020, 02:27:14 pm
content: Interesting, I don't feel the need to argue about voltage vs current. To me those are just two parameters of one thing.

author: Sam Spastic
author_rank: Regular Contributor
timestamp: March 17, 2020, 12:31:30 am
content: Been an electrician all my life since sticking the metal hanger in an AC outlet.But 120VAC 60Hz is the number one killer. Maybe because it is in every home in the US or maybe because it is just plain dangerous.Survived several episodes in my 69 years.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 17, 2020, 03:13:31 am
content: Quote from: Sam Spastic on March 17, 2020, 12:31:30 amAnd maybe because it doesn't sound very high.230v on the other hand....I was going to leave it at that, but it raises the whimsical question:With 230v "on the other hand" , what do I have on this one?

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2020, 08:53:54 am
content: Quote from: vk6zgo on March 17, 2020, 03:13:31 amLots of people shit themselves about three phase, because it's 400V, rather than 230V, but it's only 400V phase to phase. It's still only 230V phase to earth. It's unlikely someone will receive a shock from phase to phase, phase to earth is the norm, so it's really no more dangerous than single 230V phase.

author: AVGresponding
author_rank: Super Contributor
timestamp: March 17, 2020, 01:07:26 pm
content: Quote from: Zero999 on March 17, 2020, 08:53:54 amIt can be amusing however when someone who "knows everything" manages to connect two phases to something instead of a phase and neutral.Gent Vigilon fire alarm panels don't like this, and are quite expensive...

author: David Hess
author_rank: Super Contributor
timestamp: March 17, 2020, 10:57:51 pm
content: Quote from: Zero999 on March 15, 2020, 09:17:29 pmIt is not but do you have something better?And it illustrates a significant difference between AC and DC sources; the former usually lack the super low AC impedance provided by a output capacitance on a DC supply and that by itself makes DC sources more dangerous. I would much rather be shocked by the 120 or 240 volts AC present at the input of an off-line switching power supply, and I have a few times, than the 340 to 370 volts DC at the output of the rectifier or power factor correction stage which is both constant DC and supported by a lot of capacitance.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2020, 08:46:25 am
content: Quote from: David Hess on March 17, 2020, 10:57:51 pmYes, refer to thelinks to scientific studies I posted previously.I am not making this up. There is plenty of scientific evidence to support mains frequency AC being more dangerous, than the equivalent DC. It's been know for long time.QuoteYou're now arguing about the difference between an Ohm and milliohms, which are both well over an order of magnitude lower than the human body and makes no difference whatsoever. A 120V source with an impedance of 1 Ohm will pass virtually the same current though the human body, as a 120V source with 1m Ohm.The only added hazard with DC is things such as capacitors which store charge, but it doesn't change the fact that it takes more DC, than AC, to kill a human, everything else being equal.

author: Electro Detective
author_rank: Super Contributor
timestamp: March 18, 2020, 10:14:38 am
content: Only an idiot in a hurry to get to the other side, or beat coronasticks their flesh into live circuits, be they mains powered or charged capacitorsAnyone that's lived to tell the tale and sharing it here should be paid attention to and respected somewhat,as they have already been where you don't need to be, and got LUCKY to escape Death's Door..Seriously, it's embarassing to get taken out in a dumbass manner and have people bawling and tear jerking as your boxed ass gets lowered into the ground,or fried and ashes jammed into a containerStay alive, be alert and PPE prepped,and lose the risk taking smartassery = NO ONE CARESnor wants the burden and expense of hospital and funeral attendance for an idiot

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2020, 10:51:24 am
content: Obviously don't be careless around with hazardous voltages and mains otherwise you can be knocked down dead pretty quick.However, it's important to know what voltages/currents pose the greatest risk. An ignorant person might consider the 30VAC from a mains transformer in their audio amplifier to be much safer to touch, than the 50VDC lithium battery pack powering their toy scooter, because it's a lower voltage. The truth is they're both hazardous, but in different ways. The 30VAC carries the greater shock risk, because it's AC, but the 50VDC has a higher fire risk because the current isn't limited and batteries can blow up.

