5 ms·

As far as circuits go, this is about the closest high school Physics gets to truth (and it's decently close, compared to how wrong it gets e.g. capacitors): >

As far as circuits go, this is about the closest high school Physics gets to truth (and it's decently close, compared to how wrong it gets e.g. capacitors): > In high school they told me, no no, they don't move at the speed of light, just when one electron enters the conductor, another one on the other side will leave the conductor, like with peas in a straw. And this enter/leaf is at the speed of light. although "entering" and "exiting" the conductor isn't really a good description. A better way to think about it is that "conductor" is really just slang for "material that has a bunch of free electrons and very little room for more". This is the "sea of electrons" that Beaty talks about. It makes sense that, if all this sea flows steadily (i.e. at the same rate throughout the conductor), forcing a change in the rate of flow in one part of the conductor will be felt almost immediately in another part of the conductor, no matter how distant, even if the flow itself is extremely slow. (If you're thinking that this is only true if the "pipe" through which the "sea" flows is full, you're right, this is how free electrons behave in conductors; that's why Beaty insists that a good analogy for a conductor is "like a pipe which is already full of water". > At university they told me, no no, you got it all wrong, it's about the electro static and electro dynamic fields which stand orthogonal on each other and produce electro magnetic waves... what?! If they taught you that, they are most definitely wrong, it sounds loosely like induction, but with two strange names instead of "electric" and "magnetic" :-). This is a better description of the physical reality, and it does help you understand circuits better if you think about it, but not in a very practical manner.

fzzzy 10y ago
> If they taught you that, they are most definitely wrong, it sounds loosely like induction, but with two strange names instead of "electric" and "magnetic" :-). I don't think "definitely wrong" is a good description. electrostatic and electrodynamic are perfectly good, if somewhat archaic, terms for the electric and magnetic fields. (E and H fields)
- k__ 10y ago
  I probably just translated them wrong from German. But as I said, since I didn't understand it, I probably don't recall correctly what they told me. I just remember that the "particles" I had in mind somehow stopped being "the thing" and now it was all abount strange fields that worked without a physical medium and formed waves by being aligned in a specific way.
- notalaser 10y ago
  Ah. That's a terminology fuck-up on my side, then. I've never encountered this convention, but classical electromagnetism has almost two centuries of history behind it. A lot of weird names have been used for a lot of things. For what it's worth, though, these are terrible names, archaic or not :-D. If they ever were in use, I'm glad we moved on.
  - fzzzy 10y ago
    I'm not sure they are terrible. Electrostatic describes charges at rest, capable of inducing a voltage across a dielectric. Electrodynamic describes charges in motion, capable of inducing a current across a conductor. They seem like apt descriptions to me.
    - notalaser 10y ago
      It doesn't sound too bad when you put it that way, and it certainly made sense back when Ampere introduced the term, but: * It doesn't match the way we define electrostatics, magnetostatics and electrodynamics. What defines electrodynamics isn't the fact that charges are moving (they're moving if the currents are constant, too, but the magnetic fields produced by steady currents are in magnetostatics' yard) but the interaction of charges and currents (in more formulaic terms, when both charge densities and current densities are present, not only do you get both electric and magnetic fields, as in magnetostatics, but they also vary in time). * Charges in motion still produce a voltage across a dielectric. Calling the electric field they produce "electrostatic" when the charges are moving and the field is certainly not static.
      - fzzzy 10y ago
        Thanks for writing that out! Very interesting. I guess it all comes down to the fact that a magnetic field does not exist without an electric current. One way of thinking about it sees it as charges moving, and the other way of thinking about it sees it as a static magnetic field. I guess that's why the terms are archaic!
        10y ago

fzzzy 10y ago

> If they taught you that, they are most definitely wrong, it sounds loosely like induction, but with two strange names instead of "electric" and "magnetic" :-). I don't think "definitely wrong" is a good description. electrostatic and electrodynamic are perfectly good, if somewhat archaic, terms for the electric and magnetic fields. (E and H fields)

k__ 10y ago
I probably just translated them wrong from German. But as I said, since I didn't understand it, I probably don't recall correctly what they told me. I just remember that the "particles" I had in mind somehow stopped being "the thing" and now it was all abount strange fields that worked without a physical medium and formed waves by being aligned in a specific way.
notalaser 10y ago
Ah. That's a terminology fuck-up on my side, then. I've never encountered this convention, but classical electromagnetism has almost two centuries of history behind it. A lot of weird names have been used for a lot of things. For what it's worth, though, these are terrible names, archaic or not :-D. If they ever were in use, I'm glad we moved on.
- fzzzy 10y ago
  I'm not sure they are terrible. Electrostatic describes charges at rest, capable of inducing a voltage across a dielectric. Electrodynamic describes charges in motion, capable of inducing a current across a conductor. They seem like apt descriptions to me.
  - notalaser 10y ago
    It doesn't sound too bad when you put it that way, and it certainly made sense back when Ampere introduced the term, but: * It doesn't match the way we define electrostatics, magnetostatics and electrodynamics. What defines electrodynamics isn't the fact that charges are moving (they're moving if the currents are constant, too, but the magnetic fields produced by steady currents are in magnetostatics' yard) but the interaction of charges and currents (in more formulaic terms, when both charge densities and current densities are present, not only do you get both electric and magnetic fields, as in magnetostatics, but they also vary in time). * Charges in motion still produce a voltage across a dielectric. Calling the electric field they produce "electrostatic" when the charges are moving and the field is certainly not static.
    - fzzzy 10y ago
      Thanks for writing that out! Very interesting. I guess it all comes down to the fact that a magnetic field does not exist without an electric current. One way of thinking about it sees it as charges moving, and the other way of thinking about it sees it as a static magnetic field. I guess that's why the terms are archaic!
      - 10y ago