38 ms·
Why does current flow the opposite way from the electrons?
After fighting through a bunch of unhelpful answers, one gets to the bottom of things: Benjamin Franklin chose a convention that makes electrons negative, and apparently nobody knows why.
- deleted 2y ago[deleted]
- NegativeLatency 2y agoIt was only relatively recently we figured started to understand some sort of model of what the inside of the atom is: https://en.wikipedia.org/wiki/Plum_pudding_model https://en.wikipedia.org/wiki/Plum_pudding_model
- xdavidliu 2y agohow is this recent? This was like 1900.
- gavindean90 2y agoThat’s more than a hundred years after Franklin.
- zer00eyz 2y agoRome was about 2500 years ago. The first recorded name, 5000 years. Oldest human structures 10k years. Humans, about 130k years. Our oldest "ancestors" 300-400k. 3.7 billion years. For you, not so recent. In the grand scheme of things it was a heartbeat ago.
- kevin_thibedeau 2y agoThe Nobel prize for proving the existence of molecules was awarded in 1926. Less than 100 years ago. Our understanding of physical chemistry is extremely recent.
- oneshtein 2y agoIn the absence of firsthand accounts, historical sources become our sole means of understanding past events. This transition typically occurs within two generations, or roughly 50 years, of the event's occurrence.
- sethev 2y agoThe oldest living person today was born the same year Thomson published The Corpuscular Theory of Matter in 1907. So a long time ago in one sense, but not so long in the scheme of things.
- fhars 2y ago50% chance events happen all the time (well, half the time).
- drdec 2y agoI think you were right the first time. If a particular 50% chance event does not happen, then the complementary 50% chance event does happen.
- nitwit005 2y agoCould be worse. They could have chosen any term implying opposite. We could have had left and right handed charges. Although I suppose we essentially did that when naming the quarks.
- robocat 2y agoThe worst part is that up and down are not really opposites. Down is up on the other side of the world.
- technothrasher 2y agoI'm not sure I follow you there. In that sense, "down" means toward the center of the gravity well. It is the same regardless of which side of the world you're on. If you mean that "down" changes direction with reference to a straight line, ok. But how does that make "up" not the opposite of it?
- crazygringo 2y agoUp and down are opposites on the other side of the world too...
- manmal 2y agoOr amino acids. Many have a D (Dextrorotatory = right) or L (Levorotatory = left) form, indicating into which direction they rotate polarized light.
- gerdesj 2y agodexter is Latin for right and sinister is left, rotatory is probably rotation and hat fit in with polarization. Where does levor... come from for left? Perhaps a newer Latin "left" than I was taught?
- gravescale 2y agoIt comes from the Latin "laevus". Funnily enough, although "sinister" came to mean "the bad side", it may have come from Proto-Indo-European for the "favourable side".
- CapitalistCartr 2y agoA big part of this is we measure what's important to us. As an electrician, what's important is which wire is full of angry pixies. They're technical direction of travel is far less important to my job (and my safety). When doing electronics, the direction of travel becomes quite important. So there's a different point of view.
- Gibbon1 2y agoAnytime electrochemistry is involved it's important. But regular electronics not very much. I think positive and negative mostly trips up people trying to use what they think is happening to explain theory. When it's not that useful most of the time. What I could never keep straight is anode and cathode.
- justhadto123094 2y agoCAThodes are PAWsitve
- kazinator 2y agoBut if you connect a 5V battery in parallel with a 4V battery, the 5 will try to charge the 4. So the (+) terminal of the 5V battery will act as a cathode, but the (+) terminal of the 4V battery as anode. "CCD" -> "cathode: current departs" In chemistry though, cations are positive ions and anions are negative ions.
- g15jv2dp 2y agoCats are more intelligent than donkeys (âne in French). Cathode is positive, anode is negative. That's how I (and probably all French students) learned it.
- Thrymr 2y agoA CRT display is a "cathode ray tube", which shoots electrons, which are negative.
- samatman 2y ago
- bmacho 2y ago> that makes electrons negative, and apparently nobody knows why When there is a symmetry, there are choices, all the time in math, and sometime in physics too. Also I don't like calling electrons negative, they are not. Maybe you can say that their charge is -1, when you model charge with the additive structure of real numbers / integers, and you choose the protons charge to correspond to 1. Modeling charge with the additive structure of real numbers / integers is very reasonable. (You could use red and blue numbers, but that's not a widely used structure.) So you shouldn't say "electron is negative". That's weird, confusing, misleading, and trolling.
