  A vast scientific literature in physics education documents a general
widespread difficulty in dealing with Electro-Magnetic Induction (EMI) at
various levels of instruction. But, at the best of our knowledge, there is a
lack of research that compares difficulties about EMI at different educational
degrees. We discuss here a case study about Italian high school, graduate
students' and teacher's conceptualization of some aspects of EMI as a function
of the sample instruction level. We analyse the answers to a multiple choice
written questionnaire, adapted from the literature and given to a total of 49
students. Some difficulties, emerged during the exams of university students of
a physics education course while discussing their final project concerning a
didactical path about EMI for secondary school, are also discussed. We find
that some deep misunderstandings are common at all levels of education and
probably come from the very poor link, generally presented in teaching EMI,
between the Faraday's flux law and the Lorentz force.
