Having been an electrical engineer for a certain portion of my life, I’ve managed to get myself shocked on numerous occasions. It’s always been with AC voltage, and the sensation always has had a kind of intense “vibrating” quality to it. I’ve always assumed that the “vibrating” sensation was due to the 60Hz cycle of the AC voltage.
Recently, however, an old digital camera of mine finally gave up the ghost, and I decided to disassemble it. (“Disassemble” being my term for smashing it on the floor.) Well, after said disassembly, I picked up the main body of the device and noticed a big capacitor inside it. At about the same time, I must have touched two contacts that caused me to receive a shock, which involuntarily made me hurl the thing back to the floor for one last disassembly go-round.
What surprised me is that the shock I received, which must have been from DC electricity, felt no different from the old familiar, “vibratory” AC shock.
So my question is, is there, in general, a qualitative difference between the sensation of a shock received from AC voltage, versus a similar one of DC voltage?
I don’t think so. The first time I discovered capacitors was when I was screwing around inside an old vacuum tube radio that I had unplugged beforehand. I was amazed to find out that I could receive a shock when the radio was unplugged from the wall. And it was a doozie of a shock too. The difference in potential is all that’s needed.
My experience is different. I too, have gotten pulsed from big capacitors and I didn’t notice any kind of a buzz, just a really big ‘thump’ and an ache afterwards. Also, I have tangled with 60-Hz and 400-Hz AC (the latter was for an aircraft system). The former was a sort of buzzing sensation, as in the OP. The latter was more of a stinging sensation. With both there is an ache afterwards, as with the DC zaps.
Isn’t one of the traditional reasons touting the safety of AC is that DC forces your hand muscles to clench if you happened to grab a live wire or other power source? AC, on the other hand (sorry for the pun), being more “buzzy,” would allow you to let go. If that’s the case, I would imagine that they’d feel different.
Is this trait true about AC vs. DC, or just an urban legend I picked up in a badly taught Physics class?
I once worked with electric utility relaymen (the guys who wire the protection schemes and controls for substations and power plants).
Utilities use banks of batteries to operate circuit breakers and other equipment that need to be operational to start up generators or restore power)
These guys have to work behind panels in substations and other crowded places and its not unusual for them to come into contact with “house” AC and DC voltages.
A few have told me that an occasional contact with 125v AC is just an annoyance that happens and the 48V DC that they work with at some older substations isn’t too bad either.
But one guy said he once accidentally got his hand and elbow into 125V DC and had to use all of the strength in his shoulders and back to pull his hand away. The DC locked his grip and his arm strength alone wasn’t enough to overcome it.
His take was that he’d rather get into AC many times instead of DC once.
I have shocked myself deliberately on a few occasions with a small, hand-cranked DC generator and it made my hand clench up. I could only stand it for about five seconds before it became two painful. I also once shocked my arm with a 45kV stun gun which made my hand open and close rapidly. It was unpleasant, but nowhere near as painful as the generator.
How it’s cranked has no bearing on whether it’s AC or DC. That’s determined entirely by design. Those old magnetos that you used to have to crank by hand to use a telephone were DC.
Ex-Navy Electrician here. I have been shocked by 110v 60hz, 1000v 400hz, 440v 60hz and a small variety of weak DC shocks.
The 110V causes muscle contracting, it was the 3 phase 440V that “knocked me back”.
The 400hz was odd and did not cause either. Thankfully it was a minor stray voltage as 400hz was notorious for causing bad burns. It felt most like DC to me which has never been bad in my own experience. The worst DC shock I got was from a 12Vdc Boat battery.
Overall AC is more lethal which is what Edison was trying to demonstrate with his elephant execution and creation of the electric chair. AC is more likely to cause serious harm. Amperage and length of time in contact I recall are the biggest factors in causing harm though no matter what voltage, type or frequency. That was the one good thing with 440v 3 phase is that it did not you back at least.
I was working on a rectifier in a phone office one night and instead of turning off the AC I stuck my hands inside and did what I had to do. One hand was touching the grounded frame when the other hand brushed up against an exposed 240 VAC contact. I’m not sure exactly what happened next. There was a tingling sensation and then I was standing in front of the rectifier rubbing my hand wondering what happened. A few seconds were lost as I don’t know how much time passed before I moved my hands out of the cabinet. I was disoriented for a few minutes afterward.
Another time a coworker and I were hooking up a string of batteries to a power plant. The voltage was 140 VDC. I was holding the lugged end of the cable and leaned against the grounded battery rack. I felt a very slight tingling sensation and moved away from the battery rack. I then placed my hand on it and the tingling returned. The whole time I was fully aware of everything that was happening and at no time felt any disorientation.