- bmacho 2y agoRed and blue integers: there is red 1, red 2, ... 0, blue 1, blue 2, ... . Addition and subtraction as you expect. There is no ordering, also no multiplicative structure. There are 2 isomorphism into the additive structure of the integers. (Red and blue reals are defined similarly.) I find this structure to model charge better. If not for else, at least it prevents you to ask silly questions about charge.
- hawski 2y agoSo you mean red like warm water and blue like colder? Warm is + and cold is -.
- crazygringo 2y ago> So you shouldn't say "electron is negative". That's weird, confusing, misleading, and trolling. Huh? By the convention you describe (and we all share), electrons have negative charge, since -1 is negative. When speaking in the shared and understood context of charge, you shorten that to saying electrons are negative. Nothing weird, confusing, or misleading, and certainly not trolling. I'm baffled where you get that from.
- LgWoodenBadger 2y agoHe comes from an accounting background where commonly-understood terms mean the opposite of what everyone commonly understands them to mean.
- saghm 2y ago[flagged]
- urbandw311er 2y ago[flagged]
- throwway120385 2y agoBecause he didn't know anything about electrons, and the experiment he did involving rubbing amber and glass rods on fur and silk cloth only showed that something was transferred between the two materials, and that when the material containing the substance was brought near to the other material containing the other substance, the property conferred by the substances appeared to negate. If you read Teaching Introductory Physics the author very clearly points out that there is no way of knowing the direction of the charge. It must instead be decided by convention. And Franklin simply chose a convention that we stick with. This is where the need to use mathematical formalism to describe physical concepts becomes clear. Numbers and numeric quantities aren't a real thing that exists in the world. They exist only in our minds. And so does the concept of negation. Calling electrons "negative" is simply a tool for us to model how the substance behaves when it interacts with an "opposing" substance using numbers. We could just as easily have called it "black" or "white" charge, except that we then need to adapt arithmetic and algebra and calculus and so on to work with the concept of "black" or "white" quantities if we are to use them to understand the substance of charge.
- akira2501 2y agoIt really seems like had a rationale: "We suppose as aforesaid, That Electrical Fire is a common Element, of which every one of the three Persons abovementioned has his equal Share before any Operation is begun with the Tube. A who stands on Wax, and rubs the Tube, collects the Electrical Fire from himself into the Glass; and his Communication with the common Stock being cut off by the Wax, his Body is not again immediately supply’d. B, who stands upon Wax likewise, passing his Knuckle along near the Tube, receives the Fire which was collected by the Glass from A; and his Communication with the common Stock being likewise cutt off, he retains the additional Quantity received. to C, standing on the Floor, both appear to be electrised; for he having only the middle Quantity of Electrical Fire receives a Spark on approaching B, who has an over-quantity, but gives one to A, who has an under-quantity. If A and B touch each other, the Spark between them is stronger, because the Difference between them is greater. After such Touch, there is no Spark between either of them and C; because the Electrical Fire in all is reduced to the original Equality. If they touch while Electrising, the Equality is never destroyed, the Fire only circulating. Hence have arisen some new Terms among us. We say B (and other Bodies alike circumstanced) are electrised positively; A negatively: Or rather B is electrised plus and A minus. And we daily in our Experiments electrise Bodies plus or minus as we think proper. These Terms we may use till your Philosophers give us better. To electrise plus or minus, no more needs to be known than this; that the Parts of the Tube or Sphere, that are rub’d, do, in the Instant of the Friction, attract the Electrical Fire, and therefore take it from the Thing rubbing: the same Parts immediately, as the Friction upon them ceases, are disposed to give the Fire they have received, to any Body that has less. Thus you may circulate it, as Mr. Watson has shewn; You may also accumulate or subtract it upon, or from any Body, as you connect it with the Rubber or with the Receiver; the Communication with the common Stock being cut off." from Benjamin Franklin's letter to Peter Collison, May 25, 1747.
- Am4TIfIsER0ppos 2y agoElectrons were not discovered for more than a hundred years after his death. How could he have done the "right" thing other than by chance?
- luyu_wu 2y agoIMO the issue is that we used his convention even after we realized he was wrong. As a student, this trips me up immeasurably, especially after learning non-symmetric circuits.
- RevEng 2y agoWe did so because it would have been even more confusing if one day we just switched the meaning. Electricity had been studied for a hundred years by the time we understood electrons as the charge carrier. In the mean time, many formulas were derived and books were written. To flip the meaning of everything would result in mass confusion about which way we were defining current flow. To disambiguate, we would want some unique name to describe one system versus the other. And so we did: we understand a distinction between conventional current flow and electron flow.
