Why does current flow the opposite way from the electrons?
mathstodon.xyzAfter 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.
Because 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.
It 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.
It’s really strange reading the words of such an intelligent person beginning to understand something back then that is so fundamental today that even laypeople understand it more scientifically. Really weird, but really cool to get a peek back into a scientific mind in the 1700s.
> even laypeople understand it more scientifically
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?
Experimentation brings knowledge, not understanding.
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.
> It wasn't until we discovered the electron proper
I’d even say that we don’t yet fully understand the electron!
Or just separately from, like Higgs understanding and theorising a boson years before it was actually 'discovered'/detected experimentally.
Along similar lines, I recently learned about an early nuclear physics textbook written by George Gamow. The first edition came out in 1931, and the preface of the second edition in 1937 describes how the book had to be completely written because the state of knowledge had changed so radically in those few years -- most notably, by the discovery of the neutron and of induced radioactivity.
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
D'oh -- I meant to say "the book had to be completely rewritten" but it's too late to edit my comment.
I often prefer the original language of discovery. My favorite is the term accumulator compared to battery.
In German we use “Akku” which is short for “Akkumulator” for rechargeable batteries.
Or ‘pile’ in French, which is homonym for ‘stack’ because a battery is a stack of alternating materials.
I was curious and tried to find out what word Volta used when publishing his discovery, and it looks like he just used "batterie" in his letter (written in French) to the Royal Society: https://royalsocietypublishing.org/doi/10.1098/rstl.1800.001...
I was unable to find out who coined "Voltaic pile" after a few minutes of Googling.
Is that official? In spanish, decades ago, the word for battery was "Pila"
"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.
interestingly "accu" in french is also used, but only for rechargeable batteries.
same in german "Akku" can re-charge
That is a much better term, battery: inconsequential detail on how it is constructed. accumulator: what it does.
Using the word “accumulator” wouldn’t be enough to differentiate batteries from capacitors, inductors, etc. which are also accumulators.
> inductors, etc. which are also accumulators.
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.
The main way that inductors function is by storing energy in a magnetic field, exactly analogous to the way capacitors store energy in an electric field.
The voltage an inductor creates will restore the current. It's storage.
And while a capacitor's voltage is the integral of current, a battery's voltage isn't.
I think this might be why accumulate is a good term. If one needed an accumulator that regulated voltage an inductor might work.
Warning I barely know what I'm talking about.
If you apply a constant current to a capacitor, the voltage across the capacitor will increase linearly as the capacitor stores energy in the electric field.
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.
Inductors accumulate a magnetic field.
In system design that distinction may not matter.
Seems like capacitors, inductors and batteries differ only quantitively in their response curves, not in qualitatively? As in they all do different things to the circuit on the voltage, amperage and time axis? We would need separate words for them, but accumulators seems like a decent umbrella.
I like battery. A battery is a group of (one or more) (electrolytic|electrochemical|galvanic) cells. Like pile it is a collective noun.
Indeed! I love reading Benjamin Franklin for exaclty that. If you haven't read it, Walter Isaacson's biography on Franklin is absolutely fascinating. Brilliant, hilarious, driven, and wildly accomplished. The dude was (IMHO) one of the most interesting humans to have ever lived. Highly recommend.
This was how the 18th Century worked. In the 19th Century mathematical language became rigorous and formal, better able to handle more complex constructions accurately, but harder for lay people to learn, as it became a new language.
Well... going by the Fermi biography and the first few chapters of The Idea Factory (about Bell Labs) I would think this is what it always sounds like in the early stages of humans discovering a new part of nature.
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.
TBH that's how I feel trying to intuitively understand and remember the various colors of quarks and their interactions.
>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.
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.
But his choice of "positive" or "negative" are entirely a convention of how he wanted to think about things. There's nothing special about the sign other than it made it easier for him to reason about what was happening.
I had ChatGPT-4o translate this to contemporary english
> 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.
Hmm. "We rub our Tubes with Buck Skin", he says in the same letter. I was trying to work out whether the tube gets a positive or negative charge. I think it depends on what material is being rubbed with what:
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.
