How does a metal conduct electricity ?

Explanation

You would think that low-energy electron would have great difficulty in passing through a solid conductor. Inside the solid, the atoms are packed together with very little spacing between them. But it turns out that the electrons are able to travel through a perfect solid crystal smoothly and easily, almost as if they were in vacuum.
The .motion of electrons in a conductor, however, is very different from that of charges in empty space. When a steady current flows through a conductor, the electrons in it move with a certain average .drift speed..
One can calculate this drift speed of electrons for a typical copper wire carrying a small current, and it is found to be actually very small, of the order of 1 mm `s^(-1)`.
How is it, then, that an electric bulb lights up as soon as we turn the switch on?
It cannot be said that a current starts only when an electron from one terminal of the electric supply physically reaches the other terminal through the bulb, because the physical drift of electrons in the conducting wires is a very slow process
The exact mechanism of the current flow, which takes place with a speed close to the speed of light, is fascinating, but it is beyond the scope of this book.