Define the term 'drift velocity' of charge carriers in a conductor and write its relationship with the current flowing through it.

The drift velocity is defined as the average velocity with which free electrons in a conductor get drifted under the influence of an external electric field applied across the conductor. The relation between drift velocity of free electrons and the current flowing through the conductor is given by: I = neAvd , where I is the current, n is the number of free electrons per unit volume, e is the electronic charge, A is the cross-sectional area of the conductor, and vd is the drift velocity.