What governs the delay between one ball hitting the cradle and the opposite ball going up?
It's the electrical equivalent of the same thing. Specifically, electricity is delayed by the material absorbing it "elastically" for a short time before emitting it back. This is usually modeled as a capacitance and inductance on the medium.
> And also, how is it that, in general, light will continue propagating in the same direction?
It actually doesn't. It mostly follows the medium. That's why you can bend your wires and they keep working.
But if your question is why it doesn't go "backwards", they go, but there's an electrical potential there pushing your electrons on the other direction.
>It actually doesn't. It mostly follows the medium. That's why you can bend your wires and they keep working.
Sorry, its my fault for introducing light into a discussion about electric current. In fiber optics I believe they add "cladding" to achieve "total internal reflection" that somehow keeps the light going - not sure how it stays coherent though! And in electronics, I assume that the boundary of the conductor with non-conductor (e.g. air) provides a similar function. I've heard that conductors conduct almost entirely on their surface, another curious effect I'd like to undersatnd, and I'd also be curious if any applications use hollow tubes to conduct large currents and save on weight.
> And in electronics, I assume that the boundary of the conductor with non-conductor (e.g. air) provides a similar function.
Electricity inside a conductor works more like a sound wave the article talks about than optical fiber. It's not coherent or directed, you have a high "pressure" on one end pushing the electrons, and they push each other forward as a consequence. There is no care about reflections (up until radio frequencies), it just moves into the direction of less "pressure" through the medium. (Even in RF, but on those the reflections cause noise.)
Optic fiber depend a lot on conservation of momentum. Electrical current has none of that. Even the reflections are caused by the "elastic absorption" of the medium, and don't behave like a collision.
> I've heard that conductors conduct almost entirely on their surface
That's not really right. Conductors conduct through all of their area, unless you have high frequencies. At high frequencies there is magnetic interaction between the electrons so they are pushed out of the conductor's center, but this is not a universal thing.
And then, in high frequencies you don't use hollow tubes. You use thin wires, insulated from each other, knitted in a way that every wire spends the same length on the middle of the bundle.
What governs the delay between one ball hitting the cradle and the opposite ball going up?
It's the electrical equivalent of the same thing. Specifically, electricity is delayed by the material absorbing it "elastically" for a short time before emitting it back. This is usually modeled as a capacitance and inductance on the medium.
> And also, how is it that, in general, light will continue propagating in the same direction?
It actually doesn't. It mostly follows the medium. That's why you can bend your wires and they keep working.
But if your question is why it doesn't go "backwards", they go, but there's an electrical potential there pushing your electrons on the other direction.