Final answer:
The drift velocity is the average velocity of free electrons in a conductor, moving opposite to an applied electric field. The relationship between electric current and drift velocity involves the electron density and the electric charge, with the drift velocity being lower when the electron density is higher.
Step-by-step explanation:
The drift velocity of free electrons in a conductor is the average velocity with which the electrons move under the influence of an applied electric field. Given the fact that free electrons collide frequently with atoms and each other, their individual paths appear random, similar to the motion of atoms in a gas.
However, when an electric field is applied to the conductor, these free electrons start to drift in a direction opposite to the field due to their negative charge.
The relationship between drift velocity and the applied electric field can be derived from the formula I = nqAvd, where I is the electric current, n is the number density of free electrons, q is the charge of an electron, A is the cross-sectional area of the conductor, and vd is the drift velocity.
In this relationship, the current is directly proportional to both the electric field and the drift velocity. The higher the density of free electrons in a conductor, the lower the drift velocity required to maintain a given current.