Are capacitors a viable option for storing charge in electronic circuits?

[Ratch]

sophiecentaur,

The Charge that is 'in' a capacitor can be made to flow around a circuit - the same as the Ahr that are 'in' battery.

Yes, and the amount of charge expelled from the capacitor equals the amount of charge taken in, for a net change of zero. The amp-hour rating of a battery determines how much charge can be pumped around the circuit, not how much charge is in a battery.

Your obsession with this issue is spoiling the credibility of your otherwise good ideas, I feel.

My obsession with the correct description in no way spoils the credibility of my statements. How can it?

Ratch

 

[jim hardy]

Perhaps you're coming from the world of electrostatics where net charge has significance.

But in electric circuits(electrodynamics) the phrase is "Charge a capacitor " .
http://micro.magnet.fsu.edu/electromag/electricity/capacitance.html

My 1901 Electric Machinery book describes "charging a condenser" not energizing it.

My high school electronics textbooks used "charge" as did my Freshman physics text, Sears and Zemansky.

10.Ben Franklin's "single fluid theory" showed that a given body possessing a normal amount of electric fluid was called neutral. During the process of charging, the fluid was transferred from one body to the other; the body with the deficiency being charged minus and the body with the excess charged plus . But no fluid is lost.
Ben's "single fluid theory" led to the electron theory in 1900: electrons move about conductors much as a fluid might move. Nobel Prize winner and physicist, Robert A. Millikan, called Ben's experiment that led to this theory "probably the most fundamental thing ever done in the field of electricity".


11.Ben Franklin had to invent electricity terminology as he went along in his experiments. A scholar who traced Ben's vocabulary found at least twenty-five electrical terms which he was the first to use: examples -- armature, battery, brush, charged, condense, conductor, plus and minus, positively and negatively .

http://www.franklinbusybody.com/facts.asp

Ben also redesigned the Leyden jar as today's flat plate capacitor.

You're trying to rewrite history.

 

[sophiecentaur]

sophiecentaur,



Yes, and the amount of charge expelled from the capacitor equals the amount of charge taken in, for a net change of zero. The amp-hour rating of a battery determines how much charge can be pumped around the circuit, not how much charge is in a battery.



My obsession with the correct description in no way spoils the credibility of my statements. How can it?

Ratch

You have managed to conflate two things here. Whether we talk of Energy of Charge is entirely a matter of which suits the particular circumstance more. For instance, the energy in two capacitors doesn't give you any clue as to which direction the power will flow if they are connected. PD would be appropriate there. If you were designing a filter then charge / current are the relevant quantities. If you are making an electronic flash gun, it's the Energy stored that counts. Your choice of description would be totally acceptable in some circumstances but not all.

The issue of 'no charge on a capacitor' is a separate thing altogether. If you would accept that one 'charges' the ball on a Van Der Graaff generator then that must hold for any other form of capacitor. There are no extra charges available on the Earth when you 'charge a sphere' and there are none when you charge a 1μF capacitor. When one lead of a capacitor is connected to Earth, the situation is exactly the same. As Jim says, you are trying to re-write history. You have as much chance of doing that as changing the sign of charge on electrons so that the 'current direction' thing doesn't confuse students.

 

[Runei]

In regards to the battery versus capacitor question, another extremely important point is that the if the capacitor is used to power some kind of network, the voltage it supplies will drop as a decaying exponential. So the voltage will drop rather quickly.

A battery, however, is designed to deliver an almost constant voltage, even though it is half empty or fully charged. This property of the battery makes it superior to a capacitor for powering circuits, as the voltage in most applications needs to be constant. A capacitor cannot do this.

Capacitors are very important in circuits.

The three main uses of capacitors, I would say, are:

1. Power supply stabilization - You use them to remove noise on the powersupply and protect against voltage spikes.

2. Filters - Highpass, Bandpass, Lowpass, Bandstop. All these filters are used in analog signal processing in communications systems to look at the frequencies containing all the information.

3. Coupling capacitors - In amplifiers, the capacitors are used to block a DC signal and only allow the AC signal to pass. The bigger the capacitor, the lower frequencies can be passed without distortion.

 

[mheslep]

wow. Is there a reason why all the capacitor tanks have low voltage (sub 9V)?

The material & methods used for making the new super caps have a fairly low voltage breakdown, so far. The manufacturers recognize this so many of them offer pre-assembled higher voltage series capacitor arrays and associated circuitry.

http://www.tecategroup.com/store/index.php?main_page=product_info&products_id=1298&gclid=CK6P24fTsLQCFQyk4AodLAUAsw

 

[Ratch]

jim hardy,

Perhaps you're coming from the world of electrostatics where net charge has significance.

