Why does current flow the opposite way from the electrons?(mathstodon.xyz) 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. |
Anyone know?
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.
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 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....
https://en.wikipedia.org/wiki/Transistor IIRC they are also not symetric, but my knowdledge is too small even to write a good remark.
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.
In a very naive explanation, you can exchange the emisor and the collector, but in a real cirtuit it is a bad idea. (I'm not sure why. I think it may stil work but it's slower or less efficient, but I'm not sure about the details.)
On discrete transistors, they have different sizes, shapes and levels of doping.
On the "old" planar VLSI transistors, nobody even uses the names. They are both built as small as possible and there's no space to fine-tune any of their characteristics. But on some of the new 3D VLSI transistors they are different again.
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.
"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.
Sounds like he leaves it open for future "Philosophers" to update the convention as our understanding of the phenomena that he had documented improved. Smart guy in not assuming that he got it right the first time. Franklin sounds like he wasn't a "my way or the highway" type of guy.
https://en.wikipedia.org/wiki/File:Triboelectric-series_EN.s...
The tube is glass, but is the buckskin fur, or slightly furry, or leathery? That would seem to alter the charge it gets.
> We assume, as stated earlier, that electrical fire is a common element, equally shared among the three mentioned individuals before any operation with the tube begins. Person A, who stands on wax and rubs the tube, transfers the electrical fire from his body into the glass tube. Since his connection to the common stock is cut off by the wax, his body is not immediately replenished. Person B, also standing on wax, passes his knuckle near the tube and receives the electrical fire collected by the glass from A. B’s connection to the common stock is also cut off, so he retains the additional amount received. To person C, who is standing on the floor, both A and B appear electrified. C, having the normal amount of electrical fire, gets a spark when approaching B, who has an excess, and gives a spark to A, who has a deficit. If A and B touch, the spark between them is stronger because the difference in their electrical fire is greater. After they touch, there is no spark between either of them and C, as the electrical fire in all three is equalized. If they touch while being electrified, the equality is maintained, and the fire circulates continuously.
> This has led to new terms. We say B and similar bodies are positively electrified, and A is negatively electrified; or rather, B is electrified plus, and A minus. In our experiments, we electrify bodies as plus or minus as needed. These terms are used until philosophers provide better ones. To electrify plus or minus, it’s essential to know that the parts of the tube or sphere being rubbed attract the electrical fire from the rubbing object during friction. Once friction stops, these parts are ready to give the received fire to any body with less. Thus, the fire can be circulated, as Mr. Watson demonstrated, or accumulated or subtracted from any body, depending on the connection with the rubber or receiver, while cutting off communication with the common stock.
How did we wind up with electrified? Where did the f come from?
EDIT: I guess this [1].
Yes he had a rationale, the question is why it didn’t change once we knew better; he even called for it.
I mean, I think I know why it didn’t change at any given point - the standard was already in place and it always looks too difficult. But in retrospect, the effort in the 1800s would have been small compared to the effort 100 years later.
Maybe it’s still true that we should change the convention starting now, because the confusion and cost of not changing it in the future will continue to grow?
The value of the product of two electric charges is invariant to the convention chosen for the sign of the electric charge.
Numbers and numeric quantities are actually a real thing that exists in the world. They do not exist only in our minds (and in the minds of many other animals who are also able to count until some small number). And so does the concept of negation, which clearly is a property of the world, independent of humans or animals.
For other physical quantities, the sign of a quantity is not arbitrary, like for the electric charge, because those are used in expressions that are not invariant to sign changes.
For example, in naming the parts of a NPN bipolar junction transistor, the negatively connected terminal is the "emitter", and the positive one the "collector". The base-emitter diode arrow points toward the emitter.
IIRC a Veritasium video claims that these where essentially discovered by mistake in lightbulbs, so I suspect that Franklin would have had a hard time finding them...
But there is--otherwise we wouldn't know that Franklin got it backwards. He thought the charge carriers were going one way, and chose the convention he did because he thought it matched the way the charge carriers were going, but it turns out they were going the other way. The signs of the charges are a convention--and the fact that we still use Franklin's convention and it works just fine attests to that--but the direction the charge carriers move is not.
