How long would it take to replace all the electrons in a piece of wire? - Page 1
Forum section: electronics / general

author: raspberrypi
author_rank: Frequent Contributor
timestamp: February 07, 2017, 04:53:36 am
content: Ever think about it?Say you had a meter of 16ga wire. At what amps for how long would it take for each electron to be bumped out of one end and replaced in the other end? Or at what speed would a single electron make the journey though the wire?

author: switchedmodepsu
author_rank: Regular Contributor
timestamp: February 07, 2017, 04:58:12 am
content: Quote from: raspberrypi on February 07, 2017, 04:53:36 amAt the speed of light, I'd think.

author: Brumby
author_rank: Unknown
timestamp: February 07, 2017, 05:04:27 am
content: Quote from: switchedmodepowersupply on February 07, 2017, 04:58:12 amActually, no.The speed of causality is getting up there, but the physical electron movement speed - called Drift Velocity - is actually quite slow.

author: ataradov
author_rank: Super Contributor
timestamp: February 07, 2017, 05:18:56 am
content: Yeah, Drift Velocity depends on cross section of a conductor and for typical wire and normal currents, it is in single digits of mm/second.

author: onlooker
author_rank: Frequent Contributor
timestamp: February 07, 2017, 05:20:02 am
content: To be more precise, according tohttps://en.wikipedia.org/wiki/Drift_velocity#Numerical_example"Assume a current I = 1 ampere, and a wire of 2 mm diameter,... the electrons are flowing at the rate of -0.000023 m/s"

author: Rick Law
author_rank: Super Contributor
timestamp: February 07, 2017, 05:24:20 am
content: Quote from: raspberrypi on February 07, 2017, 04:53:36 amQuote from: switchedmodepowersupply on February 07, 2017, 04:58:12 amEM field would move at the speed of light, but electrons not being mass-less will by laws of physics move below the speed of light.Getting a good guess is not hard. Getting a precise answer is good bit harder.The speed of electricity over copper average about 0.5c to 0.9c according to this guy:https://www.quora.com/What-is-the-speed-of-electric-currentThat sounds within reason. I would have guess unobstructed (by EM field) around 0.7c. Your 16AWG or whatever wire, the material property of the wire is unknown, so you don't know would it be 0.5c or 0.9c speed.1Amp (pre SI unit) is approx 1Coulomb @ 6.2 x 1018x eFrom that, you can figure out(after you find the material property of your wire) how many electrons are in that piece of wire of X mm long, and how many Amps does it take topass the equivalent amountof electrons over that wire. If it is pure copper you know from the periodic table how much each copper atom weights and how many electrons are in that copper atom. But of course pure copper is impossible - at least you would have a copper oxide outer layer among other impurities.Note I carefully avoided saying the electrons are now all replaced. You are merely passing the equivalent number of electrons through the wire. Some electrons in the wire are never moved. Mostly, only the outer shell get shuffled around.The path is not direct. Electron get shuffled near atom A, atom A with an extra electron hanging around has its outer-shell over-charged resulting in another electron in the outer shell leaving to atom B, then the same things happens an another electron got captured by atom C...

author: helius
author_rank: Super Contributor
timestamp: February 07, 2017, 05:51:59 am
content: It would take a long long time.16awg is 1.31 mm2. The number of electrons in a wire is equal to its length, times cross-sectional area, times the number of electrons per unit volume. The valence orbitals of copper are such that there is one electron per atom that is free to move. So the number of electrons is equal to the number of copper atoms per unit volume.The number of atoms per cubic meter is equal to the density of copper, times Avogadro's number, divided by copper's atomic mass. Copper's atomic mass is 64, and its density at STP is 9000 kg/m3. So there are 8.5 x 1028electrons per cubic meter in copper wire.That makes 0.00000131 m2* 1 m = 1.31 x 10-6m3of copper, times 8.5 x 1028e/m3, is 1.11 x 1023electrons. A coulomb is 6.25 x 1018electrons, so that is 17800 coulombs.An amp is a coulomb per second, so at 1A, that would take nearly 5 hours. However, that is not "Allthe electrons in a piece of wire". That is only the valence electrons that are free to move; the others stay where they are.The speed component of the valence electrons due to current is called the drift speed. The drift speed equals the current density divided by the number of mobile charges per unit volume. We already know there are 8.5 x 1028electrons per cubic meter, so we need the current density J.J = I/A, the current per cross-sectional area. At 1 amp, that is 1/0.00000131 m2= 763000 A/m2.But amps are coulombs per second, and we want the speed of an electron. So we should multiply J by 6.25 x 1018, then divide by 8.5 x 1028electrons per cubic meter, to get the speed of an electron, 5.6 x 10-5meters per second, or 56 microns/s. About the thickness of a human hair per second.