Physics is the same everywhere.

But in electric circuits(electrodynamics) the phrase is "Charge a capacitor " .
http://micro.magnet.fsu.edu/electrom...pacitance.html

The first two sentences of that line say, "Capacitance is the property of an electric conductor that characterizes its ability to store an electric charge. An electronic device called a capacitor is designed to provide capacitance in an electric circuit by providing a means for storing energy in an electric field between two conducting bodies."

First it says capacitance is the ability to store charge, and then it says it is the ability to store energy. Well, it certainly stores energy, but a cap does not store charge for the reason I already gave many times. Shifting electrons from one place to another is not "charging".

My 1901 Electric Machinery book describes "charging a condenser" not energizing it.

My high school electronics textbooks used "charge" as did my Freshman physics text, Sears and Zemansky.

Lots of textual material and people call energizing a capacitor as charging it. A consensus of errors does not make it correct.

http://www.franklinbusybody.com/facts.asp

Ben also redesigned the Leyden jar as today's flat plate capacitor.

Bully for Ben. I don't deny that he was a smart, clever, and inventive man. But his fluid theory of electron motion leaves much to be desired. Fluids are not easily compressible, whereas electrons can be crowded together. Fluids have pressure, whereas electrons do not. Fluids do not have a polarity, whereas electrons do. Fluids are governed by hydraulic principles, whereas electrons are governed by quantum principles. Would you call a battery's voltage a pressure?

You're trying to rewrite history.

Nonsense, correcting a falsehood is not rewriting history.

Ratch

 

[jim hardy]

Would you call a battery's voltage a pressure?

If you read British textbooks as recent as 1960's you'll see they use the term "Pressure" instead of voltage, so in some circles yes. Tubes were called valves over there too.

Can you provide a scholarly reference for your assertion?

Go ahead, the last word is yours.

Adieu to you and Rocinante .

 

[OmCheeto]

... Fluids are not easily compressible...

You can blame this correction on Russ Waters if you like.

In physics, a fluid is a substance that continually deforms (flows) under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids.

I subscribed to this thread to add my infinite knowledge of capacitors. But seeing the high quality of knowledgeable posts*, I deemed my input unnecessary.

---------------------------------
*you know who you are. ;)

 

[Ratch]

sophiecentaur,

You have managed to conflate two things here. Whether we talk of Energy of Charge is entirely a matter of which suits the particular circumstance more. For instance, the energy in two capacitors doesn't give you any clue as to which direction the power will flow if they are connected. PD would be appropriate there. If you were designing a filter then charge / current are the relevant quantities. If you are making an electronic flash gun, it's the Energy stored that counts. Your choice of description would be totally acceptable in some circumstances but not all.

I don't understand what you mean. If you know the energy of a cap and its capacitance, then you know its voltage or the charge difference between its plates. What more do you need?

The issue of 'no charge on a capacitor' is a separate thing altogether. If you would accept that one 'charges' the ball on a Van Der Graaff generator then that must hold for any other form of capacitor. There are no extra charges available on the Earth when you 'charge a sphere' and there are none when you charge a 1μF capacitor. When one lead of a capacitor is connected to Earth, the situation is exactly the same. As Jim says, you are trying to re-write history. You have as much chance of doing that as changing the sign of charge on electrons so that the 'current direction' thing doesn't confuse students.

A Van De Graff is not a capacitor. It is a high voltage generator which separates charge by induction rather than the conduction method of a battery and capacitor. You can talk all you want about providing a conduction path between the separated charges of the ball and ground, but charges are not created or destroyed.

I am not trying to rewrite history, I am trying to correct misleading and false jargon. If everyone decided to call a electron positive, then ions and holes would have the "wrong" charge.

Ratch

 

[Ratch]

jim hardy,

If you read British textbooks as recent as 1960's you'll see they use the term "Pressure" instead of voltage, so in some circles yes. Tubes were called valves over there too.

Yes, I have also come across the words "tension" and "EMF", whatever that means. I don't care how scholarly the article is, if they equate pascals to volts, then they need to be corrected. I think valves are a better description than tubes. Valves describe the function, whereas tubes describe the shape of the electrical component.

Can you provide a scholarly reference for your assertion?

I know of no scholarly article on common sense.

Ratch

 

[Drakkith]

Capacitors may or may not store charge depending on what you mean by "storing charge". It just depends on your point of view. Seeing as how each plate has a buildup of one type of charge I personally see no problem saying they do in fact store charge.

