Nope! It's kinda silly. We all call electrons negative because of how they were labeled 250 years ago. If he had labeled them positive the math involving electric current would be a bit easier.
I’ve been hearing for years that the math involved would be easier if we switched signs on the electron but what equation specifically would be simpler? One would still have to deal with both polarities. I tutored electrical engineers for years and the biggest misconception by far was always considering the amount (or movement) of charge and the number of particles to be equivalent. Polarity was never really an issue.
But existing theory predicts all those just fine, it just happens that some things are not in the same direction, but it’s not like one can ignore direction. The math is still always there. And I argue things going in different directions is a feature, not a bug, because it reinforces the point that net charge and net particles are not the same thing.
Right, the math is the same. We face this in physics all the time. You drop a ball and it accelerates downward. Should the distance it covers be a negative number? Well, it seems linear distance should be positive, but if it is, then does down become positive? Shouldn't up be positive? Or do we reverse from end-minus-start and make it start-minus-end?
It doesn't matter. The math is all the same with just different labeling conventions.
For the general physics of electric charges, the convention that a proton is +1 and electron is -1 is somewhat useful as a reminder of the larger range of phenomena: protons carry charge, too, and a movement of positively charged molecules makes the charge carriers and current move in the same direction.
But as soon as you start working with practical, artificial electrical circuits (as opposed to, say, neurons), the electron-is-negative is a nuisance, because the charge carriers are almost always simple electrons. To visualize "stuff" moving one way, you have to visualize "other stuff" moving the opposite direction. You have to keep thinking that when you add more you get less. Visualization of electric/electronic technology would have been a lot more convenient if the convention had been that electrons were positive, protons negative.
I ran into this recently with vacuum tube diodes. There's a cloud of electrons surrounding the heated ground-plate. The source plate is at high voltage. Increasing the voltage on the grid attracts electrons, which stream from the ground and fly towards the "source." And I'm calling it "source" because the stream of electrons flowing from ground to source is a positive current from source to ground. Thanks, Ben
I haven't gone through all of your notes yet, but this would've been a godsend to go over in highschool before I started my EE classes in college. It was always obvious which students had been lucky enough to already cover the material.
Your notes are awesome.
One thing I never thought of (and still have a doubt): can you really say that adding more resistance physically slows down the electrons? I mean, how slow can you make them move then by adding mega or giga ohm resistors? In metres per second? Isn't it more like that by adding more resistors there are less electrons which are able to pass it, which makes current flow less (not slower)?
Just a random thought, without research.
I'm also speculating here, but I think resistance can manifest as slower electrons or as fewer electrons moving at the same speed.
On the wire, away from the resistors, the number of electrons that can move should stay constant, so the election drift velocity should drop as resistance increases.
One more thing to add. Electron drift velocity isn't the same as signal propagation speed. Wires can transmit information at around 2/3 the speed of light, but the drift velocity of an electron in a wire is around walking speed.
The analogy I use to explain this (which is, like all analogies of course broken at many levels): a tube full of marbles will produce a marble at the far end every time you push one new marble in, but the individual marbles travel really slow.
I used to use the scene in "the two towers" where they light the fire to let Rohan know that Gondor is in need of aid. I thinks I have to stop referencing Lord of the Rings because most high schoolers haven't seen the movie these days.
Thanks, point taken. And of course there are approximations and simplifications necessary when you try to explain this subject to high school students. I mean, that is the age when you still draw parallels from the physical world and it is easier to digest electron as a very small fast moving "ball" even though it is probably not.
Electrons move at the same speed. In a low-resistance material (metal crystal) they move in an almost strait line. In a higher resitance material they take a longer path, and must line up (stop) to make it through bottlenecks. They only seem to be moving more slowly at a macroscopic level.
Beautifully presented! Thanks for sharing, these notes are inspiring, I especially like the simplicity of the presentation's design paired with interactive elements. Too often I find material with the latter to be extremely busy. As someone interested in instruction, I'm taking notes from this!
"In 1746 Benjamin Franklin mistakenly assigned a negative value to the charge carriers that we now call electrons."
Shouldn't that read "mistakenly assigned a _positive_ value to the charge carriers that we now call electrons"?