As you say, the very fact that we know the real direction counters that. They mean that within the abstract context of electronics presented in introductory physics, the real direction of charge doesn't matter and cannot be determined. As long as you pick one consistent convention and stick to it, the math will always work out the same, since depending on convention, all the directions and signs are equally flipped. The real direction of charge only matters when you get deep into the details (eg semiconductors).
At the level of detail of introductory physics, it's effectively a symmetry, similar to how given the simultaneous flipping of charge, parity and time, you cannot tell the difference.
Nobody seems to have mentioned Holes. Holes are positive charge-carriers. Yeah - they're virtual, they're not like positrons or protons. But they behave just like electrons going "the other way".
My understanding is that a hole represents the absence of an electron. If an electron is removed (e.g. by rubbing), there's remains a physical object bearing a positive charge: the proton that was originally associated with that electron.
I haven't heard anyone talking about holes for years. Are they now deemed an outmoded concept?
[Edit: should have read further down the comments :-)]
And when we found a charge system that had 3 charges rather than just two, we did.
For those whom it isn't clear what I mean. Compass magnet's north poles point north, which is only possible if the earth's north pole is magnetically a south pole.
How did your mind gain access to this universal truth? ;)
Is math invented or discovered?
* https://www.sfu.ca/~rpyke/cafe/livio.pdf
See also "The Unreasonable Effectiveness of Mathematics in the Natural Sciences" by Wigner:
* https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness...
Fundamentally, it’s the same type of problem - and really more of a philosophical thing.
So while I agree with the GP's comment that Franklin didn't know anything about electrons, so he arbitrarily picked one as negative and the other as positive, now that we do know about the movement of electrons, it kinda sucks because I think Franklin just "picked wrong".
I.e. it would make much more sense to me if the absence of electrons (i.e. holes) were negative by convention and an abundance of electrons were denoted as positive.
I think the origin might be phallic. Rod obviously gains positive charge when rubbed, for a man from 300 years ago.
Was there some method reasonably within their reach that would have worked?
I'd guess the first thing they would try is weight. The body gaining the charge carriers should gain weight and the body supplying charge carriers should lose weight. That would probably fail because the mass of electrons is very low, and I don't think they had anything that could resolve weights that small. (I'm not even sure we have anything now that can do it).
The second approach might again use weight, but with the realizing we don't have to measure what the weight is, just whether it has increased or decreased. So take two weights that are as identical as you can make them and put them on a balance. Seal the balance in an airtight container to prevent random air currents from disturbing it (or pump out the air--the vacuum pump was invented around 100 years earlier), and put it someplace very cold and with very little temperature variation, and adjust the masses until the balance shows no apparent movement for months. Then charge one of the masses and see if the balance can still remain apparently still for months. If it can't, and consistently goes out of balances toward the charged side conclude that side probably has the charge carriers. If it consistently goes toward the other side conclude that the charged side gave up charge carriers.
I think that this too would probably fail. The mass difference is too small and isolating the balance sufficiently from outside disturbances is probably too difficult.
Could they produce a stream of charges in a vacuum? Let's say they can. Considering the material they had to work with if those were negative they would probably be electrons and if they were positive they would probably be atoms or molecules with a missing electron.
They would probably quickly discover that streams of charge in a vacuum are deflected when they bring a magnet near them and figure out that lighter charged things deflect more. They would then discover that all the negative charge streams they produce have carriers of the same mass, but the positive charge stream carries have different masses depending on how they are produced and they all have mass much greater than that of the negative carriers.
I think they might lead them to conclude that the negative charge carriers are the fundamental ones.
Part of the problem we have in trying to put ourselves in their minds is that some or most of their reasoning is unrecognizable to us as "science." If you try reading EG Newton's Principia Mathematica it's laid out in prose from first principles using geometry and is essentially unrecognizable except with a strong education in Euclid.
This lets you build diodes as a result, so assignment of electrical direction based on that phenomenon would get it correct.
EDIT: in fact with a cathode ray tube you can literally visualise charge direction from looking at a foil wheel being spun in a vacuum: https://m.youtube.com/watch?v=K2G6M3cYJZs
The author is wrong and you also. If people don't know about things then I'd rather have them stay quiet and learn about them rather than spreading misinformation.
DC Current flow: https://energyeducation.ca/encyclopedia/Direct_current#:~:te....