> Hmm. "We rub our Tubes with Buck Skin", he says in the same letter.
My immature brain didn’t get past this sentence.
He was merely investigating what happen if persons touch one another after exciting the tube, on or off wax.
Lol
> electrised
How did we wind up with electrified? Where did the f come from?
EDIT: I guess this [1].
[1] https://www.etymonline.com/word/-fy#etymonline_v_38227
There's no rationale, merely a decision. He chose Earth as the source of electric fire, instead of a sink. It's a completely arbitrary choice, as light source vs dark sucker.
He could have thought instead that A is collecting Electric Fire from the glass rod. And when B touches the rod they recharge it losing some of their Electric Fire.
“These Terms we may use till your Philosophers give us better.”
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 reason why which charge is named positive and which is named negative does not matter is because in all the equations that relate electric charge with other measurable physical quantities we never have an electric charge alone, but we always have the product of two electric charges.
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.
It didn't matter in Franklin's time, but it came to matter later, due to the discovery or invention of devices in which it matters which charge carrier is moving.
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.
So? That things "normally" should move positive to negative or vice versa is also a convention.
It helps me visually when looking at a circuit diagram if I can think about the current flowing "down", like most rivers do in the Northern Hemisphere. It's just a vague association in my mind, but it is based in physical reality.
what do you mean by most rivers flowing down in the northern hemisphere?
That convention is the result of identifying current flow as being the movement of that which we identified as positive charge.
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.
Negation, being a concept, exists only in the mind. Same with "things". A thing is a noun; a part of speech. The "real world" is undifferentiated quanta.
I have an hard time coming to terms with this platonic view of the mind, as if our minds where some kind of extradimensional aliens playing with this sandbox of "undifferentiated quanta" sometime called reality.
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.
Philosophies are tools for reasoning. I don't literally go through my life thinking "oh here's an undifferentiated quanta, time to apply some nouns to it." But if I want to adopt a scientific mindset it's beneficial to think in terms of the physical experience versus my mental model of it because I can write my mental model down, whereas I can't write physical experiences or undifferentiated quanta down. That's what makes them quanta.
We have tons of sayings for this like "the map is not the territory," "wherever you go that's where you are."
Put simply, "the map is not the territory"
It would be a bad convention for a map to use valleys to represent mountains.
If that just a nominal change, such as just switching the color convention it uses for montains vs valleys, then it would be fine.
And that's the case with positive/negative.
Or, as Monty Python has rightly pointed out, "it's only a model."
While in the mathematics of the later part of the 19th century and of the 20th century there have been developed many theories with very abstract concepts for which it may be claimed that those concepts have been invented in the minds of some mathematicians without a direct correspondence with the world experienced by them, such a claim would be false about almost any concept in the mathematics developed until the 19th century, because almost all older mathematical concepts are just abstractions of properties of the physical world.
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.
Careful!
> 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 :)
Only according to some epistemologies.
Ceci n'est pas une pipe
There is a way in that it matters: in a vacuum tube you can have cathodic rays but (pragmatically) not anodic rays.
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 a cathode is that terminal of the device where positive current escapes!
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 always mix them up... :(
If we make an oscillating circuit by hooking up an inductor and capacitor and set it in motion, the devices are constantly switching their terminal designations between anode and cathode with each zero crossing. The terms are completely useless, except when talking about vacuum tube circuits and such.
Numbers do not exist in the world. Umbers exist outside the world.
I do not know if this is a joke about shadows that I did not get, or just a typo, but numbers exist in the world.
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.
> The things are grouped in sets.
By who?
Us?
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"?
Even before the appearance of life, the things group in sets spontaneously, due to the interplay between attractive and repulsive forces and the positive feedbacks that appear in certain conditions.
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.
By themselves already.
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).
Our current universe
Numb and Number
> there is no way of knowing the direction of the charge
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.
I think they don't mean it in the literal "you physically can't tell the direction of charge at all" sense.
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.
