Where do you see electrons? Nowhere.
To really understand electricity, we have to consider more than just electrons. For example, inside a battery, we have both negative ions (cations) and positive ions (anions). And, when you draw current from the battery, they flow in opposite directions through the electrolyte inside the battery. Which one moves in the same direction as the electric charge? The positive ones, the anions. And, of course, the cations move in the opposite direction to the flow of charge, that's simple algebra. This happens inside your car battery every time you crank the starter...hardly an exotic situation.
Now let's take our gaze off our electronic workbench and look up at the ceiling. What's happening inside your old-fashioned fluorescent light? Once again, there are both positive and negative ions inside, flowing in opposite directions at any given instant. Which way does the current flow? The same way as the positive ions.
And what about current flow from an arc-welder? Inside the arc, it's hot enough to tear some electrons off atoms, so once again we end up with both positive ions and negative charges (electrons) that are free to move. Once again, they move in opposite directions. One of them (the positive ions) is heavier, has more momentum, and so hits its target harder. And that in turn changes how the weld forms, and how it behaves.
(This takes some math to work out: both positive and negative ions gain the same amount of energy moving through the arc, but the heavier ones gain more momentum. Weird, but true.)
Your average welder knows nothing of this - nothing of the microscopic theory of electric current flow in matter - but she knows about "straight" and "reverse" polarity, and what that means for the quality of the welds she makes: (
https://www.weldingschool.com/blog/welding/understanding-welding-current-and-polarity/ )
Looking a little further up, consider the sun, or any other star. The atmosphere is so hot, it's plasma, the fourth state of matter; atoms have been ripped apart by the heat into free electrons, free protons (and free neutrons, too.) When current flows through the sun's atmosphere, the protons are going one way, the electrons, the opposite way. Which way does the current flow? Same as the protons.
Inside a metal, yes, it's the electrons that move. But the physics of current flow isn't restricted just to current flow in metals. The whole point of physics is to have a single explanation that covers every possible case in the entire universe, or at least, nearly every possible case. And that includes current flow inside your car battery, inside your fluorescent light bulb, inside the arc of your arc-welder, in the atmosphere of a star, in the molten iron core of our planet, et cetera. And in many of those cases, we have to deal with moving charges that are positive, and also with moving charges that are negative. Both matter, both contribute to current flow, both need to be accounted for.
Nevertheless, all the old tube men I know drew *current* top to bottom (+ to -).
Exactly! The same direction in which positive charges would go, if there had been any positive charges. This isn't some crackpot scheme, but basic mathematics: if I start with $100 in bank A, and $100 in bank B, and then I take +1 dollar from bank A and deposit it in bank B, in which direction did the money flow? Well, I now have $99 in bank A, and $101 in bank B, so obviously the money flowed in the same direction as the +1$ did: current flows in the same direction as the positive charges.
And what if I took $(-1) from bank B, and deposited it in bank A? I added a negative $1 to my money in bank A, so I now have $99 in bank A. I removed a negative dollar from bank B, which any accountant will tell you is the same as adding a positive dollar, so I now have $101 in bank B.
So once again, the money flowed from bank A to bank B - in the opposite direction to the direction in which the $(-1) went. Money flows in the opposite direction to negative dollar bills; charge flows in the opposite direction to negative charges! Simple!
-Gnobuddy
Topic: Which Way Home?- Electron Flow (Read 10371 times)