General > General Technical Chat
"Veritasium" (YT) - "The Big Misconception About Electricity" ?
aetherist:
--- Quote from: electrodacus on May 01, 2022, 11:56:24 pm ---I do not think there is any enamel of the copper pipe (that will not be common as far as I know). Also even if there was a thin layer of enamel or paint it will not charge the capacitance in any significant way as there is about 1m of air in between.
Also even if capacitance was some other value (say closer pipes or anything like that it will still be irrelevant for the main question).
--- End quote ---
I reckon that enamel on the Cu would not change the 3.3 ns initial transient delay (the delay tween the start of the rise in the green trace & the rise in the yellow trace). But, it would change the (angle of the) rise in the yellow trace (ie the V at the bulb).
As u say, enamel would not affect much the (transient) capacitance tween the 2 wires.
--- Quote from: electrodacus on May 01, 2022, 11:56:24 pm ---The transmission line model is very accurate and just a digitization of the real transmission line as you need finite element's in order to do the calculation.
--- End quote ---
I think that a TL model can be very accurate here, after all there is almost no limit to the design of the model. But it would need to allow for slowing due to any insulation. Plus it would need some clever stuff.
--- Quote from: electrodacus on May 01, 2022, 11:56:24 pm ---So as mentioned the setup can be simplified to just a charged capacitor (in place of the battery or power supply) and a discharged capacitor that is paralleled to the charged capacitor to approximate the transmission line and even the load.
You can have the two discharged series capacitors with a resistor in the middle but since the resistor is just a wire with higher resistance is not needed and since two series capacitors are the same with a single half capacity capacitor the simplification is perfectly accurate to explain the fact that all energy from one capacitor to the other is transferred trough wires (capacitor plates are also wires).
When you connect a charged capacitor to a discharged capacitor you have two ideal capacitors in series with a resistance (ESR) so the charge capacitor is say at 20V and discharged capacitor at 0V then 20V is the drop on the series resistance ESR plus is you want a light bulb Voltage will drop on the charged capacitor as it is discharged while the voltage on the discharged capacitor increases. The current is limited by the series resistance ESR plus lamp if you want to have one there.
There is no electric field in the discharged capacitor and the field is only present when there is a delta in electrons on the two plates.
The electric field has nothing to do with the energy transfer as that is done by electrons trough the wire and the electric field is the consequence of the electron imbalance. No electron imbalance no electric field.
--- End quote ---
I reckon that if Veritasium had a capacitor instead of his bulb (resistor) then he would have measured the same delay, ie 3.3 ns. The angle etc of the rise etc of the yellow trace might have been different, but the em radiation (from near the switch, to the other wire/tube) would have did what it always duz (at least in the first 3.3 ns).
Veritasium says that the electric energy is outside the wire, u & others reckon that it is inside the wire.
Me myself i reckon that near the switch the energy is (mostly) on the wire (ie in my elektons hugging the wire). And, near the bulb the energy is initially on the wire (ie my surface elektons).
bsfeechannel:
--- Quote from: Naej on May 01, 2022, 08:19:00 pm ---Nah, the antennae successfully worked, and the capacitors charged as predicted.
--- End quote ---
Exactly. That's why I said that invoking antennas and, now, capacitors won't save your claim. These two devices show that energy resides in the fields present outside their respective conductors.
--- Quote ---Looks to me like another win for Maxwell's equations, but you are free to give a participation trophy to Poynting instead.
--- End quote ---
Oh yeah. All of them are winners: Maxwell, Heaviside, Poynting, you name it. What they predicted Nature confirmed, saving us to have to give ears to "influencers" and crackpots.
EEVblog:
Hontas Farmer is back
hagster:
--- Quote from: aetherist on May 01, 2022, 11:07:05 pm ---Veritasium duznt tell us whether the Cu tubing has an enamel coating. We all know that the speed of electricity drops from c/1 down to 2c/3 when a Cu tubing is painted or when it is insulated.
Which brings me to my main point today. Duz a lumped element transmission line model allow input for the insulation on a wire?
Duz a lumped element transmission line model allow for ground reflexion?
--- End quote ---
Your rule of thumb for the enamel affect on the speed is only approximate for very closely spaced wires, such as a twisted pair transmission line. The effect is due to the storage of charge in the dielectric, where the field pulls all the electrons slightly in one direction, they then release and create a new field. The speed results from the superposition of the source and self generated field. (Aware that the theory I describe is also only a model and there is likely a quantum explanation for it)
When you have large amounts of air in between the superposition is dominated by the field in the air. Hence speed is very close to C.
You can create a lumped element model that accounts for ground reflection, but it would be horrible. I think OpenEMS pretty much does this for it's FDTD EM simulations.
aetherist:
--- Quote from: hagster on May 02, 2022, 06:51:06 am ---
--- Quote from: aetherist on May 01, 2022, 11:07:05 pm ---Veritasium duznt tell us whether the Cu tubing has an enamel coating. We all know that the speed of electricity drops from c/1 down to 2c/3 when a Cu tubing is painted or when it is insulated.
Which brings me to my main point today. Duz a lumped element transmission line model allow input for the insulation on a wire?
Duz a lumped element transmission line model allow for ground reflexion?
--- End quote ---
Your rule of thumb for the enamel affect on the speed is only approximate for very closely spaced wires, such as a twisted pair transmission line. The effect is due to the storage of charge in the dielectric, where the field pulls all the electrons slightly in one direction, they then release and create a new field. The speed results from the superposition of the source and self generated field. (Aware that the theory I describe is also only a model and there is likely a quantum explanation for it)
When you have large amounts of air in between the superposition is dominated by the field in the air. Hence speed is very close to C.
You can create a lumped element model that accounts for ground reflection, but it would be horrible. I think OpenEMS pretty much does this for it's FDTD EM simulations.
--- End quote ---
I agree that insulation (eg a coat of enamel) would have the effects that u say. But, i am fairly certain that tests (somewhere) have shown that the speed of electricity is drastically affected as per what i said, ie 2c/3 instead of c/1 for a bare wire.
If tests for the speed of electricity when having different thicknesses of say enamel showed that the thickness had no effect (ie that the speed of electricity was 2c/3 in every such case) then that would show that i am correct. If u are correct then thickness would have a significant effect (at least over a certain range of thickness).
I thort that i had sorted this out on this thread (search "Alphaphoenix") but praps knot, koz, he (brian) didn’t divulge the exact lengths of his wires, nor did he tell us if they had enamel (but they did have enamel).
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