author: David Hess
author_rank: Super Contributor
timestamp: March 22, 2020, 04:32:06 am
content: Quote from: Zero999 on March 18, 2020, 08:46:25 amThe human body model of resistance does not account for breakdown. At higher voltages, breakdown causes the resistance of the path through the body to decrease, if only because skin is no longer an insulator. I suspect that breakdown extinguishes between power line cycles so the total integrated AC current decreases even for the same RMS voltage when comparing AC to DC. This is the same thing which makes DC more difficult to switch or fuse.All of the studies you linked relate to linear small signal rather than non-linear large signal phenomena. I can hardly blame them for this since large signal tests would be ethically questionable.

author: Zoli
author_rank: Frequent Contributor
timestamp: March 22, 2020, 05:05:24 am
content: Quote from: David Hess on March 22, 2020, 04:32:06 amWell, I just ignore(somehow) the discussion, to present two of my radically different observations:1. My buddy lick his finger before touch the fuses in the switchboard(220V), before to point out->"that's the bad!2. Workmate opens the back of a rear-projection TV, than flies back 6m(20ft), without touching anything inside.It totally depends on the person on how much potential(or even worse, field) supports; you have to learn from low levels(<12V) how much potential/field you will suport, and it can be a paiful experience.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 22, 2020, 07:23:14 am
content: Quote from: Zero999 on March 18, 2020, 10:51:24 amStatistically, your chance of a dangerous electric shock at such voltages is miniscule.I have sat on top of a rack in a tropical climate soldering tag blocks connecting phone cables some of which were "hot" with 48v DC central battery.When your hands and arms are sweaty, it is definitely an "ouch!" moment, but not an "Aieeee! I'm dying!" moment when you find one!A burn from a shorted battery is really a different thing---ordinary 12v car. batteries can cause these as well.

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2020, 09:13:50 am
content: Quote from: David Hess on March 22, 2020, 04:32:06 amI doubt breakdown would extinguish because the skin would be damaged by the electric fields and heat, it no longer be such a good insulator, even at lower voltages. Have you seen some of the gory photos of burns due to electrical shock? I bet if you tested the resistance with a multimeter, it would be much lower than healthy skin.Quote from: vk6zgo on March 22, 2020, 07:23:14 amYes, you're right, although I have had a shock from 30AC and it's definitely tingles a bit. 48VDC no, but 70VDC was noticeable, although not as bad as 30VAC.

author: David Hess
author_rank: Super Contributor
timestamp: March 23, 2020, 10:58:24 pm
content: Quote from: Zero999 on March 22, 2020, 09:13:50 amPhotographs? That 1000 volt DC shock which resulted in me launching across the garage left pinholes and charring through the skin of one finger and elbow.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 23, 2020, 11:09:15 pm
content: Sorry, but this whole discussion of which is worse, AC or DC, is simply ludicrous. It's like asking "what's worse, getting hit by a car or by a truck?".Gimme a break. There are so many variables for each particular instance that there's no "right" answer. I've always assumed that since DC doesn't go thru zero it doesn't give you an opportunity to "release" as does the AC zero crossing, but even if that's true it's a fairly useless discussion, IMO.How fast is the car going? How about the truck? Does it just clip you? Does it hit you straight on? Do you jump in time and it just hits your foot? Do you jump up and bounce off the windshield? Does it kill you or just hurt you real bad? Does the driver hit the breaks? Is it slippery? Is it a small truck? Is it a big SUV?We can spend days on end hypothesizing about various technical rabbit holes, but at some point you just have to accept that, as much as we wish there was, there's no RIGHT answer. Which is usually the case with most stuff on this planet. It depends on a bunch of stuff.Don't touch high voltage electricity. It can kill you. Look both ways before you cross. It can kill you.Next....