 

[sophiecentaur]

sophiecentaur,



I don't understand what you mean. If you know the energy of a cap and its capacitance, then you know its voltage or the charge difference between its plates. What more do you need?



A Van De Graff is not a capacitor. It is a high voltage generator which separates charge by induction rather than the conduction method of a battery and capacitor. You can talk all you want about providing a conduction path between the separated charges of the ball and ground, but charges are not created or destroyed.

I am not trying to rewrite history, I am trying to correct misleading and false jargon. If everyone decided to call a electron positive, then ions and holes would have the "wrong" charge.

Ratch

Q=CV
and E=CV²/2
Are written in a totally arbitrary form and can be re-arranged in any way you choose. They say nothing about the relative significances of the quantities involved. That is just in your head.

The reason that a VDG generator works is that the sphere has Capacitance wrt Earth and a charge builds up on it. No sphere, no build up of charge. And where does this charge come from? By displacing an equal and opposite amount of charge to earth. You could charge a paper capacitor in a similar way, with a rolling belt but the voltage you could achieve would be much less - that's the only difference. You clearly don't want to accept anything that goes against your argument about no charge being stored but, as Jim says, there are very very few instances where a charge is built up on something without a similar opposite charge ending up somewhere else. Can you think of one? An Ion Drive, perhaps?

I don;t think you can know what "conflating" means - I mean that the Charge on a capacitor and the Charging vs Energising argument are totally different issues and you are treating them as one.

Just reiterating that you are somehow right about the Energise thing gets you nowhere. The only references you have given have been non-learned web pages which have been associated, mainly with Power Engineering situations.
You clearly didn't catch on to what I was getting at but every student I have ever talked to would have understood immediately what I am referring to and I think all other readers would, too.

I know of no scholarly article on common sense.

That's no argument at all. Science is not "common sense". Much more is needed than common sense. Common sense tells us that things fall to the ground (no Science there). It tells us that "Nature abhors a vacuum" (common 'experience' but no explanation of what's happening).

If Einstein had ended his paper on Special Relativity with the argument that it's "common sense", people would have laughted because that is the last thing it is. If you don't want to relate what you write to scholarly articles then you are wasting your time on PF. Read the guidelines. It is one of the strong points of PF that we don't hold forth about unsupported theories.

 

[Ratch]

Drakkith,

Capacitors may or may not store charge depending on what you mean by "storing charge". It just depends on your point of view.

I explained many times that capacitors do not store a net charge. They only shift the charge from one plate to another. That shift of charge either takes or gives energy. Shifting a charge is not "charging", it is energizing.

Seeing as how each plate has a buildup of one type of charge I personally see no problem saying they do in fact store charge.

The opposite plate has a depletion of charge, so it could just as well be called "discharging". Therefore, the description is vague and ambiguous. Only energizing describes exactly what is going on.

Ratch

 

[Drakkith]

Drakkith,
I explained many times that capacitors do not store a net charge. They only shift the charge from one plate to another. That shift of charge either takes or gives energy. Shifting a charge is not "charging", it is energizing.

I disagree. Each plate has charged being moved onto/off of it. AKA charging.

The opposite plate has a depletion of charge, so it could just as well be called "discharging". Therefore, the description is vague and ambiguous. Only energizing describes exactly what is going on.

Ratch

Net charge builds up on each plate through the movement of charges. I'd say "charging" is fine. That's the final thing I'll say on it, as it's not on topic and it's all personal opinion anyways.

 

[Ratch]

sophiecentaur,

Q=CV
and E=CV2/2
Are written in a totally arbitrary form and can be re-arranged in any way you choose. They say nothing about the relative significances of the quantities involved. That is just in your head.

Those formulas say everything about the quantitative significances of the quantities involved.

The reason that a VDG generator works is that the sphere has Capacitance wrt Earth and a charge builds up on it. No sphere, no build up of charge. And where does this charge come from? By displacing an equal and opposite amount of charge to earth. You could charge a paper capacitor in a similar way, with a rolling belt but the voltage you could achieve would be much less - that's the only difference. You clearly don't want to accept anything that goes against your argument about no charge being stored but, as Jim says, there are very very few instances where a charge is built up on something without a similar opposite charge ending up somewhere else. Can you think of one? An Ion Drive, perhaps?

I keep repeating that I said the net charge does not change. If a charge builds up in one place and an opposite charge builds up in another place, then the net charge is zero, isn't it?

