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Veritasium "How Electricity Actually Works"

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SandyCox:

--- Quote from: electrodacus on May 08, 2022, 06:19:42 pm ---
--- Quote from: SandyCox on May 08, 2022, 06:09:30 pm ---Look at section 1.5 of Haus and Melcher.

--- End quote ---

??? Never heard of them before now and likely for a good reason.

People seems to confuse charge with energy.
Energy is the one that can not be created or destroyed just converted from one form to another.

--- End quote ---

https://web.mit.edu/6.013_book/www/

One of the best books on Electromagnetics.

electrodacus:

--- Quote from: SandyCox on May 08, 2022, 06:22:19 pm ---https://web.mit.edu/6.013_book/www/

One of the best books on Electromagnetics.

--- End quote ---

Is either that you misinterpreted what you read in the book or the book is just not as good as you say.
For a single capacitor that say it is charged so there is an imbalance of electrons on the two plates. What do you think it will happen with charge if you change the size of the plates?

I guess you realized that Q=C*V and Ec=0.5 * C * V2  are both true and nobody ever disproved the conservation of energy so it seems clear that charge will not be conserved in this example.

Q = 3C at the beginning and for case where there is no resistance so no energy lost as heat end will be Q = 4.242C
It just happens that due to the perfect symmetry of the two identical capacitors you end up with half of the energy lost as heat and so charge is conserved but this is just thanks to sysmentry you can call this a coincidence.
Try to calculate for two capacitors that are not identical and see then what you will get even with resistance and heat loss. You will be surprised. 


I guess those two are professors at MIT and same as the other professor at University of California Alex have a poor understanding of energy storage.
Alex kusenko knew that energy conservation can not be broken yet he lost due to his ability to understand energy storage.
He knew Derek was wrong he was just unable to understand himself how vehicle works thus he lost the bet.
I try to explain this first as it is simpler to explain than the "faster than wind direct down wind vehicle" but there the exact same issue exist and that is understanding what energy is.

T3sl4co1l:

--- Quote from: electrodacus on May 08, 2022, 03:52:02 pm ---While yes there will be some bounce both in the experiment with resistance and the one with superconductors the speed of electron wave is finite and there will be reflexions at the open ends so voltage will stabilize and not forever slush around as you imagine as reflected waves will interact and in time cancel each other.

--- End quote ---

Consequent does not match the antecedent.

Think: if you didn't know a damn thing about waves, you just heard someone say, "this thing is reflective therefore energy is absorbed", would you be not the least bit concerned?

The definition of something being reflective, is that it does not absorb energy, at least not predominantly so.

Indeed, some very excellent mirrors can be constructed, whether using superconductors (at radio frequencies), or stacks of dielectrics (at optical frequencies).

If the mirrors are indeed perfect, where pray tell is the energy going to go?

Indeed it is exactly the reflection which causes it to oscillate.  If the energy could be absorbed, it would, but there is insufficient resistance in the circuit to absorb it, at least before it's reflected around a few times.  There is a direct equivalence between a lumped-equivalent circuit (like the present CLC network) and a transmission line construction, and further to a full-fields (mirrors and light beams) model, assuming of course the geometry keeps the waves confined.  So it is perfectly consistent to say that energy is reflecting in this network, and that it is precisely that reflection, at each end, that causes the energy to "slosh" back and forth.

Tim

T3sl4co1l:

--- Quote from: electrodacus on May 08, 2022, 06:43:46 pm ---Is either that you misinterpreted what you read in the book or the book is just not as good as you say.
For a single capacitor that say it is charged so there is an imbalance of electrons on the two plates. What do you think it will happen with charge if you change the size of the plates?

I guess you realized that Q=C*V and Ec=0.5 * C * V2  are both true and nobody ever disproved the conservation of energy so it seems clear that charge will not be conserved in this example.

--- End quote ---

Pray tell, how much force is required to "change the size of the plates"?

Also, what meaning does "change size" have?  Surely you aren't changing just one, that accomplishes [almost] nothing.

But I would be inclined to understand this as "separation of plates", which is perfectly meaningful, a standard experiment.

And indeed, if there is a force, and changing the separation of the plates implies a change in distance... then does that not also imply.......? ;)



--- Quote ---I guess those two are professors at MIT and same as the other professor at University of California Alex have a poor understanding of energy storage.

--- End quote ---

:-DD

Tim

electrodacus:

--- Quote from: T3sl4co1l on May 08, 2022, 06:54:45 pm ---Consequent does not match the antecedent.

Think: if you didn't know a damn thing about waves, you just heard someone say, "this thing is reflective therefore energy is absorbed", would you be not the least bit concerned?

The definition of something being reflective, is that it does not absorb energy, at least not predominantly so.

Indeed, some very excellent mirrors can be constructed, whether using superconductors (at radio frequencies), or stacks of dielectrics (at optical frequencies).

If the mirrors are indeed perfect, where pray tell is the energy going to go?

Indeed it is exactly the reflection which causes it to oscillate.  If the energy could be absorbed, it would, but there is insufficient resistance in the circuit to absorb it, at least before it's reflected around a few times.  There is a direct equivalence between a lumped-equivalent circuit (like the present CLC network) and a transmission line construction, and further to a full-fields (mirrors and light beams) model, assuming of course the geometry keeps the waves confined.  So it is perfectly consistent to say that energy is reflecting in this network, and that it is precisely that reflection, at each end, that causes the energy to "slosh" back and forth.

Tim

--- End quote ---

There is not just a single wave that moves from one side to the other. and they interact with each other.
Not sure why we discus so much the ideal superconductor when you can get very similar result by just adding an inductor as intermediary energy storage to move the energy from one capacitor to another. 

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