I think there might be a difference. From our experience with air we know that blowing and sucking are not quite the same. Blown air has a much greater capacity for direction than sucked air. I would assume that this is because the when we blow we add additional molecules and we get to decide the inertia of those molecules, but when we suck we take away molecules and they have the inertia they have.
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?
Your hole-gun idea left me scratching my head.
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.
> 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.
That blade cuts both ways; the electron beam in a CRT travels through a vacuum, there's nothing to "rush in". A hole beam would have to travel through a medium with no free electrons.
I wouldn't consider the working of an electron gun to be an introductory physics context.
> but it turns out they were going the other way
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 :-)]
The concept of holes is important, but it doesn't have much practical use. It typically only comes up when you're discussing the physics of how semiconductors work, or doing similar electron-level analysis of a component.
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.
How would you have known this at first from rubbing rods and playing with static electricity?
I didn't say we can know it just from rubbing rods and playing with static electricity. The post I was responding to said there is no way of knowing it, period. Which is clearly false since we do know it now.
> We could just as easily have called it "black" or "white" charge
And when we found a charge system that had 3 charges rather than just two, we did.
Where can I learn more on this? Searching yields nothing.
I imagine they're referring to https://en.m.wikipedia.org/wiki/Quantum_chromodynamics
https://youtu.be/AOtUo25GB3c?list=TLPQMjEwNjIwMjQajcfSE5215w
Kinda
Quarks and gluons, or quantum chromodynamics
Read up on “color charge.”
It's either six vs two, or three vs one, depending on what you mean by charge.
The quarks and gluons can be red, blue, green, antired, antiblue, or antigreen.
I was hoping someone would catch that ;)
Why?
It means someone is paying attention. When introducing the topic, it's more effective to say that electricity has 2 charges while chromodynamics has 3, and let them discover that those numbers are using different units for "2" and "3" only after they decide to find out more.
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.
That strikes me as a bad way to make a forum post.
Similar reason why the earth north pole is actually a magnetic south pole :) It was decided by convention / definition.
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.
If anything, it's an issue with a magnet's naming. My understanding is that the North pole/direction got its name first.
“Numbers and numeric quantities aren't a real thing that exists in the world.”
How did your mind gain access to this universal truth? ;)
> Numbers and numeric quantities aren't a real thing that exists in the world. They exist only in our minds.
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...
Was ‘Blue’ invented or discovered?
Fundamentally, it’s the same type of problem - and really more of a philosophical thing.
We're using the term "Blue" ambiguously.
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.
Color perception depends on peculiarities of biology. Numbers and numeric quantities do not.
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...
Interestingly, this argument was weak before we ended up with truly elementary particles. Cause there’s no such thing as three apples or three people. They are unique objects with similarities defined by an observer, and then you go deeper and note that “object” is also a purely synthetic delineation. 3 is a model, not an element of reality. Even advanced maths define it as a set which contains nothing, 1 and 2 (which contains nothing and 1, which contains nothing and is preceded by nothing). Counting and measuring is equivalent to drawing lines — adding something that wasn’t there before.
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.
> [sic]Cause there’s no such thing as three apples or three people.
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.
I’d argue that is because the maths we are familiar with are familiar exactly because they are useful, and repeatedly so.
But that is a philosophical oroboros.
They are useful repeatedly because they derive from fundamental properties of the observable universe. We can imagine other sorts of universes - one with hyperbolic geometry as opposed to flat, for instance ( https://en.wikipedia.org/wiki/Shape_of_the_universe ). Parts of geometry would work differently there, and laws of motion as well. But interestingly, many fundamental rules of math would still apply. Just with different outcomes which are less useful for predicting results here.
Kind of like trying to prove Euclid's Fifth Postulate, which we know now is truly a postulate and not an axiom.
We're using the term "Blue" ambiguously.
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 interesting part is that perception is shaped by language. The Ancient Greeks did not have a word for blue, which led to things like the sky being described as "wine-colored" or "bronze". Similarly, the English "blue" is split into two in Russian: light blue (голубой – goluboy) and deep/dark blue (синий – siniy), a speaker has to choose between them when describing something.
