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| "Veritasium" (YT) - "The Big Misconception About Electricity" ? |
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| aetherist:
Thanx for your answers to my questions. Some have suggested that Veritasium Pt2-X is a triumph. Some have suggested that Veritasium Pt2-X (rise times etc)(sensitivity & screen scale etc)(reflexions etc) is severely constrained by practical switching problems & practical probing problems. I reckon that u/we can do a search on this topic for "Howardlong". See especially my reply#1048. He did his own little table-top X, using a puny 4 ft of ladder antenna. He had no such problems. And, his scope screen scale was 50 ps/div, compared to Veritasium's 50 ns/div. Howardlong used a 20 GHz scope. I am thinking that Veritasium's scope was just as good or better. I detect a continuing love affair around here for lumped element transmission line models. I wish to point out that there has never been any good correlation tween such a model & experiment for a DC transient of the Veritasium gedanken kind, albeit using 1000 m of Cu (AlphaPhoenix) or 42 m of Cu (Veritasium) or 8 ft of Cu (Howardlong) or any m or ft of Cu. I see much chatter around here re crosstalk due to radio waves, & crosstalk due to capacitance tween parallel wires, & crosstalk due to induction tween parallel wires. I wish to advise that these 3 effects are (basically) the same effect. Certainly in the case of electricity. Here the cause is em radiation. And we can add a 4th kind of crosstalk, ie induction due to static charge. Alltho here the cause is not em radiation, the cause is the electric field (there being zero magnetic field). So, what i am saying is that there is one basic kind of crosstalk. Induction. If the cause of the crosstalk is due to electrons (or ions) crossing a gap (rather than simply em radiation) then i am not sure whether i would call that a kind of induction. I would have to have a think. Some other day. If the cause of the crosstalk is due to photons (eg gamma rays), or some other exotic powerful subatomic rays, then that probly aint induction. While i'm hot. All electric radiation is em radiation. An electric field is simply em radiation (ie an em field) where the magnetic field part is nett zero due to 2 opposing magnetic fields negating. Hence in a sense charge too is em radiation. But i don’t want to start any arguments about that today. This contradicts what i said above, but i wont bother to edit that wording. |
| aetherist:
HERE IS A COPY OF MY REPLY#1048. START ##################################################################################################### Howardlong messaged me the following info. Rise time 10-90% at the scope is 36 ps. By the time it gets to the feedpoint, it'll be about 45 ps due to dispersion in the coaxial feed. Fall time looks similar visually but I didn't take a measurement. Pulse width is 608 ps. Howardlong has already mentioned that his signal crosses (first reaches) to the opposite wire in 80 ps which he says accords with the speed of light for the 24 mm distance tween the pair of wires in his 450 Ohm antenna ladder line. Howardlong in effect says that this supports Veritasium's expectation that Veritasium's bulb can possibly light (start to light) in 1/c seconds (ie 3.3 ns for Veritasium's 1000 mm spacing). These kinds of transients have at least say 4 stages. I wanted to have a closer look at Howardlong's experiments to look at the first stage, stage-1 of his transient. But i will come back to that another day. Today i will jump ahead & look at stage-2 of his transient. Howardlong X using 4 ft of ladder antenna line (wires 24 mm apart). He got 12 mV, with 58 mV in the other wire, which is 20.7% (20 GHz scope). Schantz X using 100 ft of 300 ohm twin lead antenna line (wires 7 mm apart). He got 60 mV, with 340 mV in the other wire, which is 17.6% (100 MHz scope). AlphaPhoenix X using 1000ft of 24AWG enameled copper wire (wires 250 mm apart). He got 0.2 V, which climbed to 1.7 V, which is 11.8%(100 MHz scope). Actually his source is 5.0 V, so 0.2 V is 4.0%. Silicon Soup (youtube) does a Finite-Difference Time-Domain simulation (1000 mm), gets a 0.3 mA signal from a 1.47 mA current, which is 2.0% 20.4%, for a mini-version of the Veritasium circuit. I don’t know how his pseudo-signal happens (its something to do with Maxwell)(displacement current perhaps). All of the above percentages are astonishingly high. But i think i know what happens. A step signal (voltage)(current)(Heaviside might say that the step signal is energy current)(Dollard might say impulse current)(is say elektons) propagates say to the right along the right half of our circuit, along the say bottom wire. The bottom wire in that half is gradually flooded with negative charge (elektons), starting at the source (at the midpoint of the circuit), the flooding progressing to the right towards the short at the end. The growing negative charge on the surface of the bottom wire gradually repels more & more free surface elektons on (along) the top wire, some go right (to the end), & some go left (to our bulb). The