Current flow from positive to negative terminal in a circuit. But the charges which are moving in the circuit are the electron that is moving from the negative terminal to the positive terminal. Why we chose the opposite direction as electric current, not the real one?
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Possible duplicates: https://physics.stackexchange.com/questions/17109/why-is-the-charge-naming-convention-wrong/17131, https://physics.stackexchange.com/questions/285983/what-is-the-difference-between-conventional-current-and-electronic-current/285986, https://physics.stackexchange.com/questions/381275/conventional-current-and-electric-current/445240 – Puk May 18 '23 at 05:05
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But the charges which are moving in the circuit are the electron moving from the negative terminal to the positive terminal
This is not generally true. In a typical circuit you may have negative electrons as charge carriers in wires, with negative electrons in n-type semiconductors, positive holes as charge carriers in p-type semiconductors, and both positive and negative ions as charge carriers in batteries. And outside of ordinary circuits you can get both positive and negative charge carriers in plasmas and particle beams. To make a blanket statement that the charge carriers are always negative is simply wrong.
Why we chose the opposite direction as electric current, not the real one?
Why should an electron be positively charged? It has no more claim than a proton.
In any case, the stated direction of current flow is the real one. What matters in Maxwells equations is the current density $\vec J= \rho \vec v$. If $\rho<0$ then $\vec J$ correctly points in the opposite direction of $\vec v$. And all of the electromagnetic effects depend on $\vec J$, not $\vec v$. So there is no sense in which it is the wrong direction.
In dealing with circuits you may as well ignore electrons and just think about the actual electric current which goes from positive to negative regardless of the sign of the charge carriers
Dale
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semiconductor holes are convenient mathematical trickery. The underlying thing is all the electrons in the almost filled band moving. So, really, the case we are most likely to get is positive ions moving in a solution. – naturallyInconsistent May 18 '23 at 09:14
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@naturallyInconsistent it is more than mathematical trickery. In classical EM, the way to experimentally determine the sign of the charge carriers in a solid is through the Hall effect. In a p-type semiconductor the Hall effect experimentally indicates positive charge carriers. So if it is trickery at all it is certainly more than just mathematical trickery. At least classically I know of no experiment that indicates anything other than positive charge carriers there – Dale May 18 '23 at 11:13
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I know that. It is very useful trickery, but it is still trickery. I am not saying that we would want to choose to do anything else. I'm simply stating that it is a fact that holes are the collective effect of an almost-filled band worth of electrons moving, and that gives the illusion of holes being the ones moving. – naturallyInconsistent May 18 '23 at 13:16
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@naturallyInconsistent I don't know. I think it is a bad idea to call it trickery when the Hall effect experimentally demonstrates that the charge carriers are positive. Why should we take time dilation as something other than trickery if we insist on positive holes as trickery? Where do you draw that line? Trickery isn't a scientific assessment, it is a pejorative term, one that I don't think is merited here since the most directly relevant experimental test is easy, clear, and conclusive. Anyway, the case is strong enough for me to feel comfortable leaving it in the answer – Dale May 18 '23 at 13:36
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Because before the textbooks cover holes, they first prove that a full band cancels out, and so holes are the effect of full band minus a few electrons. Proved that the missing few electrons would behave as if the charge carriers are positive holes. – naturallyInconsistent May 18 '23 at 13:40
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@naturallyInconsistent not just "would behave as if" but "does behave as if". In the end, the only reason that we accept any of our scientific models is because the world does behave as if they were correct. Again, the statement that the charge carriers in a p-type semiconductor are positive is both theoretically and experimentally justified. I am comfortable leaving it in the answer – Dale May 18 '23 at 13:44
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The fact of the matter is that holes are non-existent. We could equally have tracked every electron moving in the band, and obtained the same result. It is just convenient, not necessary. – naturallyInconsistent May 18 '23 at 13:45
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@naturallyInconsistent no, that is definitely not correct. The electrons in a band are not individual particles that you can track individually and that have individual behavior. They behave collectively together with each other and with the lattice. And that still doesn't address the classical Hall effect. Regardless of what you use quantum mechanically to explain it, the classical experimental result is unambiguously positive charge carriers – Dale May 18 '23 at 13:48
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Break out your solid state physics textbook and take a look inside. We have no choice but to integrate over all the filled elecrons, with the Fermi-Dirac distribution, and thermal corrections, if that is what you want. – naturallyInconsistent May 18 '23 at 13:51
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Yes, integrate over filled electrons, not "track electrons". We have to integrate precisely because we cannot track. Individual electrons are not trackable, not as a matter of limited technology but as a fundamental part of what makes electrons what they are. – Dale May 18 '23 at 13:54
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You do the same thing with holes. That is what it means to keep track of. Just terminology. – naturallyInconsistent May 18 '23 at 14:00
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Well, this is easy to answer. The current flow is determined by the direction of the electric field. It was thought that the positive charges was the moving charges so, when EM theory was being discovered, everything was doing in that base. This is why the direction of the current flow follows the natural move of the positive charges, but the real flow, goes in the other way.
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