The wavelengths may have always existed but colors only become a thing when we draw the arbitrary lines between them.
In English, speakers are forced to make the same light/dark distinction between pink/red and orange/brown as well. I don’t think most native speakers of English think of orange as the same as light brown.
Ah hah! This explains something.
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!
You may be interested in https://blog.xkcd.com/2010/05/03/color-survey-results/ if not seen it yet. If you desaturate the main chart to around 70%, #8a3324 lands onto a red-brown-orange triangle. I think I agree with that someone, cause at 70% the whole orange region sort of bleaks away.
In a way he was right, if he was describing the movement of "holes", or the lack of an electron.
This is exactly why I think he was wrong. Normally, pretty much everywhere else we use the terms, "positive" denotes the presence or addition of something, while "negative" denotes the absence or subtraction.
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.
This is pretty much spot on. It sucks after 250 years of hindsight, but I would encourage anyone who wants to think like Franklin to buy an amber rod, a glass rod, a piece of real fur, and a piece of silk, and try experimenting with them and see if you can intuit from physical experiment what the fire is made of and how it passes from one material to another. You can't without the benefit of future knowledge.
This is what it feels like to stand on the shoulders of giants.
What is an amber rod?
Just what it sounds like: a rod made of amber[1].
[1]: https://en.wikipedia.org/wiki/Amber
Not really, we talk about bubbles moving up, not water moving down.
Current is bubbles.
We do talk about water moving down though. There is no reason current should be bubbles.
A rationalization after the fact is different from a reason.
In semi-conductor design discussions around transistors and motion of electrons, it’s often much more convenient to talk about hole (bubble) migration than electron migration.
It’s really a moot point as to whether the abstraction used to solve problems matches with the physicalist interpretation of reality.
> rods
I think the origin might be phallic. Rod obviously gains positive charge when rubbed, for a man from 300 years ago.
> If you read Teaching Introductory Physics the author very clearly points out that there is no way of knowing the direction of the charge
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
Suppose that they had realized back then that electricity was going to become one of the most important technologies humans have in the future and decided that they should make a major effort to figure out the direction of the charge so future generations wouldn't get stuck with the wrong convention. All the top scientists, engineers, inventors, and crackpots in the world try to come up with some way to tell.
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.
If they even had a corpuscular theory of matter, they might have considered weight. But this was firmly back in the Enlightenment "Natural Philosophy" kind of thinking when materials were "imbued" with properties like gravity and levity or heat and cold. Some of the people working on these things also had a keen interest in alchemy and the search for a philosopher's stone.
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.
Thermionic electron emission in a vacuum tube would let you distinguish between electron and element: the electrons are liberated much more easily then the source material and result in current flow through the circuit.
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
Charge 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.
Exactly this!
Even the use of 'flow' is misleading. It's barely trickling through the wire...
Exactly, 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 :)
Should I think about it as ripples traveling through the magnetic field like a wave?
As a matter of fact, yes! This YouTube video is probably one of the most amazing things I have ever seen, he measured the change in voltage traveling along a Y circuit, where one end is open and one is closed.
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.
https://youtu.be/2AXv49dDQJw?si=Bu50bjG6jkt1ktSQ
Sort 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
And why magnets work due to relativity https://youtu.be/1TKSfAkWWN0
A 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.
Actually both wires are full of angry pixies, it's just that you have angry pixies in your body that match the ones in one of the wires, so you don't notice when you touch one, and strongly notice when you touch the other.
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.)
I was under the impression that we primarily ground one side to prevent atmospheric charge and/or things like lightning strikes causing large voltage differentials to occur between power lines and grounded objects (it's probably a bit of a fire and safety risk if the wires coming into your house could be sitting many kV above earth potential).
Yes. If you have an electrical network that isn't grounded anywhere you can't get a shock from touching only one wire because there wouldn't be any current flow. If you repair electronics you might do that to a single device with an isolating transformer, or if you are a hospital you might do that to the entire building.
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.
The commonplace example of this would be a battery, correct? You can touch + or - separately and feel nothing.
I thought that was safe because the voltage/current isn't enough to go through skin or something like that.
