This lecture covers the concept of inductance, energy calculation in a magnetic field, and the relationship between magnetic flux and induced voltage in a coil. The instructor explains the impact of varying current on magnetic flux, the direction of magnetic flux, and the calculation of induced voltage in a coil. The lecture also delves into the self-inductance of a coil, the relationship between magnetic field strength and magnetic flux density, and the inductance of ferromagnetic materials. The instructor demonstrates how to calculate inductance in ferromagnetic and non-ferromagnetic materials, emphasizing the importance of material properties in determining inductance.