author: Zero999
author_rank: Super Contributor
timestamp: March 23, 2020, 11:41:56 pm
content: Quote from: engrguy42 on March 23, 2020, 11:09:15 pmIf you apply that kind of logic you might as well say being hit by a ping pong ball travelling at 15mph is as bad as a truckQuoteThere is clearly a right answer. The voltages, frequencies and currents which are deemed to be hazardous are clearly defined by the safety standards and other factors such as the environment i.e. whether it's wet or dry are taken into account.QuoteWell duh, the ICE defines it as above 1000VAC RMS of 1500VDC, well over ten times the voltage required to kill you.https://en.wikipedia.org/wiki/IEC_60038You shouldn't touch low voltages either, because they can kill too, just not quite as quickly or dramatically.Extra low voltage, below 120VDC or 50VC is low risk, therefore doesn't need the same degree of precautions as low voltage; only basic insulation is required and no earth/ground necessary. Below 60VDC or 25VAC, no insulation from the user is required in dry areas. In "other areas" i.e. more damp places, it goes down to 30VDC or 12VAC.All of the regulations are based on the research I linked to a few posts ago. They didn't decide on what voltages can currents are low or high risk on theories, but empirical data.https://www.eevblog.com/forum/beginners/ac-or-dc-which-is-more-dangerous/msg2960074/#msg2960074Quote from: David Hess on March 23, 2020, 10:58:24 pmI didn't want to post any pictures here because they're not pretty. You can Google them if you like.Yes, charring and pinholes will drastically reduce the skin's resistance. You would have had the same or worse with a 1kVAC low impedance voltage source and given the increased risk ventricular fibrillation posed by AC, you might not have survived, although if the current didn't travel through your heart, you probably would have been okay, just suffered more muscle damage.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 12:16:23 am
content: zero999, I think you're missing the point...The question is "Which is more dangerous, AC or DC?"My point is that nobody can say one is equivocally more dangerous in all situations than the other because it depends on many, many factors. As an engineer I'm sure you can make a list of those factors. Is there a path for the electricity thru your heart so it can kill you? Did you touch with only one hand and you're wearing insulated shoes so the impedance to ground is much higher? What was the voltage level?All you can do is define one very clear and specific set of circumstances to determine (as you say) the RISK of being, for example,killedfor different types of individuals and characteristics, but that is not a clear answer on which is more dangerous in all cases. And dangerous is a very relative and non-specific term that is virtually meaningless.If you want one to be more dangerous that's certainly up to you, but nobody can say that "AC is always more dangerous than DC" or vice versa.And BTW, a ping pong ball filled with lead going at 15mph and falling on your skull is probably more dangerous than a truck hitting you if it's your son's toy plastic truck going at 1 ft per minute.It depends.

author: AVGresponding
author_rank: Super Contributor
timestamp: March 24, 2020, 12:32:11 am
content: No.For a given system energy level, AC is more dangerous to humans than DC. Period.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 12:37:05 am
content: Quote from: AVGresponding on March 24, 2020, 12:32:11 amReally? So for those guys working on helicopter platforms, standing on energized high voltage (500kV AC, ie, 500 thousand volts) power lines, it's more dangerous than standing naked in a bathtub touching a 500VDC power supply?The energy level for the AC is VASTLY GREATER than the DC in this case.You sure 'bout that??

author: AVGresponding
author_rank: Super Contributor
timestamp: March 24, 2020, 12:40:12 am
content: Yes. If they don't equalise properly, it would blow the helicopter clean out of the sky.EDIT: And by the way, you're comparing apples with oranges.When all parts of the system are at the same potential, there is no energy flow.If the guy/gal in the bath is holding a non-earth referenced supply, then there won't be any current flow.The helicopter is the part of the system generating the potential difference btw; it's static from the blades.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 12:57:08 am
content: Youre proving my point. It depends. If this, if that....

author: AVGresponding
author_rank: Super Contributor
timestamp: March 24, 2020, 01:07:42 am
content: All right, let me state it as clearly and unequivocally as possible.Where the RMS voltage and current capacity are equal, and the human is the current path to ground, the AC will always damage/kill the human first.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 01:11:48 am
content: And if in one case ground is an insulating rubber sheet 6 inches thick and the other its a pool of water?This can go on forever.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 01:32:09 am
content: How about if the AC conductor touches your big toe and flows to ground, but with the DC you grab 2 conductors with your hands so it flows thru your heart?

