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In the study of electrical engineering circuit diagrams it is usually the norm to show the + ( positive ) polarity as the direction of motion. However in reality the electron is the elementary particle that is actually moving so the diagram is actually in reverse. After some research the only explanation I can find on the internet is that when Benjamin Franklin first conceived of a positive and negative aspect and he just guessed at direction and got it wrong and engineers have been reluctant to undo all the legacy diagrams. I don't know if I believe this story. I don't see how someone can guess the "wrong" direction since Franklin did not know about the electron. Wouldn't the better question be why didn't J.J Thompson name the electron to be + since that was the direction of motion in all circuit diagrams? Obviously I am in error somewhere but need help sorting the historical details.

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    $\begingroup$ The theories of positive and negative electric fluids long predate the discovery of electrons, Franklin developed just such a theory, see What is the history of electric current and resistance? For the kinds of calculations that the diagrams are used for it makes no difference which direction is "right", so there was little incentive to make the changes. $\endgroup$ – Conifold Mar 29 '17 at 1:00
  • $\begingroup$ And there are any number of materials where the entity carrying the current is positively charged. Even in metals one has situations where holes, not electrons, are carrying the current as can be readily determined with Hall measurements. The joys of solid state physics... $\endgroup$ – Jon Custer Mar 31 '17 at 18:51
  • $\begingroup$ I don't understand the title. Shouldn't it say "...why...diagrams don't ..."? $\endgroup$ – Ben Crowell Apr 1 '17 at 0:28
  • $\begingroup$ The title is confusing. As Jon points out and rightly so quantum mechanics opens a new horizon! My problem is that since the motion direction has been given to the electron due to atomic considerations why wasn't the electron thought of as the positive charge when first discovered since Franklin was the first kid on the block who decided + would mean the "fluid" that moves. It's a subtle point and my confusing title didn't help. $\endgroup$ – Sedumjoy Apr 1 '17 at 19:34
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    $\begingroup$ Well, accidents happen even in science. Usually, the current flow can be discussed, calculated, used without ever considering what might be moving inside of the conductors. Except for when you are analyzing the innards of transistors or diodes and such devices where knowledge of actual charge carriers do matter in understanding how these devices operate. As they say though in EE classes, "just go with the flow and think positive current carried by little tiny circles inscribed with a plus sign". $\endgroup$ – K7PEH Apr 17 '17 at 2:49

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