General > General Technical Chat
Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
electrodacus:
--- Quote from: cbutlera on July 16, 2022, 09:06:11 pm ---
I think I have got it! There is some method to your apparent madness. I also apologise for poking a little fun at you last year, when I first joined in a little with this discussion and thought that you were trolling. I now think that you genuinely believe that you have a good understanding of Physics.
It looks like you are doing the following:
You have a picture in your head of energy flowing from the wind treadmill through the vehicle and into the road treadmill. You also picture some additional energy flowing from the wind treadmill and into the vehicle that can be used to accelerate the vehicle.
You have labelled what you regard as the motor as G, and the generator as M to humour the rest of us, because you are convinced that the opposite is the true direction of energy flow.
You first calculate the rate of work done on the road treadmill, which you call Pin.
You then calculate the rate of work done by the wind treadmill, which you call Pout. You surmise that this must be equal to Pin (you think that it must be coming from somewhere) plus the rate of work done on the device labelled 'M'.
You conclude that the net power going into the vehicle is the difference Pout - Pin.
The fundamental problem is that you understand what energy is and can visualise it flowing around. You need to unlearn this. I don't know what energy is, and neither does anyone else with a reasonably good grasp of physics. Richard Feynman didn't know what it was, and said the following.
"It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity, and when we add it all together it gives “28”—always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas."
This comes from the Feynman Lectures on physics page [url]https://www.feynmanlectures.caltech.edu/I_04.html[/url]. It is well worth reading this page.
It is better to think of energy as nature's checksum. Conceptually make your calculations using position, force, mass, time and their derivatives. Then calculate the total energy at the beginning and end to make sure you haven't made an error, or at any intermediate point if you wish.
Of course for complex systems, such a gas, calculating all of the positions, velocities and forces is impractical. So using conservation of energy is a very useful shortcut, but it brings nothing new to the table. It isn't an additional constraint on Newtonian mechanics, just a useful consequence of it.
If you are really determined to just use energy in your mechanical calculations you could use Lagrangian Mechanics, which is formulated in terms of energy. It uses the Principle of Least Action to calculate the way in which a mechanical system will evolve with time. But you need to learn to walk before you can run, so I would not recommend taking that path for the time being.
I'm not saying that you shouldn't be using energy and power in your calculations, just don't try to visualise it. Keep your visualisations to intuitive concepts like position, mass and force etc. You seem to have a good grasp of these, except when you think that they conflict with conservation of energy. When that happens you defer to treating the conservation of energy as showing the real truth.
What you should do when you see such a conflict is to go back through your calculations and look for the error. Energy is your checksum, and if it doesn't appear to agree with what the forces, masses, positions and velocities are telling you then there must be an error.
To try and bring this back to the battery, the switch and the light bulb, which is the correct topic for this thread. Don't ask how the energy gets from the battery to the light bulb. Instead ask how the electrons make the journey, and how the electromagnetic field makes the journey. If you know those two things, then you know everything that you need to know. Asking how the checksum made the journey doesn't mean anything.
--- End quote ---
I will agree that the way I make the calculations is maybe unusual but it is correct and consistent with all real world tests.
You say in so many words that I consider energy conservation as the checksum and you are correct because energy conservation is a law that nobody ever disproved.
As for my setup it is done so it exactly represents the blackbird with the treadmill model of blackbird being the easiest to visualize.
G / generator wheel is the same as the wheels driving the propeller on blackbird either the large one or the treadmill model.
The road treadmill is the treadmill used to demonstrate the propeller model can advance against the treadmill direction and it is represented as the case B) in my examples.
The propeller was replaced with a wheel as that is what a propeller is other than propeller travels through a medium and a wheel on the surface of a medium and thus it is the motor wheel.
The wind treadmill represents the air that is stationary in case B) same as in the treadmill test conducted indoors.
The reason why treadmill propeller model managed to move forward is due to pressure differential stored while it was placed on the treadmill and kept there with the hand.
The pressure differential storage is eliminated when propeller is replaced with a wheel M and since that is on a solid surface the air compressibility no longer plays a role.
