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| Veritasium "How Electricity Actually Works" |
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| Naej:
--- Quote from: bsfeechannel on May 06, 2022, 04:10:52 pm --- --- Quote ---For the same reason: opening the valve emits a sound wave, because you're violently compressing/accelerating water. Just as in the experiment proposed, it's a tiny amount of energy. --- End quote --- The amount of energy is irrelevant. What you are not paying attention is that the energy that arrives first through space is not a spike of energy. It is a sustained continuous step and it does not disappear. When the rest of the energy flowing through space guided by the wires finally arrives, it is just added to the initial step. Comparing Derek's and Alpha Phoenix's setup, you'll see that the step "duration" is proportional to the length of the line. If it were 300km, it would "last" 1s. If it were infinite, it would last as much as you'd want. So, it is not a "transient", it is "standient", that doesn't go away. --- End quote --- Derek clearly talked about the earliest event and not what happened next, so I talked about it. If you want to know what happens next, it's in the line after: --- Quote ---Also there's a pressure wave propagating inside the pipe, much like there's a potential wave propagating along the wire (telegrapher's equations also work for the pipe). --- End quote --- It certainly deserves to be separated because the physical behavior is quite different: in the first part, you emit/receive radio waves, and it is why you get the d/c delay, but quickly decays; after, you have capacitive coupling, with a much higher power/duration and no radio waves emitted. In both cases, you observe the exact same thing with pipes (given the impedance of air/metal/water, there's usually a very good shielding) --- Quote from: bsfeechannel on May 06, 2022, 04:10:52 pm ---Another problem is that some people who do not accept that the energy flows through space, are prepared to understand that the Poynting vector, perpendicular to the surface of the load, really conveys the energy that it will dissipate. But they don't understand that the wires are also resistors, and that the Poynting vector, perpendicular to whatever surface of the wire, be it radial or axial, will cause that energy to be dissipated by the wire. In other words, you cannot hand energy to a wire in one side and expect that this energy will reappear at the other side. The wire will dissipate it entirely. --- End quote --- Yes I can. Energy flows in wires and reappear in a lightbulb/engine/LED. --- Quote from: bsfeechannel on May 06, 2022, 04:10:52 pm ---You can prove that by connecting any piece of wire to the poles of a battery. The energy will not be transferred from the negative pole to the positive pole. It'll simply be dissipated. Completely. Sounds ridiculous, but people do not connect the dots. --- End quote --- Yes energy is transferred from the battery to the short, through the wire. Saying it flows from the battery to the vacuum and then from the vacuum into the wire is not wrong, but it definitely sounds ridiculous. |
| aetherist:
--- Quote from: electrodacus on May 07, 2022, 10:39:08 pm ---I promised an explanation of what happens in the waveform captured by Derek. Below with red is the voltage across the 1KOhm resistor with green is the supply voltage just after that R4 but it is an ideal voltage source so is basically the 20V supplied. You can see that from simulation "LTspice" you get the same small power to resistor that is byproduct of charging the transmission line capacitance (I only simulated half the circuit as it is symmetrical). Then at around 32ms current electron wave will travel half the line so at this time all line capacity is charged tho the part that charged first has already discharged not fully but significantly. Then as the electron travels on the other side of the transmission line the capacitance is being discharged starting with that far end continuing to maintain that limited amount of power for the lamp/resistor until about 65ns when the electron wave that left the source has finally arrived and rump up the lamp at full power (in fact slightly over as the remaining energy in capacitors is now basically fully discharged). The inductors are also charged but at steady state they still contain significant amount of energy that will be delivered when switch is turned off. (Attachment Link) Below is the power graph (area under the graph represents energy). Here you can see that significantly more power is provided by the source than what it ends up as heat on the lamp/resistor in the first 65ns and that difference is stored energy. The wires are much lower resistance so while there is some thermal energy wasted there it is insignificant compared to the 1K resistor. (Attachment Link) --- End quote --- Nice. The full current bit is of course a no-brainer – ie the rise starting at 60.0/65.5 ns & finishing at 80.0 ns – plus the reflexion at 136.1 ns is standard stuff. But i am very interested in the rise from 4.1 ns to 21.1/24.8 ns -- & the plateau of 3.7V at 24.8 ns, falling to 3.1V at 63.0/65.5 ns. The 4.1 ns is only a ruff estimate, & it confirms Veritasium's claim of 3.3 ns (ie 1/c) from his first youtube gedanken. So, can u get LTSpice to confirm the delay & rise & plateau in the first 65.5 ns? In particular the weird angle of the initial rise from 4.1 ns to 21.1 ns. AlphaPhoenix also got that there falling plateau in his AlphaPhoenix Xpt1 (pt2 yet to come)(if ever). |
| electrodacus:
