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50,000 Amps
November 6, 2012 12:33 PM   Subscribe

Is 50,000 amps enough to melt a crowbar?
posted by Confess, Fletch (66 comments total) 18 users marked this as a favorite

 
Wait he's touching it? I wish I were that confident in the laws of physics.
posted by These Premises Are Alarmed at 12:45 PM on November 6, 2012


Why wasn't he wearing his HEV suit to do this test? It can protect from all manner of electric interference, including resonance cascades.
posted by deezil at 12:47 PM on November 6, 2012 [14 favorites]


Shake hands with danger seems... somehow understated here.
posted by odinsdream at 12:51 PM on November 6, 2012


Voltage is pretty low. The danger from touching the way he did would be from the heat more than the shock.
posted by 2N2222 at 12:51 PM on November 6, 2012 [3 favorites]


This transformer is set up in such a way that it steps down the voltage from the variac to less than a volt. It's not really any more dangerous than a battery providing a couple volts as long as what you're putting across the output of the transformer has enough resistance to limit the current to a reasonable value.
posted by Quack at 12:52 PM on November 6, 2012 [1 favorite]


Induced levitation and melting
posted by odinsdream at 12:52 PM on November 6, 2012 [5 favorites]


Man, there's a lot of scary there. When he lights the cigarette off of the crowbar, I imagined him handing it over to a friend, who grabs the crowbar. I have my mother's morbid imagination.

Now if someone can explain why it isn't arcing like a sonofgun, I'd appreciate that. Is it a relatively low voltage transformer? Why no lightning storm of nuclear proportions?

Edit: I knew I shoulda waited for yall to chime in first. Thanks.
posted by Xoebe at 12:54 PM on November 6, 2012


The danger from touching the way he did would be from the heat more than the shock.

I have a bit less confidence in my ability to predict where flying hot shards of material land than he does.
posted by odinsdream at 12:54 PM on November 6, 2012


Metafilter: enough resistance to limit the current to a reasonable value.
posted by herbplarfegan at 12:58 PM on November 6, 2012 [6 favorites]


Why did none of the bars weld themselves to the contacts? Just not hot enough, or something more complicated?
posted by jedicus at 12:58 PM on November 6, 2012


15 amps is enough to melt a good sized welt onto a metal nail puller. I know this because of reasons.
posted by bondcliff at 12:58 PM on November 6, 2012 [14 favorites]


I have a bit less confidence in my ability to predict where flying hot shards of material land than he does.

He's got a coffee cup there for that. What could possibly go wrong?
posted by The Potate at 1:00 PM on November 6, 2012 [1 favorite]


If you watch a few more of his insane videos you can also tell he's in a attic.

Also, notice that the floor is carpeted.
posted by Confess, Fletch at 1:02 PM on November 6, 2012 [7 favorites]


No safety glasses either.
posted by Confess, Fletch at 1:03 PM on November 6, 2012


It's only one or two volts. As he mentions near the end, he could touch the terminals if he wanted to.
posted by StickyCarpet at 1:05 PM on November 6, 2012


Now if someone can explain why it isn't arcing like a sonofgun, I'd appreciate that. Is it a relatively low voltage transformer? Why no lightning storm of nuclear proportions?

Normally, we use transformers to bump our electricity up to high voltage (and low current).
The voltage is sometimes high enough to ionize the air and push a current through it.

He's using a transformer to take 220 V wall power and bump it down to low voltage (and high current).
posted by sebastienbailard at 1:06 PM on November 6, 2012 [2 favorites]


All electricians in London are like this.
posted by urbanwhaleshark at 1:07 PM on November 6, 2012 [7 favorites]


Quack: This transformer is set up in such a way that it steps down the voltage from the variac to less than a volt. It's not really any more dangerous than a battery providing a couple volts as long as what you're putting across the output of the transformer has enough resistance to limit the current to a reasonable value.
The current is limited to 50,000 Amps, so... what were you saying about safe current levels?

The real reason this is safe is the intrinsic resistance of the human body. The maximum amperage that can flow through a human is Voltage/Resistance. Low voltage, moderate resistance*, very limited current.

