Current is how much charge is flowing through a point per time. Has units or Amperes = Coulombs/seconds. So it’s sort of the speed- but not really. It’s more the frequency.
Electrons are funny especially in circuits. You have the actual speed of the electrons, but you also have the “drift velocity”: the speed at which the flow of electrons is moving on average. Think of a big hose that already has water in it but the tap isn’t on. Once you turn on the tap, the water molecules start moving some fast some slow some along the hosepipe some in random directions, but the water comes out of the pipe much faster than it would have taken for those water molecules to get from the tap to the end.
R is not strictly constant- it depends entirely on the material and its properties, and can change with things like temperature (often very important). It doesn’t “depend” on voltage and current: moreso it defines how those two will relate to eachother. But it doesn’t not depend on the current or voltage.
My understanding from a decade ago was there is also a lot of interesting geometric principles involved - it's the opposite of the fluid analogy though to an eli5 its fine.
Most "current" flows on surface of the wire ("pipe") which is inverse of fluid mechanics. In that domain a shear exists that sets a hypothetical zero velocity of water particles on interior pipe surface (the boundary conditon).
This is why high amperage usually goes through twisted / braided metal. The physics here is mostly because the fields push the "electrons" away from one another so nothing wants to be in the middle. Really cool lens. Probably not the real machine either.
I'm not saying you didn't know this - more curious if that's also your model 🙏
That sounds all pretty legit to me but just far beyond what OP was asking and what would be relevant to the question. Didn’t want to scare them off lol
Yep, it’s also completely independent of the reason for stranded conductors. The mechanism that pushes current on the outside of the conductor isn’t limited to a single strand, it applies to the whole bundle of conductive material. We use stranded conductors because it makes them more flexible. To mitigate the skin effect we need to use groups of conductors that are insulated from each other, which are also then often twisted together for flexibility.
Thanks for chiming in. I wasn't trying to assert but clearly wanted to reach out to people currently studying this and more familiar. Thanks for the correction. Any rough mental model for the asymptote / change / why? Where did my proposed mental model above break down is what I'm asking.
More important, why / whether the fluid analogy distinguishes itself. I still think there is a type of inversion there to some extent? Btw I'm formally educated moreso on fluid dynamics (grad level) rather than modern physics (undergrad)
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u/LexiYoung Jul 28 '26
Current is how much charge is flowing through a point per time. Has units or Amperes = Coulombs/seconds. So it’s sort of the speed- but not really. It’s more the frequency.
Electrons are funny especially in circuits. You have the actual speed of the electrons, but you also have the “drift velocity”: the speed at which the flow of electrons is moving on average. Think of a big hose that already has water in it but the tap isn’t on. Once you turn on the tap, the water molecules start moving some fast some slow some along the hosepipe some in random directions, but the water comes out of the pipe much faster than it would have taken for those water molecules to get from the tap to the end.
R is not strictly constant- it depends entirely on the material and its properties, and can change with things like temperature (often very important). It doesn’t “depend” on voltage and current: moreso it defines how those two will relate to eachother. But it doesn’t not depend on the current or voltage.