Question

The electron drift arises due to the force experience by electrons in the electric field inside the conductor . But force should cause acceleration . When then do the electrons acquire a steady average drift speed ?

Answer 1

Due to the force experienced by the external electric field, each 'free' electron inside the conductor does accelerate and increase drift speed until it collides with a positive ion of the metal. It loses its drift speed after collision but starts to accelerate and increase its drift speed again only to suffer a collision again and so on. On the average, therefore, the electrons acquire only a drift speed.