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Veritasium "How Electricity Actually Works"

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electrodacus:

--- Quote from: snarkysparky on May 22, 2022, 12:36:41 pm ---Electrodacus has agreed that there is power available to do work in the return circuit. And that this current flowed in and out of  the capacitor terminals.   As to whether this power went "through" the capacitor i guess we will never agree. 

Am I correct ?

--- End quote ---

The energy will go in a capacitor when it is charged and out of the capacitor when it is discharged. There will never be a case where energy goes through capacitor unless the capacitor is defective in the sense that plates are shorted.
Energy flows through a resistor / wire but flows in or out of a capacitor.


As I see that problem was not solved I will provide the correct results.

12V ideal voltage power supply no internal resistance
2x 0.5Ohm wires connecting a 1000uF capacitor also with no significant DC ESR compared to wire resistance so we ignore for simplicity.

Initial connection we get:
The supply providing 144mWs in order to charge the capacitor with 72mWs worth of energy  0.5 * 0.001F * 12V2
The other 72mWs end as heat on the wires that have 1Ohm of resistance.

If now after capacitor is charged we reverse the polarity of the power supply:
The supply will provide 288mWs and all of that will end up as heat on the wires so 288mWs of heat on wires while capacitor will still have the 72mWs stored from the initial connection.
So since capacitor was already fully charged even if it will be discharged and charged with reverse polarity all energy provided by the source will end up as heat on the wires.
If you disagree with this results we can discuss in more details what happens.
This is for the questions about AC supplies that a few of you asked. So this will be the first cycle.
After this first cycle if power supply keeps switching polarity (AC) then all energy will end up as heat/doing work as capacitor remains with same charged energy as it is discharged and then charged with reverse polarity for each half cycle.

So no energy passes through the capacitor. The current in the wires is due to capacitor being discharged (energy out) and charged (energy in) on each half cycle in case of AC.

Alex Eisenhut:
What happens to the energy when you charge a capacitor, then move the plates apart?
What about when charging an inductor?

bsfeechannel:

--- Quote from: EEVblog on May 11, 2022, 11:03:52 am ---For me the question is entirely about DC and energy inside vs outside the wire. Nothing to do with switches, transmission lines, capacitors, inductors, transformer theory, antenna theory etc etc.

--- End quote ---

Which begs the question, is really such a thing as DC? For practical purposes we treat DC as a current that has existed since before the beginning of the universe and will last forever, but in reality whatever the current, it started at some definite point in time in the past and will stop in a foreseeable future. So, what we call DC is in fact just a very wide rectangular pulse. It is essentially transient as anything else, because impermanence seems to be the norm in nature.

If that is so, Heaviside must have thought that, well, if whatever rectangular pulse sent through a transmission line seems to show that energy is conveyed through the space between the wires, why not DC?

electrodacus:

--- Quote from: bsfeechannel on May 22, 2022, 04:11:53 pm ---Which begs the question, is really such a thing as DC? For practical purposes we treat DC as a current that has existed since before the beginning of the universe and will last forever, but in reality whatever the current, it started at some definite point in time in the past and will stop in a foreseeable future. So, what we call DC is in fact just a very wide rectangular pulse. It is essentially transient as anything else, because impermanence seems to be the norm in nature.

If that is so, Heaviside must have thought that, well, if whatever rectangular pulse sent through a transmission line seems to show that energy is conveyed through the space between the wires, why not DC?

--- End quote ---

Energy will not travel through the space between wires no matter if you have DC, or AC.
It is very easy to see that with DC as the energy storage is not involved.
At power up the energy storage is charged  and at power down the energy storage is discharged. At all times electrical energy travels inside the wires.

TimFox:
Can energy (or power) at an appropriate frequency propagate down a waveguide, inside the metal walls?

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