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We know that "conventional current" is the historical notion of the flow of positive charges. And that, in reality, the charge carriers are negatively charged electrons and that they flow in the opposite direction.

For simple circuits, it makes no difference: a battery in series with a resistor and a lamp has the same behavior whether we think of positive charges moving "left" through the lamp or negative charges moving "right." We can also think about more complex circuits containing nonlinear elements like transistors - again, we qualitatively understand the circuit's behavior in the same way regardless of the conceptual direction.

Are there any circuits whose qualitative practical behavior is difficult or impossible to understand if we're thinking about current flow in the "conventional" direction? Where we really need to think of electrons flowing in the proper direction to understand why a certain LED turns on, or why a frequency response curve has a dip in it at a certain place, or why a certain EMI effect is happening?

Edit: I'm not concerned with intimate understanding of, say, quantum-level processes that happen in semiconductors, unless the notional current direction in such processes has a behavioral impact that would be of concern to an electrical engineer (or a consumer).

TypeIA
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  • For every circuit there seem to be people that understand it, so clearly it is not impossible to do so... – PlasmaHH Mar 24 '17 at 13:20
  • Since "conventional current" is an abstract description that has no physical properties other than reverse electron flow, then they can not be separated. However, by definition, ABSTRACT means someone can modify the definition to mean something else. – Trevor_G Mar 24 '17 at 13:24
  • Once could, and we do, argue all the time whether "current" passes though Capacitors when we know the electrons don't. So that may be your answer right there. – Trevor_G Mar 24 '17 at 13:26
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    I have had experience of a colleague who got himself tied into knots with this trying to explain the operation of a flyback diode. While the question is interesting I suspect the answers are going to be opinion based. – RoyC Mar 24 '17 at 13:26
  • No. As far as I know only the flow of holes and electrons in doped semiconductors require detail understanding of the roles of electrons. (...and the roles of holes. :-) – skvery Mar 24 '17 at 13:27
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    Well the first thing that comes to my mind is vacuum tubes. Especially for special cases like CRTs where the only logical way to understand what is happening, at least to me, is to actually consider the direction of the electrons. I don't know that this is a problem with solid state circuits however. I've always found it convenient to mentally switch between electron flow or so called "hole flow" in circuits involving transistors. – Randy Mar 24 '17 at 14:28
  • @Randy Yup. which brings us to the age old question... Is there "current" in a vacuum... not opening that can of worms. – Trevor_G Mar 24 '17 at 14:33
  • Why does this question come up every 3 months in some form or another? Just learn when and where and use both systems. In vaccum tubes and plasma devices its not that hard to figure out and if you design those you learn the rules really quick – Voltage Spike Mar 24 '17 at 15:53
  • @laptop2d Are you sure _this_ question has come up before? I'm not asking about the meaning or merit of the convention, but rather whether there are any common circuit behaviors that are conceptually "asymmetric" with regard to flow direction. Could you please provide links to any previous equivalent questions? I'd like to read the answers. Either way I do not understand the reason for your hostility. – TypeIA Mar 24 '17 at 16:45
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    I'm sorry that your sensing 'hostility' because I don't see anything that I wrote that would imply hostility directly towards you. But yes, in some form or another there are plenty of questions that ask about current direction and electron current, more me an myself *I ask why is this type of question even a thing?* – Voltage Spike Mar 24 '17 at 17:56
  • @laptop2d It's a "thing" because it's something I've wondered about, hoped people more educated than myself would be able to answer, and hoped others like myself might like to learn too. I'm not an electrical engineer, or even a particularly skilled hobbyist. Is that not precisely what this site is for? I'm sorry that my lack of knowledge and desire to ask a question troubles you. I did search existing questions before posting. None seemed to cover this particular aspect of conventional current. If I'm wrong, please post a link, because I'd like to read the answers. – TypeIA Mar 24 '17 at 19:36
  • `We know that "conventional current" is the historical notion of the flow of positive charges.` Incorrect. `in reality, the charge carriers are negatively charged electrons and that they flow in the opposite direction.` Also incorrect. https://electronics.stackexchange.com/a/39852/142 https://physics.stackexchange.com/a/17131/176 – endolith Jan 09 '18 at 21:07

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There are several levels at which we can try to understand the behaviour of an electronic circuit.

There is circuit theory, with Ohm's Law, Thevenin etc., a flow of current, voltage drops etc.

There's physics, with electrons, atoms, movement of holes

There's physics, with Maxwell's equation, propagation of waves along wires to components

There's physics, with quantum theory, forces between electrons being mitigated by photons

You always use the one most suitable for the questions you're trying to answer. If you are doing circuit theory, with conventional current, that is quite capable of handling frequency response of filters, lighting of LEDs. Swap the sign of conventional current, and all your equations have the potential to move a minus sign from one side to the other, but all the conclusions remain identical.

If you want to design a new LED substrate, or a Hall sensor, then you need to worry about atomic physics and what electrons and holes are doing.

Neil_UK
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Qualitative, no, but quantitative yes. Although you specifically excluded quantum effects in semiconductors, the behavior of p-type semiconductors does show some effects. In p-types, current takes place as vacancies in the electronic structure move around. Since such movement is more complicated than a simple electron displacement, you get effects such as decreased speed in pnp BJTs, and increased on-resistance in p-type MOSFETs (for the same die area).

WhatRoughBeast
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I'll give a thermionic valve as an example (ie, a tube). Or a cathode ray tube.

In this type of device, current is a flow of electrons traveling through vacuum. They are emitted from the heated cathode, and there is no way to understand how it all works if you picture positive charges traveling the other way around.

bobflux
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