* Moderate resistance assumes that the individual's body part making contact has intact skin. Dry feet and/or shoes are a good idea, too.
posted by IAmBroom at 1:07 PM on November 6, 2012


jedicus: Why did none of the bars weld themselves to the contacts?

Looked to me like that's exactly what was happening -- he was settling them into place while they welded themselves to the bus bars he was using. When he zoomed in on the bars afterward, you could see the residue from the welding that had happened, parts of the "electrode" left behind.

The reason he was still able to take them off again was because they were still hot; had he allowed them to cool, I suspect they've have been quite thoroughly welded.
posted by Malor at 1:08 PM on November 6, 2012 [2 favorites]


This just further confirms to myself that I do not understand electricity at all. People who really understand electricity basically have a superpower, in that us mere mortals have no clue if we can touch things, if things will shock us, what we should or shouldn't stick in where or why.

I was once trying to follow some online instructions to put together a few LEDs for a project and wanted to use one of those wall warts as that what the tutorial was using as well. I happened to have a friend who is an electrical engineer and asked him if the thing looked safe.

And in Electricity Superhero mode, he just shrugged it off and said it wouldn't be a problem and "just duct tape a rope to the wall wart."

"What will that do?"

"Well if things go haywire and it starts glowing orange and is about to light on fire, you can just pull on the rope instead of grabbing the flaming orange brick!"

And that is when I went to the store and bought 4 pre-made battery-powered LED lights.
posted by This_Will_Be_Good at 1:10 PM on November 6, 2012 [10 favorites]


This guy either knows exactly what he's doing, or is merely exceptionally lucky. But I will forgive all that for making the video that makes vinyl snobs come out in hives.
posted by scruss at 1:18 PM on November 6, 2012 [5 favorites]


Xoebe: Is it a relatively low voltage transformer?
Yes. Arcing requires kilovolt-level voltage.
posted by IAmBroom at 1:19 PM on November 6, 2012


That angle-grinder turntable video actually frightens me more than the high-amperage transformer video. Imagine what would happen if the record (which was never designed to be spun anywhere close to that fast) suddenly gave up and disintegrated into its component pieces? God damn.
posted by Scientist at 1:26 PM on November 6, 2012


Imagine what would happen if the record (which was never designed to be spun anywhere close to that fast) suddenly gave up and disintegrated into its component pieces? God damn.

Carbon and hydrogen? Holy shit!!!
posted by 2N2222 at 1:28 PM on November 6, 2012 [2 favorites]


What is that godawful contraption for?
posted by valkyryn at 1:30 PM on November 6, 2012


This just further confirms to myself that I do not understand electricity at all.

Power is the Voltage times the Current.
P = I * V

en.wikipedia.org/wiki/Transformer#Ideal_power_equation

For a transformer, the power in is the same as the power out.
So, it it takes V1 and outputs V2, the currents change, I1 -> I2, like so:
P = V1 * I1 = V2 * I2

So that could be 100 Volts * 5 Amps into 1000 Volts * 0.5 Amps, or something more like this guy's setup:
P = 100 Volts * 5 Amps = 1 Volt * 500 Amps.

Practical Electronics for Inventors is a good book for learning this stuff; good for beginners without oversimplifying.
posted by sebastienbailard at 1:32 PM on November 6, 2012 [1 favorite]


What is that godawful contraption for?

Melting crowbars, obviously.
posted by Floydd at 1:33 PM on November 6, 2012 [3 favorites]


Hahaha, I wonder if the folks at UL ever consider nutjobs running stuff like this in their home attics.
posted by Matt Oneiros at 1:39 PM on November 6, 2012 [3 favorites]


Arcing is related to voltage only. Here's a calculator which tells you the arc distance based on voltage (up to the vacuum HV level, at least).
posted by bonehead at 1:40 PM on November 6, 2012


In the turntable video the sound when it is winding down from high speed was so
damn cool.
posted by Phantomx at 1:40 PM on November 6, 2012


Wow, that's a lotta copper. I wonder what that thing cost him....
posted by schmod at 1:45 PM on November 6, 2012


"that copper might be worth more than the man's house!"
posted by fearfulsymmetry at 1:51 PM on November 6, 2012 [2 favorites]


What is that godawful contraption for?

