jeffrey samuel
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dc maybe -ve or +ve but it must not vary
Positive varying voltages/currents in the first half of the cycle and non-varying second half are also called DC?
That's what it is called pulsating?
Thanks
Jack
Sorry, I have come back.
In physics, I remember there is one thing called displacement current, where energy stored in magnetic fields are transformed into electric fields in between the cap and transformed back into magnetic fields on the other side of the cap for continuous currents. So my question is if the energy has 'passed' thru the cap, that means no energy is stored in the capacitor during the positive cycle. To have the smoothing out effect, during the positive cycle must have some stored energy inside the cap, so that there is some to release during the negative cycle. So where has the energy gone?
To have the smoothing out effect, during the positive cycle must have some stored energy inside the cap, so that there is some to release during the negative cycle. So where has the energy gone?
There are people who say the energy is stored in the plates.
The best I can manage to explain it in my mind is that one plate acquires a surplus of electrons, as compared to the other plate. Hence it is charged.
One plate acquires a surplus of electrons, the opposite plate loses the same number of electrons. It takes energy supplied by a voltage to imbalance the plates like that. That causes an electric field to form, which stores the energy. A capacitor has the same net charge when the plates are imbalanced as when they had when there was no voltage across them, specifically zero. For that reason, a capacitor is never "charged", it is energized. I explained this many times before in other threads, so there should not be any wonderment in your mind about what happens. Do you have any questions or doubts about what I avered?
electric field
energized
I looked at the videos, and found them confusing to say the least.
I don’t know why anyone should be so pedantic over ‘charged’ and ‘energised’.
Would you disagree with that?
The SI unit of quantity of charge is the coulomb; it is the charge transported by a steady current of one ampere in one second.
If a voltage source were applied to a capacitor that had no voltage across its terminals, a current would flow into the capacitor for such time as it took for the current to reduce to zero.
A charge equal to the product of current flow in amperes and time in seconds would have passed from the source to the capacitor – so the capacitor could be said to have been ‘charged’.
Hmmm, okay, I knew I had to be careful what I say.
Such as if someone were to bring up a situation where one plate is charged to 10V and the other plate to 20V. How do we sum that one up?
Or both plates charged to 10V? How do we sum that one up?
Or both to 1000V?
We might think of that as being a static charge. But I read that the nature of static electricity is really no different from low voltage. It's just that static is known for odd behavior such as making hair stand on end, and making sparks, etc.
No argument from my end. After all, we can't call it a magnetic field. Magnetism is not present.
So it must be something else. But is the electric field of the same nature as a static charge? If not then which situation should be called which?
Suppose we energize a capacitor's plates to 10V and 0V? Then we separate the plates to a distance of 1 inch? Is it still a capacitor?
To a separation of 1 foot?
When does it stop being a capacitor? How do we sum up the situation at that stage?
Fortunately we do not necessarily have to know the exact terminology of how a capacitor works, in order to use one in a project.
Watching an animated simulation (my videos) is a step removed from participation. It's second best, no doubt about it. I will have to work further on perfecting my simulator.
The voltage source received as much charge back from the capacitor as it supplied. All you can say about that senario is that the plate charges are imbalanced. You can say one plate is charged, but then you have to also say the opposite plate is discharged. So what is the status of the capacitor? How do you resolve that ambiguity? Since there is energy present in the capacitor, and a voltage difference across the capacitor when the plates are imbalanced, then energized is the logical, sensible and correct word to describe a capacitor in that situation.
You could also say that as there is a voltage difference between the two plates of the capacitor, then one plate has a acquired a charge relative to the other one (C = F x V).
All but the most pedantic (and I consider myself among the ‘all’ group) might then consider the capacitor to be ‘charged’.
But I can understand your attitude – because I abhor the current use of the terms ‘positive’ and ‘negative’ as an upmarket replacement for ‘good’ and ‘bad’!
I’m pebe, not pepe.pepe,
The SI unit of capacitance, of course.What is F in the equation?
It is not descriptive enough to say that one plate acquired a charge relative to another. Do you mean that one plate acquired 4 coulombs of charge, and the opposite plate did not get any? So the cap would then have a net charge of 4 coulombs? It doesn't happen that way. One plate acquires 4 coulombs, and the other plate loses 4 coulombs for a net charge change of zero.
Don't try to understand my attitude. Try to understand my reasoning.
Speaking of reasoning, I don't understand how your statement about positive/negative vs good/bad ties into what we are discussing.
I’m pebe, not pepe.
What is F in the equation?
The SI unit of capacitance, of course.
It is pointless to talk about a ‘net charge’ of zero, just as it would be pointless to say the ‘net voltage’ of a sinusoidal waveform is zero.
Quote from Wikipedia: “Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them”.
Hence F = C/V. If calculated for a net charge of zero, then the capacitance, F, would be infinite.
I cannot. I understand that a capacitor can hold a charge on its plates, between its plates, or wherever. And I consider a capacitor with a voltage between its terminals to be 'charged'
This is hard core Argument here and each and every post is having many things to ponder on. Come on guys do tell What is the actual thing happening in a Capacitor?
Do you accept the formula "Charge = Capacity x Voltage" to be true?Wikipedia is known for being wrong at times. That is because they allow people who are not expert in their field to post articles, and I don't know if there is any editor who checks the accuracy of what they post.....
Do you accept the formula "Charge = Capacity x Voltage" to be true?
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