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Arouse1973

Adam
Dec 18, 2013
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OK - no problem.
It was my intention only to start/enable in this forum a discussion about a more generalized definition of the quantity we call "current". It seems, however, nobody is interested.
(Let me add: I am sure such a generalization is possible).
I wonder how a current clamp would react (theoretically) if it could be brought between the plates.

The generally accepted term "Electrical Current" is the flow of electrons. This has been wildly used for many years but Electrical Current can happen without electrons. Example is the electrical current in ice is produced by + ions or it can be both electrons and ions like in a spark. So another more accurate term was created and that is Electrical Current is the flow of charged particles.

So in my view the term displacement current comes from the fact that the charged particles are indeed moving in and out of the capacitor and not flowing in a loop gives rise to the term displacement current. I guess you could call the current in any a.c circuit all displacement currents. Because the charged particles don't flow they just wiggle. Could you still call this little wiggle a flow well I suppose it is a very small and quick flow. But we distinguish it from a main flow of charged particles by giving it another name.

You take your capacitor, it is not that different from an antenna and antennas use displacement currents to work. The capacitor could be considered as a very close transmitter and receiver. sometimes this analogy is used to help people understand how they work. The capacitor is also sometimes referred to an open circuit transmission line and uses the TEM principle to work.

But at the end of the day if you are dealing in just ordinary electrical circuits then the words flow of electrons for current is quite acceptable.

Now if you want to know where the energy comes from that's a different story and is to do with particles of quantum light, the Photon.

One last thing not to upset the apple cart. I have just discovered there has been for a few years now debate as to whether there is an such a thing as displacement current at all. James Maxwell did very well 200 years ago but it is slowly being disproved because two antenna types were developed at costs of many $1000. But these antennas performed quite differently than originally calculated. Hence the move a head to disprove displacement currents altogether. But I am quite happy for now going along with this.

That's my take on it anyway if your interested.

Thanks
Adam
 

LvW

Apr 12, 2014
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So in my view the term displacement current comes from the fact that the charged particles are indeed moving in and out of the capacitor and not flowing in a loop gives rise to the term displacement current. I guess you could call the current in any a.c circuit all displacement currents. Because the charged particles don't flow they just wiggle.
Is this (to "wiggle") not dependent on amplitude and frequency? I think, in case of a low-frequency signal with a sufficient amplitude, the current during a part of the period can be nearly regarded as a rising dc signal?
One last thing not to upset the apple cart. I have just discovered there has been for a few years now debate as to whether there is an such a thing as displacement current at all. James Maxwell did very well 200 years ago but it is slowly being disproved because two antenna types were developed at costs of many $1000. But these antennas performed quite differently than originally calculated. Hence the move a head to disprove displacement currents altogether. But I am quite happy for now going along with this.

Adam, thank you for replying. And special thanks for the last paragraph with information about recent debates about displacement currents. I didn´t hear about this.
What do you think about my hypothetical question regarding current clamp?
 

Arouse1973

Adam
Dec 18, 2013
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Well I think yes because I have read somewhere that people have done this on the edges of capacitors but the field is very very small.
Adam
Is this (to "wiggle") not dependent on amplitude and frequency? I think, in case of a low-frequency signal with a sufficient amplitude, the current during a part of the period can be nearly regarded as a rising dc signal?


Adam, thank you for replying. And special thanks for the last paragraph with information about recent debates about displacement currents. I didn´t hear about this.
What do you think about my hypothetical question regarding current clamp?

Dc is in one direction so I suppose until it reaches maxima it is in one direction but then changes direction as it passes through 0V to some minus value and so it is ac.
Adam
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Dc is in one direction so I suppose until it reaches maxima it is in one direction but then changes direction as it passes through 0V to some minus value and so it is ac.

Well, you're probably talking about a step response or similar. When considering AC, the formulae assume you're in a steady state condition, and thus apply to DC with that constraint.

You might consider the response to a capacitor with a constant current source connected across it.
 
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