I don;t think you can know what "conflating" means - I mean that the Charge on a capacitor and the Charging vs Energising argument are totally different issues and you are treating them as one.

Yes, I do know what conflate means. If I did not, I could look it up in a dictionary. They are not totally different. The first above is what the charge separation is, and the second is how it got that way. So what is the point?

Just reiterating that you are somehow right about the Energise thing gets you nowhere. The only references you have given have been non-learned web pages which have been associated, mainly with Power Engineering situations.
You clearly didn't catch on to what I was getting at but every student I have ever talked to would have understood immediately what I am referring to and I think all other readers would, too.

I never said that describing a capacitor as being energized doesn't get you anywhere. Energizing is correct no matter what the application of a capacitor is.

That's no argument at all.

It is not an argument, it is a statement of fact.

Science is not "common sense". Much more is needed than common sense.

No one said common sense was everything in science.

Common sense tells us that things fall to the ground (no Science there). It tells us that "Nature abhors a vacuum" (common 'experience' but no explanation of what's happening).

Common sense does not tell us those two things. Those are observable phenomena. Common sense is how one arranges and relates facts into a coherent principle.

If Einstein had ended his paper on Special Relativity with the argument that it's "common sense", people would have laughted because that is the last thing it is. If you don't want to relate what you write to scholarly articles then you are wasting your time on PF. Read the guidelines. It is one of the strong points of PF that we don't hold forth about unsupported theories.

Not unless Einstein showed how common sense applied to his theories, which he did mathematically and descriptively. But I did not propose a theory, I proposed a change in nomenclature, and explained why it was better. So far, no one has shown it to be wrong. I only see vague statements from detractors like "everyone says it the old <wrong> way", or "that is what they said <wrongly> in the beginning".

 

[Ratch]

Drakkith,

I disagree. Each plate has charged being moved onto/off of it. AKA charging.

No, it is AKA "changing". One plate is being charged, and the opposite plate is being discharged. Both operations have the same importance and value. So, as I asked before, are you going to call it "charging" or "discharging"; and if you pick one over the other, what is your reason?

Net charge builds up on each plate through the movement of charges. I'd say "charging" is fine. That's the final thing I'll say on it, as it's not on topic and it's all personal opinion anyways.

No, net charge is the total of the two plates, not a single plate. Why is "charging" better than the other plate "discharging". Surely, you will agree that "energizing" describes it unambigiously.

Ratch

 

[Drakkith]

Surely, you will agree that "energizing" describes it unambigiously.

Ratch

I think charging describes it unambiguously once you understand how a capacitor works, so I see no issue here.

 

[Ratch]

Drakkith,

I think charging describes it unambiguously once you understand how a capacitor works, so I see no issue here.

Well, I think I know how a capacitor works as well as anyone, and I explained why there is an ambiguity in meaning. Won't you show me where I am wrong about that? Just making a proclamation without explanation in not meaningful.

Ratch

 

[Drakkith]

Drakkith,



Well, I think I know how a capacitor works as well as anyone, and I explained why there is an ambiguity in meaning. Won't you show me where I am wrong about that? Just making a proclamation without explanation in not meaningful.

Ratch

You aren't wrong. This isn't about wrong or right, but about personal opinion.

 

[Greg-ulate]

Ratch,

Everyone says Charge interchangeably with Energize in the context of batteries and capacitors... I bet you say "Hey where is my battery charger?" when you need to "Energize" the batteries in your phone or whatever.

Nobody says "I have a capacitor C net charged to V volts and therefore it stores CV^2/2 Joules of energy," so your argument is basically a Straw Man argument. Just because the net charge doesn't change, that doesn't make it wrong to say charged. Current flows out of one leg and into the other, one plate becomes charged with respect to the other plate. Then it stays there. It's stored there. Capacitors store charge.

I noticed that you have argued this point in other instances and while it is technically correct, and everything else you have to say is astute and meaningful in the context of the conversation, arguing this point is not constructive.

 

[Greg-ulate]

Surely, you will agree that "energizing" describes it unambigiously.

Ratch

Firing a capacitor out of a cannon would also energize it, so its not any less ambiguous than saying charge.

 

[sophiecentaur]

We are all aware of this and the term " charge" incorporates this knowledge. Just what is your point? Do you seriously expect to change this established terminology? Don't hold your breath.

 

[Ratch]

Drakkith,

You aren't wrong.

Thank you. I wanted to see that.

This isn't about wrong or right, but about personal opinion.

I can't do anything about that.

Greg-ulate,

I bet you say "Hey where is my battery charger?"

I am careful not to say that.

