If the positive plate on a charged capacitor will pass current to the negative

[Ratch]

Nevertamed,

they are not just 2 floating caps, they are two points with a imbalance of charge between them, one fully negative charged plate (from the first capacitor) and one fully positive charge plate (from the second capacitor), forget the fact both plates belong to different capacitors, they are still 2 points with a voltage present, if you set a path there will be a current until the charge depletes

I cannot visualize what you are describing without calling the the second capacitor floating. A schemat is needed.

i didnt say caps and batts are identical, i said "in a way, caps are a lil like a battery" i meant they both have similarities

I think the differences outnumber the similarities.

maybe they like speaking metaphorically like lots of people...

They are supposed to be a technically oriented organization, not an entertainment production company. They could have come up with something much better like "exterior excursion", or like they did in the beginning, "extra-vehicular activity' (EVA), both of which are correct. It is a shame that the lame-stream media just swallowed it, and gave them a pass. Ratch

 

[Ratch]

sophiecentaur,

I googled 'equivalent circuit capacitor antenna' and got more hits than I had time to read. They establish the principle that I'm getting at. The fact that antennae are mostly used for AC is not a hinderance because the situation for the DC condition is only arrived at after a change - not DC - in the situation.

I sure am glad I can see a schematic. I never would have understood the circuit without it. I can't argue with you because I don't quite know what you are proposing. Antenna circuits desire resonance, which means some inductance, too. This is probably a good time to end this thread, because the explanations are too involved and complex to benefit anyone.

Ratch

 

[Ratch]

sophiecentaur,

Both would be correct and acceptable in the appropriate context.

That is the point, both are correct.

If we are talking about Charge (which I though we were), then why not allow our experiment to "charge a capacitor"?

That is the point, caps do not get charged.

If we are talking about supercapacitors and road transport then it's arguable that 'energising' them would be appropriate

Energizing a capacitor is always correct.

but did we ever in this World, talk about Energising a Battery?

No, but it would be a correct description of an action.

"Energiser" is a trade name for Ever Ready High Power batteries but that, I think, is aimed at describing what they actually do to your toys and not what Ever Ready do to their batteries.

Yes, you are correct.

Anyway, I did that diagram (above post). Hope it makes sense for you.

Nice diagram. I guess you are saying that there are a couple of capacitors that will be energized when the battery becomes active. At least I know where the caps are located and their relationship in the circuit.

OH - I just spotted what you wrote about permittivity of free space etc.. Dielectric constant is used to say how the effective permittivity is affected by adding a dielectric, surely. If space has a dielectric constant of Unity, then the quantity is totally redundant. But. again, is this really relevant to the price of fish and chips?

It shows that everything has dielectric constant, and the dielectric constant of materials is relative to the permittivity of free space.

Ratch

 

[sophiecentaur]

sophiecentaur,
I sure am glad I can see a schematic. I never would have understood the circuit without it. I can't argue with you because I don't quite know what you are proposing. Antenna circuits desire resonance, which means some inductance, too. This is probably a good time to end this thread, because the explanations are too involved and complex to benefit anyone.

Ratch

Any wideband antenna cannot be highly resonant. The best you can do is to get as wideband a match as possible. Matching is the only reason to aim at resonance and the resonant half wave dipole is only the start in the art of antenna design. Many receiving antenna operate far from resonance - your portable VHF sound receiver antenna (a simple version of an unbalanced radiator, which would never be satisfactory for transmission aamof) being a typical example.
In any case, I only introduced the antenna idea as an example of reducing a circuit to its 'equivalent' components (with or without inductance). If you are not aware of this as a general way of approaching problems then it could be worth your while to follow it up. It is a very powerful tool, used in many instances.

This may be a 'personal view' as my original idea was to suggest a possible approach to the original problem that was posed. I have not seen any alternative proposed on this thread so it at least suggests a way through.

 

[justsomeguy]

I have not seen any alternative proposed on this thread so it at least suggests a way through.