AC Current flows both ways: https://energyeducation.ca/encyclopedia/Alternating_current
Even the use of 'flow' is misleading. It's barely trickling through the wire...
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 :)
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.
Although I suppose we essentially did that when naming the quarks.
Using "positive" and "negative" would have been a disaster. What charge does a positive antiquark have?
Where does levor... come from for left? Perhaps a newer Latin "left" than I was taught?
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.
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.
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.
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.
If a particular 50% chance event does not happen, then the complementary 50% chance event does happen.
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...
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.
See the Reproduction section of: https://en.wikipedia.org/wiki/Seahorse for details
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.
Like bubbles rising in water, the holes “travel” opposite the potential that’s pulling the surrounding electrons the other way.
I read somewhere that this was also common in the USSR but can't find any references. Perhaps someone here will remember.
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.
You'll find basic electrical circuits books sometimes have an electron flow edition.
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.
I find this structure to model charge better. If not for else, at least it prevents you to ask silly questions about charge.
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.
> makes electrons negative
It is not true, and trolling.
On top of that if we did not ground one side of the electrical network, you could touch either wire and feel nothing. That's called an isolated ground, and is not commonly used except in hospitals and some other specialty settings.
(If you wonder, we ground one side because if two different people both happened to touch a wire, current would flow between them using the each.)
What I could never keep straight is anode and cathode.
It makes perfect sense! Cations, you see, are attracted to anions. And reduced by cathodes. Anions? Attracted to cations. And oxidized by anodes.
Whereas cations are oxidized by anions, and anions are reduced by cations.
The only alternative here would be if cathodes and cations were positively charged, and anodes and anions were negatively charged. But then cathodes would reduce anions, and cations would also reduce anions. Even worse, anodes would oxidize cations, and anions would also oxidize cations.
And we can't have that. It would just be too confusing.
I believe https://chemistry.stackexchange.com/questions/16785/positive... is correct.
We call gravity "yer çekimi", which literally means "the pull of ground". The meme is "Ya yer çekimi yoksa da gök itimi varsa?" which translates to "What if the gravity doesn't exist but sky-push does?".
It would definitely surprise me since I know that this theory — since it's such an obvious hypothesis — has been proposed multiple times since Newton's own (it's now colloquially called "Le Sage's theory of gravitation" [0], but it had many other proponents including Kelvin, H. Lorentz and Thomson) and it has always failed to accomodate the equivalence of graviational and inertional masses: after all, the gravity is not proportional to the cross-section of the bodies, and graviational shielding does not exist — experiments done by Eötvös were quite decisive in that regard.
[0] https://en.wikipedia.org/wiki/Le_Sage%27s_theory_of_gravitat...
(for those of you who don't know, the super simplified explanation in physics 101 is that the normal force is the vector that pushes up while gravity pushes down for objects that are resting on top of each other)
So I guess the one who named it "the normal force" would be more correct that he ever imagined if your theory of gravity was the real correct one!
It turns out it doesn't quite work, but it is interesting enough try that does get enough things right that quite a few well known physicists over the years have taken a look at it. The Wikipedia article on it covers a lot of them [1].
Feynman talks about it briefly in section 7-7 of volume I of the Feynman lectures [2]:
> Many mechanisms for gravitation have been suggested. It is interesting to consider one of these, which many people have thought of from time to time. At first, one is quite excited and happy when he “discovers” it, but he soon finds that it is not correct. It was first discovered about 1750. Suppose there were many particles moving in space at a very high speed in all directions and being only slightly absorbed in going through matter. When they are absorbed, they give an impulse to the earth. However, since there are as many going one way as another, the impulses all balance. But when the sun is nearby, the particles coming toward the earth through the sun are partially absorbed, so fewer of them are coming from the sun than are coming from the other side. Therefore, the earth feels a net impulse toward the sun and it does not take one long to see that it is inversely as the square of the distance—because of the variation of the solid angle that the sun subtends as we vary the distance. What is wrong with that machinery? It involves some new consequences which are not true. This particular idea has the following trouble: the earth, in moving around the sun, would impinge on more particles which are coming from its forward side than from its hind side (when you run in the rain, the rain in your face is stronger than that on the back of your head!). Therefore there would be more impulse given the earth from the front, and the earth would feel a resistance to motion and would be slowing up in its orbit. One can calculate how long it would take for the earth to stop as a result of this resistance, and it would not take long enough for the earth to still be in its orbit, so this mechanism does not work. No machinery has ever been invented that “explains” gravity without also predicting some other phenomenon that does not exist.