- imchillyb 2y agoIf one takes into account the field dynamics, the electrons are indicators of electromotive force and not the originator. The electromagnetic field connects the circuit and then _drags_ the electrons with it in a flow. Technically the opposite flow theory would be the opposite reaction to the field drag. Every action has an equal and opposite reaction. The equal reaction would be the electrons being dragged with the field. The opposite would be the current flow we observe. I can't wait until we can more clearly and accurately view the different fields that make up everything we know. It's fields all the way down.
- IAmNotACellist 2y ago>It's fields all the way down. But what even IS a field, other than a thing through which scalar, tensor, or vector values can be expressed over some dimensionality? Also gravity. It seems at some point we have to just accept there's this currently irreducible thing permeating all of the thing we call everywhere.
- tdeck 2y agoEveryone is giving correct answers so I'll just add something: in some parts of the world the convention has been to consider current flowing from negative to positive. For example in Scotland it's often taught that way apparently: https://www.mrsphysics.co.uk/blog/why-electron-flow-scotland-does-things-differently/ https://www.mrsphysics.co.uk/blog/why-electron-flow-scotland... I read somewhere that this was also common in the USSR but can't find any references. Perhaps someone here will remember.
- pwg 2y agoFrom reverse engineering a few low cost Chinese imports (i.e., the 'odd brand names one finds on Amazon') I discovered that some Chinese engineers also design electronics using the convention of current flow from negative to positive.
- speakeron 2y agoHow can you tell from analysis of the physical circuit what assumptions the designer made about the flow of current? Surely the components (electrolytic capacitors, diodes, transistors, etc) are the same and can only work in one direction. Is it that the ground plane is connected to the positive terminal of the power supply?
- sobellian 2y agoCharge carriers aren't always electrons anyway, so you're restricting yourself by thinking of current as electrons moving. Even in the usual case where electrons are the charge carrier, it is only the small net movement of zillions of electrons back and forth which produces a current. So in any case current is a macrostate and electron movement is a microstate, and sign convention won't change that.
- tedk-42 2y agoExactly this! Even the use of 'flow' is misleading. It's barely trickling through the wire...
- spaceywilly 2y agoExactly, I see many questions that start with “If the electrons are flowing from the negative terminal…” The movement of electrons is inconsequential. It’s the magnetic fields between electrons that provide the power in an electric circuit. These fields actually don’t even travel through the wires! They move around the space outside the wires. Ask anyone who has routed a differential signal pair :)
- Spivak 2y agoShould I think about it as ripples traveling through the magnetic field like a wave?
- lugoues 2y agoSort of, electricity and magnetism are two sides of the same coin, electromagnetism, so it's waves in the electromagnetic field with the wire acting as a wave guide. (as far as I understand) Veritasium has a video that goes over this. It was pretty controversial at release but it gives a good overview. https://youtu.be/oI_X2cMHNe0 https://youtu.be/oI_X2cMHNe0 And why magnets work due to relativity https://youtu.be/1TKSfAkWWN0 https://youtu.be/1TKSfAkWWN0
- spaceywilly 2y ago
- arnarbi 2y agoOthers have answered correctly (it was an arbitrary choice), but fwiw I always found it helpful to think of current as the direction of the “holes” where electrons can be. Like bubbles rising in water, the holes “travel” opposite the potential that’s pulling the surrounding electrons the other way.
- boring-alterego 2y agoFun fact when in 2 year school for electronics engineering technology we learned the current flow with the electrons, and in my 4 year electrical engineering school I learned it by following electron holes. You'll find basic electrical circuits books sometimes have an electron flow edition.
- electrodank 2y agoAny recommendations for the circuit books?
- daxfohl 2y agoSame reason male seahorses get pregnant.
- jonny_eh 2y agoThis must make some people in Congress really angry.
- lioeters 2y agoWait until they hear about some mushrooms with more than twenty thousand genders.
- gerdesj 2y agoNo the males don't get pregnant or give birth. They brood, ie they look after the little ones. See the Reproduction section of: https://en.wikipedia.org/wiki/Seahorse https://en.wikipedia.org/wiki/Seahorse for details
- hiccuphippo 2y agoRelevant xkcd https://xkcd.com/567/ https://xkcd.com/567/
- xaellison 2y agocame to comment this :)
- deleted 2y ago[deleted]
- loandbehold 2y agoDo electrons actually flow when current moves? Apparently not https://youtu.be/bHIhgxav9LY https://youtu.be/bHIhgxav9LY
- beryilma 2y agoI dont understand all the details, but Veritasium and others on YouTube have videos on how the current/electron flow is also an illusion. Since electricity and magnetism are really fields per Maxwell equations, the current flow and other electrical things that we attribute to the inside of the wire are really happening outside of the wires as electric fields. They have a much better explanation than mine certainly...
