PROPOSAL FOR A DIDACTIC SEQUENCE FOR TEACHING ELECTROMAGNETISM: ANALYSIS OF THE TEMPORAL VARIATION OF THE MAGNETIC FIELD USING SMARTPHONES

Abstract

This work aimed to evaluate two practical activities to analyze the temporal behavior of the magnetic field generated by aligning a compass needle close to a copper wire subject to the passage of a stationary current and a solenoid under the same conditions. After evaluating these activities, a didactic sequence was developed as a proposal to insert these experiments into a physics class for 3rd year high school students. Using low-cost materials, a replica of Ørsted's experiment and a solenoid were made with a copper wire, which carried an electric current when connected to two 1.5 V AA batteries. With the Phyphox application installed, it was possible to obtain the components and module of the magnetic field resulting from the vector sum of the local and current-induced fields and a graph of its intensity as a function of time using the “Magnetometer” function. For measurements made with the compass, a graph representing a damped oscillation was obtained, arising from the restoring force associated with the return of the needle to the north-south direction and the friction with its support. The amplitude decreased with each turn until the compass aligned with the external field. In measurements carried out with the solenoid carrying current, it was found that the magnetic permeability of the medium exerts a significant influence on the resulting magnetic field: the insertion of an iron core significantly increased its modulus, enabling the attraction of iron filings placed nearby. Furthermore, the change in the direction of the field was recorded when the polarity of the wires was changed. Although the activities evaluated are recurrent in physics teaching, the insertion of smartphones in these activities made it possible to analyze various aspects of the magnetic field, such as its vectorial character, its cause and effect relationship with the intensity of the current, its dependence with the magnetic permeability of the medium, its little explored temporal behavior and some attributes of ferromagnetic materials. Furthermore, the use of smartphones makes these activities more dynamic and interactive, inserting students as protagonists in the teaching-learning process and contributing to a better understanding of these concepts.