The answer was given a page or so back, though not in direct reply to the OP. His question was:

...plate of a different capacitor, why won't the positive end of a battery (lets say AA) pass current to the negative plate of a different AA battery. Does it have something to do with the chemical reaction that happens inside the battery?

The answer is a simple "yes" to his final question. Batteries generate electricity via chemical reaction, they do not store it. Electrons do not travel from one plate in the capacitor to the other as they do between battery terminals -- except when the dielectric has failed.

If you just connect two dissimilar terminals of two batteries together and leave the other two terminals hanging, no reaction takes place. No reaction means no ions or free electrons are created, which means no voltage differential and no current.

 

[Ratch]

sophiecentaur,

Any wideband antenna cannot be highly resonant. The best you can do is to get as wideband a match as possible. Matching is the only reason to aim at resonance and the resonant half wave dipole is only the start in the art of antenna design. Many receiving antenna operate far from resonance - your portable VHF sound receiver antenna (a simple version of an unbalanced radiator, which would never be satisfactory for transmission aamof) being a typical example.
In any case, I only introduced the antenna idea as an example of reducing a circuit to its 'equivalent' components (with or without inductance). If you are not aware of this as a general way of approaching problems then it could be worth your while to follow it up. It is a very powerful tool, used in many instances.

This may be a 'personal view' as my original idea was to suggest a possible approach to the original problem that was posed. I have not seen any alternative proposed on this thread so it at least suggests a way through.

How did you get involved is describing a half wave resonant dipole VHF antenna? I am sure the OP has no idea what you are talking about. I see it as a solution in search of a problem.

Ratch

 

[sophiecentaur]

You brought up the resonance idea, seemingly in an attempt to discredit a useful approach to a problem. I just pointed out that equivalent circuits are used all over and cited antennae as an example. Why did you use an irrelevant idea to reject a perfectly valid point? Is there anything wrong with using Capacitance to explain what happens when you connect charge polarised objects? If you don't understand it then don't reject the idea per se. Get informed rather than getting cross.

 

[sophiecentaur]

The answer was given a page or so back, though not in direct reply to the OP. His question was:

The answer is a simple "yes" to his final question. Batteries generate electricity via chemical reaction, they do not store it. Electrons do not travel from one plate in the capacitor to the other as they do between battery terminals -- except when the dielectric has failed.

If you just connect two dissimilar terminals of two batteries together and leave the other two terminals hanging, no reaction takes place. No reaction means no ions or free electrons are created, which means no voltage differential and no current.

This question doesn't need to apply just to batteries. It applies to any two sources of emf connected in series. Introducing the chemical generation of ions just muddies the water and misses the essentials of the problem. There is no answer unless the absolute potentials of one terminal of each battery is specified. If you assume that they are both the same voltage and their negative terminals are connected to Earth (a nominal zero potential) then, when one battery is removed and its negative terminal is connected to the positive terminal of the other, charge will flow and that charge will be determined by the capacity of the 'upper' battery to Earth, because the 'lower' battery will maintain its emf wrt ground by passing just enough charge so that Q=CV. The C2, in my earlier diagram is the equivalent of the capacity of 'everything' that becomes connected to the lower battery positive terminal.

 

[Nevertamed]

You brought up the resonance idea, seemingly in an attempt to discredit a useful approach to a problem. I just pointed out that equivalent circuits are used all over and cited antennae as an example. Why did you use an irrelevant idea to reject a perfectly valid point? Is there anything wrong with using Capacitance to explain what happens when you connect charge polarised objects? If you don't understand it then don't reject the idea per se. Get informed rather than getting cross.

love it

 

[sophiecentaur]

love it

Handbags at dawn?

 

[justsomeguy]

This question doesn't need to apply just to batteries. It applies to any two sources of emf connected in series. Introducing the chemical generation of ions just muddies the water and misses the essentials of the problem.

I thought the "problem" was the OP asking why you can measure (and use) voltage between the leg of one capacitor to another even though each one has a leg disconnected, but why you cannot do this with batteries? This is very much the essential of the problem the OP asked, and the answer given is correct.