- gus_massa 2y agoThose videos are misleading. Electrons flow inside the wires. They just flow much slower than what you would expect. When you close a circuit, the information that it was closed goes very fast but the electrons flow slowly. (It happens also with water, if you have the shower with only very hot water and you open the cold one, the output of the shower changes almost instantly but you need like a second to get the mixed water with that is warm.) What flows outside the wires is the energy. It's very unintuitive but it's true. Feynman has a nice lecture about it. But note that most of the energy flows very close arround the wires, a very small part wanders far away. There is an exception when you have a radio transmissor with an antena and a reciver. Then the energy flows just through the air (or vacuum). Also when you have a light lamp or a laser. Actualy every electric circuit emit some radiation as a bad radio tranmisor. But most of the times you can ignore it.
- int_19h 2y agoThe more straightforward analogy with water is a pipe that is completely filled. Even if the water moves very slowly, the fact that it has started moving is immediately detectable as some of it will start spilling from the other end of the pipe right away. If you have a turbine installed at the other end, it will also start spinning right away. Moreover, if you make the pipe wide enough, even very slowly moving water will move a lot of volume in a short period of time, and thus transmit a significant amount of energy to the turbine.
- sobellian 2y agoCurrent really isn't flowing through the air. The relevant equation for resistive materials is J = sigma E; J is current density, E is the electric field, and sigma is resistivity. Air's resistivity is huge - if you pump any significant current through air you will cause arcing. What really happens when you transmit energy through air is charge accumulation. Think of a parallel-plate capacitor - electrons accumulate on one side of the plate and holes on the other side. If you draw a black box around the system, it looks like current is flowing through it. But no significant current is actually going through the dielectric, or you will ruin the capacitor. Electrical engineers model the phenomenon that Veritasium pointed out as capacitive coupling. In a circuit diagram, we would literally just draw an additional capacitor in between the relevant circuit elements. In DC, this doesn't really matter after a certain settling time because the capacitor has settled to a certain charge. But in AC (or DC right after you flip the switch) it is non-negligible. Edited to add - to be clear, there IS an electric field in the air - but the current density is negligible unless you've caused dielectric breakdown.
- AnotherGoodName 2y agoIt wouldn’t surprise me if at some point in the future we realise mass shields us from a gravitational field that pushes everything in all directions at once as opposed to our current thinking that mass emits a field that pulls us towards it. Eg. imagine the earth below you shielding you from a force that otherwise pushes all mass in all directions constantly. You’re now more shielded from the push in the direction of the earth so you feel pulled that way. It’s the same thing. Just a sign change from a convention we had no real basis to believe one way or the other.
- bequanna 2y agoAs a layperson, that makes sense to me. It also explains the time dilation effect when near a large mass.
- AnotherGoodName 2y agoThinking of it as directional action potentials that are blocked by mass? I agree it does feel intuitively nicer that way honestly.
- bequanna 2y agoYep. Coming from everywhere and moving outward in all directions at all times and ‘absorbed’ or ‘blocked’ by mass
- marmadukester39 2y agoPhysicists: Has anyone ever looked into this?
- abecedarius 2y agoYes. https://en.wikipedia.org/wiki/Mechanical_explanations_of_gravitation https://en.wikipedia.org/wiki/Mechanical_explanations_of_gra... (but I only play a physicist on HN)
- bilsbie 2y agoI’ve always wondered if there are any applications where it matters which way the electrons are going. Anyone know?
- tonyarkles 2y agoCathode Ray Tubes probably wouldn't work very well if they sucked electrons away from the screen instead of launching them towards it. At a deeper level it does start to matter when you get down to the physical level of transistors because electrons and holes (places in a crystal lattice where an electron could go but isn't there) move differently. P-type transistors generally can't be made as conductive as N-type transistors because, with plenty of handwaving, negative charge due excess electrons move easier than positive charge due to a lack of electrons.