If you have to ask...
posted by tommasz at 1:53 PM on November 6, 2012


This guy's a lunatic and his videos are a lot of fun. I have to say, though, that while I appreciate his electrical work, for my money his masterpiece is still throwing a large rock into a washing machine.
posted by ZaphodB at 2:04 PM on November 6, 2012 [5 favorites]


He definitely knows what he's doing, which is the reason that he can do risky, hilarious things without losing too many of his lives. It still isn't safe by any means, but it comes across as more like being a stunt driver and less like working on a lathe with loose clothing or hair. I've heard that he does some sort of industrial electrical work professionally (though I'm not sure). Here he is on Health and Safety Common Sense. There is so much amazing, insane stuff on his channel, don't miss the other videos. He left youtube for a bit; it's great to see him back!
posted by nTeleKy at 2:19 PM on November 6, 2012


IAmBroom: The current is limited to 50,000 Amps, so... what were you saying about safe current levels?

The total current the transformer can handle in the secondary is limited to ~50,000A if the output voltage is 1V, and his guesstimate of it being a 50KVA transformer is right. KVA ratings are also for steady state not transients so really the transformer could probably survive a much higher current for a shot amount of time.

At 1VRMS you would need 20u ohms to reach that kind of current. Most anything you put across that transformer should have a much higher resistance than that and if not said item would quickly become an open circuit. That's not to say running even a 10th of that current through something won't heat it up to levels that can cause some kind of thermal danger.

What I was alluding to but didn't say, and you covered, is that the reason he is safe from electrical shock is that the output voltage on the secondary is low and humans have decently high resistance when our skin is dry. That's not to say that if he managed to lower his resistance by poking a hot sharp piece of metal through his skin that this thing wouldn't pump enough current through him to stop his heart but I'm not really even sure that's possible.

Some quick calculations for fun:
Skin has a resistance value varying from 1k to 100k ohms depending on how wet/salty it is. Even if we assume that the secondary is putting out 5VRMS, which is ~7V peak, and an electrical resistance of 1k ohms then the current through whatever path it takes will be 7mA at the peak of the sine wave. Wikipedia says that ~60mA for AC is what it takes to kill a person provided it's not via a path that's already through the skin. So we're off by an order of magnitude assuming he hasn't provided a more direct path through the skin to his heart.

I think this is a case where wearing gloves isn't a horrible idea, but really I'd be more worried about burning myself.
posted by Quack at 2:36 PM on November 6, 2012 [3 favorites]


Anything that lets you use a crowbar as a incandescent light is probably not the best thing to do in your attic.
posted by eriko at 2:49 PM on November 6, 2012 [3 favorites]


That was, um, quite impressive. Sort of like a backwards Tesla coil.

Somebody asked why it didn't weld the scary hot steel things to the copper bus bars: it's very, very difficult to weld copper to steel, because a) they don't melt together to form an alloy and b) they have different coefficient of expansion and that will tear the weld apart if you don't take steps to prevent it and c) a bunch of other things I don't know. But based on my knowledge due to experience (not all of it bad), I wouldn't expect welding to occur.

And, yes, the resistance is what is limiting the current through the crowbar. All other things being equal, the bigger the conductor, the higher the current.

I first learned this as "all other things being equal, the strength of an electromagnet is proportional to the mass of the copper in the windings." The size of the wire and the number of turns are extraneous.

The electromagnet in question was an early experiment that led to MRI scanners. It was so strong that it would grab a BB so hard that it would either a) slip out of your grasp or b) trap your hand against the pole of the magnet.

It all comes down to the mass of the coil. Same thing goes for transformers.
posted by warbaby at 2:51 PM on November 6, 2012 [3 favorites]


was that his bedroom?
posted by marvin at 2:53 PM on November 6, 2012


Crowbar?
posted by thewalrus at 2:54 PM on November 6, 2012


I just looked it up, and it appears fairly common for British house circuits to be 30 or 32 amps @ 240 volts, but that's apparently the max load for the whole house... it's wired in a large ring. Individual plugs, it appears, are supposed to be fused for 13A max. (I assume newer houses may have multiple rings.)