author: AVGresponding
author_rank: Super Contributor
timestamp: March 24, 2020, 02:13:10 am
content: In neither of those scenarios is AC/DC the relevant variable.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 07:25:00 am
content: Quote from: AVGresponding on March 24, 2020, 02:13:10 amHuh?? Your statement was "Where the RMS voltage and current capacity are equal, and the human is the current path to ground, the AC will always damage/kill the human first."My points prove it depends on the conditions, and your (or any other) blanket statement about AC vs DC is just not true or relevant. There are many variables.What about AC with a lot of harmonics, as in the real world. What about if the harmonics even cause it to look closer to a square wave (ie, alternating DC). How much harmonics can you have and still have your assertion be true? And what about DC with a lot of ripple, or even the unidirectional AC out of a bridge rectifier. Is RMS AC worse than that? You need to specify the parameters of the sources that make your assertion true. What about frequency of the AC? What about somebody working with a high voltage microwave transmitter?And you need to define "ground". Is AC always worse than DC, independent of the parameters of the "ground"? "Ground" is not a thing, it's a concept, and varies all over the place in the real world. If you're standing on asphalt "ground" it's very high resistance and acts like an insulator. If you're standing in a pool of muddy water, that's entirely different. Is your body tied to a copper rod stuck deep into the ground like the ground outside your house? You need to define what you mean.And is AC always worse than DC, no matter where on the body the person makes contact? Or how they make contact? Is touching AC with one hand worse than grabbing two DC conductors with both hands?And what about clothing, like shoes? Is AC always worse than DC, even if the person is wearing insulated shoes when touching the AC, and standing in water when touching DC?And once you answer all of those (and more), and make a list of all the requirements and specifications that define when your point is valid, ask yourself in what way is that relevant or useful in the real world.Whether AC or DC is "more dangerous" depends on the specifics of the situation, and many, many different parameters. And ultimately, in the real world, it's pretty much irrelevant.

author: Zero999
author_rank: Super Contributor
timestamp: March 24, 2020, 08:45:51 am
content: Quote from: engrguy42 on March 24, 2020, 07:25:00 amNo, you've clearly missed the point.Assumingeverything else is equal, i.e. current, the path through the heart etc. mains frequency AC (50 or 60Hz, not microwave) stands a much higher chance of causing death, than the same DC. There have been plenty of experiments done on this, going back over 100 years now. They deal with the ripple, frequency etc. I've linked to some of them and going by your response, you clearly haven't read them, so I'm not going to bother finding any more, but the information is out there, if you wish to find it.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 08:50:38 am
content: But in the real world, everything else is NEVER equal. That's why its an irrelevant exercise.

author: engrguy42
author_rank: Frequent Contributor
timestamp: March 24, 2020, 08:56:27 am
content: BTW, answer me this...Are you going to walk up to an exposed high DC voltage, and then look over at an exposed AC voltage of the exact same RMS value, and say to yourself "hmmm, I'll grab the DC voltage, but not the AC cuz it's more dangerous"?I hope not.Don't touch exposed electricity without proper protection. AC, DC, doesn't matter. Don't be stupid.

author: Zero999
author_rank: Super Contributor
timestamp: March 24, 2020, 10:47:41 am
content: Quote from: engrguy42 on March 24, 2020, 08:56:27 amWhat about low voltage?QuoteWhat? Don't touch exposed electricity, even a 9V battery?Clearly a line needs to be drawn somewhere!A panel of experts, probably consisting of engineers and medical doctors, were involved in drawing up the standards. They would have looked at all the evidence available to make assessments of the degrees of risk associated by different currents, DC, AC (low frequencies through to audio and high frequencies) and the electrical resistance of the human body, before deciding what voltage is hazardous under which circumstances. In light of all the evidence they set lower voltage limits for mains frequency AC, than DC, because it presents a higher hazard, everything else being equal. Of course nothing is equal in real life, but if one follows the safety standards, they'll make good risk assessments and products which don't kill people.