author: Rick Law
author_rank: Super Contributor
timestamp: February 07, 2017, 06:25:00 am
content: Heliusjust shown how many damn electrons are involved in a tiny wire. Which actually points out something far more interesting you can ponder (than speed of electrons traveling)...One might have imagined, if I make moon-shine, and my alcohol droplet condensed from vapor will vary in size depending on humidity in the air, air temperature...How did the universe managed to make so many identical electrons?A Chinese made electron is going to be exactly like an electron made in the USA. They can use their own high energy collider to create an electron using power from the world's largest dam; we could use powered from diesel generator to power a collider in the (never constructed) Texas super collider. Yet if we both made an electron, they will be exactly the same...How did the universe do that?Well, may be those cheap LiIon cells from China do put out smaller electrons just to save a few bucks.

author: Ian.M
author_rank: Super Contributor
timestamp: February 07, 2017, 06:32:25 am
content: https://en.wikipedia.org/wiki/One-electron_universe

author: Brumby
author_rank: Unknown
timestamp: February 07, 2017, 06:33:24 am
content: String theory.You want proof? ..... How aboutstring cheese.

author: Vgkid
author_rank: Super Contributor
timestamp: February 07, 2017, 06:39:57 am
content: I had never heard about the "String Theory" until a guy mentioned it in one of my college math classes. We never discussed it(or got that far) in my university physics class.

author: Rick Law
author_rank: Super Contributor
timestamp: February 07, 2017, 07:13:19 am
content: Quote from: Ian.M on February 07, 2017, 06:32:25 amI learned of this "one electron universe" in 1973. It was fascinating but an unsatisfactory explanation then. The trouble only got worst.Neither it, nor string theory can survive the inflation phase of the universe formation. To survive means it has to take hold before inflation (so information can be passed along to the entire universe to make them consistent), and the results has to remain consistent post-inflation. If it is to occur post-inflation, than information must be passed from one end of the universe to the other end at speed faster than the speed of light.I like to see (one of the) string theory takes hold and develop to a point where it is the model to explain everything at least in particle physics, but it isn't there yet. To fully explain formation, we will now have to factor in dark energy and dark matter.There is so much to learn, yet even if I am just 1 year old today, there is not enough time left to understand them all.

author: Halcyon
author_rank: Unknown
timestamp: February 07, 2017, 07:40:36 am
content: I think you guys are onto a audiophool winner here. "Fast Electron Replenishing Cable". Think of all the good you could do ;-)Beats the crap out of "directional" cables as the electrons can travel either direction!(Cut me in for 20% of your profits)

author: Doc Daneeka
author_rank: Contributor
timestamp: February 07, 2017, 06:24:46 pm
content: When I last brushed up on my QM, I read that all electrons are in fact absolutely identical: when you talk about a number of them you have to talk about the combined wave function which represents all of them; there are no 'individual' electrons as such. So the answer is both instantaneously and infinitely long... or some such thing....close?

author: Vtile
author_rank: Super Contributor
timestamp: February 07, 2017, 08:23:14 pm
content: I must admit I had forgotten the speed difference of electron and the wave.

author: TimFox
author_rank: Super Contributor
timestamp: February 07, 2017, 08:41:30 pm
content: I remember a few years ago when the Des Plaines river (in Illinois) was in flood, comparing the current (water velocity) with the time it took the crest of the flood to move a few miles, and thinking of the analogy.

author: Rick Law
author_rank: Super Contributor
timestamp: February 07, 2017, 09:43:09 pm
content: Quote from: Doc Daneeka on February 07, 2017, 06:24:46 pmNo that doesn't follow. Even when viewed as a wave, it doesn't make it travel instantaneously.Viewing it as a wave merely means you are looking the the wave properties of the particle. Wave properties are properties such as formation of an interference pattern, passing from one side of the wall to the other using two holes at the same time. Stuff like that.The particle properties of this wave is that it is not mass-less. So, not only can this wave not travel instantaneously, it cannot even travel at the universe's top speed which is c.

author: Vtile
author_rank: Super Contributor
timestamp: February 07, 2017, 09:48:20 pm
content: Yep, in the cablesonars/radarsreflectometers that is easily seen, if I'm understood correctly. I should repair mine, to get it finallyplayworking order.

