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Author Topic: Silly question about capacitors  (Read 28990 times)

Farmhand

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Re: Silly question about capacitors
« Reply #30 on: February 15, 2014, 06:51:27 AM »
I fail to see how anyone could not agree that if you lower 5000 liters (kg's) of water closer to the ground you would not be lowering the (GPE) of it. Energy must be dissipated, but it
could be used partly for other purposes, exactly like the principal of the Hydro electric power generator, just one example.

As with the low loss series inductor the storing of some of the energy in the magnetic field could increase the efficiency of the transfer. Like storing momentum. Or as you like to say MileHigh "like a flywheel".  The thing is that when I transfer water and equalize rain water tanks so I can catch more water, I know I am reducing the "head" of the water in the fuller tank, but it doesn't matter because I only want the water. And the rain will refill the tanks and recharge the "head" of water for free.  ;D So it makes sense to "just do it" when the time is right, there must be a reason to do a thing or it is 100 % waste.

Cheers

Trust me, I don't pump water up high so I can let if fall under the force of gravity to use it.  ;) I catch it up high if I want to use it by gravity force.

..

MarkE

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Re: Silly question about capacitors
« Reply #31 on: February 15, 2014, 07:12:41 AM »
I fail to see how anyone could not agree that if you lower 5000 liters (kg's) of water closer to the ground you would not be lowering the (GPE) of it. Energy must be dissipated, but it
could be used partly for other purposes, exactly like the principal of the Hydro electric power generator, just one example.

As with the low loss series inductor the storing of some of the energy in the magnetic field could increase the efficiency of the transfer. Like storing momentum. Or as you like to say MileHigh "like a flywheel".  The thing is that when I transfer water and equalize rain water tanks so I can catch more water, I know I am reducing the "head" of the water in the fuller tank, but it doesn't matter because I only want the water. And the rain will refill the tanks and recharge the "head" of water for free.  ;D So it makes sense to "just do it" when the time is right, there must be a reason to do a thing or it is 100 % waste.

Cheers

Trust me, I don't pump water up high so I can let if fall under the force of gravity to use it.  ;) I catch it up high if I want to use it by gravity force.

..
Farmhand, if one wanted to extract the energy that otherwise goes to heat then one would need to devise a machine that has a highly variable impedance.  Throughout the transfer the machine needs to represent an impedance that is proportional to the difference in head between the two tanks.  At the start of the transfer, that is not too difficult as the difference is quite substantial.  Near the end of the transfer, the machine needs to present an impedance that is almost zero.  One might imagine a wide water wheel with a tapered diameter that slides along its axis, positioned by a lever connected to floats in each of the two tanks.

Farmhand

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Re: Silly question about capacitors
« Reply #32 on: February 15, 2014, 08:12:29 AM »
Farmhand, if one wanted to extract the energy that otherwise goes to heat then one would need to devise a machine that has a highly variable impedance.  Throughout the transfer the machine needs to represent an impedance that is proportional to the difference in head between the two tanks.  At the start of the transfer, that is not too difficult as the difference is quite substantial.  Near the end of the transfer, the machine needs to present an impedance that is almost zero.  One might imagine a wide water wheel with a tapered diameter that slides along its axis, positioned by a lever connected to floats in each of the two tanks.

I'm not wanting to design a machine. I'm just saying that for people to say half the energy is lost as heat and that is that is not telling the entire story I don't think.

Going back to the electrical model, how much energy is lost in the circuit I posted with a load when the switching is done so as to get good use of the inductor ? As compared to not using a load and an inductor ?

One of my points is that if there is a good reason to do it then the loss is regrettable but acceptable. If there is no good reason then it is just an experiment to show the loss of a pointless procedure. Like i said I only want the water but if I wanted to I could lower the water and cause it to do work on the way down but not much that would be worth the effort.

I made no claims, I'm simply trying to explain it in a way that people with a lesser training can understand better. Like the bricks analogy. Why make one big stack if you want two small ones anyway ?

