In electrical engineering, as in other academic disciplines, there exist special, threshold concepts, where students often get stuck but which once grasped reveal new ways of thinking about a subject. Two surveys, student interviews and focus group discussions, and students’ assessment were directed at learning of threshold concepts and their pre-cursors. Results suggest that one of the precursor concepts, current flow, may be a threshold concept in itself. A model of precursor and threshold concepts assessment and additional student-support for learning threshold concepts is suggested.