elektons pushed right (along the top wire) tend to bunch up, because they are propagating in the same direction as the propagating step (in the bottom wire). The result is that say 50% of the escaping elektons in the top wire go left & 50% go right. The elektons propagating left create a flow of elektons flowing left through our bulb, which manifests as a voltage drop across our bulb. Our bulb turns on (weakly) a little after d/c seconds, ie as soon as (enough) elektons start to flow (leftwards) through the bulb on our top wire. Our bulb glows brighter as the flow of elektons through the bulb increases. After a short time the flow through our bulb reaches its initial maximum (say 10% of the current in the bottom wire). [In the Veritasium gedanken (wire spacing d is 1000 mm) this would be a little after 1/c.] Eventually the step (propagating right) in our circuit will get to the end of the bottom wire & will enter the top wire (via the short), & go to our bulb. When the main signal reaches our bulb the bulb will achieve full brightness, ie there will be a big sudden jump step in the voltage. [In the Veritasium gedanken the main signal would reach his bulb in 1 second (his half circuit is 1 light second long).] The elektons escaping to the left will give a current & voltage (signal) at the midpoint of our top wire (ie at our bulb). The size of the signal will depend on the wire spacing. The signal will begin to grow as soon as the E×H radiation reaches across, ie the delay is d (metres)/c (m/s), where d is the spacing, & c is the speed of light in the medium (usually air). More exactly, the delay will depend on the location of our switch, relative to our bulb. [In the Veritasium gedanken this switch-to-bulb distance is approx the same as the spacing tween his wires anyhow.] I doubt that a (simple conventional) LCRX lumped element transmission line model can predict transient current, using a simple LCRX paradigm, using simple speed of light. Any such model needs smarter components. And truer speeds (& truer flow of surface elektons). However i have never had any hands-on experience with transmission lines, or TL models (or the application of electricity theory of any kind). However the repulsion of the elektons from (along) our top wire is not unlike the action of lots of little capacitors tween the bottom wire & the top wire. Perhaps someone could do a (simple conventional) transmission line model for Howardlong's experiment. END ################################################################################################################ |
| Sredni:
--- Quote from: electrodacus on May 01, 2022, 04:52:41 am --- --- Quote from: Sredni on May 01, 2022, 04:27:05 am ---You think that KCL holds, in the first few nanoseconds? --- End quote --- Has significantly more energy left the battery than got to the load/lamp ? Do you agree that energy conservation can not be violated ? If so then any difference should have ended up as heat and or stored in some form. --- End quote --- it's going into building the fields that will make the steady-state power transfer possible. Or, if you dislike the idea of fields storing energy, it is going into separating the surface charge that will create the electric field inside the good conducting wires and the badly conducting load and that are responsible for the the local dissipation of energy in situ. --- Quote ---If you will have a sensitive enough thermal camera you will see that all energy delivered to the Load/lamp was trough the wires (not outside the wires) as you will be able to see the IR losses (yes for those first few nanoseconds). --- End quote --- No, you will see the resistor of the lamp getting hotter while the wires are cold. And even in steady state you would see the lamp filament very hot and the wires not even lukewarm. You can't see the 'transfer' of energy: you can only see where it is dissipated. |
| bsfeechannel:
--- Quote from: Naej on May 01, 2022, 08:59:09 am ---If you want to do scipop with antenna then you a) use the word antenna b) don't take as the only example unintended antennae. Why are you so fixated on the magical words "the energy is in the fields" when it's only science-babble (not even wrong) ? How many mistakes are ok if you utter the magical words? (I forgot the part where resistance is explained, which is completely wrong) --- End quote --- And if you conjure the RF spirits with the magic word antenna you think that you'll ward off the curse of the energy in the fields, don't you? --- Quote ---And: wires are pipes, they are pipes for current and pipes for energy. --- End quote --- Your theory lost. Nature won. Learn to live with that. |
| bsfeechannel:
--- Quote from: pepsi on May 01, 2022, 04:36:29 am ---Is this for real? Tell this to the national electricity grid. Let's get rid of poles and wires and beam MW of power to customers :-DD --- End quote --- Not a bad idea. The problem is the cost of the wave guides. If we only had some kind of guide for LF AC fields to carry the energy... Sigh. I think we'll have to wait for the invention of wires. |
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