As you claim to understand please share the results of the 3 examples. If you can not do that you can not claim to understand.
electrodacus:
--- Quote from: Naej on July 16, 2022, 09:09:08 pm ---The total force is equal to 0 and you said that the vehicle accelerates.
So: did you read Newton's second law? What does it say on the vehicle acceleration in A, B and C?
I already did provide the results: vehicle won't accelerate and you have surplus power from one wheel in A/C.
--- End quote ---
No force equals zero. I refer just at the braking force when you want to generate 10W will need to to have an equal and opposite force on the motor wheel else you can not produce anything.
So in case A) where braking force is 5N this could not exist without the equal and opposite force at the wheel M.
There is a net power 20W in this case and so there is a net force in the same direction.
I made a calculation a bit earlier about the speed of the vehicle after one millisecond and if I remember correctly was around 0.06m/s so the net force at that moment will have been 20W/0.06m/s = 333.33N
This is of course idea case and so in real life that net force after first ms will have been smaller both due to friction losses but also due to materials not being an ideal solid they have either an elastic or plastic deformation. The elastic deformation means energy is temporarily stored thus force will not tend to infinite when vehicle starts to move.
Where is that so called surplus power going ? Is that so called surplus power the 20W and -4W that I calculated ?
The negative power is to show the direction that vehicle will move. witch is opposite for case C vs case A
Naej:
--- Quote from: imo on July 16, 2022, 09:39:22 pm ---
--- Quote from: cbutlera on July 16, 2022, 09:06:11 pm ---..
"It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. However, there are formulas for calculating some numerical quantity, and when we add it all together it gives “28”—always the same number. It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas."
..
--- End quote ---
We have got something like Planck's scale, time, force, length, energy, temperature, volume, area, density, frequency, momentum, acceleration.. Why we cannot define the smallest blobs of energy then?
@Nominal Animal: the issue I see is the e-field in a good conductor is almost zero, therefore there is almost none force which would push or pull the electrons somewhere. I think the drift speed (some XXum/sec in a copper wire at 1Amp current) is there only because the e-field is "almost zero" but not zero. There is the chaotic movement of free electrons in the conductors with Fermi speeds of 1570km/s but their vectors are random..
--- End quote ---
Who said they were the smallest? A black hole merger has a power close to the Planck power.
electrodacus:
--- Quote from: Nominal Animal on July 16, 2022, 09:37:34 pm ---Okay, I'll make myself the laughing stock of everybody here, voluntarily, and will bite.
Current is defined as the net rate of flow of electric charge through a surface or into a control volume. Electrons are one possibility for carrying such charge. There are many different forms of energy, of which "electrical energy" –– really, easily accessible electric charges (batteries, accumulators, capacitors) or currents (DC or AC, like the mains current in your home) –– is just one form. All transfers of energy can be considered energy flow.
When sufficiently isolated conductors are used, the current flows in the conductor. For alternating currents, the current flows mostly on the surface of the conductor.
If the conductor becomes sufficiently hot, or the voltage between the conductor and a nearby other conductor becomes high enough, you can get an arc of electrons –– even if in vacuum. This can burn through the isolating material, and in a gaseous atmosphere, create a plasma arc. This, too, has useful properties.
Because moving charges always generate an electromagnetic field, it is also possible to couple another conductor inductively (via the magnetic field) or capacitively (via the electric field). (The high potential difference between the conductor and a nearby isolated conductor is one way this coupling can occur; capacitively.) Although the field interactions then carry energy from one conductor to the other –– very much inducing useful current or voltage in the other conductor ––, we do not usually call this kind of energy flow "current", because the interaction is through photons, non-charged particles.
(One exception is with coupled inductors, such as in transformers. This is because current induces a magnetic field which in turn induces a current, and it is just easier for humans to say that "current is transferred", because saying "current in A generates a magnetic field that couples to B inducing a current". But, in a strictly physical sense, the energy transfer is mediated by photons there, and there is no "current flow" between the two.)
