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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?

#211

Post by speakeron »

pwg wrote: post #135
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.

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?

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

#213

Post by ars »

SoftTalker wrote: post #202
wongarsu wrote: post #189

Earlier quoted context omitted.

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.)

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

#214

Post by coldtea »

kazinator wrote: post #197
adrian_b wrote: post #125

Earlier quoted context omitted.

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…

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.

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

#215

Post by coldtea »

bithive123 wrote: post #165
adrian_b wrote: post #125

Earlier quoted context omitted.

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…

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.

Only according to some epistemologies.

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

#216

Post by coldtea »

kazinator wrote: post #199
joquarky wrote: post #169

Earlier quoted context omitted.

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.

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

#217

Post by coldtea »

juliushuijnk wrote: post #177
adrian_b wrote: post #171

Earlier quoted context omitted.

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…

> The things are grouped in sets. By who?

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).

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

#218

Post by lazide »

timschmidt wrote: post #210
wruza wrote: post #209

Earlier quoted context omitted.

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 (whic…

> [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 e…

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.

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

#219

Post by detourdog »

B1FF_PSUVM wrote: post #113
a1445c8b wrote: post #73

Earlier quoted context omitted.

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.

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.

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

#220

Post by afiori »

kazinator wrote: post #194
afiori wrote: post #191

Earlier quoted context omitted.

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... :(
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