These sources discuss the fundamental connection between electricity and magnetism, explaining that moving electric charges, or electric currents, are the origin of magnetic fields. They detail how this relationship was experimentally confirmed by Hans Christian Oersted and led to the field of electromagnetism. The texts further explore the magnetic fields generated by various conductor configurations, including straight wires, circular loops (espiras), and solenoids, providing the relevant mathematical formulas and the right-hand rule to determine field direction. They also touch upon the properties of magnetic permeability and present practical examples and exercises related to these concepts.