..

A good example of Power is not Energy and Energy is not Charge ect. ect..


dieter

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Re: Silly question about capacitors
« Reply #33 on: February 15, 2014, 10:34:56 AM »
Wow, the lots of replies indicates that there is still a little bit of a paradoxon going on.


Personally I find it best to be compared to water. The deeper you get, the higher the pressure, in an exponentional amount, probably just like a cap: ^2.


Take a full waterbottle, make a pinhole near the bottom and see how the pressure is constantly reduced. Even atlhough there is more pressure-energy stored in the 8 to 16v, it can only flow to cap B until both have the same pressure.
Still having problems with the heat dissipation. Is gravity heat dissipation? Considering the need of flow from + to - (or in reverse, depending on popular naming) is just like gravity, I am not sure if you can explain gravity by heat dissipation. What is gravity anyway, as it is opposite to conservative models of centrifugal force.


As we see, we can utilize the energy flow with a load, but this will slow down the pressure equalisation. Now, does that mean we can lower the energy requirement to fill cap A to 16v when we allow more time to be "consumed"?

MarkE

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Re: Silly question about capacitors
« Reply #34 on: February 15, 2014, 12:15:30 PM »
I'm not wanting to design a machine. I'm just saying that for people to say half the energy is lost as heat and that is that is not telling the entire story I don't think.

Going back to the electrical model, how much energy is lost in the circuit I posted with a load when the switching is done so as to get good use of the inductor ? As compared to not using a load and an inductor ?

One of my points is that if there is a good reason to do it then the loss is regrettable but acceptable. If there is no good reason then it is just an experiment to show the loss of a pointless procedure. Like i said I only want the water but if I wanted to I could lower the water and cause it to do work on the way down but not much that would be worth the effort.

I made no claims, I'm simply trying to explain it in a way that people with a lesser training can understand better. Like the bricks analogy. Why make one big stack if you want two small ones anyway ?

..

A good example of Power is not Energy and Energy is not Charge ect. ect..
Farmhand you can and should answer your first question by replacing the load resistor with a capacitor of like size as the input capacitor and operating the circuit until the input capacitor depletes to 50% of its starting voltage.  For your machine more than 50% will be lost, because you will have the switching losses on top of the transfer losses.

If your intent is to retain the 50% energy, then you need a third energy store to hold that energy. 

This particular problem is one of energy, so we have to stick with accounting for energy:  beginning, middle, and end.

MarkE

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Re: Silly question about capacitors
« Reply #35 on: February 15, 2014, 12:24:29 PM »
Wow, the lots of replies indicates that there is still a little bit of a paradoxon going on.


Personally I find it best to be compared to water. The deeper you get, the higher the pressure, in an exponentional amount, probably just like a cap: ^2.


Take a full waterbottle, make a pinhole near the bottom and see how the pressure is constantly reduced. Even atlhough there is more pressure-energy stored in the 8 to 16v, it can only flow to cap B until both have the same pressure.
Still having problems with the heat dissipation. Is gravity heat dissipation? Considering the need of flow from + to - (or in reverse, depending on popular naming) is just like gravity, I am not sure if you can explain gravity by heat dissipation. What is gravity anyway, as it is opposite to conservative models of centrifugal force.


As we see, we can utilize the energy flow with a load, but this will slow down the pressure equalisation. Now, does that mean we can lower the energy requirement to fill cap A to 16v when we allow more time to be "consumed"?
The water case is like a capacitor, but the pressure does not go up exponentially, anymore than the voltage on a capacitor goes up exponentially with stored charge.  What goes up quadratically in each case is the stored energy.