For AA batteries that's true. But licking a 9V battery gives you a notable shock. Any wet skin should work to some degree at 9V, but the tongue is very sensitive so it brings the most dramatic effect.
Licking across both terminals? Or licking just one?
If you lick just one, you feel nothing. You have to lick both.
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.)
Anytime 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.
It's easy! Cations are positively charged, so cathodes are, uh, negatively, charged. With anions and anodes it's the other way around.
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.
The other day, I was reading a chemistry book at the point where it "helpfully" listed four different mnemonics for the same thing -- cations vs. anions, or maybe it was cathodes vs. anodes, or anyway, you know, something in that vicinity.
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...
It doesn't help that very many explanations on the web of anode/cathode are wrong, or at least misleading, and only cover catalytic or galvanic cells.
I believe https://chemistry.stackexchange.com/questions/16785/positive... is correct.
The terms "anode* and cathode have their own problems. The cathode is that terminal of a device where positive current emanates. The (+) terminal of a batter is normally a cathode, but when the battery is being charged, it becomes an anode.
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.
A CRT display is a "cathode ray tube", which shoots electrons, which are negative.
My personal mnemonic for that is that the letter A is often used for getting the opposite meaning of words (moral/amoral, sexual/asexual), and even moreso in my native (non-english) language. Thus my brain wired itself to associate "anode" with negative. It's quite a stretch but my mind seems to form a bunch of these weird mnemonics.
CAThodes are PAWsitve
But 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.
Cats 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.
It 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.
What you are describing is a meme in my country, used to make fun of religious anti-evolution people who claim "evolution is only a theory and not a proven law, thus doesn't exist".
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 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.
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...
Well I guess that explains why "the normal force" is the one that counteracts gravity.
(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!
Turn it into a theory that predicts exact quantities (accelerations) and I will start paying attention.
The idea he's describing is Le Sage's theory of gravity, and it does correctly predict many of the things Newtonian gravity predicts. Specifically it predicts an inverse square attraction between pairs of bodies and that the attraction is proportional to the masses of the bodies.
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...
[2] https://www.feynmanlectures.caltech.edu/I_07.html
Well why wouldn’t it? The mathematical constants could remain the same as in the current theories.
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
Newton's Philosophiae Naturalis Principia Mathematica (published 1687) contains a mathematical (geometric actually) proof that the gravitational attraction between the Earth an a man standing on the surface of the Earth is the same as it would be if all of the mass of the Earth were at its center. There's another proof that if the man is standing at the bottom of a one-mile hole, and the Earth is assumed to be a perfect sphere, then the attraction is the same as if the Earth's radius were one mile less than it actually is (i.e., the attraction between the man and the shell of mass higher in altitude than the man is exactly zero because the attraction from the various points in the one-mile-thick shell exactly cancel out).
That is that kind of thing I mean: proofs and calculations, not "why wouldn't it?"
Hey thank you for your reply. I learned several interesting examples from your first paragraph in the comment.
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.
As a layperson, that makes sense to me. It also explains the time dilation effect when near a large mass.
Thinking of it as directional action potentials that are blocked by mass? I agree it does feel intuitively nicer that way honestly.
Yep. Coming from everywhere and moving outward in all directions at all times and ‘absorbed’ or ‘blocked’ by mass
Physicists: Has anyone ever looked into this?
Yes. https://en.wikipedia.org/wiki/Mechanical_explanations_of_gra...
(but I only play a physicist on HN)
The 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.
The theory of charges has Z/2 symmetry.
This 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.
Could 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.
Up and down quarks have names that make perfect sense, they are derived from the isospin which in turn derives from spin (spin-1/2 was the only other well-known object in physics that had the same symmetry properties). Which one is up and which one is down is the only arbitrary choice.
Using "positive" and "negative" would have been a disaster. What charge does a positive antiquark have?
Or amino acids. Many have a D (Dextrorotatory = right) or L (Levorotatory = left) form, indicating into which direction they rotate polarized light.
dexter 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?
It 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".
