Is it the volts or amps that kill?
electricity is dangerous but what is it that makes some sources lethal and others not one way to find out [Music] but seriously this is an important question and it's one that gets more wrong answers than right ones now there are a few reasons why I'm making this video for one I want to clear up some common misconceptions about electricity and I want to do it with some not so safe demos but the main reason is somebody called me wrong on the Internet is it the volts or amps that kill a while ago I made a short video on the topic and in summary I said that you can't pin all electrical hazards on the short answer like Volt or amps and boy this made a lot of people mad all these people flaunting their professional qualifications telling me that I'm wrong well I say no you if I'm wrong about something I do want to be corrected but one of my biggest pet peeves is when somebody flaunts their fancy qualifications while also giving out incorrect information now I'll be honest I'm not an electrician or an engineer but I do have a bunch of terrifying electrical devices as well as the fancy equipment needed to put some numbers behind my claims most importantly is that I'm willing to do some crazy stuff to prove a point in fact I'm willing to put myself into circuits that should be lethal by their logic so yeah let's get started oh yeah before I go on I should warn you that all the crazy stuff you're about to see was done completely for educational purposes and in fact if you were to try any of this stuff at home you'd probably die so yeah please don't try this at home taming electricity is one of Mankind's biggest achievement using electricity we can light our homes cook our food and use these nightmare bricks to watch Horrors happen in real time electricity isn't all sunshine and Roses though it can shock you it can burn you it can even kill you but what is it exactly about electricity that makes it dangerous well this is a complicated question and the answer depends highly on the source of that electricity first let's consider our biggest design vulnerability when it comes to electricity and that's the nervous system nerve cells work on electrical signals that are a small fraction of a single volt so it really doesn't take much to override these with outside memes I mean anybody who's selected nine volt battery knows how easily a mere 9 volts overpowers all the signals going to your tongue oh now if there's any electrical system in your body that you don't want to mess with it's in the heart the heart has its own set of pacemaker cells that work separately from the brain like other nerve cells in the body they deal with voltages of less than a tenth of a single volt it doesn't take much of a shock to mortally interfere with the signals that set the heart rhythm and this is why most electrical fatalities are cardiac related even if the heart does manage to get spared by a shock electricity can still cause Burns nerve damage flash blindness and plenty of other not so fun experiences harpoonie bodies are simply no match for angry electrons now that we've looked at our design vulnerabilities oh holy let's start playing with some fun electrical sources to see if it's the volts or amps that play a bigger role going off of my previous comments it seems that most people with professional experience that is just the current that kills it turns out there are some problems with that here I've hooked up a car battery up to these steel rods now this battery can dump up to a thousand amps yet touching these bare rods doesn't do anything to me oh you think the battery's dead nope the thing is that battery can dump a thousand amps but not through me it's only a 12 volt Source after all and my Skin's resistance is high enough to block all but a minuscule amount of current from going through my body this is Ohm's Law in action you can't always use this logic when judging the hazard of an electrical source but does work for low voltages like this here I have a different flavor of high current power supply it's a Step Down Transformer I wound years ago and it's held up surprisingly well in this ice cream bucket being a Transformer is AC unlike the battery but the voltage is still way too low to shock me check out the current when I drop a quarter across it that's over a thousand amps of course just because these low voltage High current sources can't shock doesn't mean they're completely safe they can still burn you by simply heating things up it's also possible to get shocked indirectly like by rapidly disconnecting them from an inductive load like this electromagnet because you get a big voltage Spike by doing this so this all makes it seem like it's the volts that matter here right let's take a look at this electrical shock hazard chart there's actually nothing about voltage on here at all only current what gives this assumes that that Source can put that current through U which means it has to have a sufficiently high voltage to do so as well as a low enough impedance but what kind of voltages are we talking about here according to the Chart less than 100 milliamps of current can be lethal my body's resistance is about 250 000 ohms so according to Ohm's law I need a voltage of about 25 000 volts to kill me seems simple enough right let's go ahead and put that idea to practice let me use this apple as a model of the human body it has an even higher resistance than me about 10 million ohms in order to put a lethal current of 100 milliamps through it Ohm's law says I need a million volts why don't we test that out you can watch the voltage here in the current here a couple notes about the setup I'm using a voltage divider so I don't kill my meter which means the actual voltage is 10 times higher than what the meter shows as for the current I'm measuring the voltage drop across a 1 ohm resistor which means the voltage measured is the current going through it in amps all right let's slowly crank up the voltage there oh it's conducting look at that the Apple's dead Ohm's lost it I need a million volts yet it was passing 100 milliamps at barely over a thousand volts what gives it turns out you can throw Ohm's law out the window in situations like this because the Apple experienced something called dielectric breakdown when the voltage across an insulator reaches a high enough point the molecules in it get shredded by the electric field this means the insulator suddenly becomes a conductor and will allow a huge amount of current to pass through it Ohm's law does not tell you when this happens for human skin this point is roughly about 500 volts or so but this varies considerably of course if you get poked by a live wire it won't take nearly as much voltage to be a problem of interesting note is that the electric chair only has a voltage of about 2 000 volts based on Ohm's law and a skin