The concept of field acquire the ontological status of a physical entity when we consider dynamic situations. In this context rise up typical disciplinary knots that are source of learning problems for students, connected to: the sources of time depending fields, the electrodynamic of moving conductors, the nature of electric and magnetic fields as components of the electromagnetic field. A discussion of these principal knots on electromagnetism, and an analysis of the related learning problems provide one of the tree vertex of the triangle founding a research aimed to design a teaching/learning path on electromagnetic field.
