I for one am not booing you, RoGeorge; I am only saying it is not an intrinsic property of all capacitors (and because of
wording, that makes me disagree with your statement/poll).
(This is also at the core of my recent one-sided arguments about learning things, even if those feel like rants or useless whining to others.)
Let me repeat an example I've already mentioned recently elsewhere in this forum.
At least here, in school, kids are taught that electrons orbit atomic nuclei.
The core problem is the definition of "orbit". (In physics and chemistry, they're not called "orbits", they're called "orbitals", "orbital shells", and so on.)
Yes, the electron does have properties that are analogous to rotating around a center: angular momentum, something like an orbital radius, and even spin (analogous to "direction of rotation").
But the fact is that those electrons aren't actually
moving, they're delocalized around the nucleus. This delocalization can be described using quantum mechanics, so well that the best models we have (most accurate with respect to real-world measurable properties) of how molecules behave and react, are based on the quantum mechanical modeling of just the outermost interacting electrons! No fitting to real-world data, just pure math and some physical constants, and out pops our best predictions of what certain molecules are like, and what their properties are.
What does it matter, then? The orbit model gives an intuitive grasp of the
properties – radius and angular momentum in particular; and even spin! – and those are what even physicists and chemists work with, so there's no harm, right?
Wrong. When a charged particle like an electron is deflected, accelerated, or decelerated by another charged particle, like an atomic nucleus or another electron, it radiates energy. We call this phenomenon
Brehmsstrahlung, or "braking radiation". It happens for all charged particles, and is fundamentally due to conservation of energy. So, it is fundamental to charged particles, including electrons.
The problem occurs when one tries to integrate the two, Brehmsstrahlung and electron orbits. I
fear that most people simply decide that somehow an electron orbiting an atomic nucleus, or flitting about in a metal lattice, is just an exception to Brehmsstrahlung, give a quick
, and ignore the dichotomy. That is magical thinking, and leads to the inability of correctly choosing which "model" applies in which situation – so those people can recite information, but not apply it in real world to solve a problem or predict or estimate physical phenomena.
But, there is no dichotomy, only an incorrect description and thus incorrect understanding. It would have been not that hard to explain correctly in the first place:
delocalization looks like the electron is "blurred" across its "orbital", which looks more like a cloud than a ring; but if you measure it, it is like putting a stick into the spokes of a fast-turning bicycle wheel: you'll see one quite clearly. The properties these delocalized electrons have, are almost exactly like if the electron was orbiting the nucleus like a moon orbiting a planet, and that's why we use that analog; but the actual physical description is much weirder, and involves quantum mechanics.
Trying to fix the mislearning later requires "un-learning" – or at minimum, accepting you were taught an incorrect thing because someone thought that teaching the actual thing was too hard.
Now, in the capacitor case, the staircase effect is not due to any intrinsic property of capacitors, but due to capacitors being part of an electrical circuit. You can extend this into the capacitors themselves, if you model a long skinny capacitor charged or discharged at one end, in which case the capacitor itself becomes part of the circuit – transmission line, really. The model breaks down if you have either very short transmission lines, or if the transmission "line" does not have a clearly defined length, so that the change in the electromagnetic field (in the transmission line) does not have a clear wavefront anymore.
I suppose the reason for emphasizing the transmission line model is to break through some preconceptions the students might have, and make sure they understand that the transmission line model applies to even circuits on a circuit board – even if in practice it only matters enough to worry about when delivering power via relatively long transmission lines. That it is not something that applies to, well, actual transmission lines, but is a model that accurately describes what happens in circuits.
The laws that we use every day to describe electrical circuits or networks – Kirchhoff's laws, Ohm's law, Norton's theorem, Thévenin's theorem – are models that do describe the behaviour of the circuit or network, but themselves are the result of more fundamental descriptions of charges; they describe the behaviour, not what is nor why. The underlying reality is much, much weirder, but these models give us tools to work with such systems without getting too bogged down into the weirdness.
That's basically what my own field, molecular dynamics simulations with classical potential models is, "classical" meaning just "non-quantum-mechanic". We can do QM for maybe a system with a thousand electrons (but that may take a week to a month, depending on how large a computing cluster you can grab), but that's just a pretty small molecule – and we need repeated boundary conditions, too, which can be an issue if we want surface phenomena. With less reliable/accurate but much simpler classical interaction models we can model systems with hundreds of millions to billions of atoms, getting into things like corrosion and damage resistance, defect migration in the large scale (and self-healing materials), ion implantation, sputtering, and so on, and get very useful real-world results.
Home
Help
Search
Login
Register
Poll
