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Veritasium "How Electricity Actually Works"
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hamster_nz:

--- Quote from: electrodacus on May 02, 2022, 01:17:51 am ---
--- Quote from: hamster_nz on May 02, 2022, 01:07:32 am ---You say "There is no electric field before closing the switch". I don't think this is true. Here is the same diagram with two negative charges electrons sitting between the plates of your capacitor(s). What way do they move? and why do they move, and what provides the energy for them to move?


  ________________ common plate
  +  +  +  +  +  +  +

     -                 -

  _______/  ________
  -----------

Also the positive charges are way too close together. Their mutual repulsion will cause them to spread out over the plate pretty much uniformly.

Also the unconnected wire will have potentials at either end, as one end is closer to a large static charge.

--- End quote ---

That is incorrect and I noticed the same wrong explanation in Derek's video. The electrons and holes will be equal and they will extend just up to the switch even on the common plate.
Only after the switch is closed electrons and holes will move symmetrically on top and bottom plate.
Keep in mind the drawing is nowhere near to scale. There may be just 0.1mm between plates and plates may be a few meters long for the charged capacitor and then for the discharged capacitor that represents the transmission line the distance between plates may be order of magnitude higher but even if the same 0.1mm there charge will end at the switch both on top and bottom plates.

--- End quote ---
Lol - if that is the case, when you close the switch, what makes the electrons move across the switch? It seems you are saying that they are quite happy being all bunched up in a huddle on the left...

You never did say what happens to the two charges floating in the middle of the capacitor (assuming they are free to move if they have any force on them).
electrodacus:

--- Quote from: hamster_nz on May 02, 2022, 01:27:50 am ---Lol - if that is the case, when you close the switch, what makes the electrons move across the switch? It seems you are saying that they are quite happy being all bunched up in a huddle on the left...

You never did say what happens to the two charges floating in the middle of the capacitor (assuming they are free to move if they have any force on them).

--- End quote ---

Yes that is exactly what I'm saying and I'm fairly sure that I'm correct. They will move across the switch when switch is closed and symmetrically on the top plate.
After the right side is charged they will be also uniformly distributed across the entire new capacitor that has now higher capacity.
This is assuming that distance between plates is the same on the left side and right side else if say on the right side the distance between plates is larger (lower capacity) there will be proportionally less electrons on that side.
hamster_nz:

--- Quote from: electrodacus on May 02, 2022, 01:33:25 am ---
--- Quote from: hamster_nz on May 02, 2022, 01:27:50 am ---Lol - if that is the case, when you close the switch, what makes the electrons move across the switch? It seems you are saying that they are quite happy being all bunched up in a huddle on the left...

You never did say what happens to the two charges floating in the middle of the capacitor (assuming they are free to move if they have any force on them).

--- End quote ---

Yes that is exactly what I'm saying and I'm fairly sure that I'm correct. They will move across the switch when switch is closed and symmetrically on the top plate.
After the right side is charged they will be also uniformly distributed across the entire new capacitor that has now higher capacity.
This is assuming that distance between plates is the same on the left side and right side else if say on the right side the distance between plates is larger (lower capacity) there will be proportionally less electrons on that side.

--- End quote ---

No, the charges floating in the middle between the plates - the extra '-' signs... I'll go back to your original diagram, so I'm not changing two things at once.

 ________________ common plate
 +++++++

     -                 -   << These guys which way do the move and why.

  _______/  ________
  -----------

If they are free to move, which way to they go and why?
electrodacus:

--- Quote from: hamster_nz on May 02, 2022, 01:40:08 am ---
No, the charges floating in the middle between the plates - the extra '-' signs... I'll go back to your original diagram, so I'm not changing two things at once.

 ________________ common plate
 +++++++

     -                 -   << These guys which way do the move and why.

  _______/  ________
  -----------

If they are free to move, which way to they go and why?

--- End quote ---

Not sure why you had to draw those ones as they are already on the diagram. And yes they are incorrectly drawn under the bottom plate (limitations of this CAD tool :) ).

The ++++ and ------ symbols in my diagram represents holes and electrons in the plates/wires as that is what is of interest in this discussion.
They will move when switch is closed and they will move symmetrically on the top and bottom plate's.

To maybe help you understand that there is symmetry between the charges on the top and bottom plate imagine there is also a switch on the top plate exactly above the one on the bottom and now thing what will happen if you start with both switches open and only close the top one.
Do you think there will be any current trough that closed top switch ? If not that means charges remain arranged the same as they where before you closed that switch.
hamster_nz:

--- Quote from: electrodacus on May 02, 2022, 02:24:46 am ---
--- Quote from: hamster_nz on May 02, 2022, 01:40:08 am ---
No, the charges floating in the middle between the plates - the extra '-' signs... I'll go back to your original diagram, so I'm not changing two things at once.

 ________________ common plate
 +++++++

     -                 -   << These guys which way do the move and why.

  _______/  ________
  -----------

If they are free to move, which way to they go and why?

--- End quote ---

Not sure why you had to draw those ones as they are already on the diagram. And yes they are incorrectly drawn under the bottom plate (limitations of this CAD tool :) ).

The ++++ and ------ symbols in my diagram represents holes and electrons in the plates/wires as that is what is of interest in this discussion.
They will move when switch is closed and they will move symmetrically on the top and bottom plate's.

To maybe help you understand that there is symmetry between the charges on the top and bottom plate imagine there is also a switch on the top plate exactly above the one on the bottom and now thing what will happen if you start with both switches open and only close the top one.
Do you think there will be any current trough that closed top switch ? If not that means charges remain arranged the same as they where before you closed that switch.

--- End quote ---
They will not move symmetrically, because there is no symmetry to begin with.

Electrostatics is relatively easy so I wrote a quick solver for distribution of 50 + charges and 50 - charges on 10m and 5m wires one 1m apart. (so a 10:1 aspect ratio).

You can make what you want of this, but the net horizontal force on each charge (other than those at the ends of the 'wires', where they are constrained) is zero.
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