[1] https://en.wikipedia.org/wiki/Le_Sage%27s_theory_of_gravitat...
Both the constant G for gravitation and g for the acceleration for gravity on earth.
I am not a physicist so I may be getting something wrong
(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.
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.
It's also usually brought up early on when teaching new students about circuit physics, but it's really not something that comes up in an EE's day to day.
Maybe it's more relevant if you're deep into analog or RF black magic, I wouldn't know.
I just let my eyes skip over that list. I refuse to be the Jaguar in "Just-So Stories" https://etc.usf.edu/lit2go/79/just-so-stories/1294/the-begin...
You can see the voltage “ripple” through both branches of the circuit, reflect of the ends of the branches, and eventually settle into steady state. There are limits to this way of thinking (for example, water can’t travel in the space between “tubes”, but electricity can), but it is a very good way to approximate it.
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
And why magnets work due to relativity https://youtu.be/1TKSfAkWWN0
Funnily enough, although "sinister" came to mean "the bad side", it may have come from Proto-Indo-European for the "favourable side".
I wonder whether the old Latin (right == good/left == dodgy) thing has been perpetrated here or it it is coincidental.
I also wonder whether old Latin speakers really had a snag with sinister ie left handers or is that a modern affectation.
The terms anode and cathode should be burned. We don't use them much in modern electronics. E.g. we don't say that the positive power pins of a CPU are anodes, or that ground pins are cathodes.
"CCD" -> "cathode: current departs"
In chemistry though, cations are positive ions and anions are negative ions.
The world is composed of things. The things are grouped in sets. Numbers are equivalence classes of sets.
The set of the medium-sized planets of the Solar System is equivalent in number with the set of the big planets of the Solar System and also equivalent in number with the set of the big satellites of Jupiter (i.e. 4).
Such equivalences between sets of things exist regardless if there are any sentient beings that recognize those equivalences and there are circumstances when for instance the evolution in time of some sets of things is determined or influenced by the relationship between the numbers of things that compose each set.
By who?
If one take the position tha minds are not part of the "real world" then you end up defining "reality" by some random model.
It is just as absurd as saying that the only thing that exists is my own perception and you are "just" a ghost my mind is "thinking into existence".
It sounds less crazy only because we are used to reductionism being generally more useful, but what is the usefullness of concepts like reality and existence when defined to mean that we and our minds (the only thing we perceive) are not "real" or do not really "exist"?
The world is not made of a homogeneous substance, but there are various kinds of groupings at various levels, nucleons and electrons group in atoms, atoms group in molecules, molecules group in pebbles, stars group in galaxies and so on.
E.g. there are 10 rock formations in this part of the desert, and 2 rocks in the other side.
There is a clustering (set) of 10 vs 2 even if we aren't there to measure them and group them.
As are other sets co-existing (like the whole desert has 12 rock formations, while some other has only sand).
Carefully qualifying every single statement causes people to stop listening, because they don't care. It's better to correct oneself after-the-fact. Make it a topic of discussion once people are hooked. Introducing a simple error for someone to unravel does that.
You still haven't explained why it isn't true, or why it's trolling. Just saying those things doesn't make them true.
I can tell that English is not your native language from the number of grammatical errors you're making, so perhaps you're confused about something linguistic here?
1. the air is negative
2. the air's temperature is negative
3. the air's temperature is -1°C
1. the electron is negative
2. the electron's charge is negative
3. the electron's charge is -1 p
I hope this answer is satisfactory, I hope to end this conversation, I don't like it.
Again, it's clear English isn't your native language, and I suspect you're simply making a mistake about how English is used. Which is not uncommon -- I've made plenty of mistakes thinking that how something worked conceptually in English would apply to another language too, and then being corrected by a native speaker.
In English, it's perfectly conventional to say "the electron is negative" when you're talking about charge. It is linguistically and conceptually correct. There is nothing "fishy" and certainly nobody is "trolling", which is an unfair and uncharitable accusation for you to make.
Perhaps it isn't correct to say in your native language, I don't know. I'm sorry you didn't like this conversation, but hopefully you can use it as a learning opportunity.