resistance of a hundred thousand ohms this shouldn't be lethal but this logic doesn't work here because the skin can't hold off that kind of voltage it's funny because it Ohm's law he's hardly a law in the physical sense because it fails all the time many simple devices violate ohmic Behavior LEDs many light bulbs even the full Bridge rectifier do not obey Ohm's law if you want to play it safe stick with voltages under 50 volts because that's the limit where OSHA says the voltage is not high enough to electrocute there's another issue relying on Resistance when you're dealing with AC if you've ever been shocked by a live wire without touching ground at the same time you've experienced this what's completing the circuit here a capacitor of course notice how the resistance of this capacitor is so high that it can't be measured by my meter yet it still can pass a bunch of current that's because AC can pass through a capacitor you have a capacitance too which is why you can feel a shock from touching a single Live Wire at this point in the video I know there will still be people out there that argue it's just the current that kills because that's what's shown in those graphs right or maybe a little concede the idea that voltage does play a role but still current in the end doing the damage well this is the point where I start putting myself in the circuits that should be lethal under that premise even this very charred acknowledges it's more than just the current that kills there's a whole axis in time and the chart is only valid for a small range of frequencies as well so let's switch it up a bit using something else we experience static electricity anytime you receive a static shock the voltage you're being exposed to is quite High much higher than what you get out of an outlet in fact going off the distance The Arc can jump in open air this voltage is several thousand volts most people will tell you the reason it doesn't kill you is because it's low current but let's put that to the test right here I've abandoned graph generator it's capable of generating very high DC voltages similar to what you get from a static shock just on steroids this is a mechanical device that uses a rubber belt to transfer charge to the spherical top load the voltage is generated here are enormous over a hundred thousand volts although the voltages are huge the charge that accumulates on the sphere is still pretty tiny only a couple millionths of a coulomb even so this minuscule amount of charge is able to produce a force that overcomes the gravitational pull of the entire planet the charges are small but what about the currents I mean they must be small if I can touch them without dying right wow let's go ahead and test that out once again I'll be measuring current via a 1 ohm resistor but this time with an extra fancy resistor that I built based on a video by Vitaly it minimizes inductance to get an accurate reading I should note that I've referenced vitaly's videos more than anyone else in my channel you should definitely check him out for some cool high voltage experiments alright let's measure the current of that pulse look at that that was 40 amps considering the voltage here was on the order of a hundred thousand volts the electrical power there was over a million Watts the idea that static shocks are low current is a myth when you get shocked by Static you're eating amps of current ow so why don't you go to heaven when you get a static shock because you've been naughty but seriously if you look at the DC shock hazard chart you'll see that currents of a fraction of an amp can be lethal what gives well the chart clearly suggests there is a strong time dependence here the shorter the duration of the shock the more current your body can handle which makes sense really current alone doesn't tell you how much charge is transferred or for how long it happens current is just a rate of charge transfer after all it's just like how your speed on a highway doesn't tell you how far you've gone or for how long you've traveled when it comes to a static shock those huge currents are happening for an extremely short duration on the order of a microsecond this sibling isn't enough time to cause significant damage to a person so no it's not just the current that kills and these 40 amp static shocks are proof of that ow I know that even this isn't going to be enough for some people microsecond pulse that's cheating well if I'm going to go through the trouble of making this video I might as well murder the idea that's just the current that kills so I'm going to do something clinically insane to prove my point so I've built this Tesla coil here now this is not an ordinary Tesla coil it's switched with a monster Soviet vacuum tube and with a power draw of 15 kilowatts it's one of the most powerful vacuum tube driven coils in existence this unusual combination of raw power and vacuum tube technology gives it some unique properties nowadays most Tesla coils are switched with solid state circuits these are more efficient and they're typically pulse operation allows them to make longer arcs for a given power draw than a vacuum tube coil my giant tube driven coil doesn't stand out in raw Arc Length it's the longest Arc it'll make is only about 2 meters or so where it does shine is in its ability to make a white hot Arc to a grounded object each straight up looks and sounds like like a substation fault when it's running it also melts the steel screwdrivers I use as breakout electrodes it truly is a terrifying sight to behold I know what you're thinking it must be hard to resist touching something that looks as crazy as that right well I have given in to the Temptation and no I'm not very sane for doing this however I do use a steel file to distance myself from that white hot Arc but of course I'm still conducting pretty much the full current there besides it doesn't stop the ark from jumping directly to me occasionally so why doesn't it kill me most people will tell you it's because Tesla coils operate with gigantic voltages but very little current it's funny because when it comes to electricity there's no bigger mythological Beast than the Tesla coil all aspects of Tesla coils are filled with misconceptions in the public eye their operation their history their hazards they're all littered with myths now to be fair they are mysterious devices and although their construction can be simple the details of how they operate can get quite sticky let's try and put some numbers behind this coil is the current really that low what's the output voltage like let's start with current I've worn this current Transformer with as many wire turns as there are ohms of resistance across it that way its voltage readout is identical to the current and amps of a wire going through the middle feeding the grounded wire of my secondary coil through this