How much of the overall energy is carried by the conductor, and how much by electromagnetic field interactions, depends completely on the topology: what kind of curve the conductor forms, and whether there are other conductors nearby so that they can couple to the EM field generated by the current flowing in this conductor.
The question posed in the thread title, "Don't electrons push each other", is a complex one.
The simple answer is that "That's a wrong question, because they interact. 'Push' is a completely wrong concept here.".
The complicated answer is quantum mechanics behind particle-wave duality. In essence, electrons are both fields and particles. When we look at interactions like the details of how electrons move in a conductor, we really need to look at the fields instead of considering them as particles, because electrons exhibit almost completely field-like behaviour there, and they interact in rather unintuitive ways. Their behaviour has just about nothing to do with the marbles most people think about when they think about electrons; instead, they are delocalized, like smeared over a possibly very large volume. The field of physics involved in this is electrodynamics, or if we get to high energies or really fast phenomena, quantum electrodynamics.
In a way, if we look at electrons bound to atoms or to a lattice like most metals, interacting electrons do not just 'push' but 'pull' and even 'twist' each other, depending on their quantum properties. (The last depends on the orbital magnetic dipole moments of the interacting electrons, and is often neglected.)
For example, the interaction between iron (Fe) and chromium (Cr) atoms in for example stainless steel, producing its corrosion resistance, involves these "magnetic" 'twisting' interactions between electrons.
But even that is just a crude analog, and probably makes any physicists reading this laugh at me for trying to describe it this way... It is one of those things that really is logical and rational, not "magic" at all, but is just not easily intuitively understood, because normal human-scale world does not contain suitable analogies at all.
--- End quote ---
Yes in Derek's example current flows through conductor.
The electric and magnetic field around a moving charged particle is conservative thus it is important to talk about energy storage, and it is also the reason Derek measures a current through the lamp much faster than the ns it will take for electron wave at almost the light speed to get there.
The energy is all converted in to photons but not instantly due to thermal storage.
Derek used thick copper pipes as the "wire" and a short 1kOhm resistor as the lamp/load.
If you can imagine a "wire" of that same length as his loop but so thin that the resistance was 1kOhm for that length and nothing else connected.
Then the "lamp" will have been all that long path so if it could get hot enough that it will all glow then you could visualize the path that energy travels through as it will be the wire and energy (all of it) is dissipated as radiated electromagnetic energy (photons) at hundreds of THz.
So all energy delivered by a battery or charged capacitor is delivered through wire and then from the wire all that energy is radiate as electromagnetic radiation.
So taken that long wire with 1kOhm resistance at 20V that will be 0.4W of power for one second will be 0.4Ws same as 0.4J
If you removed the source after 1s that energy will still be mostly stored in the conductor as thermal energy and over the next few minutes will be slowly related to space as photons.
There is nothing else 0.4Ws of stored energy will be transferred to wire (wire temperature will increase) and that energy will slowly be radiated to space.
There is no ridiculous energy exiting the battery in the vacuum or air around and from there enter the wire.
Naej:
--- Quote from: electrodacus on July 16, 2022, 10:21:08 pm ---
--- Quote from: Naej on July 16, 2022, 09:09:08 pm ---The total force is equal to 0 and you said that the vehicle accelerates.
So: did you read Newton's second law? What does it say on the vehicle acceleration in A, B and C?
I already did provide the results: vehicle won't accelerate and you have surplus power from one wheel in A/C.
--- End quote ---
No force equals zero. I refer just at the braking force when you want to generate 10W will need to to have an equal and opposite force on the motor wheel else you can not produce anything.
So in case A) where braking force is 5N this could not exist without the equal and opposite force at the wheel M.
--- End quote ---
So there is an equal and opposite force, but the total force is not equal to 0. Well. What are these ghost forces then?
--- Quote from: electrodacus on July 16, 2022, 10:21:08 pm ---Where is that so called surplus power going ? Is that so called surplus power the 20W and -4W that I calculated ?
The negative power is to show the direction that vehicle will move. witch is opposite for case C vs case A
--- End quote ---
Are you sure? What is the kinetic energy after a power of -4W during 1s? It should be -4J, with an imaginary speed I guess.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version