It isn't like "the air is negative", which has many context dependent meanings.
That is that kind of thing I mean: proofs and calculations, not "why wouldn't it?"
I do think your last sentence here was unnecessary though:
”That is that kind of thing I mean: proofs and calculations, not "why wouldn't it?"”
When I said “why wouldn’t it” I was asking out of genuine curiosity. There really wasn’t any need to criticize that part. It came off as maybe more hostile than I think you intended.
Again I most certainly appreciate you taking the time to type up the rest of your comment though because I did learn quite a bit from those examples you posted so I am indeed sincerely grateful for that.
But at the scale of a national grid it's basically impossible to ensure that the entire grid is isolated from the ground all the time. Stuff breaks. And if the network is grounded in some far away place but not anywhere near you you get exactly the effect you describe: you have some unknown and potentially large voltage differential towards ground because the literal ground doesn't have the same potential everywhere. So instead you give up and tie one of the potentials to ground, and do that as often as viable.
It's only a "cathode ray" because it's reversed inside the tube: the terminal where positive current comes out of the device is where the negative current emanates internally to go to the other terminal.
An electron beam shooting out of a device is an anode ray.
I would suspect that the same goes for electrons.
An electron gun would (as used in old CRT monitors), would be a very striking example of this - I doubt we could make an electron-hole gun (though shooting positive ions could work, but that's not quite the same thing) - but it may be possible to observe in more normal conditions too?
An electron gun produces a beam that contains only electrons; there is no conductor, and I think holes can exist only in the presence of a conductor. So you can't shoot a beam of holes through a vacuum. But if the material between the gun and the screen were a semiconductor, maybe you could draw pictures on the screen using a beam of holes? I mean, I don't see why a beam of holes can't be focused just like a beam of electrons.
Wouldn't electrons rush in to fill the holes from every direction, rather than just the intended one? That's what my intuition says anyway. So yeah, my guess would be that it is in fact not possible.
My immature brain didn’t get past this sentence.
(but I only play a physicist on HN)
It's not a convention that like charges repel.
If we agree that current is the flow of positive charge, then it has to go away from positive, toward negative.
Using positive quantities for current and charge is a good thing; we aren't constantly dealing with negative numbers to measure common situations like how much current is flowing through a wire.
This is what it feels like to stand on the shoulders of giants.
Current is bubbles.
A rationalization after the fact is different from a reason.
It’s really a moot point as to whether the abstraction used to solve problems matches with the physicalist interpretation of reality.
The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered.
So there are two different "Blues;" signifier and signified.
The number of quarks in a proton or neutron is always 3.
There are a fair number of dimensionless physical constants: https://en.wikipedia.org/wiki/Dimensionless_physical_constan...
You can choose different number systems to represent the values symbolically, but the numbers will always be the same. At least in this universe.
Wildly, parts of physics are only possible to describe adequately using imaginary numbers, which suggests that we could have chosen a better name for them: https://www.sciencenews.org/article/quantum-physics-imaginar...
The fact that particles have identity is also vague, afaiu, so existence of numbers or their non-biological origin is not as easy to prove by example as it seems.
I understand what you're saying. Occurrences like https://en.wikipedia.org/wiki/Ring_species demonstrate that the idea of "species" isn't firm and that what truly matters is each individual and their unique circumstances. But this seems to me to be more a limitation of language and philosophy than a repudiation of math.
As you pointed out, it's all equivalent to drawing tally lines, counting pebbles, sliding counters on an abacus, or counting fingers and toes. Despite the fractal nature of coastlines and the constant exchange of matter and energy between adjacent parts of the universe, it is possible to agree upon useful delineations. And there is not any alternative maths which happens to describe practical observations in a way which does not reduce to the maths with which we are familiar.
The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered.
So there are two different "blues;" sigmifier, and signified.
The wavelengths may have always existed but colors only become a thing when we draw the arbitrary lines between them.
I’ve literally had an argument with someone where they insisted burnt umber was not orange or orange like.
Which, uh - maybe? But c’mon. It’s totally somewhat Orange!
I understand how it make sense saying that the concept of spedrunning is completely absent in Ocarina Of Time and only exists in the player playing the game, but I do not see how this would be a good philosophy to apply to ourselves.
