calculate the magnetic flow variation through the area making up the real circuit instead of calculating it through the area swept by the mobile conductor or, when a closed circuit does not exist, they do not find the area of integration to calculate the magnetic flow variation, which would be the area swept by the mobile conductor. This should come as no surprise given that usual teaching, as long as Faraday’s Law is applied, calculates the magnetic flow variation through the circuit area and not through the area swept by the conductor. We have seen that the method taught occasionally gives a false result—but of course not in cases usually analyzed with the students.