This lecture covers the concept of demagnetization field, comparing external and internal fields in non-ellipsoidal bodies. It explains the equilibrium orientation of magnetization, torque, and the impact of geometry on demagnetization. The lecture also discusses the relationship between magnetic induction, magnetization, and magnetic field, as well as the energy stored in magnetic materials. Additionally, it explores the concept of shape anisotropy and the variation of demagnetizing field along the length of a bar magnet.