Gravity is not heat dissipation.  Nor is gravity analagous to heat dissipation.  Gravity is not opposite to centrifugal force.  Gravity is an acceleration between masses.  Gravitational fields have to the best of our ability to evaluate them always behaved in a conservative manner.  Centrifugal force, is a reaction force to centripetal force.  Neither is conservative.

dieter

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Re: Silly question about capacitors
« Reply #36 on: February 15, 2014, 06:32:57 PM »
I meant conservative in the way it is seen from science, a conservative view, contrary to  to be openminded for a new view, like, we thought we are attracted by the ground, but now the new view seems to be that we are repelled from the sky.


Not sure tho if gravity is yet officially understood by science. I mean, other than Newtons apple.

MarkE

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Re: Silly question about capacitors
« Reply #37 on: February 15, 2014, 07:34:21 PM »
I meant conservative in the way it is seen from science, a conservative view, contrary to  to be openminded for a new view, like, we thought we are attracted by the ground, but now the new view seems to be that we are repelled from the sky.


Not sure tho if gravity is yet officially understood by science. I mean, other than Newtons apple.
We float ever so gently in the sky as it buoys us slightly from the earth that so strongly attracts us.

Farmhand

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Re: Silly question about capacitors
« Reply #38 on: February 16, 2014, 07:07:58 AM »
Farmhand you can and should answer your first question by replacing the load resistor with a capacitor of like size as the input capacitor and operating the circuit until the input capacitor depletes to 50% of its starting voltage.  For your machine more than 50% will be lost, because you will have the switching losses on top of the transfer losses.

If your intent is to retain the 50% energy, then you need a third energy store to hold that energy. 

This particular problem is one of energy, so we have to stick with accounting for energy:  beginning, middle, and end.

Fine by me, I was first to mention Poynt99's very good paper on the subject and in the actual post where I said there was no loss of "Charge" I was referring to the charge only as I also said that the capacitor actually stores charge and the charge was conserved. The wasting of energy by the exercise described in the first post is not contested by me.

When i said there is no loss I was referring to the charge and I never mentioned energy in that post. I don't think you are the maker of the rules as to what I can say in any given post.

The charge is conserved but the energy is lost. The fact that the energy is lost is obvious. I was merely pointing out that if done a different way it can produce less loss. A different way means a different setup.

The actual experiment described in the first post will always produce a loss of 50% of the potential energy, but the charge will be conserved. Happy.  Sheez.

..

When we release the pressure of certain pressurized gas vessels cold is produced rather than heat. True. This is the result of a loss of energy is it not ?

..

Here is the post below I think might be irking you, quoted in total.

Quote
There is no loss of "charge".

Did no one look at the "Charge" in "Coulombs", If we take 2 x 10 000 uF capacitors and we have one at 16 volts the electronics assistant tells me it has 160 Millicoulombs of charge.
Now if I was to connect the two caps together and equalize the charge which results in both having 8 volts across them then the electronics assistant tells me they will both have 80 Millicoulombs of "charge" in them so added together there is still 160 Millicoulombs of charge, so no loss.. Where is the loss. The energy in a capacitor is really only "potential energy". I think the capacitor actually stores "charge", not "energy".

The voltage increase on a capacitor has a non linear effect on the "potential energy". meaning from 0 to 8 volts is less "potential energy" than from 8 volts to 16 volts, the voltage increase is the same but the potential energy increase is not.

Cheers
..

I also stated to Tinsel that I may not have worded the post well. and my intention was to say that there is no assurance that the potential energy will be transformed into useful work at any specific rate of efficiency.

..


MarkE

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Re: Silly question about capacitors
« Reply #39 on: February 16, 2014, 07:33:04 AM »
Fine by me, I was first to mention Poynt99's very good paper on the subject and in the actual post where I said there was no loss of "Charge" I was referring to the charge only as I also said that the capacitor actually stores charge and the charge was conserved. The wasting of energy by the exercise described in the first post is not contested by me.

When i said there is no loss I was referring to the charge and I never mentioned energy in that post. I don't think you are the maker of the rules as to what I can say in any given post.

