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

[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

 

[Ratch]

jim hardy,

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.

Any capacitor imbued with energy is energized, and has a voltage across its terminals. All capacitors have the same net charge, specifically zero.

Sorry, but Esmeralda doesn't sound very credible.

Why not?

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.

That capacitor holds a voltage. Its net charge is the same before and after it is energtized and shorted.

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

Not by me.

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.

Connected or not, any cap with a voltage across its terminals in energized.

Ratch

 

[jim hardy]

I'll remember those things when traveling in your world.

Esmeralda seems clueless how a flash works.

Step 1

Energize the capacitor by making the connection between the battery and the flash capacitor. When you make the connection between the battery and capacitor, the capacitor will begin to absorb the electricity that is being released by the flash battery. Most capacitor run flash cameras have either a light that shows the capacitor is full or a soft tone that builds as the capacitor is being filled. When the tone stops, the capacitor is ready to release enough energy to operate the flash.

The connection is from the battery to the step up voltage converter, which energizes it. Upon energization, the stepup converter commences charging the capacitor to somewhere in the 350 volt range.
The "tone" is its stepup transformer raising the voltage .
Connecting the battery to the capacitor would charge it to battery voltage, ~1.5 volts.

But its okay, you explained your terms clearly. I can understand you now.

old jim

 

[Nevertamed]

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

Ratch

i don't need help for your obstinacy, i think you do

P.S. please don't argue about the definition of obstinacy, i know what will happen afterwards