author: David Hess
author_rank: Super Contributor
timestamp: February 07, 2017, 10:59:55 pm
content: Quote from: Rick Law on February 07, 2017, 07:13:19 amEntanglement does not solve this?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 07, 2017, 11:21:07 pm
content: It's a meaningless question, because all electrons are identical. You could just as well ask how long it would take the electrons to be replaced from the wire into my body; the answer is the same: it doesn't matter!If you change the problem so that identification is possible, then the answer is either the drift velocity, or the carrier diffusion velocity, whichever is higher. (Few conductors operate with a drift velocity higher than the thermal velocity, i.e., ballistic rather than drift motion. An example is electrons in a Gunn diode, which is really a monode: just a lump of doped GaAs that exhibits negative resistance, thanks entirely to its material properties, no junction needed!)A possible substitute could be an ionic conductor, like heated ZrO2, which carries current through mobile O2-ions and lattice defects.The experimental design might be like so:Set up a ZrO2plate, with metallized grids on either side, with an atmosphere of18O2on one side. The exchange of O2with the ceramic surface, introduces different nuclear isotopes into the composition (which starts as mostly16O). As16O is displaced with18O isotopes, labeling is achieved, and observation of the process is possible.You might analyze the results by drawing various currents through the samples, for different times, at different temperatures, then sectioning the samples. (The samples should be relatively stable at room temperature, because the ions freeze in place.) An atomic fluorescence spectrometer should be able to resolve the isotopic differences without too much hardship, I think?It would be an interesting graduate experiment, but rather useless in results, as it should be expected to give the identical result that chemical diffusion and electronic transport are known to achieve. (And, anomalous results could depend on impurities in the materials, so you might not learn anything even from very precise measurements.)Tim

author: linux-works
author_rank: Super Contributor
timestamp: February 08, 2017, 12:03:30 am
content: Quote from: Rick Law on February 07, 2017, 06:25:00 ambut there is a difference.the chinese electrons seem ok, at first; but an hour later, you'll just need more.(lol)

author: Gregg
author_rank: Super Contributor
timestamp: February 08, 2017, 01:38:29 am
content: The problem with trying to remove the electrons form your wire is that they always return; at least in our physical world. Electrons in a wire work a lot like a string of balls in a Newton’s cradle; when you drop one in on one end another pops out the other end, only to return and eventually reach equilibrium.Then there is the case of shorting out your 16 ga wire with something like 480 volts and hundreds of amps which results letting out the magic smoke with all of the angry pixies soaring away to deposit the wire material on any surfaces available; like sputtering a metallic coating on a silicon wafer.Enclosed are a couple of pictures of the aftermath after some hapless electrician burned through two ¼ inch thick layers of copper bus bar with a little over 500 volts DC from a big bank of lead acid batteries of a 750 KVA UPS installation. All electrons were present and accounted for in the final tally; they were just attached to the copper plating everything including the Fluke meter at the bottom of the enclosure that the electrician failed to use.Tossing your wire onto the surface of the sun may disassociate the metal atoms, but I doubt you could measure the result. Here on earth, you may be able to put tiny samples of your wire into the Haldron collider and knock a few of the outer electrons off the sample. Even the electrons from arc welding, Tesla coils and lightning always return to equilibrium.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 08, 2017, 01:43:25 am
content: Quote from: raspberrypi on February 07, 2017, 04:53:36 amTo replace ALL THE ELECTRONS?Disregarding the 'all electrons are the same one' mind-bender, the answer is... forever.Because only the outer shell electrons are free to move in the solid. Regardless that those ones only drift very slowly (less than walking pace) under an applied field, the vast majority of the metal atom electrons are not going anywhere. Short of you heating the wire into a completely disassociated plasma of nuclei and free electrons. Even then, good luck separating them significantly.Aside: I'd never heard of the 'all electrons are one' thing before. Bizarre.That's a lot of copy and paste, or 'electron shortcuts'. I wonder who has the copyright on the original one? Hopefully no DRM takedown notices in our future. All your electrons are belong to us.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 08, 2017, 01:52:31 am
content: Why don't HVDC enclosures have plastic covers/baffles to reduce the chance of a foreign object setting off an arc flash?

