Can electrons "fly" between capacitor plates?

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SUMMARY

The discussion clarifies that electrons do not "fly" between capacitor plates; instead, they move through the circuit connected to the capacitor. When a voltage is applied, charge builds on the plates, creating an electric field that influences charge movement in the circuit without crossing the dielectric gap. This phenomenon is explained through the concept of "displacement current," which accounts for the apparent flow of current in a closed loop involving capacitors. The energy is stored in the dielectric material rather than on the plates themselves, and excessive voltage can lead to dielectric breakdown, causing capacitor failure.

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  • Understanding of capacitor function and structure
  • Familiarity with electric fields and charge movement
  • Knowledge of displacement current and its implications
  • Basic principles of dielectric materials and their properties
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Electrical engineers, physics students, and anyone interested in understanding capacitor behavior and charge dynamics in electrical circuits.

  • #31
FeynmanFtw said:
No, not about the light bulb, but about the non uniform surface charge. That paper simply goes on to show how we can see A surface charge. It doesn't explain anything about how it varies across the wire's length.

As explained in the Sefton paper, the circuit is a loop with turns or bends instead of a infinitely thin straight wire.
At bends in the wire there must be some additional unbalanced charge in order to change the
direction of the field and the current. To see how a distribution of surface charge can direct the flow
of mobile charges and also adjust itself to achieve that result, imagine an electron drifting a long a
wire and approaching a bend. The only way that it can get around the bend on a smooth path is for it
to be pushed or pulled around the corner by some other charged particles that are lying in wait for it.
If that were not so, the electron would keep going and run into the surface of the wire. If it does that
and sticks there it may, in turn, lie in ambush for another electron coming along behind it. So the
first electron, which does not quite make it around the bend, will help to push the next one around.
This process may continue until the surface charge builds up just enough to keep all the conduction
electrons on track. In ways like this the whole system will very quickly adjust itself until there is
just the right distribution of surface charge to ensure a smooth and continuous drift of conduction
charge along the wire. The reason that everything adjusts so quickly is that changes in electric field
propagate at the speed of light.

Another good article.
http://www.matterandinteractions.org/Content/Articles/circuit.pdf
 
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  • #32
he only way that it can get around the bend on a smooth path is for it
to be pushed or pulled around the corner...

You're giving me a deja vu to fluid mechanics course Freshman year...
... graphical solutions...That old British term "Pressure" for volts...

if electron mass =
9.10938291 × 10-31 kilograms

a coulomb should be roughly 5.4e-12 kg
so at meager velocity of electron drift centrifugal force won't make much voltage between inside and outside of the bend
but it's finite.
 
  • #33
FeynmanFtw said:
No, not about the light bulb, but about the non uniform surface charge. That paper simply goes on to show how we can see A surface charge. It doesn't explain anything about how it varies across the wire's length.
q' =C'⋅V(x)
C'...capacity per unit length of wire
V(x)...potential (voltage) at place x of the wire
 
  • #34
nsaspook said:
As explained in the Sefton paper, the circuit is a loop with turns or bends instead of a infinitely thin straight wire.Another good article.
http://www.matterandinteractions.org/Content/Articles/circuit.pdf

True, but then you could imagine stretching out parts of the circuit and making a loop akin to a rectangle (with slightly curved edges). Needless to say, thanks for the second article, I'll have a look at that this week.
 
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  • #35
x86 said:
This article looks amazing. I'm reading it now. Thank you.
I encountered your thread today and found it interesting. I have a question: if there is a capacitor with "perfect vaccum" as dielectric part, will electrons fly through instantly and completely?
 
  • #36
Jackson Lee said:
I encountered your thread today and found it interesting. I have a question: if there is a capacitor with "perfect vaccum" as dielectric part, will electrons fly through instantly and completely?

If you have perfect vacuum you also have a perfect insulator under normal operating conditions (no thermionic or field emission) in a vacuum plate capacitor so NO electrons will bridge the gap (fly) at any speed.

In devices like tubes where electrons do move from cathode to plate the speed is limited to something less than c (speed of light).
 
  • #37
nsaspook said:
If you have perfect vacuum you also have a perfect insulator under normal operating conditions (no thermionic or field emission) in a vacuum plate capacitor so NO electrons will bridge the gap (fly) at any speed.

In devices like tubes where electrons do move from cathode to plate the speed is limited to something less than c (speed of light).

Sorry, I don't understand. Why does perfect vacuum lead to no field emission? I suppose if it is perfect vacuum between gap, then there is nothing could affect electrons to bridge the gap. Is it wrong?
 
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  • #38
Jackson Lee said:
Sorry, I don't understand. Why will those lead to your conclusion(NO electrons will bridge the gap (fly) at any speed)?

Electron flow would be current, in a perfect vacuum there is no current flow because there are no particles with charge in the gap to move from plate to plate.
https://www.physicsforums.com/threads/perfect-insulator.543656/
 
  • #39
nsaspook said:
Electron flow would be current, in a perfect vacuum there is no current flow because there are no particles with charge in the gap to move from plate to plate.
https://www.physicsforums.com/threads/perfect-insulator.543656/
I mean before the electrons' "possible tourist", the gap between plate is in perfect vaccum. At that time, the electric field built by charges on capacitor could exist, moreover, considering there is no other dielectric material affect electrons' moving process, they will accelerate towards the opposite bank.
 
  • #40
Jackson Lee said:
I mean before the electrons' "possible tourist", the gap between plate is in perfect vaccum. At that time, the electric field built by charges on capacitor could exist, moreover, considering there is no other dielectric material affect electrons' moving process, they will accelerate towards the opposite bank.

'Perfect' vacuum means no particles ever, anywhere in that space. So if there are particles in the space we then have http://dictionary.reference.com/browse/partial+vacuum (even if it is very high quality) and the space is not a perfect insulator. So yes, in reality there are no 'Perfect' vacuum systems and there is a extremely small current from a random electron escaping the surface of the capacitor plate, past the space charge near that plate and being accelerated to the other side but that leakage current is not the subject of this thread.
https://www.physicsforums.com/threads/can-electrons-fly-between-capacitor-plates.798051/
 
  • #41
nsaspook said:
'Perfect' vacuum means no particles ever, anywhere in that space. So if there are particles in the space we then have http://dictionary.reference.com/browse/partial+vacuum (even if it is very high quality) and the space is not a perfect insulator. So yes, in reality there are no 'Perfect' vacuum systems and there is a extremely small current from a random electron escaping the surface of the capacitor plate, past the space charge near that plate and being accelerated to the other side but that leakage current is not the subject of this thread.
https://www.physicsforums.com/threads/can-electrons-fly-between-capacitor-plates.798051/
Thanks a lot for your answer. And I want to know further, after the dielectric material is moved out from gap, will breakdown become much easier?
 

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