If you could actually safely pull 30A from a 240V circuit, that would be about 7200 watts. I suspect, though I don't actually know, that this would not be enough to melt a crowbar.... that would be 7200 amps at 1 volt. I'm guessing, therefore, that he's probably running a custom circuit from the main house feed, and that could be pretty much any size.

I'm kind of jealous of the 240V standard. Pulling from 240V, but with the 15 to 20A ratings we have on most of our plugs, we could have much more functional devices, especially heaters of various sorts. You could have a hotplate, for instance, that could put out a serious amount of power... you could easily stir-fry on a 240V plugin hotplate, for instance, where 120V just can't maintain heat properly. Or you could have an electric kettle that boiled water at fairly ridiculous speed.

I think, from my amateur, fumbling understanding of electricity, that we could just double the voltages, and get appliances that were twice as powerful, without having to gut the wiring in our houses. I believe wiring is based on amperage, not voltage. We'd probably just have to replace wall plates, and possibly fuse boxes.

But standards.... standards, they have massive inertia.
posted by Malor at 2:56 PM on November 6, 2012 [1 favorite]


I assume newer houses may have multiple rings.

Quite so.

Higher-draw appliances -- typically electric stoves and electric shower heaters -- get dedicated point-to-point circuits rather than sitting on the ring main.

And yes, UK electric kettles do come to a boil *considerably* faster than US ones.
posted by We had a deal, Kyle at 3:09 PM on November 6, 2012


BTW, I was confused a bit. Here in the US, a 400 mil cable is 400kcmil, or 400 Thousand Circular Mils, where one circular mil is the area of a circle with a diameter of 1 mil, or 1/1000th of an inch.

But I've seen 400kcmil cable, and that stuff he's using is a lot bigger.

In the UK, a 400mil cable is a cable with 400 square millimeters of area, which is why it looks like a 750kcmil cable, because, for all intents, it is (well, it works out to 789kcmil...).

And he has *three* of them.
posted by eriko at 3:12 PM on November 6, 2012


Is it wrong that I want to call my kids home from school to watch this whole channel?
posted by bystander at 3:15 PM on November 6, 2012 [1 favorite]


Well you can install additional 240 V circuits in your house in good old North America, if you want to; my parents did that for my mom's pottery kiln (well, they had it done, by an electrician).
posted by Monday, stony Monday at 3:24 PM on November 6, 2012


Here he is generating a pretty strong Corona Wind. Even though it’s not as “DESTRUCTION!” as some of the other videos, I really like the 12,000W Metal Halide light that he fires up in his backyard…and house. But check out his computer skills and delicious electric-cooked cake. His upgraded plasma balls unfortunately didn't last too long. Sometimes, though, he pulls a bit too much current and the voltage in his neighborhood drops until the electric meter blows! (Watch it until the end before you get too shook.) Here’s his welcome back video.

I think, from my amateur, fumbling understanding of electricity, that we could just double the voltages, and get appliances that were twice as powerful, without having to gut the wiring in our houses.

Yep, all the electric baseboard heaters in my house are run off of 208V for this reason (which you probably have if you've got a newer building, but your appliances and outlets/plugs may not be designed for).

Discovery World, a museum here in Milwaukee, used to blow up a piece of ~12ga wire in one of their stage shows by discharging some serious capacitors through it. IIRC, that was also about 50,000A. It was a pretty big bang and some serious showers of sparks. They've got some really nice Tesla coils, too, but I don't remember the specs off the top of my head.

Is it wrong that I want to call my kids home from school to watch this whole channel?

Nope! You might even inspire an interest in electricity that stays with them for the rest of their lives. Do emphasize, however, that although experimentation can be fun, exciting, and even educational, they should check with you before doing any of it alone (and you should check with an informed friend if you're unsure of the safety of any given experiment). If they take an interest and you just tell them they can't do anything because you don't understand it and there's a potential for danger, there's a good chance they might just do it on their own anyway - with no supervision. Ask me how I know! I used to cover up the burning smell in the basement with hairspray. I didn't really even comb my hair much back then, but it was the only thing I had around. Why did I have a can of hairspray in the basement? Yes, it involved a lighter...I will say that after some years, I do understand my parents prohibition of making fireworks in the basement, though, for what that's worth.
posted by nTeleKy at 3:24 PM on November 6, 2012 [2 favorites]


Wait, people run baseboards on 120 V?

