This lecture covers the revision of the sinusoidal regime, series and parallel impedances, voltage and current dividers, the Thévenin principle, and the concept of impedance in the context of the permanent sinusoidal regime. It explains how the permanent sinusoidal regime applies to both periodic and non-periodic signals, introducing the definitions of resistance, reactance, and complex impedance. The lecture also delves into the concept of complex admittance and its role in generalizing Ohm's law for circuits with resistive, inductive, and capacitive elements.