There is no answer unless the absolute potentials of one terminal of each battery is specified.

If there is no reaction taking place, as there cannot be when one of the terminals is not connected, then the potential is zero.

If you assume that they are both the same voltage and their negative terminals are connected to Earth (a nominal zero potential) then, when one battery is removed and its negative terminal is connected to the positive terminal of the other, charge will flow and that charge will be determined by the capacity of the 'upper' battery to Earth, because the 'lower' battery will maintain its emf wrt ground by passing just enough charge so that Q=CV. The C2, in my earlier diagram is the equivalent of the capacity of 'everything' that becomes connected to the lower battery positive terminal.

You need to doublecheck this I think. What do you suppose is generating the electrons in the 'upper' battery? If no reaction is taking place, then no ions are being created, and thus no free electrons. It's like suggesting there will be voltage output from a generator that isn't even running as long as you connect it the right way.

 

[Ratch]

sophiecentaur,

You brought up the resonance idea, seemingly in an attempt to discredit a useful approach to a problem.

You brought up the antenna idea, seeming in an attempt to pettifog the problem.

I just pointed out that equivalent circuits are used all over and cited antennae as an example.

Don't you think we all know that?

Why did you use an irrelevant idea to reject a perfectly valid point?

You mean inductance? I was not rejecting anything, I was saying that it had to be considered.

Is there anything wrong with using Capacitance to explain what happens when you connect charge polarised objects?

Nothing at all, provided you submit a clear concise explanation that the OP can understand of how it applies to the question he asked.

If you don't understand it then don't reject the idea per se.

It is your idea, so it is up to you to explain it in a way that the OP and I can understand it.

If you don't understand it then don't reject the idea per se. Get informed rather than getting cross.

So that is where you come in. Inform me.

Ratch

 

[jaydnul]

"But a battery is a electrochemical device, and does not use a electrostatic field to maintain its voltage like a cap does."

That was exactly what i was looking for. Thanks Ratch

 

[Nevertamed]

"But a battery is a electrochemical device, and does not use a electrostatic field to maintain its voltage like a cap does."

That was exactly what i was looking for. Thanks Ratch

If the positive plate on a charged capicitor will pass current to the negative...plate of a different capacitor, why won't the positive end of a battery (lets say AA) pass current to the negative plate of a different AA battery. Does it have something to do with the chemical reaction that happens inside the battery?

A: YES


P.S. ha ha ha would be shorter that way xD

 

[Ratch]

Nevertamed,

If the positive plate on a charged capicitor will pass current to the negative...plate of a different capacitor,

Caps are not charged, they are energized. There will have to be a conduction path for charge to move anywhere. You seem to be describing a floating capacitor, so there is no conduction path. You need to produce a schematic so we know what you are avering.

Does it have something to do with the chemical reaction that happens inside the battery?

A: YES

The chemical reaction of a battery is quite different than the differential equation that describes the voltage/current relationship of a cap.

Ratch

 

[sophiecentaur]

Nevertamed,



Caps are not charged, they are energized. There will have to be a conduction path for charge to move anywhere. You seem to be describing a floating capacitor, so there is no conduction path. You need to produce a schematic so we know what you are avering.



The chemical reaction of a battery is quite different than the differential equation that describes the voltage/current relationship of a cap.

Ratch

Why do you keep on about this? This idea seems to be entirely your own. Can you support it with a reference? If you can't then why not let it drop?
When current has stopped flowing and, assuming there is no self-discharge in a battery, there is no difference in essence between the excess charges on the terminals and the charges on the terminals of a Capacitor. When a small enough charge flows elsewhere, you can assume the PD across either component remains the same.
This is why I have been suggesting the use of equivalent components. As you claim to be familiar with the idea then why not accept the approach as a start to understanding the problem?
You say that I need to explain myself but my simple diagram should be enough to make the point. Any structure / component will exhibit Capacitance - either wrt infinity, a local Earth or another structure / component. If you don't like the term "parasitic" then what would you prefer? You can put these parasitic Capacitances onto an equivalent circuit and that gives you a chance of solving the problem with the usual circuit analysis tools at your disposal.
It would help to have the OP clarified with a diagram but I thought the strong implication was that we start with two batteries or capacitors that had been charged from the same source - so there would initially be 0V PD between the two positive terminals and the two negative terminals.

