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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?

#141

Post by tzs »

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…

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.

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

#142

Post by lupire »

adrian_b wrote: post #125
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…

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.

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

#143

Post by lupire »

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…

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.

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

#144

Post by lupire »

wycy wrote: post #36
akira2501 wrote: post #28

Earlier quoted context omitted.

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…

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.

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.

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

#145

Post by lupire »

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.

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

#146

Post by denton-scratch »

pdonis wrote: post #32
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…

> 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…

> 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 :-)]

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

#147

Post by [deleted] »

tzs wrote: post #141
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…

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 the…

[deleted]

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

#148

Post by kabouseng »

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…

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.

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

#149

Post by kqr »

lupire wrote: post #144
wycy wrote: post #36

Earlier quoted context omitted.

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.

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.

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

#150

Post by verbalstoner »

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.
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