The Great White North's inhabitant's mind, she is blown.
posted by Monday, stony Monday at 3:28 PM on November 6, 2012


Malor, I just looked at the supply board coming into my one bedroom flat, and that's rated 100 amps at 415V (triple phase), and dated 1967. The meter's rated to 100A at 240V, though, and has two 50A trip switches coming out of it (for the shower and the oven), as well as 30A for the main (wall sockets) and a lighting circuit.

But that's fairly typical for here, and I suspect not so far off what's being run in the US.
posted by ambrosen at 3:30 PM on November 6, 2012


Yeah, I think the secondaries might be over engineered. Although, he didn't crimp the connectors, so he's going to be limited there. I'm surprised that didn't melt.

Now if someone can explain why it isn't arcing like a sonofgun, I'd appreciate that. Is it a relatively low voltage transformer? Why no lightning storm of nuclear proportions?

1- It was arcing pretty good, I was reflexively looking away so my retinas wouldn't burn.

2- But the reason it wasn't lightning is because arcing needs voltage. To simplify it very much, voltage pushes, and amperage gets pulled. If you imagine the flow of electricity as the flow of water, voltage is water pressure. Amperes is sort of the supply available. Like if you dig a canal lower than the ocean, the ocean will fill the canal because it has a lot of "amps" available.

So what he did was basically build a very high capacity wall wort. It's putting out 3 volts of potential, and it just has a LOT of capacity. He could hook a tiny 3v lightbulb up to it and it wouldn't burn out. But unlike a low capacity transformer, which would burn out instantly, he can also put a crowbar on it and it won't.
posted by gjc at 3:33 PM on November 6, 2012


I think, from my amateur, fumbling understanding of electricity, that we could just double the voltages, and get appliances that were twice as powerful, without having to gut the wiring in our houses. I believe wiring is based on amperage, not voltage. We'd probably just have to replace wall plates, and possibly fuse boxes.

That is true. The US system is versatile in that residential service usually comes in as two 120v legs that are 180 out of phase from each other so we can make use of 240 volt appliances. Good luck finding a 240 volt kettle, however.
posted by gjc at 3:40 PM on November 6, 2012


Previously(ish)
:)
posted by anonymisc at 3:40 PM on November 6, 2012


This guy's a lunatic and his videos are a lot of fun. I have to say, though, that while I appreciate his electrical work, for my money his masterpiece is still throwing a large rock into a washing machine .

"Oh, and I did get in trouble for wrecking those flowers."
posted by KokuRyu at 4:03 PM on November 6, 2012 [2 favorites]


Oh man, Photonic Induction is hilarious, and so chipper. I'd noticed I wasn't seeing anything new on my subscriptions, but I didn't realise he'd actually dropped off youtube. Glad to see he's back.
posted by lucidium at 4:13 PM on November 6, 2012


Also, watching that video actually makes me feel as if my computer is about to explode in my face.

I'd be afraid to live with him. I seem to recall him mentioning a previous partner left him for laser related reasons.
posted by lucidium at 4:18 PM on November 6, 2012


I think, from my amateur, fumbling understanding of electricity, that we could just double the voltages, and get appliances that were twice as powerful, without having to gut the wiring in our houses.

I knew a guy in college who informally rented a small house from a physics professor. The physics professor apparently had strong feelings on electrical standards, and the house was wired for 220v (but using normal US sockets). He had to warn guests not to plug anything in, ever.
posted by miyabo at 4:20 PM on November 6, 2012 [3 favorites]


Great, now I'm hooked on these videos :) Thanks to nTeleKy for the additional links, I definitely recommend checking out the blown electric meter video in particular - very cool.
posted by photo guy at 4:31 PM on November 6, 2012


ambrosen: But that's fairly typical for here, and I suspect not so far off what's being run in the US.

Well, here in the US, my house has a 300 amp main feed, though I'm not sure if that's 120V or 240V amps. 100 amps goes to the heat pump, and then 200 go into the house proper. The house circuits are all wired point-to-point, at 120 volts. Most have 15A per circuit, but the ones to the kitchen and the one I put in specially for my computer room are all 20A.