I was thinking about your mention that the Inductances would also need to be considered. This would be true if you wanted to describe the changing situation when the re-connection was made but, as we are discussing the final state of things, with no current flowing, Inductance is hardly relevant.

 

[sophiecentaur]

You need to doublecheck this I think. What do you suppose is generating the electrons in the 'upper' battery? If no reaction is taking place, then no ions are being created, and thus no free electrons. It's like suggesting there will be voltage output from a generator that isn't even running as long as you connect it the right way.

Could you explain what you mean here? There is an emf across a battery even when not connected to a load. That must imply an imbalance of charges. The chemical reaction stops because charges are not being removed via a connected circuit and the potentials balance out within the cell. There will be an 'real' Capacitance across the plates and terminals of the battery which will be 'storing' this unbalanced charge. The Capacitance, itself will be small because the separation is relatively great - but still finite (in the order of a few pF). The fact that a lot of current can flow when the circuit is connected, without much reduction in PD, gives a very high equivalent Capacitance. But the response to an instantaneous load is not instant (in the order of ms) due to the time for the chemical processes to get going so there is not a simple equivalent Capacitance value.

Your analogy with a generator would be more accurate if you were to compare the generator on load and off load but still running at constant speed.

 

[Ratch]

sophiecentaur,

Why do you keep on about this?

Because energizing in the truth and charging is not.

This idea seems to be entirely your own. Can you support it with a reference? If you can't then why not let it drop?

I support it with an explanation which no one has refuted. "Charge" is the wrong descriptive.

When current has stopped flowing and, assuming there is no self-discharge in a battery, there is no difference in essence between the excess charges on the terminals and the charges on the terminals of a Capacitor. When a small enough charge flows elsewhere, you can assume the PD across either component remains the same.

If all you are talking about is an unchanging voltage and no charge flow, then yes, they would be equivalent. But a cap's voltage is because of a charge difference between its plates. A battery's voltage is because of valance electron displacement of its two metal terminals due to chemical reaction, and not electron crowding and separation due to a dielectric as in a capacitor. If we use a miniature DC generator, then there would be a third way to make a voltage. Neither of those ways are equivalent to each other except in narrow circumstances.

This is why I have been suggesting the use of equivalent components. As you claim to be familiar with the idea then why not accept the approach as a start to understanding the problem?

As I explained above, equivalents are only valid in certain circumstances.

You say that I need to explain myself but my simple diagram should be enough to make the point. Any structure / component will exhibit Capacitance - either wrt infinity, a local Earth or another structure / component. If you don't like the term "parasitic" then what would you prefer? You can put these parasitic Capacitances onto an equivalent circuit and that gives you a chance of solving the problem with the usual circuit analysis tools at your disposal.
It would help to have the OP clarified with a diagram but I thought the strong implication was that we start with two batteries or capacitors that had been charged from the same source - so there would initially be 0V PD between the two positive terminals and the two negative terminals

Yes, capacitance is everywhere, but we usually ignore it because it is insignificant in most cases. I don't think the OP was thinking of any other capacitance other than the two caps he was asking about.

I was thinking about your mention that the Inductances would also need to be considered. This would be true if you wanted to describe the changing situation when the re-connection was made but, as we are discussing the final state of things, with no current flowing, Inductance is hardly relevant.

And in the final state of things, with no voltage changing, neither is capacitance.

Ratch

 

[justsomeguy]

Could you explain what you mean here? There is an emf across a battery even when not connected to a load. That must imply an imbalance of charges. The chemical reaction stops because charges are not being removed via a connected circuit and the potentials balance out within the cell.

