This article describes a teaching sequence in which we have experimented digital resources of “online university (UeL)” site related to Electrostatics module with students of the first year of preparatory classes for engineering schools. We briefly remind the conceptual difficulties faced by the first cycle university students in the domain of Electrostatics. The sequence description experienced during three consecutive years in two versions is followed by an analysis of students’ perception of UeL site. This analysis shows that students are widely satisfied of the content, clarity and motivation provided by this site towards learning. Then, we study the contribution of UeL to conceptions of students participating in the experiment of the Electrostatic field created by a point charge and of the superposition principle of fields created by two point charges. The results show that when UeL resources are integrated into self-learning situation accompanied with a tutor or a teacher, they permit a good appropriation of these concepts and a better interpretation of situations used as evaluation instrument.