This lecture covers the concept of cyclotron motion, where a charge moves in a magnetic field, and the calculation of the magnetic force acting on a current-carrying wire. It explains the trajectory of a charge in a magnetic field, the Lorentz force law, and the integration of forces on individual charges to determine the magnetic force on the wire. The lecture also discusses the parameters involved in evaluating the magnetic force and provides examples of calculating the force on individual charges and current-carrying wires.