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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?

#221

Post by static_motion »

Gibbon1 wrote: post #24
CapitalistCartr wrote: post #6

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.

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.

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.

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

#222

Post by amluto »

adrian_b wrote: post #174
bithive123 wrote: post #165

Earlier quoted context omitted.

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.

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 19…

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 :)

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

#223

Post by Spivak »

spaceywilly wrote: post #188
tedk-42 wrote: post #30

Earlier quoted context omitted.

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?

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

#224

Post by timschmidt »

lazide wrote: post #218
timschmidt wrote: post #210

Earlier quoted context omitted.

> [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.

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.

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

#225

Post by wruza »

lazide wrote: post #183
labster wrote: post #182

Earlier quoted context omitted.

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.

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

#226

Post by marshray »

coldtea wrote: post #214
kazinator wrote: post #197

Earlier quoted context omitted.

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.

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

#227

Post by privacyking »

verbalstoner wrote: post #150
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...

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?

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

#228

Post by kazinator »

coldtea wrote: post #214
kazinator wrote: post #197

Earlier quoted context omitted.

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.

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.

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

#229

Post by kazinator »

afiori wrote: post #220
kazinator wrote: post #194

Earlier quoted context omitted.

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.

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

#230

Post by kazinator »

lupire wrote: post #142
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…

Numbers do not exist in the world. Umbers exist outside the world.

Numb and Number
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