This article shows the results of an intervention of the active type using electromagnetic technology. The motivating experience of the intervention manages to be the center of attention of the students in the classroom. In this way the teacher can establish a connection by developing the understanding of the concept of relative humidity in firewood. The intervention was carried out in the two semesters of 2017, in the construction materials class of the technology career in construction. The samples were of similar gender and age group. The measured variables were five, which determine the understanding of concepts such as: typification, classification, recognition and differentiation. The results obtained were significant, showing its enormous potential as an element to be used in the class.