In politics in the UK, there is a left and right side of the "house". Currently the Conservatives are the right and Labour are the left. Neither party existed when the UK Parliament was initially created.
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.
Knowing that ambidextrous thus means "both right (hands)" makes me marvel at how such a brazenly politically incorrect figure of speech has for so long remained undetected by the cultural police thanks to a linguistic camoflauge that mimics medical-sounding jargon.
The worst part is that up and down are not really opposites. Down is up on the other side of the world.
Up and down are opposites on the other side of the world too...
I'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?
If 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.
>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.
This 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.
That 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.
50% chance events happen all the time (well, half the time).
I think you were right the first time.
If a particular 50% chance event does not happen, then the complementary 50% chance event does happen.
Electrons were not discovered for more than a hundred years after his death. How could he have done the "right" thing other than by chance?
IMO 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.
We 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.
I 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...
Those 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.
The 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.
Current 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.
That Veritasium video has been completely debunked by people dedicated to studying and especially working with electricity. Derek is a hack and you should look for real science channels, not popsci slop.
What's a good source that explains the truth then?
I don't want to go screen videos right now, but his is vague and misleading about what it means for a bulb to "turn on". Putting current into a wire will also put a temporary tiny current spike into any adjacent wires. But that's it until the main current gets all the way around the loop.
"are really fields per Maxwell equations" ignores quantum mechanics. Einstein got his Nobel prize for showing the fields interact as quanta such as photons and electrons. You can see the electrons doing their thing if you put them through a cathode ray tube as found in old analogue oscilloscopes
Same reason male seahorses get pregnant.
No 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 for details
This must make some people in Congress really angry.
Wait until they hear about some mushrooms with more than twenty thousand genders.
Others 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.
It 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
how is this recent? This was like 1900.
The 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.
In 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.
The 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.
Rome 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.
That’s more than a hundred years after Franklin.
I 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_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.
Always use Maxwell's corkscrew rule.
Everyone 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...
I read somewhere that this was also common in the USSR but can't find any references. Perhaps someone here will remember.
From 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.
How 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?
This 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.
It 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.
Fun 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.
Any recommendations for the circuit books?
We don't even know why Ken Thompson chose ! for negation, and he is alive.
Presumably because it looks like "¬": that sign used to have very long vertical stroke, like "|" does.
In my mind it’s always “not!”
It 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(
If 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.
Do electrons actually flow when current moves? Apparently not https://youtu.be/bHIhgxav9LY
> 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.
Red 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.
So you mean red like warm water and blue like colder? Warm is + and cold is -.
> 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.
He comes from an accounting background where commonly-understood terms mean the opposite of what everyone commonly understands them to mean.
I am not sure what this means? Is this pure lies and insults? I don't see anything else here? In that case, fuck you very much :shrug:
I mean I quoted baez, but I quote it again:
> makes electrons negative
It is not true, and trolling.
OK... so you've quoted them again.
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?
I hope this answer is satisfactory, I hope to end this conversation, I don't like it.
Thank you for explaining your viewpoint. And I have to say I'm sorry, but you're just simply incorrect about this.
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.
I think you'll find that most people who would understand 2 and 3 would also understand the meaning of "the electron is negative" perfectly well, as humans (and at this point, probably LLMs too lol) can infer that the intent is to say 3, especially in this casual context of a social media discussion among normal people.
It isn't like "the air is negative", which has many context dependent meanings.
Wait, but protons would be negatively charged and particle physicists are going to be angry about it?
I’ve always wondered if there are any applications where it matters which way the electrons are going.
Anyone know?
Cathode 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.
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 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.
> 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.
I agree, but think you are talking about the differences of the NPN and PNP transistors, but I'm talking about the differences of the emisor and the collector in the same transistor.
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.)
> I'm not sure why.
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.
I was taught this in elementary school, I suppose not everyone knows.
Relevant xkcd https://xkcd.com/567/
came to comment this :)
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To be more specific, it's very relevant, but it's also already in the article.
Whoops, I viewed it on mobile and didn't scroll past seeing the Wikipedia link and missed that the image was below