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| "Veritasium" (YT) - "The Big Misconception About Electricity" ? |
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| bsfeechannel:
--- Quote from: aetherist on March 13, 2022, 10:07:27 pm ---https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity In metals. [000 ] Like balls in a Newton's cradle, electrons in a metal quickly transfer energy from one terminal to another, despite their own negligible movement. [00 ] A metal consists of a lattice of atoms, each with an outer shell of electrons that freely dissociate from their parent atoms and travel through the lattice. This is also known as a positive ionic lattice.[10] [0 ] This 'sea' of dissociable electrons allows the metal to conduct electric current. [1 ] When an electrical potential difference (a voltage) is applied across the metal, the resulting electric field causes electrons to drift towards the positive terminal. [2 ] The actual drift velocity of electrons is typically small, on the order of magnitude of meters per hour. However, due to the sheer number of moving electrons, even a slow drift velocity results in a large current density.[11] [3 ] The mechanism is similar to transfer of momentum of balls in a Newton's cradle[12] [4 ] but the rapid propagation of an electric energy along a wire is not due to the mechanical forces, [5a ] but the propagation of an energy-carrying electromagnetic field [5b] guided by the wire. [6 ] Most metals have electrical resistance. [7] In simpler models (non quantum mechanical models) this can be explained by replacing electrons and the crystal lattice by a wave-like structure. [8] When the electron wave travels through the lattice, the waves interfere, which causes resistance. [9] The more regular the lattice is, the less disturbance happens and thus the less resistance. [10 ] The amount of resistance is thus mainly caused by two factors. [11] First, it is caused by the temperature and thus [12] amount of vibration of the crystal lattice. Higher temperatures cause bigger vibrations, [13] which act as irregularities in the lattice. [14 ] Second, the purity of the metal is relevant as a mixture of different ions is also an irregularity. [15 ] The small decrease in conductivity on melting of pure metals is due to the loss of long range crystalline order. [16] The short range order remains and strong correlation between positions of ions results in coherence between waves diffracted by adjacent ions. [000 ] says that electrons transfer energy, via bumping. --- End quote --- Nope. It saysn't. It just says that energy is transferred quickly with little movement. --- Quote ---[0 ] says that a metal can conduct electric current. [1 ] says that electons drift koz of an electric voltage field. [3 ] says the mechanism is similar to bumping. What mechanism? Voltage? Drift? Transfer of energy? Who knows! [4 ] is confusing. It says that [4a] bumping does not propagate electric energy along a wire. Or, [4b] it says that bumping does not produce the rapid propagation seen of electric energy along a wire. Or [4c] perhaps both. --- End quote --- It is confusing because Maxwell's demon whispered in your ear that electrons are bumping each other, when the "wiki" never said that. Quite the opposite, it is saying that (what would be equivalent to) the "bumping" is not mechanical. Caveat analogiam, which in this text is only there to give you an intuitive understanding of how fast energy travels from one point to another with little actual movement. --- Quote ---[5a ] is a killer. Just when u were getting used to words like Newton cradle electron drift wire electric energy conduction voltage field etc, it suddenly foists on us an energy carrying em field. [5b] guided by the wire. Where is this field? In the wire? On the wire? Around the wire? Is this energy electric energy? Does the field carry the energy? Or is the energy in the field? In other words duz the field possess the energy or does it simply transmit it, or perhaps both? --- End quote --- Electromagnetism is not for everyone. It seems. |
| adx:
--- Quote from: aetherist on March 15, 2022, 12:38:37 am ---I would love to see a test for a steel clad copper wire. Old (electron) electricity might say that the conductivity for DC should be say 95% (if area of steel is say 10% of total area)(koz most of the drifting electrons would live in the Cu), whereas new (electon) electricity might say 15% (koz all of the electons would live on the Fe)(& based on Fe having 6.00 times the resistance of Cu). --- End quote --- I'm tempted to do that. While trying to find ways to DIY re-plate soldering iron tips a couple of years ago, I tried the sillyest thing I could think of which was electroplating in some used de-rusting solution, and it seemed to work first time. But I've got other things to do, other replies... |
| bsfeechannel:
--- Quote from: penfold on March 14, 2022, 08:33:06 am ---Let's not forget that engineers and physicists have very different job descriptions. --- End quote --- In short, physicists study the fundamental laws of nature, while engineers study machines. --- Quote ---That doesn't necesarily prelude a person of either primarily physics, primarily engineering, or primarily mathematics background from working either job function or using i, j, I, J, i, j, I or J as a complex unit or 'current-(density)' variable. The interesting question there would be: which scientific descoveries arrived from which practice of which principals by a practicioner of which background? --- End quote --- Paul Dirac and John Bardeen, two Nobel laureates in advanced hacking, had a background in electrical engineering. Paul Horowitz and Winfield Hill, the authors of the Art of Electronics, are two physicists in engineer's clothing. |
| aetherist:
--- Quote from: bsfeechannel on March 15, 2022, 01:22:20 am --- --- Quote from: aetherist on March 13, 2022, 10:07:27 pm ---https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity In metals. [000 ] Like balls in a Newton's cradle, electrons in a metal quickly transfer energy from one terminal to another, despite their own negligible movement. [00 ] A metal consists of a lattice of atoms, each with an outer shell of electrons that freely dissociate from their parent atoms and travel through the lattice. This is also known as a positive ionic lattice.[10] [0 ] This 'sea' of dissociable electrons allows the metal to conduct electric current. [1 ] When an electrical potential difference (a voltage) is applied across the metal, the resulting electric field causes electrons to drift towards the positive terminal. [2 ] The actual drift velocity of electrons is typically small, on the order of magnitude of meters per hour. However, due to the sheer number of moving electrons, even a slow drift velocity results in a large current density.