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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?

#151

Post by XorNot »

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…

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

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

#152

Post by denton-scratch »

im3w1l wrote: post #133
dotnet00 wrote: post #110

Earlier quoted context omitted.

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 t…

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.

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

#153

Post by mensetmanusman »

remram wrote: post #114
mensetmanusman wrote: post #87

Earlier quoted context omitted.

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.

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

#154

Post by scotty79 »

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…

> rods

I think the origin might be phallic. Rod obviously gains positive charge when rubbed, for a man from 300 years ago.

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

#155

Post by scotty79 »

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…

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.

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

#156

Post by janto »

kabouseng wrote: post #148
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.

If anything, it's an issue with a magnet's naming. My understanding is that the North pole/direction got its name first.

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

#157

Post by SoftTalker »

wongarsu wrote: post #124
FLT8 wrote: post #96

Earlier quoted context omitted.

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 i…

The commonplace example of this would be a battery, correct? You can touch + or - separately and feel nothing.

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

#158

Post by michaelrpeskin »

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.

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

#159

Post by im3w1l »

denton-scratch wrote: post #152
im3w1l wrote: post #133

Earlier quoted context omitted.

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 t…

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…

> 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.

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

#160

Post by utensil4778 »

jstanley wrote: post #37
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.

> 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.

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