- gus_massa 2y agohttps://en.wikipedia.org/wiki/Hall_effect https://en.wikipedia.org/wiki/Hall_effect If you put a magnetic field that is perpendicular to the current, you get a charge in one dide of the wires that depends on the moving charges. This is used to measure magnetic fields. https://en.wikipedia.org/wiki/Vacuum_tube https://en.wikipedia.org/wiki/Vacuum_tube usualy you heat only one electrode, but you must heat the correct one so electrons can jump to the other electrode. https://en.wikipedia.org/wiki/Cathode-ray_tube https://en.wikipedia.org/wiki/Cathode-ray_tube I'm not sure if it'a a different example or just a variation. Anyway, you can have a lot of fun changing the pressure of the gas, and the electric field https://www.daviddarling.info/encyclopedia/D/discharge_tube.html https://www.daviddarling.info/encyclopedia/D/discharge_tube.... https://en.wikipedia.org/wiki/Transistor https://en.wikipedia.org/wiki/Transistor IIRC they are also not symetric, but my knowdledge is too small even to write a good remark.
- marcosdumay 2y ago> https://en.wikipedia.org/wiki/Transistor https://en.wikipedia.org/wiki/Transistor IIRC they are also not symetric They kinda are. Solid state conductors have those virtual particles called holes, that represent the global state of "having fewer electrons around here". You can have transistors where the electrons are carrying charge or where holes are. But the properties of holes and electrons are not completely symmetric. Holes disperse each other more strongly.
- Yaa101 2y agoIt does not, it just seems that way. The electron just jumps to an empty slot in the next atom (metals have empty electron slots in their atoms, that is why they conduct energy) and leaves a bit of energy in the current one. So if the electron jumps to the next atom on the right, the current seems to go left.
- noobermin 2y agoI was taught this in elementary school, I suppose not everyone knows.
- vagab0nd 2y agoThe sign of the electron doesn't matter in this case. The definition of the direction of the current itself is also arbitrary. So are the definitions of positive and negative terminals. In fact, it is my understanding that most of the "left/right", "positive/negative", "north/south" definitions in EM are by convention. So the first guy calls it whatever they want and it doesn't matter at all.
- soloist11 2y agoThe theory of charges has Z/2 symmetry.
- lupire 2y agoThis is really a type error. In some systems, there really is a positive. Such as temperature e with absolute 0, and where numbers multiply together into the same dimension so multiplication is not symmetric under sign change. (Although this is usually also a type error!) In other systems, there are a pair of opposite directions, and it's not correct to consider one positive one negative, but merely opposite. Both poles should be signed, and values never multiplied into the same dimension, and names distinctly, even if we must choose a convention when modeling them with computers.
- michaelrpeskin 2y agoThis doesn't really answer the sign problem (which is just an arbitrarily chosen convention), but I view it more as "the field makes the electrons move". The rule of thumb I always use is that at household voltages and currents in copper the electrons move a few tens of microns per second. If your lights are on all day the electrons might move a meter or so from where they were when you turned the switch on.
- MarcScott 2y agoI fondly remember watching kids in physics exams trying to answer questions using Felming's left hand rule. (https://en.wikipedia.org/wiki/Fleming's_left-hand_rule_for_motors) https://en.wikipedia.org/wiki/Fleming's_left-hand_rule_for_m... You could watch them hold up both hands, wondering which one to use, then trying to dislocate their wrists as they aligned fingers and thumb with the diagram on the exam paper.
- dboreham 2y agoAlways use Maxwell's corkscrew rule.
- thriftwy 2y agoIf you lick the positive pole of AA battery while touching the other end you get a sour taste. But there's no taste change when you do the opposite.
- mikewarot 2y agoIt could be because in electroplating, metal flows from the positive terminal to the negative, because the metal ions are positive. However... electroplating wasn't invented until after his death.... oops. 8(
- kazinator 2y agoWe don't even know why Ken Thompson chose ! for negation, and he is alive.
- Charon77 2y agoWait, but protons would be negatively charged and particle physicists are going to be angry about it?
- DidYaWipe 2y agoThis is great. I'm glad I'm not the only one this annoyed about the mixed messages in electronics. It really does mess you up as you try to learn and reason about how circuits work, when the first thing you learn in school is that electrons flow from negative to positive.
- yarg 2y agoThat explanation seems wrong - or rather it seems to address a completely unrelated question. The convention by which an electron is negative and a proton positive is arbitrary and could be flipped; Indeed it could be replaced by any pair of charge definitions x and !x. However that has zero impact on the direction of a current's flow through a conductor (that's a physical process and is not defined or impacted by the established conventions). I'm not sure what the real answer is, by my high school physics teacher told me that the charge is carried not by the electrons, but by the gap (a virtual particle) that flows backward as the electrons move forward. (Similar to the way that a gap in traffic propagates backwards.) I have no idea how wrong this is, so hopefully check the comment below from whoever bothered to correct me.