General > General Technical Chat
Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
electrodacus:
--- Quote from: Nominal Animal on July 22, 2022, 02:49:43 am ---
It depends on the geometry of the wires.
The geometry of the transmission line determines how the energy flows!
If you use a coaxial cable, the initial pulse is a waveform with lots of high-frequency components, and they will propagate as an electromagnetic field in the dielectric insulator between the core and the shield. As described by the transmission line model, you'll get reflections (of those waves) until the system reaches steady state. Then, in the steady state, the electromagnetic field in the dielectric stays constant (except for thermal noise and external perturbations), and the energy flows within the core conductor, as current.
Something very similar happens when the circuit is disconnected, too. Because of those constant fields, the circuit doesn't just immediately cease, as the remnant EM fields do their reflection stuff again.
If you ignore those initial non-equilibrium states, you do not have a full physical picture or model of what is happening. By using approximations that ignore those, and by not defining the properties of the transmission lines in sufficient detail, you can make and prove any claim correct. It is a useless argument.
--- End quote ---
We are discussing the exact setup that Derek made no coaxial cables involved.
there was about 21m of wire/pipe on each side of the circuit symmetrically.
Say we leave the 20V battery he had and will consider that a constant voltage supply.
The left side say it had 9Ohm and the right side 1Ohm exactly the same geometry just much thinner pipe but same external diameter and no 1kOhm reistor that is removed just this transmission line.
Say the switch was closed for 5 seconds (just some arbitrary amount of time) the circuit is opened.
Over those 5 seconds 20V/10Ohm = 2A * 20V * 5 seconds = 200Ws (200 Joules if you prefer) where delivered to this transmission line / load
How come 90% of the energy is on the 9Ohm side and just 10% on the 1Ohm side while you have the exact same geometry on both sides?
hamster_nz:
--- Quote from: electrodacus on July 22, 2022, 03:03:54 am ---
--- Quote from: Nominal Animal on July 22, 2022, 02:49:43 am ---
It depends on the geometry of the wires.
The geometry of the transmission line determines how the energy flows!
If you use a coaxial cable, the initial pulse is a waveform with lots of high-frequency components, and they will propagate as an electromagnetic field in the dielectric insulator between the core and the shield. As described by the transmission line model, you'll get reflections (of those waves) until the system reaches steady state. Then, in the steady state, the electromagnetic field in the dielectric stays constant (except for thermal noise and external perturbations), and the energy flows within the core conductor, as current.
Something very similar happens when the circuit is disconnected, too. Because of those constant fields, the circuit doesn't just immediately cease, as the remnant EM fields do their reflection stuff again.
If you ignore those initial non-equilibrium states, you do not have a full physical picture or model of what is happening. By using approximations that ignore those, and by not defining the properties of the transmission lines in sufficient detail, you can make and prove any claim correct. It is a useless argument.
--- End quote ---
We are discussing the exact setup that Derek made no coaxial cables involved.
there was about 21m of wire/pipe on each side of the circuit symmetrically.
Say we leave the 20V battery he had and will consider that a constant voltage supply.
The left side say it had 9Ohm and the right side 1Ohm exactly the same geometry just much thinner pipe but same external diameter and no 1kOhm reistor that is removed just this transmission line.
Say the switch was closed for 5 seconds (just some arbitrary amount of time) the circuit is opened.
Over those 5 seconds 20V/10Ohm = 2A * 20V * 5 seconds = 200Ws (200 Joules if you prefer) where delivered to this transmission line / load
How come 90% of the energy is on the 9Ohm side and just 10% on the 1Ohm side while you have the exact same geometry on both sides?
--- End quote ---
"exactly the same geometry just much thinner pipe " :-DD
Take away either pipe, and see how much energy is delivered by the remaining one...
electrodacus:
--- Quote from: hamster_nz on July 22, 2022, 03:18:33 am ---"exactly the same geometry just much thinner pipe " :-DD
Take away either pipe, and see how much energy is delivered by the reaming one...
--- End quote ---
Outside diameter of the pipe is the same. The thickness of the wall is lower so that resistance is 9x higher.
So line capacitace will be the same in both cases.
Nominal Animal:
--- Quote from: electrodacus on July 22, 2022, 03:03:54 am ---
--- Quote from: Nominal Animal on July 22, 2022, 02:49:43 am ---It depends on the geometry of the wires.
The geometry of the transmission line determines how the energy flows!
--- End quote ---
We are discussing the exact setup that Derek made no coaxial cables involved.
--- End quote ---
But Derek did not specify the setup exactly, he makes approximations and simplifications that makes "the exact setup" ambiguous and up to interpretation.
It really is like starting with "Let's model humans as toroids, with nutrition flow through the hole occurring in one direction only", and then explaining mental issues as stemming from having mouth and ass connected to the same tube, and from being jealous of turtles that can do cloacal respiration too.
To be specific, the situation when the circuit is closed or opened, between the two steady states (no energy flowing, and energy flowing steadily), is where the interesting stuff happens. It is not an orderly progression marching through the system; it is a wavelike phenomena best described by quantum electrodynamics (in the physical sense), and well enough described by the transmission model if the properties of the system are specified in enough detail.
Even in a single conductor you get electromagnetic waves flowing through the conductor. If there is anything nearby the conductor, in these situations the system can actually behave like (be a) waveguide for these waves, so that while the current flow in such parts of the system is minimal, a lot of energy can still flow; and only when the steady state is reached, does the current flow match the energy flow through the system.
I really don't know how to better explain this. The transmission model is good, especially in the sense that you cannot just say that the conductor is a transmission line and get results that match the real world, because you do need to model the actual properties – geometry – of the system to apply the transmission line. On the other hand, if you define your transmission line ignoring things that do affect it in the real world, you can get whatever results you want; it just doesn't match real world anymore, and you're just babbling on about an imaginary system.
electrodacus:
--- Quote from: Nominal Animal on July 22, 2022, 03:39:33 am ---We are discussing the exact setup that Derek made no coaxial cables involved.
--- End quote ---
But Derek did not specify the setup exactly, he makes approximations and simplifications that makes "the exact setup" ambiguous and up to interpretation.
It really is like starting with "Let's model humans as toroids, with nutrition flow through the hole occurring in one direction only", and then explaining mental issues as stemming from having mouth and ass connected to the same tube, and from being jealous of turtles that can do cloacal respiration too.
[/quote]
I made it more clear saying it is symmetrical and you have 10m on each side plus 1m so 21m of wire/pipe on each side and the battery is a 20V constant and pipe resistance is total 10Ohm with 9Ohm for one half and the other half with 1Ohm.
I also specified a period for witch the switch is closed 5 seconds so we can discuss about all energy delivered by battery to circuit and where will that energy end up and in what form.
After those 5 seconds most of the energy that left the battery those 200Ws are still there as they increased the temperature of the pipe and so most of that was still not radiated to space.
But the half that has 9Ohm while having the same surface area (same external diameter for the pipe) will end up much warmer than the other part and will radiate over time much more electromagnetic radiation to space in the form of infrared photons as 90% of the energy from battery was delivered there.
Do you think that measuring anything external to wire like electric or magnetic field will help you know how much energy was dissipated to each side ? Since if energy was delivered from outside to the wire surface then you should be able to make measurements related to that.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version