I confess that I have a particular aversion to this specific philosophy/POV because I feel like it is riding on the respectability and "coolness" of science to sound more serious while being just another metaphysics without (IMHO) any* particularly good qualities.
* Ok, I admit that it has at least a good quality: it is a good example of a non-religious metaphysics to give to people that cannot imagine a non-religious metaphysics.
We have tons of sayings for this like "the map is not the territory," "wherever you go that's where you are."
And that's the case with positive/negative.
For instance, what happens when you connect the two electrodes of a battery to the pins of a semiconductor diode will differ depending on whether you negate the battery or not (i.e. you revert or not its connections). What happens with a ball (or with a thrown stone) will differ depending on whether its velocity is positive or negative, and so on.
Additions and subtractions of physical quantities, therefore also negation, happen in the physical world regardless of the presence of sentient beings.
Humans can recognize such properties of the world and give them names and integrate them in coherent mathematical models, but the base concepts are not inventions, they are the result of empirical observations.
> What happens with a ball (or with a thrown stone) will differ depending on whether its velocity is positive or negative, and so on.
The velocity of a ball is a vector. Using a positive or negative number to describe it is a manner of convention. When you say that you threw a ball with “positive 7 mph” velocity, you need to explain what you mean.
One might argue that there really is a ball and that it has a velocity and that the velocity really is an element in a vector field originating [0] at the center of mass of the ball. Debating to what extent this is fundamentally true or is just a useful concept that people came up with would be interesting.
[0] In general relativity, space is not Euclidean (nor is it a flat Minkowski space), and velocity vectors are only really meaningful in association with a point in spacetime. You can read all about tangent bundles in Wikipedia :)
However if you set things up so that one terminal of a 9v battery is grounded, and you lick the other terminal (just one), you would feel something.
(You would also have to be grounded, at 9v that would probably require barefoot on slightly wet ground. At 120v it's a lot easier to be grounded, but the principle is the same - you only feel the electricity because the ground itself provides a return path.)
But that is a philosophical oroboros.
Laypeople use more scientific-sounding words, sure, but what more scientific way is there to understand something than to have discovered it yourself through experiment?
Franklin did not understand electricity, but merely observed it.
It wasn't until we discovered the electron proper and Maxwell did his work that we-- anyone-- understood electricity.
Understanding comes from scientific and academic rigor after the discovery.
I’d even say that we don’t yet fully understand the electron!
It's fun to think about a time when this stuff that we now take for granted as basic physics was not just new and poorly understood, but the forefront of knowledge was advancing so rapidly.
I haven't been able to find an online copy of the 1931 edition, but the 1937 edition is called Structure of Atomic Nuclei and Nuclear Transformations, and it's available through the Internet Archive: https://archive.org/details/in.ernet.dli.2015.501245
It's just that our most recent theories have been so rich that we have happened to discover many things theoretically before we find them in real life. (Theory has preceded practice in recent decades, rather than the other way around which is historically more common.) I'm not sure this will always be so, it might be a temporary leap.
I was unable to find out who coined "Voltaic pile" after a few minutes of Googling.
"Pila" is a heap of countable physical units, either stacked or disordered. But pila is commonly a fixture for liquids, like septic tank is pila séptica
And batteries were mostly lead-acid. Hence, a pile for/of acid.
In what sense do inductors accumulate?
Batteries and capacitors accumulate (i.e. integrate) current.
Inductors differentiate current: v = L di/dt means you get voltage out of current changes.
And while a capacitor's voltage is the integral of current, a battery's voltage isn't.
Warning I barely know what I'm talking about.
If you apply a constant voltage to an inductor, the current through the inductor will increase linearly as the inductor stores energy in the magnetic field.
Perhaps part of why the intuition can break down is that in real life, inductors tend to be much "leakier" energy storage devices than capacitors. If you store some energy in an inductor and then change the voltage across it to zero (practically: short its terminals together), in theory a perfect inductor will maintain a constant current forever and the energy stored does not change. In practice inductors (with an exception for things like superconducting magnets) are made from wire that has a resistance, and so the current in a real shorted inductor will eventually decay to zero. This means that in practical terms inductors are mostly only useful for short term energy storage. On the other hand, real-life insulating materials (like air, vacuum, or Teflon) can can be pretty close to perfect insulators allowing real capacitors to store energy more or less indefinitely... certainly on timescales of years.