The charge is conserved but the energy is lost. The fact that the energy is lost is obvious. I was merely pointing out that if done a different way it can produce less loss. A different way means a different setup.

The actual experiment described in the first post will always produce a loss of 50% of the potential energy, but the charge will be conserved. Happy.  Sheez.

..

When we release the pressure of certain pressurized gas vessels cold is produced rather than heat. True. This is the result of a loss of energy is it not ?

..

Here is the post below I think might be irking you, quoted in total.
..

I also stated to Tinsel that I may not have worded the post well. and my intention was to say that there is no assurance that the potential energy will be transformed into useful work at any specific rate of efficiency.

..
I haven't seen anyone contest the conservation of charge.  The only issue to cover is whether and if so how to avoid the energy loss.  As you pointed out the energy loss appears in the resistance.  If one can make the resistance a reflection of a useful load, then the internal 50% energy loss is mitigated by some amount of useful external work done.

forest

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Re: Silly question about capacitors
« Reply #40 on: February 16, 2014, 10:09:53 AM »
what about the change of two charged capacitor connection from parallel to series ? how law of conservation of charge apply to that situation ?

dieter

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Re: Silly question about capacitors
« Reply #41 on: February 16, 2014, 10:16:32 AM »
But Resistance in series adds up to more resistance and therefor more loss, isn't it?


I'm back at square one, heat dissipation is no explanation to me. If there was really more "pressure" in the 8 to 16 volts, then the 2 caps simply should be equalized at 16- ((sqr(16)/2)^2)=12 volts. Because the electricity does not jump across the room and run away, nor have I ever seen a cap getting excessively hot simply by charging and uncharging it within its supposed specs.


You may call me silly , hence silly questions, but the paradoxon is yet unexplained to me. I'd rather see there are many paradoxons in established sience that are always "talked to death" in the sense of "science knows everything". No offence tho. Maybe I'm just not getting it.

dieter

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Re: Silly question about capacitors
« Reply #42 on: February 16, 2014, 10:23:22 AM »
forest, actually the initial experiment is in series, even a loop in series. Of course, the cap must have polarity, like electrolytics do have, otherwise it would be parallel and serial in the same time. (in this little 2 caps experiment
Or did I misunderstand your question?

MarkE

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Re: Silly question about capacitors
« Reply #43 on: February 16, 2014, 10:29:00 AM »
what about the change of two charged capacitor connection from parallel to series ? how law of conservation of charge apply to that situation ?
Charging up one capacitor with capacitance C and then connecting it in series with another discharged capacitor with the same capacitance C has the same effect on energy loss as the situation in the OP.  And as Dieter pointed-out once the switch is closed the two parallel capacitors are in series in the loop.

MarkE

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Re: Silly question about capacitors
« Reply #44 on: February 16, 2014, 10:34:18 AM »
But Resistance in series adds up to more resistance and therefor more loss, isn't it?


I'm back at square one, heat dissipation is no explanation to me. If there was really more "pressure" in the 8 to 16 volts, then the 2 caps simply should be equalized at 16- ((sqr(16)/2)^2)=12 volts. Because the electricity does not jump across the room and run away, nor have I ever seen a cap getting excessively hot simply by charging and uncharging it within its supposed specs.


You may call me silly , hence silly questions, but the paradoxon is yet unexplained to me. I'd rather see there are many paradoxons in established sience that are always "talked to death" in the sense of "science knows everything". No offence tho. Maybe I'm just not getting it.
What increasing the resistance does is increase the amount of time that it takes to transfer the charge.  It does not change the percentage of energy lost transferring the charge.
If you want to see capacitors get hot doing this we can set up an experiment that will heat them nicely by choice of capacitor and the test circuit.  Ceramic and film capacitors can handle very high ripple currents. Electrolytic and double layer capacitors are a different story.  Ripple current ratings and limiting internal heating of electrolytic capacitors is an important aspect of power converter design in converters that use electrolytics.