Nobody says "I have a capacitor C net charged to V volts and therefore it stores CV^2/2 Joules of energy," so your argument is basically a Straw Man argument.

No one says "I have a cap C energized to V volts and therefore it stores CV^2/2 joules of energy either, but so what is the point? What does that statement prove or disprove?

Just because the net charge doesn't change, that doesn't make it wrong to say charged

If I have a jar half filled with water, and turn it upside down so that the liquid switches to the top part of the jar, does that mean I filled the jar with liquid?

Current flows out of one leg and into the other, one plate becomes charged with respect to the other plate.

One plate becomes imbalanced with respect to the other plate. Moving a charge is an energy changing operation, not a charging one.

Then it stays there. It's stored there. Capacitors store charge.

If you move the contents of a cupboard from one shelf to the other, you are not storing anything.

...while it is technically correct,...

Thank you. I wanted to see that.

Firing a capacitor out of a cannon would also energize it, so its not any less ambiguous than saying charge.

It would not give the cap any electrical energy, which is what we are talking about.

sophiecentaur,

We are all aware of this and the term " charge" incorporates this knowledge. Just what is your point? Do you seriously expect to change this established terminology? Don't hold your breath.

No, the term charge is a misnomer in this case. As I showed in some examples in a previous post, some folks do use the correct terminology.

Ratch

 

[sophiecentaur]

@Ratch
You and the others who use your terminoligy are in a minority and your just "goin' on" about it gets you nowhere. That particular expression is dimensionally correct, unlike "volts going through you". "electromotive force" and "electrical resistance tries to stop the current" etc. and, it is perfectly acceptable.
Why waste you time on this when you are demonstrably quite capable of making worth while comments on other topics? You should pick your battlegrounds in places where you have a chance of winning.
Have a stress free and terminology free Christmas. I hope that when you charge your glass with wine, it doesn't discharge out of its other end.

 

[jim hardy]

ratch wrote

I know of no scholarly article on common sense.

I'll resist the obvious.

Try Asimov, On Physics and View from a Height. And Don Quixote.

 

[the_emi_guy]

Ratch,

Give us one example of where the term "charging" would be appropriate usage.

 

[Ratch]

sophiecentaur,

You and the others who use your terminoligy are in a minority ...

I would rather be in the correct minority than the wrong majority.

jim hardy,

Try Asimov, On Physics and View from a Height. And Don Quixote.

Fiction writers? By the way, what does "common sense" have to do with this argument? I am either right or wrong. Some of you said I was right even though I should use wrong nomenclature.

the_emi_guy,

Give us one example of where the term "charging" would be appropriate usage.

Ratch

I can't think of any for capacitors, and I have not seen any in the arguments against my position.

 

[the_emi_guy]

You can't think of *any* circumstance where you could correctly use the term "charging". We should remove it from our technical vocabulary entirely?

 

[sophiecentaur]

Ratch
You are losing your Capacity to see reason. That's a chargeable offence, I think. It goes against current thinking and is Potentially troublesome. Why resist? You will feel more at Ohm with things if you conduct yourself better. Your powers of Induction should bring you to a terminal conclusion. Or is it a case of Do or Die - electric?

 

[jim hardy]

deleted, on second thought...

Merry Christmas to all !

 

[sophiecentaur]

And to you Jim and all the others

 

[Drakkith]

Well, I think this thread has run its course...

 

[Ratch]

sophiecentaur,

I admit I am biased toward TRUE meaning of words, and not the FALSE impression caused by the time decay of proper usage. The timely constant reminder I give when I talk about misnomers shows my incapacity to conduct myself as though they were never spoken. My inability to go with the current flow is intrinsic within me. For that I apologize.

Ratch

 

[Drakkith]

There's no reason to be rude.

 

[jim hardy]

This is what happens when you get your "knowledge" from answers dot com...

http://wiki.answers.com/Q/How_do_capacitors_store_a_charge

Capacitors don't really store charge at all. They allow negative charge to be transferred from one plate to the other, thus establishing an electric field between their plates. But there is no net increase in charge -the amount of charge on the capacitor's plates, after 'charging', is exactly the same as there was before 'charging' -it's just moved around! What capacitors 'store' is energy, not charge.

Read more: http://wiki.answers.com/Q/How_do_capacitors_store_a_charge#ixzz2G2TVMN7k

Scholarship on the subject was dismissed in post # 45

I know of no scholarly article on common sense.

and then common sense was dismissed in post # 62

By the way, what does "common sense" have to do with this argument?

Silly me - i came in thinking it was a discussion.