undefined | Better HN

0 pointsnandomrumber11mo ago0 comments

Problem is electricity is kinda three different things, as far as models go.

1) DC; 2) low frequency AC; 3) Radio frequency circuits

With DC, the water in pipes analogy is close enough to be useful.

With low frequency AC, like mains electricity at around household voltages, there are additional considerations to make the water in pipes analogy to be useless enough we generally require people to be licensed to work with it.

Radio frequency electronics is indistinguishable from magic.

0 comments

tlb11mo ago

The pipes analogy gives people a wildly unrealistic idea of the speed of electron movement in a wire. They only move a few mm/s at max current in copper wire. Electrons take minutes to go down the power cable from your PSU to your GPU. At GHz frequencies, they move less than an atom diameter.

km6GEwiQqsyEKQH11mo ago

How come? It seems it is very analogous to water in a pipe. Let's say I have a 30 m long garden hose. The water in it moves (in the order of magnitude of) 10 m/s in it. If the water is turned off, and I hold my thumb at the end of the hose and turn the tap on, I feel the water pressure almost immediately (the speed of mechanical waves in water). So it is obvious that there are two speeds. One is the speed of propagation and one is the speed of the medium, and they are way different.

nandomrumberOP11mo ago

All models are wrong, some are useful.

If you go on to study electronics / electricity beyond junior schooling level, you’re going to be exposed to progressively less wrong models.

Or watch three YouTube videos, there was some action from the big guns a couple years ago.

j / k navigate · click thread line to collapse