This is half the story. It's not just that electrons are not being removed, but that no more are being freed either. There are a finite number available from when the reaction was last stopped.

There will be an 'real' Capacitance across the plates and terminals of the battery which will be 'storing' this unbalanced charge. The Capacitance, itself will be small because the separation is relatively great - but still finite (in the order of a few pF). The fact that a lot of current can flow when the circuit is connected, without much reduction in PD, gives a very high equivalent Capacitance. But the response to an instantaneous load is not instant (in the order of ms) due to the time for the chemical processes to get going so there is not a simple equivalent Capacitance value.

No, there is no capacitance in an ideal battery. In the real world there is a tiny bit of charge left on the plates after the reaction is stopped, but it's negligible and easily drained. Once that's done, there is no more current flow despite the chemistry of the battery being in a state to produce much more. You have not supported your claim that:

(air) --- +[B1]- --- +[B2]- --- (ground)

Will result in real current flow for any duration. Once the plate of the imaginary capacitor is drained, there is no more current flow, despite there being plenty of reactants left in the battery to produce more.

Your analogy with a generator would be more accurate if you were to compare the generator on load and off load but still running at constant speed.

No, it was more accurate the way I described it. The chemical reaction is the generator. As long as there are no reactions taking place, there is no power generated. That reaction simply cannot take place if one of the terminals is disconnected.

A battery is not a capacitor. There is not a vast reserve of free electrons you can draw on as long as you wish without the chemistry taking place. The chemistry cannot take place as long as one of the terminals is disconnected. It's a furnace and the flow of fuel is interrupted. There may be some residual heat in the system that you can use, but that's it.

 

[sophiecentaur]

sophiecentaur,



Because energizing in the truth and charging is not.



I support it with an explanation which no one has refuted. "Charge" is the wrong descriptive.

But no reference or even a quote with your personal terminology being used elsewhere? That's hardly PF style for asserting "truth".

If all you are talking about is an unchanging voltage and no charge flow, then yes, they would be equivalent. But a cap's voltage is because of a charge difference between its plates. A battery's voltage is because of valance electron displacement of its two metal terminals due to chemical reaction, and not electron crowding and separation due to a dielectric as in a capacitor. If we use a miniature DC generator, then there would be a third way to make a voltage. Neither of those ways are equivalent to each other except in narrow circumstances.

But the chemical reaction in a battery doesn't continue all the time. It stops when the potential builds up (no load) and the chemical potential is equalised. Batteries have a long shelf life because the reaction is only there when charge is allowed to flow and the Potential drops to permit it. What is the difference for the plates of a charged capacitor and the plates of a battery? Electrons are built up on one and depleted on the other in both cases (due to electric fields). In a DC generator, the PD is caused by EM induction. Could you explain the difference in detail, as far as the charges on either side of the emf source are concerned?

As I explained above, equivalents are only valid in certain circumstances.

Yes, capacitance is everywhere, but we usually ignore it because it is insignificant in most cases. I don't think the OP was thinking of any other capacitance other than the two caps he was asking about.

You ignore a component when its value is small enough to ignore it in the circumstance. In the case of the two batteries (or two capacitors) the capacity is what it is and the charge the is displaced is given by Q=CV. I assume you are familiar with that expression. The relevant capacity is small - a few pF and so is the charge imbalance (a few pC). Without using vague terms like "floating cap" (which is something that happens when you falll in the water ), can you explain it in better terms than that? I was suggesting that the OP could actually get an answer by considering the other capacitances involved in his experiment. Many explanations on PF involve introducing additional variables and mechanisms. I wish your objections could include some formulae or figures. It would give them some weight (PF style again).

And in the final state of things, with no voltage changing, neither is capacitance.

Ratch

What voltage change do you refer to? Which capacitance is changing, too? If you put a DVM across two previously charged capacitors in series (or two batteries) what voltage would you expect to measure?

