On Fri, Oct 31, 2025 at 10:37:23PM +0000, fxkl47BF@protonmail.com wrote: > On Fri, 31 Oct 2025, David wrote: > > > On Fri, 31 Oct 2025 at 22:09, David <bouncingcats@gmail.com> wrote: > > > >> Hi, there's more explanation here: > >> https://en.wikipedia.org/wiki/Drift_velocity > > > > Sorry, I forgot to mention, their example: > > https://en.wikipedia.org/wiki/Drift_velocity#Numerical_example > > > > Similar to Thomas, calculates a drift velocity of 20 micrometers > > per second for 1 ampere in a 2mm copper wire. > > > > But the final sentence on that page is interesting: > > "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." > > > > all that make my head hurt Don't worry. What I (kind-of) calculated was just the electron's average movement due to the electrical current. The other velocity above is the jitter due to thermal movement, and since electrons are very light (~ 1/1000 as heavy as a hydrogen atom), they are quite fast. So imagine that as an electron soup jittering as mad, bumping into those copper atoms bound in their crystal structure, and flowing really slowly as a group from - to +. Semiconductor's electrons tend to flow faster (if at all possible) for a given current, because there are less available of them. Or you have to put so much potential difference to achieve said "given current" that you burn your nose ;-) > i program i saw recently about the sun said a proton created near the core can take millions of years to reach the surface > talk about a traffic jam (I read that you corrected that to photon in your other mail). Yes, it gets to play with lots of ions along its path. Plus, the sun is big. VERY big. Cheers -- t
Attachment:
signature.asc
Description: PGP signature