--- Quote from: aetherist on May 07, 2022, 11:37:18 pm ---Nice. The full current bit is of course a no-brainer – ie the rise starting at 60.0/65.5 ns & finishing at 80.0 ns – plus the reflexion at 136.1 ns is standard stuff. But i am very interested in the rise from 4.1 ns to 21.1/24.8 ns -- & the plateau of 3.7V at 24.8 ns, falling to 3.1V at 63.0/65.5 ns. The 4.1 ns is only a ruff estimate, & it confirms Veritasium's claim of 3.3 ns (ie 1/c) from his first youtube gedanken. So, can u get LTSpice to confirm the delay & rise & plateau in the first 65.5 ns? In particular the weird angle of the initial rise from 4.1 ns to 21.1 ns. AlphaPhoenix also got that there falling plateau in his AlphaPhoenix Xpt1 (pt2 yet to come)(if ever). --- End quote --- You have a capacitor with air as dielectric and very long plates (the wires). That initial rise in voltage is due to capacitance of the transmission line not being charged all at once as the line is long and the electron wave needs time to get from one side to the other. The transmission line is simulated as multiple inductors and capacitors but they are ideal so it is consider the distance between plates is infinitely small so there no 3.3ns or so delay to correspond with the 1m distance between the plates (wires) in the real example. That can be added to simulation but is not the relevant part. If you bring the wires closer you will get rid of those 3.3ns (reduce that time significantly) but the energy transfer will be done in the exact same way. All energy travels trough wires and that initial energy is due to capacitive coupling so you are charging the capacitor (energy flows in the capacitor being stored there for later used and does not flow trough capacitor). If that was the case then you will not need to close the switch to transfer energy as the switch is also a capacitor. |
| aetherist:
--- Quote from: electrodacus on May 07, 2022, 11:51:43 pm --- --- Quote from: aetherist on May 07, 2022, 11:37:18 pm ---Nice. The full current bit is of course a no-brainer – ie the rise starting at 60.0/65.5 ns & finishing at 80.0 ns – plus the reflexion at 136.1 ns is standard stuff. But i am very interested in the rise from 4.1 ns to 21.1/24.8 ns -- & the plateau of 3.7V at 24.8 ns, falling to 3.1V at 63.0/65.5 ns. The 4.1 ns is only a ruff estimate, & it confirms Veritasium's claim of 3.3 ns (ie 1/c) from his first youtube gedanken. So, can u get LTSpice to confirm the delay & rise & plateau in the first 65.5 ns? In particular the weird angle of the initial rise from 4.1 ns to 21.1 ns. AlphaPhoenix also got that there falling plateau in his AlphaPhoenix Xpt1 (pt2 yet to come)(if ever). --- End quote --- You have a capacitor with air as dielectric and very long plates (the wires). That initial rise in voltage is due to capacitance of the transmission line not being charged all at once as the line is long and the electron wave needs time to get from one side to the other. The transmission line is simulated as multiple inductors and capacitors but they are ideal so it is consider the distance between plates is infinitely small so there no 3.3ns or so delay to correspond with the 1m distance between the plates (wires) in the real example. That can be added to simulation but is not the relevant part. If you bring the wires closer you will get rid of those 3.3ns (reduce that time significantly) but the energy transfer will be done in the exact same way. All energy travels trough wires and that initial energy is due to capacitive coupling so you are charging the capacitor (energy flows in the capacitor being stored there for later used and does not flow trough capacitor). If that was the case then you will not need to close the switch to transfer energy as the switch is also a capacitor. --- End quote --- If the gap is small then nonetheless the capacitor sits in the middle of a 1000 mm long short, & the speed of electricity is c/1 in the short, hence LTSpice should still give at least 3.3 ns. And, if modelled correctly, LTSpice should give the funny rise & the funny falling plateau. Re the switch, this might be a capacitor, but before it is closed the circuit is in steady state. |
| electrodacus:
--- Quote from: aetherist on May 08, 2022, 12:22:31 am ---If the gap is small then nonetheless the capacitor sits in the middle of a 1000 mm long short, & the speed of electricity is c/1 in the short, hence LTSpice should still give at least 3.3 ns. And, if modelled correctly, LTSpice should give the funny rise & the funny falling plateau. Re the switch, this might be a capacitor, but before it is closed the circuit is in steady state. --- End quote --- A capacitor with a 1000mm gap between plates will require 3.3ns and one with 1mm gap will require 3.3ps LTspice as far as I know has no option to specify the gap between plates and all comercial capacitors even the very high voltage ones will typically have much less than 1mm gap as the smaller the gap the larger the capacity. So there is nothing strange or not understood about that 3.3ns. When you close the switch exactly at that contact interface one electron will move from one side of the switch to the other and if a capacitor is in series in the loop as is the case in Derek's experiment then it takes 3.3ns for an electron on the other side of the 1m thick dielectric (air) to feel the effect and vacate a space. In the battery the space is much smaller so when switch is closed and one electron moves on the other side of the switch the electron wave will travel in to battery say maybe 100mm from the switch then inside the battery the gap say is 1mm and so that electron that left from battery to switch will cause an electron from the wire connected on the other side of the battery to be accepted in the battery and so if total distance is 101mm in a straight line it may take as little as 0.33ns but likely it can not capacitively couple in straight line so it will be an ark maybe say 150mm so around 0.50ns then both sides are coupled at the same time with the wire above that is at about 1m thus 3.3nm + 0.5ns will be the total time from closing the switch until the first packet of energy is transferred from battery to the capacitor (transmission line is a capacitor) and since the lamp is in series between this two 1m capacitors all current used to charge the capacitor also will go through the lamp and be lost as heat and maybe photos. |
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