will give the current output of my Tesla coil well here we go all right it triggered look at that that's 3.2 amps of current that's not low current at all in fact that's actually terrifying if you doubt my measurements let's try that again with this ancient RF ammeter this nearly 100 year old meter is quite simple it's just based on a thermocouple which actually means it'll measure lower frequency and even DC current just fine too let's run it hooked up to the Tesla coil all right here we go well there's an amp at least now I don't want to kill the meter so I'm probably just going to stop it here I ended up buying an even bigger meter so let's give this one a go all right here we go [Music] okay I'm at full power now it's reading only a little over an ant now I measured 3.2 amps earlier which is the correct measurement here actually they're both right this old meter reads the RMS current and I looked at the P current using my current Transformer since the output is a sine wave at 50 duty cycle that means that these measurements line up pretty much perfectly pretty cool right all right so the current is actually quite high but what about the voltage let's try to measure the output voltage with this vacuum capacitor voltage divider here we go huh I'm only at a couple percent of max power here and it's already at 50 000 volts now I don't want to cook myself with x-rays I'm not going to push it I can still estimate the voltage at max power if I make the admittedly rough approximation that the coil is purely inductive this gives a result of about 100 000 volts which is about what I expect really The Arc itself claims the voltage pretty well so that's why the voltage doesn't rise that much with considerably higher input power hold up a hundred thousand volts at 3 amps does that make sense that's like 300 000 Watts that's 20 times more power than I'm giving it yes it actually checks out but the kicker is that that power is nearly all reactive Tesla coils are resonators after all sloshing charge back and forth and rigging up huge voltages at significant current you still can extract more energy than you put into them however since the current and voltage are nearly completely out of phase even so the real power output is still significant and that Arc there is still burning many thousands of real Watts so back to the original question why doesn't it kill me when I touch it the current is not low and although that power is mostly reactive I'm still conducting amps of current for a substantial amount of time when I do this what's going on here many Tesla coil Builders will tell you it's the skin effect at play here at high frequencies currents in a conductor are magnetically pushed to the edges this effect is a critical consideration when it comes to designing a Tesla coil in fact the currents in this thick cable are almost completely restricted to the outer 200 microns because of this so does this mean the current just travels along my skin when I touch it nope the skin effect is only significant at these frequencies when dealing with a good conductor like copper when the material is resistive like flesh that goes out the window you can see this by cooking food in the microwave the frequency there is over 10 000 times higher than my Tesla coil yet it can still warm food quite a bit below the surface so no it's not the skin effect either so what is it then well it turns out our nerves aren't quite so susceptible to high frequencies and somewhere beyond 10 kilohertz the polarity flips too fast at a polarize a nerve cell membrane this means your nerves pretty much don't register it and that's why it doesn't electrocute electroboom actually mapped out his own response to different electrical frequencies and published this chart with his results of course just because it doesn't kill instantly does not make it safe touching a Tesla coil output is never really safe you can get severe internal burns when conducting big RF currents I don't make a habit of touching arcs and I keep my contacts brief I should point out that the power supply driving the coil is absolutely lethal and touching that would kill you before you hit the floor the funny thing is that the Tesla coil steps up the voltage and current of the supply while also making it less lethal due to the higher frequency high frequency is also part of what keeps you from getting Zapped by touching a plasma globe the voltage on the outside is actually quite significant but a combination of the high frequency output as well as the fact that it's a high impedance Source prevents you from getting Zapped now of course high frequency won't protect you from something driven by a lethal high voltage source lacking isolation my demon circuit is a classic example of this the flame Arc there is running at over 13 megahertz yet touching it would still kill you via the DC Supply running it since there's no isolation there so what is it that makes exposure to some electrical sources lethal and others not well it's a combination of volts and amps and frequency and duration as well as some other stuff that determine whether it's dangerous or not and for the record that's exactly what I said in my original 40 second video to elaborate on the other stuff part The Source impedance as well as where on your body you get shocked are big players as well no I don't intend this video to be an all-encompassing guide to electrical hazards I do hope it clears up some common misconceptions out there I will say that high voltage low impedance sources are ruthless when it comes to user error there's a reason why the microwave oven Transformer kills more science hobbyists than anything else there's no room for a mistake one final thing I'd like to address is all the comments I get from people that are surprised I'm still alive every time I upload like come on I realize I work with a lot of extremely dangerous stuff but I really do take considerable precautions and that's why I'm still uploading I will say that if it is electricity that ends up taking me out it's probably not that could be this kind of stuff it's gonna be my favorite power supply of all clouds I gotta get out of here you know [Applause] that was pretty cool oh one more thing I'd like to shout out the YouTuber tested to destruction he's a high voltage YouTuber that embarked on using the monster gu39b Tetro to build a Tesla coil at the same time I did we tested a bunch of different designs and shared our results with each other he's got a lot of crazy high voltage stuff on his channel so you should check him out I'd also like to thank all my patrons on patreon especially for supporting me when I was in the middle of a move and unable to make new content finally I'd like to thank all those professionals out there that encouraged me to make this video thank you you silly garloids stay safe out there
2023-02-04 05:43
