This lecture covers the fundamental concepts of charge transport in semiconductors, focusing on charge mobility, relaxation time approximation, and scattering phenomena. The instructor discusses the Drude model for electron gas and its application to electron transport, emphasizing the relationship between current density and electric field. Key topics include the mobility of various materials, the impact of band gaps on mobility, and the engineering of one-dimensional channels in two-dimensional electron gases (2DEG). The lecture also addresses scattering sources, including lattice phonons and crystal defects, and introduces Matthiesen's rule for estimating total mobility. The instructor explains how to tune channel properties and the significance of quantum conductance in semiconductor devices. The session concludes with practical examples and questions regarding the effects of geometrical parameters on charge transport, providing a comprehensive understanding of the principles governing semiconductor behavior in electronic applications.