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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).

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closed as primarily opinion-based by Voltage Spike, uint128_t, ThreePhaseEel, Dmitry Grigoryev, brhans Mar 30 '17 at 17:46

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ For every circuit there seem to be people that understand it, so clearly it is not impossible to do so... \$\endgroup\$ – PlasmaHH Mar 24 '17 at 13:20
  • \$\begingroup\$ 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. \$\endgroup\$ – Trevor_G Mar 24 '17 at 13:24
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    \$\begingroup\$ 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. \$\endgroup\$ – RoyC Mar 24 '17 at 13:26
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    \$\begingroup\$ 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. \$\endgroup\$ – Randy Mar 24 '17 at 14:28
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    \$\begingroup\$ 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? \$\endgroup\$ – Voltage Spike Mar 24 '17 at 17:56
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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.

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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).

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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.

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