Exploding Wires

published on July 12, 2020

Neal our technician suddenly gotinspiration from his old physics teacherhe's devised a machine which will allowhim to put a high current through apiece of thin wire and as he turns theknob the current goes up and up and upuntil the wire fails no I'm ready when

You are for this one so we started withcopper what happens is that as you putthe current through the copper he getshotter and hotter and hotter and in thiscase copper melts before it catches fireso suddenly you see the wire sagging

Down and down and down and eventually itbreaks and as it breaks there is a flashas the copper vaporizes and you mayremember that copper gives a nice greencolor in the vapor so you see a veryquick flash of green light

So Neil had a great ambition to try andburn aluminium so he got piece ofaluminium wire and heated it up but likecopper aluminium melts before it catchesfire in air so suddenly you'd startsagging sagging sagging and after a

Little bit its breaks Neil was a bitdisappointed nothing burnedso we tried magnesium didn't havemagnesium wire so we tried magnesiumribbon that's relatively flat materialand as you heat that because the heated

Metal expands the magnesium startedarching upwards and then suddenly itdrooped there as probably many of youknow that once you set fire to magnesiumit keeps burning so the whole lot burntaway with clouds of white sort of smoke

Which essentially is finely dividedmagnesium oxidemagnesium is a metal that once you lightit it generates so much heat that theburning becomes self-sustaining it'sprobably because the metal doesn't

Conduct away the heat very much from thearea that's burningwhereas aluminium and copper if you setit on fire and remove the source of heatit quickly goes out probably the metaljust cools down too fast

Neal suddenly remembered he had somespecial wire he took Brady to hisspecial store he calls it the dark holedoesn't want me going there and mightstart taking things from it in the darkhole was the remains of a

Superconducting magnet a very powerfulmagnet that was used in an instrumentsome years ago the magnet consists of acoil and Neil cut off a piece of thisalloy the wire that's used for thesemagnets has to be insulated otherwise it

Would short-circuit and it's insulatedwith varnish so as it heats up there's abit of smoking as the varnish vaporizesslightly disappointingly it behaves muchthe same as the other metalsSAG's flashes and breaks

Next Neil produced a piece of tungstenwire tungsten wire is what's used inold-fashioned lightbulbs it was reallyinteresting as you heat it up it getshotter and hotter tungsten has thehighest melting point of any of the

Metals that we used and it starts toburn doesn't melt at all and just getsthinner and thinner and thinner until itfails he ended up with quite aterrifying looking spike a really narrowtungsten so professor this did fail

Quite quickly but light bulbs don't failquickly ideally what's the differencebetween this and a light bulb thedifference from the light bulb is thatin a light bulb the tungsten is not ashot as at the end of Neil's experiment

And of course the bulb itself is filledwith argon gas rather than with air Neiland I were both really quite fascinatedby this very narrow spike that is madeand I think it is because one part ofthe wire must have started getting

Thinner than the rest and thereforehotter and therefore preferentially thehottest part will have burnt fastestBrady really wanted to do gold Neil wasa bit reticent gold is expensive so heput a glass dish underneath now I must

Say that gold was probably the mostdisappointing of them all because itheated up it melted it brokeit didn't give a really very convincingflash Gold doesn't have a beautifulgreen color like copper but Brady was

SatisfiedAnil didn't lose any gold I think themost exciting metal and this was a realsurprise was molybdenum when we heatedup molybdenum even when I was watchingthe camera from the distance there

Seemed to be some sort of pulsating onthe pictureand when we looked at the metalafterwards it was extraordinarybecause instead of having a smooth wirethere were little blobs of molybdenum

Metal all the way along the wire andthese blobs were really quite evenlyspacednow it turns out that this phenomenonhas been seen in exploding wires usingvery high speed cameras

I think it's unusual i and none of mycolleagues had seen like anything likethis beforenow you probably or some of you whospecialist in this area probably havesome really good explanation of why this

Happened I think what happened is thatthe molybdenum ëtil began to melt on thesurface of the wire so you imagine thewire covered with a thin layer of liquidand because liquid has surface tensionthis is why liquid forms drops I think

