# How Fast Do Electrons Actually Move in a Wire?

###### By Anupum Pant

Unlike Alternating current which reverses polarity several times in a single second, direct current doesn’t do that. It is a unidirectional flow of charge. So, if you have an extremely long wire, with a switch in between, that connects a little battery in Dubai and a tiny bulb in San Francisco, how long do you think it would take the bulb to light up, when the switch is turned on?

It’d be almost instantaneous. “Almost” because it’d have a huge but finite speed. And by “it” I mean the speed at which the charge flows. Not the electrons.

The speed at which charge or electricity travels down a cable is actually the speed of the electromagnetic wave, not the movement of electrons.It is fast and depends on the dielectric constant of the material.

Electrons in an electric wire move very slowly. So slow, that it would be wise to measure their speeds in millimetres per hour. That is almost like honey flowing on a 2 degree incline. And yet, electricity is able to move across so fast because an electric wire is like a pipe filled with marbles (where marbles are electrons). When you push a marble from one end of the pipe, the marble at other end comes out, without the marble itself moving through the pipe.