author: anfang
author_rank: Regular Contributor
timestamp: February 08, 2017, 02:06:02 am
content: Someone's been swigging too much paint thinner

author: TerraHertz
author_rank: Super Contributor
timestamp: February 08, 2017, 02:35:04 am
content: Quote from: Gregg on February 08, 2017, 01:38:29 amLooks like the experiment was inconclusive. Lucky you have a second panel over to the left to try it again. This time take a video?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2017, 04:14:49 am
content: Yikes! Was that just the arc flash, or was it sustained (poorly fused, or unfused for that matter)?Having worked on 480VAC industrial equipment myself, I can simply say this:Don't fuck around. Treat it carefully, with respect.Fuses are there for a reason, and guards, PPE, and safety procedure are there for a reason.Don't die.Tim

author: bson
author_rank: Unknown
timestamp: February 08, 2017, 04:35:53 am
content: The problem with electrons is you can't have only one.

author: Gregg
author_rank: Super Contributor
timestamp: February 08, 2017, 04:36:58 am
content: It was DC fed by the battery bank which was connected prior to landing the wires in the disconnect cabinet. It should have been connected in the cabinet first and every wire tested with a meter prior to final connection. The battery bank is capable of thousands of amps for many minutes and because it is DC the arc sustained itself until the wire and bus bar burned far enough apart to stop. The batteries are about 20 inches wide and 24 inches tall; the cables are parallel 750 MCM.

author: station240
author_rank: Unknown
timestamp: February 08, 2017, 04:12:59 pm
content: Quote from: TerraHertz on February 08, 2017, 01:43:25 amMy thoughts on the matter also, it's not possible to replace all the electrons.A copper atom has 11 valence electrons, in the two outermost valence shells.But it has 29 electrons, so you can only replace 38% of the electrons.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2017, 04:23:15 pm
content: Quote from: Gregg on February 08, 2017, 04:36:58 amSo there's no fusingatthe battery?If it was me, I'd want a fuse on there, early and often... even just while wrenching it together.But I don't know what SOP is, as far as distributing and fusing such sources.Quote from: station240 on February 08, 2017, 04:12:59 pmWith zero energy barrier to the exchange*, it would be foolish to think the electrons wouldn't swap constantly between locations!*Again, assuming one could ID electrons, which one cannot; for the same reason, the electrons on Pluto have zero energy barrier to exchange with the electrons in any wire, or any other combination of exchanges. They're all identical!Also also, copper "gives up" about one electron per atom, to the conduction band, so it wouldn't be quite correct to estimate the quantity of free electrons as the valence band, either. But again -- it doesn't matter --there's only ever been one electron, for all matter, for all time! (Even the occasional positron is just an electron rewinding backwards through time!)Tim

author: Gregg
author_rank: Super Contributor
timestamp: February 08, 2017, 09:32:22 pm
content: Tim,The battery current protection is the breaker in the cabinet. It is a shunt trip breaker that the UPS controller can trip if there is a problem as well as standard breaker function of being able to manually turn it off for things like battery maintenance. The breaker is located within 10 feet of the connection end of the battery string. Usually there are two parallel connected redundant UPS units feeding the same load so that one at a time can be taken off line for maintenance. Sometimes two battery strings, each with their own shunt trip breaker are connected to each UPS unit to allow for battery maintenance.The pictures were from a new installation at a data center. Standard procedure is to connect the DC cabling to the breaker cabinet before connecting the battery end. Then at the battery end everything but the battery terminal plate being connected gets blanketed from all other terminals and ground. Then each cable is checked with a volt meter and ohm meter to ensure the correct cable is connected to the proper terminal. The cables should be labeled on both ends during installation, but still must be double checked with a meter.This incident didn't happen on one of my projects and the contractor was banned from the job. (I retired from the power end of electrical engineering working for a large data / telco / cellphone company.) I used to print some of my pictures to show contractors why they needed trained people on the job.In operating facilities there are standard and custom SOWs (scopes of work) that delineate step by step the procedures for almost anything that may affect the network and most of this stuff gets done between midnight and 5 AM. On new construction, however, there isn't as much oversight as was the case here. If an electrician that has only household and light commercial experience and thinks that this stuff is the same only with bigger wires is turned loose on something with over 500 volts of DC and over 10K amps available their first mistake may be their last. Luckily the guy that vaporized the bus bar survived but did suffer some severe burns to his face and arms. Stupidity should be painful, too bad his supervisor didn't get to share the pain.I have lots of good stories of how not to do things.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2017, 10:42:39 pm
content: Ah, yeah, that sounds good.Guess I can't say nobody got hurt, but at least nobody died either!Don't be afraid to share your wisdom. There's no shortage of newbies here, some of whom may be going into power and electrical jobs some day.Tim