 

[Ratch]

sophiecentaur,

But no reference or even a quote with your personal terminology being used elsewhere? That's hardly PF style for asserting "truth".

A consensus does not determine the truth. Reason and facts do. Everyone I discussed this with cannot refute me, yet they prefer to "go with the flow" even though they know it is descriptively wrong. As is "current flow" also wrong.

But the chemical reaction in a battery doesn't continue all the time. It stops when the potential builds up (no load) and the chemical potential is equalised. Batteries have a long shelf life because the reaction is only there when charge is allowed to flow and the Potential drops to permit it.

Yes, agreed. Let's see where this takes us.

What is the difference for the plates of a charged capacitor and the plates of a battery? Electrons are built up on one and depleted on the other in both cases (due to electric fields).

I thought I made it clear in post #48 where I said "A battery's voltage is because of valance electron displacement of its two metal terminals due to chemical reaction, and not electron crowding and separation due to a dielectric as in a capacitor." So no, it is not the same in both cases.

In a DC generator, the PD is caused by EM induction. Could you explain the difference in detail, as far as the charges on either side of the emf source are concerned?

The DC generator has no dielectric, therefore, its voltage will be only by EM induction as you stated, and not by charge separation and crowding or spacing out of electrons.

You ignore a component when its value is small enough to ignore it in the circumstance. In the case of the two batteries (or two capacitors) the capacity is what it is and the charge the is displaced is given by Q=CV. I assume you are familiar with that expression. The relevant capacity is small - a few pF and so is the charge imbalance (a few pC).

I agree with the above.

Without using vague terms like "floating cap" (which is something that happens when you falll in the water ), can you explain it in better terms than that?

A floating cap is a topology, not a verb. It means that one of it terminals is left "floating", i.e. it is not connected to anything.

I was suggesting that the OP could actually get an answer by considering the other capacitances involved in his experiment. Many explanations on PF involve introducing additional variables and mechanisms. I wish your objections could include some formulae or figures. It would give them some weight (PF style again).

The OP asked for a qualitative explanation, not a quantative one.

What voltage change do you refer to? Which capacitance is changing, too? If you put a DVM across two previously charged capacitors in series (or two batteries) what voltage would you expect to measure?

I was answering your previous statement where you said "with no current flowing, Inductance is hardly relevant."

I answered "And in the final state of things, with no voltage changing, neither is capacitance." So in the proper context, you should have interpretated it as I saying capacitance is not relevant if voltage is not changing. You instead interpreted it as I as saying that capacitance changed.

Ratch

 

[sophiecentaur]

I am afraid I'll wait to change my description of what we do to capacitors until I see it in wider use. Good luck with your educational crusade.
As for the rest of your post, it contains nothing but assertions and no explanations so it doesn't take us any further.
To be fair to both of us, the original scenario is a bit vague so we may be talking at cross purposes about all this.

 

[jim hardy]

methinks there's accepted terminology in any field and for discussion to be meaniingful, one needs to use it.

That's why study in any field begins with vocabulary,

and a good textbook has a definition of terms at beginning of each chapter.

 

[Ratch]

jim hardy,

methinks there's accepted terminology in any field and for discussion to be meaniingful, one needs to use it.

That's why study in any field begins with vocabulary,

and a good textbook has a definition of terms at beginning of each chapter.

That is all fine and good. But how does that apply to what we were discussing?

Ratch

 

[Nevertamed]

Nevertamed,



Caps are not charged, they are energized.

Ratch

oh lord...

 

[jim hardy]

But how does that apply to what we were discussing?

well, i interpreted several posts as spiralling around the meaning of "charge" vs "energize"

and if i missed where either was defined, it's my bad.

So i was trying to provoke a clarification .

 

[Ratch]

jim hardy,

So i was trying to provoke a clarification .

A noble endeavor. Here are some examples.

