Electrostatic charge and law of conservation of energy

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Vanadium 50 said:
Whoa...whoa...whoa!

This is starting to sound less and less like a request for knowledge and more and more like a defense of a perpetual motion machine. Please note that this is a closed topic.
That theory was made by me in an attempt to understand what's going on...but it failed to explain things.

The simplified version of the machine is the capacitor arrangement which I'm discussing with born2bwire.

Ok, I'll have a look at the image charge method.
 
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It should be noted that if you're checking someone for a certain type of behavior (for e.g trolling), then considering you are not a professional psychologist, you will be able to see that person exhibiting the behavior even if he/she actually does or not exhibit it.

Same is the case here, you're scrutinizing my every post and trying to see if I'm forcing my points...and you will actually conclude that even if I actually have not.

Since I really don't have a say in PF, you're free to lock the thread, and I'm free to have my opinion of PF.
 
  • #28
Dale
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Please examine the link I posted very carefully:
http://farside.ph.utexas.edu/teaching/em/lectures/node89.html

The derivation is not terribly complicated and the beauty is that once you have understood it you realize that the details of the specific scenario are completely irrelevant. If your analysis violates the conservation of energy then it necessarily also violates Maxwell's equations. The details are not important and only serve to confuse you.

In your case your misunderstanding of EM appears to be two-fold, first you did not understand the relationship between voltage, current, and power, although I believe that you understand that now. Second, you seemed to understand the idea of resistive drag, but misunderstood that it always opposes the motion.
 
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Please examine the link I posted very carefully:
http://farside.ph.utexas.edu/teaching/em/lectures/node89.html

The derivation is not terribly complicated and the beauty is that once you have understood it you realize that the details of the specific scenario are completely irrelevant. If your analysis violates the conservation of energy then it necessarily also violates Maxwell's equations. The details are not important and only serve to confuse you.

In your case your misunderstanding of EM appears to be two-fold, first you did not understand the relationship between voltage, current, and power, although I believe that you understand that now. Second, you seemed to understand the idea of resistive drag, but misunderstood that it always opposes the motion.
I really do not understand vector calculus...so I think I should drop the subject now and come back after learning a bit more...like the mathematics involved and Maxwell's equation. It will take time since science is not my subject anymore, and I have lots of other things to do. Furthermore I have lots of doubts remaining in electrostatics, and I need to clear them (for e.g. how can we say that under any conditions metals cannot have a charge).

As of the very fundamental principle of field an point charges; how can we ensure that a field coupled with a handful of charges cannot defy this laws...you have given the link to that, I understand but there are lots of ways the field and lots of point charges can be arranged and I've not seen a proof that ensures that there's no way to make these 2 components work against the law of conservation of energy (if that link is not a proof).

One such arrangement is a typical metallic plate in a field. A field has the ability to pull the electrons in a metal forward, exposing a positive charge on the other sides of the metal...no doubt the field does work to pull the electrons but again there is an exposed positive charge that too can do work...it generates a field of it's own, or actually the original field is propagating through this exposed positive charge...if we have such infinite identical plates lined along their area vectors, each field generated though the exposed positive of the plate will do work to pull the electron in it's nearby plate...work is being done by the original patch of field many times.
 
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Vanadium 50
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I really do not understand vector calculus...
how can we ensure that a field coupled with a handful of charges cannot defy this laws...you have given the link to that, I understand but there are lots of ways the field and lots of point charges can be arranged and I've not seen a proof that ensures that there's no way to make these 2 components work against the law of conservation of energy (if that link is not a proof).
Look at those two quotes together. You seem to be saying that because you don't understand the proof, you think it's invalid. That's not a very strong argument.
 
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Look at those two quotes together. You seem to be saying that because you don't understand the proof, you think it's invalid. That's not a very strong argument.
Yes, that's why I said I'll come back after understanding them...apparently there are a few things I need to learn -

1) Image charge method.
2) Vector calculus
3) Maxwell's equation
4) Those derivations.
 
  • #32
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there are lots of ways the field and lots of point charges can be arranged and I've not seen a proof that ensures that there's no way to make these 2 components work against the law of conservation of energy (if that link is not a proof).
The link is exactly such a proof. Note that it is general and makes no assumptions about the specifics of the charge or current distribution. Therefore it applies for any arbitrary arrangement.
 
  • #33
Born2bwire
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I apologize for the misunderstanding, A already had a charge.



Why will I have to move it? Suppose A has been given a positive charge, then that will automatically develop a positive charge on the back side of B...which if earthed will make a current flow which will do work.

I think I'm getting close to understanding this, thanks...with such effort, I will hopefully, understand.



No no, again sorry for the misunderstanding, A was previously charged.



Yes, I agree with that. But the charge stored in A does have a limit of it's energy...I mean there is some limited amount of energy in it that can be harvested...that is x...but we get back 3x doing the procedures...it should have been x.

I know this is an argument, that's why I also posted the machine...the red plate there is A, and it has to be charged only one.



If the infinite conductor is not grounded, then work will not be done on doing so...this is the actual case (art. Actual case)
A is can never be "previously charged." To charge up A you have to do work. If you consider A to be charged without any energy investment then no wonder you have difficulty keeping track of the energy of the system. Whether I have B connected to ground while I charge up A or if I connect B to the ground after I charge up A is immaterial, it is the same physics in the end. However, you keep on insisting to do this in a manner that is far more convoluted than it need be. As far as I am concerned, my previous post should contain all the general physics to describe your problem. The only caveat is the energy I quoted for case three. Obviously that is a bit sleight of hand but it is also obvious that if we place a load between B and the ground that extracts X amount of energy per unit of charge, then we would similarly modify the change in energy in part 2 by the amount qX.
 

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