My understanding is that current flow is like when you have a garden hose that is already full of water: as soon as you open the tap, water instantly comes out of the other end of the hose.
So when a generator pushes current through a power grid, do the electrons move at the speed of light (as many believe), or is it more a case of them all bumping each other along instantaneously,, as with the molecules of water in the garden hose?
In: Physics
It is a great question. The analogy of water flowing in a pipe, sort of breaks down once you get to the level of electrons and such.
1) Electrons are not massless particles. Therefore electrons cannot travel at the speed of light. The explanation is from Einstein: that anything with mass would need infinite energy to accelerate to the speed of light.
2) What is “moving” at the speed of light is the change in the electromagnetic field. The term used is propagate rather than move.
3) The speed of individual electrons cannot actually be measured with precision. But the presence of a voltage in wire will induce a “general flow” of electrons in one direction. (Imagine water in a turbulent river – we cannot say what speed any particular drop of water is moving but we can tell how fast the entire flow is moving in general) This flow speed is called “drift velocity” and is called drift because in most circumstances it is VERY slow.
4) Drift velocity direction depends on which side of the wire has higher voltage relative to the other. In power grids, the voltage is AC, so it swings from positive to negative. In effect the drift velocity switches each time the voltage switches signs and therefore the average drift velocity in the power grid is ZERO. That is, electrons aren’t “shooting out” at one end of an electric cable.
So one can imagine electrons essentially moving backwards and forwards but not really going anywhere. This is just an illustration – electrons don’t organize themselves like balls of stuff and their actual motion isn’t like cars going down a road.
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