1). This is an example of someone asking how to de-energize a capacitor safely.
http://answers.yahoo.com/question/index?qid=1006021608394

2). This is an article about energizing and de-energizing a load involving switching capacitors. They never say "charging". http://helios.acomp.usf.edu/~fehr/312ecm381.pdf

3). Another article about energizing capacitors, where they mention energizing capacitors 8 times. See the title of Fig. 3. http://www.southernstatesllc.com/assets/documents/2091/original/Capacitor_Switching_and_Capacitor_Switching_Devices_Mypsicon_2009.pdf?1274707457

4). An article about power factor capacitors. See the fourth paragraph which says, "When the motor is energized, the capacitor is energized. When the motor is de-energized, the capacitor is de-energized." Their words, not mine. http://myronzucker.com/Resources/Capacitalk100.html

5). Wanna learn how to energize and de-energize a electric energy storage device? Read on. http://www.freepatentsonline.com/7157884.html

6). Get taught by a lady, no less, on how to energize a capacitor. http://www.soyouwanna.com/run-capacitor-31920.html

7). These folks will test your capacitor before you energize it. Their words, not mine. http://www.hdelectriccompany.com/hd-electric-products/etm/transformer-and-capacitor-tester/Quick-Check.htm

8). Look at the second sentence from the end of the abstract. http://www.atpower.se/Papers/Ananlysis of voltage transients in a medium voltage system.pdf


Nevertamed,

oh lord...

Is that a plea for help, or an acknowledgment that you are in over your head?

Ratch

 

[sophiecentaur]

I looked at those links. Most but not all of them worked. I am now a bit more convinced about how commonly the term 'energise' is used in certain restricted circumstances - practical ones when a capacitor is, in fact, used to store energy explicitly. I needn't bother with a google search with 'charged capacitor' we know there would be a deluge of both peer reviewed academic papers, practical applications (and textbooks). I will still stick to charging capacitors until I need to 'store energy'.

 

[jim hardy]

Fair enough.

Perhaps the understanding gap comes down to local dialect.

I grew up in an industrial power environment. We "Energize" equipment to make it run, ie connect it to its power mains.

A capacitor in that AC transients paper is 'energized' when in use because it's connected to its mains. "Charged" would be the wrong term because it's charged, discharged, and recharged opposite polarity with every line cycle.

HD Electric company tester checks utility size capacitors before connecting them to the powerlines ; a good idea because powerline level faults are quite pyrotechnic. They didnt say how it works.

Sorry, but Esmeralda doesn't sound very credible.

MyronZucker clearly shows connection to mains as 'energizing' his capacitor bank.
USF.edu seems also to use 'energize' in the same sense; and he has a nice bit on why switch contact design is such an art - transient current and arcing .

Okay, all that said:

In my background, to "Charge" a capacitor implies to connect it to a source of DC and allow charge(Coulombs) to accumulate per Q = C*V . I do that sometimes just to see if it holds charge, ie checking its insulation resistance.
The energy stored is 1/2 C*V^2 and sometimes i'll short its leads and estimate from size of the spark whether its capacity seems intact. An analog meter is real handy for that test, observe how fast the cap discharges.

So given my background i was a mite puzzled by what appeared to be use of the terms interchangeably.

A cap that is charged has energy stored in its dielectric, but i was taught to call it charged. because it may not be connected to a power source anymore. Be careful when picking up capacitors...
One that's "energized" is definitely connected to a power source.

"Toto, I may not be in Kansas anymore."



old jim

 

[Ratch]

sophiecentaur,

I looked at those links. Most but not all of them worked. I am now a bit more convinced about how commonly the term 'energise' is used in certain restricted circumstances - practical ones when a capacitor is, in fact, used to store energy explicitly. I needn't bother with a google search with 'charged capacitor' we know there would be a deluge of both peer reviewed academic papers, practical applications (and textbooks). I will still stick to charging capacitors until I need to 'store energy'.

As I said in post #51, a consensus does not determine the truth, but reason and facts do. Those of us in the know find it hard to describe a capacitor as "charged", when we know otherwise.

Ratch