Question

How electric current flows in solids?

Answer 1

Flow of electric current in solids: In solids, the positive charges are associated with atomic nuclei. As the nuclei are firmly packed and closely held by inter-atomic forces, therefore, positive charges cannot drift.
On the other hand, negative charges (electrons) are not held firmly. Thus, when a potential difference, however small, is applied, they start drifting from a lower to a higher potential. The continuous drift of electrons through the body of a solid conductor constitutes the current.