We had a saying at that job–DC is much more forgiving than AC. DC gently lets you know when you’ve messed up–AC tries to kill you for making a mistake.
This is my longwinded way of agreeing with Omegaman–DC ain’t shit.
The path through the body the lenght of the path will determine the total resistance. The higher the resistance the lower the bite.
In 40 years I have been bitten many times in many ways. Also is the power source. From 24 vdc to 200 vdc and 24 vca to 10,000 vac.
Another factor is the power source. A cap is a low source of energy. The 10,000 was a boiler burnner igniter the voltage decaded rapidally.
Next to the boiler the harddest that I got hit with was the 120 VDC off an traction elevator cabinet. Thank God the relays opened because I could not let go. AC buzzes and most of the time you can let go, hurts like hell but you normally get off it by jumping. With a solid DC you do not jump just contract.
How many here have had or seen a charged cap tossed to someone?
The same thing is true of the third rail on railway lines, in the UK these are DC and are much more dangerous than similar voltage AC because DC can cause your muscles to contract so you stay on the line and cook, whereas with AC you can either remove yourself or are sometimes pushed away by the shock. Luckily I’ve not had an encounter with either, but in a previous job I trained to work on the railway and they drummed in the safety issues of electricity.
Over my career I have usually been on the delivering side of DC shocks , typically for dangerous heart rhythms. These are external DC shocks, short duration, 20-400 joules (monophasic in older defibrillators; biphasic w/ lower voltage in newer ones), that temporarily stun (depolarize) and therefore reset the entire myocardium. Naturally I’ve also received a few AC shocks in the course of my marginally competent home electrical repairs.
We are taught in medicine that AC is a little more dangerous than DC for precipitating ventricular fibrillation, and the cycle rate may also play a part for a given AC current in how dangerous it is. DC is apparently more inclined to produce total cardiac standstill–standstill in all muscles, for that matter. Lightning, for instance, stuns the heart more often than producing fibrillation. Because ventricular fibrillation is self-sustaining, it’s more dangerous than depolarizing every cell to a standstill at the same time. (As an aside, this is why rescue breathing for a lightning victim can save their life; the heart recovers before the diaphragm…)
I have a gut feeling the sensation from DC v AC can be different but as I think about it I wonder whether or not this difference is related to the duration of the shocking current rather than whether or not it’s AC v DC per se.
A single burst discharge from a capacitor (like the flash capacitor in the OP’s camera) or like the cardioversion current we use in the Emergency Department is a fairly brief single wham. An ongoing current is going to feel different, right? If we give an alert patient a cardioversion shock (or if their defibrillator goes off giving them an internal shock) they invariably complain, but the sensation is described as a vicious thump. It doesn’t seem like it’s that nasty buzzy feeling you get when you are wiring up the dishwasher without bothering to turn off the breaker.
My sense from talking to a wide variety of people shocked in many different ways (AC; DC; lightning; big voltage; little voltage; medical cardioversions; internal defibrillators…) is that the sensation varies according to the strength and location of the shock and the duration of current more than anything else, but I haven’t seen any long-duration DC shocks so I can’t say for sure there is no difference. Except for lightning I’m not sure I have seen any big-current DC shocks.
For lack of a better way to summarize it, it seems to me DC tends to be more of a stun sensation and AC more of a buzz. I offer that observation as a relatively ignorant one due to the caveats above, however.
I’ve seen charged loose caps used as practical jokes multiple times on board the ship. Never tossed though. Usually the cap was charged and left on the deck and then you ask a bootcamper or BM type to grab that part and bring it over.
No offense, guys, but I don’t believe you. I haven’t been shocked enough to know firsthand, but if you can’t see the lights flickering, why should I believe you can ‘feel’ the shock flicker?
I think it is highly more likely that the shocks differed in sensation due to variations in the amount of power supplied to your body, rather than the polarity reversing sixty times a second.
We had one when I was a kid. A kick for sure, but I got the same results with a charged automotive points condensor on many occasions. Perhaps you missed the part where I said I was grounded. Lost some hair on that excursion. I will say regular ac current is nothing more than a shock. I’ve burnt my fingers before, but nothing.
I guess as with all current it’s the amperage that kills.
, typically for dangerous heart rhythms. These are external DC shocks, short duration, 20-400 joules (monophasic in older defibrillators; biphasic w/ lower voltage in newer ones), that temporarily stun (depolarize) and therefore reset the entire myocardium. Naturally I’ve also received a few AC shocks in the course of my marginally competent home electrical repairs.