Oh sorry it is Lessons in Electric Circuits, the book that was the origin of the AAC book / this website (unless I'm wrong). I learned it is called that from the "Read before posting" message for new members.What is this "LIEC" thing?
Oh sorry it is Lessons in Electric Circuits, the book that was the origin of the AAC book / this website (unless I'm wrong). I learned it is called that from the "Read before posting" message for new members.What is this "LIEC" thing?
Thank you.
The thinking is often the other way around: an open wire as a capacitor.
What would be a reasonable way to describe the purpose of the insulator between the two metal plates, if we don't know enough to say no significant current passes between them? Or even, as other members state, current does literally flow between them.But what you won't learn is just how a field can act over a distance, with no medium in between. How exactly does a magnet work, or gravity? You have to study to an advance level to begin to grasp how a simple magnet works, beyond precisely describing what anyone can see.
thank you.I have oft seen them described as analogs of each other, as one does in voltage the other does in current.
Do you mean something besides leakage current?I would not say it is controversial rather it is plain and simply incorrect. A current does indeed flow between the plates.
In theory you don't need the insulator. A vacuum would be a superior insulator for stopping any leakage.What would be a reasonable way to describe the purpose of the insulator between the two metal plates...
Thank you for widening the perspective, I will definitely need this stuff for further studies. For the purposes of reaching a working description or even a provisional description of what the insulator is for, do you disagree that the insulator or dielectric is there to force charges to accumulate in the metal plates, and to carry the EM field?Perhaps this is a good time to consider just what is meant by the term 'capacitor'....
The purpose of the dielectric material is to increase the relative permittivity of the space between the plates, thereby reducing the field strength for a given charge and increasing the capacitance. A good dielectric will have many electric dipoles that rotate to absorb the electric field. The permittivity is a characteristic of space, and the relative permittivity or "dielectric constant" is a way to characterize the reduction in effective field because of the polarization of the dielectric. Since more charge will then be necessary to achieve the same field strength as in free space, and C=Q/V, capacitance is increased by the presence of a dielectric material....a provisional description of what the insulator is for...
Have you considered how would charging and discharging be affected by different values of capacitance?Is there an explanation how this would affect charging and discharging of capacitor physically?
I know this by using time constant RC but I would like to understand how this happens in physics.Have you considered how would charging and discharging be affected by different values of capacitance?
So here is what I infer:The purpose of the dielectric material is to increase the relative permittivity of the space between the plates, thereby reducing the field strength for a given charge and increasing the capacitance.
Thank you.
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I wonder why I have never seen a comparison made between transformers and capacitors: transformers require a changing field for voltage to be induced, hence they don't work for DC, can only work for AC. Capacitors require a changing field for current to be induced, hence they "block" DC and "pass" AC.
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I think everyone agrees with this stuff. The problem is more in the basic description... I'm sure there are other newbies out there too who are wondering how current can flow THROUGH the metal plates when there is an insulator between them. Why doesn't the basic description of capacitors say immediately that this insulator prevents current flow BUT is designed to carry a changing field that helps to induce current.... etc. Why do basic definitions of capacitors not focus on the changing field in the insulator?
Why is it that saying
---that current doesn't flow between the metal plates but rather current is induced via a change in the field inside the insulator/dielectric--.
why is that so controversial? I mean, it is in LIEC. Why are people fighting over "current flow" and why do so many refuse to accept the term "displacement current" or "induced current" when it is a better descriptor of what capacitors do?
So, would my simplistic explanation- that the presence of the dielectric forces charges to accumulate on either plate, and this accumulation produces a field in the dielectric -- would this be acceptable as a provisional description, considering all the unknowns?Hi again,
Some good points.
What the real question is, is it that the current is 'induced' or is the current 'produced' from the changing field?
In the vacuum capacitor however, we cant seem to be sure if there are new electrons introduced or not. In other words, did any electrons from terminal A ever reach terminal B as there is in a transformer secondary circuit loop? It seems that the electrons for the current in terminal B might come from the plate itself, and they may have come from that plate as the result of the field forcing them out of that plate, at least temporarily. This view is interesting to me because there are physical limits to how long we can actually do this and that is matched by the fact that there must be a limited amount of electrons in one plate, no matter how large. These two limiting factors are in agreement, although yes it is not direct proof.
But the only other possibility is that the electrons are able to change form from an electron to a field 'photon' and then back again on the other plate.
There is another theory in physics that states that there is no real 'identity' for a single particle.
Hi again,So, would my simplistic explanation- that the presence of the dielectric forces charges to accumulate on either plate, and this accumulation produces a field in the dielectric -- would this be acceptable as a provisional description, considering all the unknowns?
Interesting explanation! However, I think you answer based on what is observed from reality not that rigorous proof.Hi again
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What else might be interesting to look at though might be why some actual dielectrics produce a capacitance that is greater than other dielectrics. If we build up a voltage on the one with more capacitance (and 'better' dielectric) we see more energy stored than with the other. But then again that voltage would have been 'harder' to build up on the one with the better dielectric, requiring more electron movement. This would be analogous to a hard piece of rubber versus a soft piece of rubber. The hard piece would be harder to compress and thus store more energy while the soft piece would be easier to compress and thus store less energy. Perhaps the electrons undergo a stress from their natural motions that force them to change position long enough to see the overall capacitance effect. There are so many involved that this could be true, although some calculations might help here.
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