Comment by spaceywilly
6 days ago
Well, the water analogy actually holds up quite well if you consider the charge field moving, not the electrons themselves. This guy has a lot of great videos using water channels to explain electricity. It is fascinating how under a high speed scope, you can see the electrical Charge “flow” like water down each branch of a circuit.
Even rubber dams stretched across pipes work exactly like capacitors. Firstly, they block DC: water cannot flow. But back and forth movement is conveyed (AC passes). Less capacitance in series, more in parallel. Two such dams in series do not have more capacitance because to get one to stretch, the other must stretch; they partially cancel. And since there are two, more pressure is needed to get the same stretch. (Same as more voltage needed to cram in the same charge: less capacitance).
Inductance doesn't have an analog. To some extent, the inertia of the fluid cam model some of it, I suppose. Like what is "water hammer" in plumbing? The circuit is too suddenly broken, but the water wants to keep moving. There's gotta be a resulting momentary pressure rise there in the closed-off line, similar to voltage rising in an interrupted inductor. If the valve were some weak piece of crap relative to the mass of the water, the water would break it: like arcing.
Inductance is like a pipe with a flywheel inside it. the water pushes through the impeller/flywheel. the flywheel resists any changes to motion.
Or just a long pipe where the inertia of the water resists change in motion. This is what causes the "water hammer" effect which is a problem for plumbers, but a great thing for all kinds of fun experiments, e.g. creating predictable cavitation [0].
[0]: https://www.researchgate.net/publication/321225042_A_novel_w...
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This was the stunning one to me. Just blew my mind literally observing it run up a dead end wire and slosh and rebound like water.
Previously I was used to thinking of dead ends as simply functionally inert. That without a circuit, nothing at all happens in the dead end wire other than the potential for something to happen.
Sure I know something more than nothing actually happens since there is an elevated charge there. But still just the mental model shorthand is that no circuit = no nuthin.
But it's not. It's actually like a pipe with a little bit of air to allow for some compression, and even the dead end has a small flow that travels to the end and builds up against it, then rebounds back and eventially levels out at some homogenious but now higher pressure.
That just boggles me! I love it.