AFAIK, every plug in the house has a dedicated wire back to the breaker box, which is somewhat unusual. It's fairly common for older houses to have 1 20A circuit per room, with 2 or 3 outlets that all pull from that circuit. It's not a ring circuit like in the UK, though, which apparently allows for using wiring that's about half as thick... it's just an extended pair of wires, with 2 or 3 outlets as 'takeoffs'.

miyabo: The physics professor apparently had strong feelings on electrical standards, and the house was wired for 220v (but using normal US sockets).

Yeow! We have US plugs for that. I think it's outright illegal in many states to run 220V to an outlet that looks like a 120 volt. Even a 20A outlet has one of the blades turned sideways, indicating that a device can safely pull 20A from that circuit. Devices with normal vertical prongs are only allowed to draw 15A, the limit on many older household circuits. (it's getting more common to actually wire them for 20, as was done in my house for the kitchen outlets... individual devices can only pull 15, but you can usually plug in two medium-drain devices and have them work, like a microwave oven and a coffeepot, if the circuit fuse is 20A.)

I'd probably rewire at least a couple of plugs for 220, if I could easily get appliances that used it.
posted by Malor at 5:08 PM on November 6, 2012


One of the nice things about the 230/240V world is that you can get a washing machine which heats its own hot water, requiring only a connection to a cold water tap and a drain. At least that was the case with mine which was on its own 230V 10A circuit.
posted by thewalrus at 6:54 PM on November 6, 2012


nTeleKy writes "Yep, all the electric baseboard heaters in my house are run off of 208V for this reason (which you probably have if you've got a newer building, but your appliances and outlets/plugs may not be designed for)."

That's unusual, 208 is a 3phase voltage and most houses only get single phase power.

gjc writes "Good luck finding a 240 volt kettle, however."

That's the easy part, just order one up from the UK. You have to change the cord end to a NEMA equivalent but the kettle would work fine.

miyabo writes "The physics professor apparently had strong feelings on electrical standards, and the house was wired for 220v (but using normal US sockets). He had to warn guests not to plug anything in, ever."

Foolish and illegal. Regular duplex receptacles are available in a 240V configuration as are cord ends. This is the reason we have electrical inspectors.

Malor writes "AFAIK, every plug in the house has a dedicated wire back to the breaker box, which is somewhat unusual. "

That's really unusual and somewhat wasteful; you've easily got 4x as many home runs and breakers than you'd need. That's a lot of copper.

Malor writes " I think it's outright illegal in many states to run 220V to an outlet that looks like a 120 volt."

Everywhere in the States and Canada.

On the 240 wall outlet and appliance thing: With the right wiring (Three Wire Edison or I think it's called a Multi Wire Branch Circuits in the states) you can even have the same receptacle service both 120V appliances and 240V appliances. The wiring to support this was pretty common in Kitchens before GFCI requirements.
posted by Mitheral at 8:36 PM on November 6, 2012 [1 favorite]


50000 amps of current, 0.5 amps of stage presence.
posted by wolfdreams01 at 8:50 PM on November 6, 2012 [1 favorite]


If you want high current, and high voltage, enough obliterate things, he doesn't disappoint.
posted by eye of newt at 10:11 PM on November 6, 2012


He's got a coffee cup there for that. What could possibly go wrong?

Judging by his accent, I'm pretty sure that's a cup of tea. Which... obviously offers more protection.
posted by rh at 11:22 PM on November 6, 2012


That's unusual, 208 is a 3phase voltage and most houses only get single phase power.

My mistake, it is actually 240.
posted by nTeleKy at 8:34 AM on November 7, 2012


If you want high current, and high voltage, enough obliterate things, he doesn't disappoint .
posted by eye of newt at 1:11 AM


I like how you can see the burn marks on the carpet when he displays the microwave capacitors.
posted by orme at 9:30 AM on November 7, 2012 [1 favorite]


...what we should or shouldn't stick in where or why.

I find that most things in life revolve around the resolution to that question.
posted by cthuljew at 12:23 PM on November 7, 2012 [1 favorite]


No doubt the sort of thing Tesla did to amuse himself on quiet evenings about the Niagara Falls plant.
posted by Twang at 3:55 PM on November 7, 2012


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