That the liquid separated into littledrops because the surface tension pulledit together and so you get what wouldnormally be little drops of liquid butthey solidified so we've somehow gotthem fossilized along this wire all my

Colleagues that I've shown these bits ofwire to have got really excited it'sreally surprising that you can get suchan even spacing I did a bit of researchon this phenomenon and I came across aword I'd never heard before called

Angeloids angeloidsis the word that mathematicians use todescribe this sort of object I would bevery interested to hear from any of youwho has a really good explanation ofwhat happened Neil thinks that the

Spacing might be related to thefrequency of the mains so he's keen totry and use direct current rather thanalternating current and see whether weget the same effect I think there'll beno difference I had the idea that we

Should turn the apparatus through 90degrees so the wire is vertical and itwould be much more difficult for it tosag and what we found was indeed itdidn't sag so much at least until itbreak and we got a much better shot of

The flesh ofgreen light as the cup of vaporizedthere was still slight bending but itwas much less than before just as wewere packing up I persuaded Neel to makea coil of copper we put this coil

Vertically my idea was that the coilwould be floppier than the straightpiece of wire so it might sink morebut then it collapsed quitespectacularly once it's brokenbut I think chemically what was

Interesting to me was that if you lookedat the bit that was broken you could seethe black copper to oxide on the surfaceof the copper showing that there was atleast some reaction with oxygen but verymuch less than saying the burning

Magnesium I was really grateful to Neilbecause he devised a demonstration whichalmost turned into an experiment whichmade me think I never thought that pieceof molybdenum wire could be in the leastbit interesting and Here I am

The day after Neil did the experimentstill thinking about it and anythingthat makes scientists think is reallygood and anything that makes us thinkdifferently is brilliantyou

You

Related Videos

all right so the other day I said with my kids watch TV you probably familiar with these reality shows where they put a bunch of clueless people put them in an...
well a mathematician and I like action movies particularly die hard is one of my favorite you know action movie and as a one which has a couple of Matt's p...
so today we've got a very very special guest who is going to perform an incredible feat for you to introduce the special guests abroad my multiplying monke...
one of the first videos we did for for this channel was about the Futurama theorem which is a pretty amazing thing it's about mind switching mathematics an...
well last weekend i actually did a talk on mats in the simpsons here in melbourne and i'm going to split this up into three different videos so today you g...
so recently a few people left comments to the effect that mythology is Illuminati confirmed and they based these you know comments on a couple of things they s...
I'm assuming that you you just watched the Illuminati confirmed video and that you're a hardcore mathematician and that you now want to prove that your...
well i love simpsons giuseppe loves the simpsons everybody loves the simpsons and if you look at the views yeah it's really everybody who loves the simpson...
today I've got something lined up which is going to be really really useful for people who have trouble memorizing that times table well we've come ver...
I'm assuming everybody here also watches numberphile Giuseppe by watching number files numberphile is great so does in case you don't watch numberphile...
okay so to start off I've got four four images for you so look at them one two three four now quick question what do all of them have in common well I woul...
as you can see I'm quite serious about juggling have been serious about juggling for decades used to busk and do all sorts of things now what I want to sho...
so recently we did a video on the most mysterious and beautiful identity in mathematics e to the PI I is equal to minus one comes up three times in the Simpson...
oh you're probably all familiar with this puzzle here so we've got a picture distributed on 15 tiles and we've got an empty square and this is empt...
today M stands for Mandelbrot set before scene at night let's zoom in what you find is all these amazing pictures here like these little baby Mandelbrot&#3...

PI MUST DIE !!!

7 months ago
I don't know about you but I sometimes get really really sick of pie so last week I enlisted the help of some friends at the tech wonder club we're tra...
a lot of you will be familiar with this strange identity here one plus two plus three plus dot dot equal to minus 112 now when you think about it this looks to...
you hello everybody I'd like to talk about a little problem that has intrigued people ever since we discovered mirrors let's have a look at what I see ...
exciting news everybody just a couple of days ago I solved the 40 Rubik's cube for the first time not many people have done this so I thought I'd do a ...
today I want to let you in on a really neat trick that I learned from a very famous mathematician how to subtract infinity from infinity to get exactly pi so f...