[11] [3 ] The mechanism is similar to transfer of momentum of balls in a Newton's cradle[12] [4 ] but the rapid propagation of an electric energy along a wire is not due to the mechanical forces, [5a ] but the propagation of an energy-carrying electromagnetic field [5b] guided by the wire. [6 ] Most metals have electrical resistance. [7] In simpler models (non quantum mechanical models) this can be explained by replacing electrons and the crystal lattice by a wave-like structure. [8] When the electron wave travels through the lattice, the waves interfere, which causes resistance. [9] The more regular the lattice is, the less disturbance happens and thus the less resistance. [10 ] The amount of resistance is thus mainly caused by two factors. [11] First, it is caused by the temperature and thus [12] amount of vibration of the crystal lattice. Higher temperatures cause bigger vibrations, [13] which act as irregularities in the lattice. [14 ] Second, the purity of the metal is relevant as a mixture of different ions is also an irregularity. [15 ] The small decrease in conductivity on melting of pure metals is due to the loss of long range crystalline order. [16] The short range order remains and strong correlation between positions of ions results in coherence between waves diffracted by adjacent ions. [000 ] says that electrons transfer energy, via bumping. --- End quote --- Nope. It saysn't. It just says that energy is transferred quickly with little movement. --- Quote ---[0 ] says that a metal can conduct electric current. [1 ] says that electons drift koz of an electric voltage field. [3 ] says the mechanism is similar to bumping. What mechanism? Voltage? Drift? Transfer of energy? Who knows! [4 ] is confusing. It says that [4a] bumping does not propagate electric energy along a wire. Or, [4b] it says that bumping does not produce the rapid propagation seen of electric energy along a wire. Or [4c] perhaps both. --- End quote --- It is confusing because Maxwell's demon whispered in your ear that electrons are bumping each other, when the "wiki" never said that. Quite the opposite, it is saying that (what would be equivalent to) the "bumping" is not mechanical. Caveat analogiam, which in this text is only there to give you an intuitive understanding of how fast energy travels from one point to another with little actual movement. --- Quote ---[5a ] is a killer. Just when u were getting used to words like Newton cradle electron drift wire electric energy conduction voltage field etc, it suddenly foists on us an energy carrying em field. [5b] guided by the wire. Where is this field? In the wire? On the wire? Around the wire? Is this energy electric energy? Does the field carry the energy? Or is the energy in the field? In other words duz the field possess the energy or does it simply transmit it, or perhaps both? --- End quote --- Electromagnetism is not for everyone. It seems. --- End quote --- No, i am happy with all of my wordage. But u make it sound like wiki didnt mention the Newton's Cradle at all. Newton's Cradle is nothing but mechanical. They might not mention bumping, but they mention collision strike etc. It would be good to make a cradle better suited to drifting electrons. I think using (instead of balls) say 100 strong magnetic discs, with large gaps tween discs, hanging on very very long cords (cords are double cords, in a Vee). The discs are all turned so that they are all positive to positive or negative to negative, ie they all repel the adjacent disc. Disc1 is then slowly pushed closer to disc2, & disc2 slowly swings towards disc3, & disc 3 swings towards disc4, etc. Disc1 is pushed along at a constant slow speed, past where disc2 initially was, & then past where disc3 initially was, etc. All of the disc to disc gaps gradually get smaller. The last gap tween disc99 & disc100 is perhaps always the largest. There is no actual contact tween discs. At least not for a while. There will be a visible wavefront of moving discs. The speed of the wavefront will be much faster than the speed of disc1. Actually the wavefront will move at almost the speed of light. But this will involve microscopic movement of the discs. The larger movements/wavefront more obvious to the eye would be much slower than the speed of light. And here we come back to the fact that the wavefront of drifting electrons in a copper wire must be much slower than the needed speed of light. |
| penfold:
--- Quote from: aetherist on March 15, 2022, 02:32:49 am ---[...]But u make it sound like wiki didnt mention the Newton's Cradle at all. Newton's Cradle is nothing but mechanical. They might not mention bumping, but they mention collision strike etc. [...] --- End quote --- There is the added complication of it being a 3-dimensional... and added complexity of the stationary lattice of positive ions. In the nano-meter and pico-meter scale, the inverse square law makes for almost unimaginable/unrelatable force to mass ratios and impossibly high numbers of involved particles (~10^28 for a small amount of copper). Naturally, to deal with the 'movement of electrons' as a field in a conventional sense, there's no real scope to find exact solutions as one could in a diabolical multi-body problem, there are thermal fluctuations and random lattice defects, so only a statistical representation is possible... luckily for such a huge number of particles, it averages out quite nicely. The other thing with the fixed lattice is that relatively minor variation in charge distribution produces a massive 'rectifying' force, and most likely below the amount caused by random thermal fluctuations. --- Quote from: aetherist on March 15, 2022, 02:32:49 am ---[...] There will be a visible wavefront of moving discs. The speed of the wavefront will be much faster than the speed of disc1. Actually the wavefront will move at almost the speed of light. But this will involve microscopic movement of the discs. The larger movements/wavefront more obvious to the eye would be much slower than the speed of light. And here we come back to the fact that the wavefront of drifting electrons in a copper wire must be much slower than the needed speed of light. --- End quote --- We know that fields exist outside the conductor, that the magnitudes of those fields and their vector product is proportional to energy flow. We know that the propagation speed of the E and B fields is affected by the presence of and transfer of momentum to electrons and dielectric properties that we call inductance and capacitance. We also know that the transfer of energy from one point in the circuit to another doesn't rely on a continuous uniform current density along the path of the wire... why must the speed of electrons match the speed of energy? |
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