The Veritasium youtube etc tells us that drifting electrons drifting at (Veritasium says) 0.3 mm/s in the lab frame have the same spacings (center to center) as the Cu nuclei (ie protons)(which are stationary in the lab frame).
Veritasium & Co have to invoke that postulate, koz they know that a stationary charge is not attracted or repelled by a wire carrying an electric current.
But, if, when there is zero electric current, the electron to electron spacing is the same as the proton to proton spacing, then, when the current is turned on, & electrons drift, surely STR demands that in the lab frame the electron to electron spacing will be contracted.
In which case the wire will have a negative charge in the lab frame.
STRIKE-1. So, the STR explanation of the magnetomotive force fails at the first pitch, which was an easy meatball.
However, i will keep going, koz this Einsteinian farce has an astonishing number of fudges pushes & stupid postulates.
A more sensible application of STR demands that the current carrying wire has zero charge when the wire is moving at V/2, ie at a half of the drift velocity, ie at 0.15 mm/s (if Veritasium's 0.3 mm/s is true).
When/if the wire is moving at 0.15 mm/s, then in the wire's reference frame the protons will have a relative V of 0.15 mm/s to the left, & the electrons will have a relative V of 0.15 mm/s to the right, in which case the spacings for the protons & the spacings for the electrons will be both contracted by the same amount, in which case the wire will have a neutral nett charge.
The silly STR push, that the wire has a neutral charge when the wire is stationary, ie when the electrons are drifting at 0.3 mm/s, must be one of the stupidest postulates that i have seen.
Why hasn’t it been debunked before. Why did it have to wait for me to come along, a mere civil engineer, allergic to electricity, to point the problem out to all u EEs.
Veritasium's 0.3 mm/s is very fast, by a factor of 10, ie 0.03 mm/s is more likely. Wiki gives an example of 0.023 mm/s for 1 Amp in a 2 mm dia Cu wire.
Notice that in the Veritasium youtube the electrons are drifting at about 1 m/s (judging by the size of Veritasium's head). Whereas the total distance of drift would have been only say 77.4 mm, based on his 0.3 mm/s for the whole 258 seconds (4:18) of his whole youtube. This 77.4 mm would be about 1.5 diameters of his drawn circular electrons. But if based on 0.03 mm/s then the total drift would have been 7.74 mm, ie say 0.15 dia. His electron speed of 1000 mm/s is 33,333 times faster than 0.03 mm/s.
My above numbers are a bit unfair (& silly). He drew his wire to appear to be say 300 mm dia (judging by the size of his head), hence if the wire is meant to be say 2 mm dia then the drawing is a 150 times magnification. Hence his 0.3 mm/s should have given a drawn drift speed of 45 mm/s instead of his actual drawn speed of 1000 mm/s. And, as i said, his 0.3 mm/s should have been more like 0.03 mm/s, which would have needed a drawn drift speed of 4.5 mm/s. Just saying. More tomorrow.
https://en.wikipedia.org/wiki/Drift_velocityNumerical example
Electricity is most commonly conducted through copper wires. Copper has a density of 8.94 g/cm3 and an atomic weight of 63.546 g/mol, so there are 140685.5 mol/m3. In one mole of any element, there are 6.022×1023 atoms (the Avogadro number). Therefore, in 1 m3 of copper, there are about 8.5×1028 atoms (6.022×1023 × 140685.5 mol/m3). Copper has one free electron per atom, so n is equal to 8.5×1028 electrons per cubic metre.
Assume a current I = 1 ampere, and a wire of 2 mm diameter (radius = 0.001 m). This wire has a cross sectional area A of π × (0.001 m)2 = 3.14×10−6 m2 = 3.14 mm2. The charge of one electron is q = −1.6×10−19 C. The drift velocity therefore can be calculated:
Therefore, in this wire, the electrons are flowing at the rate of 23 μm/s. At 60 Hz alternating current, this means that, within half a cycle, the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch.
By comparison, the Fermi flow velocity of these electrons (which, at room temperature, can be thought of as their approximate velocity in the absence of electric current) is around 1570 km/s.[2]