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Why does current flow the opposite way from the electrons?

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Re: Why does current flow the opposite way from the electrons?

#131

Post by mr_mitm »

philipov wrote: post #105
throwway120385 wrote: post #13

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 Introduct…

> 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 .

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.

Re: Why does current flow the opposite way from the electrons?

#132

Post by marcosdumay »

gus_massa wrote: post #77
bilsbie wrote: post #68

I’ve always wondered if there are any applications where it matters which way the electrons are going. Anyone know?

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/Catho…

> 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.

Re: Why does current flow the opposite way from the electrons?

#133

Post by im3w1l »

dotnet00 wrote: post #110
pdonis wrote: post #32

Earlier quoted context omitted.

> 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 conv…

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…

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?

Re: Why does current flow the opposite way from the electrons?

#135

Post by pwg »

tdeck wrote: post #19

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.

Re: Why does current flow the opposite way from the electrons?

#136

Post by tim333 »

beryilma wrote: post #65

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...

"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

Re: Why does current flow the opposite way from the electrons?

#137

Post by dahart »

akira2501 wrote: post #28
throwway120385 wrote: post #13

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 Introduct…

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 imme…

“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?

Re: Why does current flow the opposite way from the electrons?

#138

Post by sethev »

xdavidliu wrote: post #27
NegativeLatency wrote: post #3

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 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.

Re: Why does current flow the opposite way from the electrons?

#139

Post by vagab0nd »

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.

Re: Why does current flow the opposite way from the electrons?

#140

Post by ArnoVW »

mrunkel wrote: post #94
detourdog wrote: post #38

Earlier quoted context omitted.

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.
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