Drift velocity refers to the average velocity attained by charged particles, such as electrons, in a material due to an electric field. Electrons in a conductor propagate randomly at the Fermi velocity, resulting in an average velocity of zero. However, applying an electric field adds to this random motion a small net flow in one direction, which is the drift velocity. The drift velocity is proportional to current and is also proportional to the magnitude of an external electric field in a resistive material. Thus, Ohms law can be explained in terms of drift velocity. The formula for evaluating the drift velocity of charge carriers in a material of constant cross-sectional area is given by u = j/(nq), where u is the drift velocity of electrons, j is the current density flowing through the material, n is the charge-carrier number density, and q is the charge on the charge-carrier. The drift velocity of an electron for a unit electric field is known as the mobility of the electron. The net velocity at which these electrons drift is known as drift velocity, and it is measured in m/s or m2/(V.s) .