In this work, we propose an inexpensive laboratory practice for an introductory physics course
laboratory for any grade of science and engineering study. This practice was very well received by
our students, where a smartphone (iOS, Android, or Windows) is used together with mini magnets
(similar to those used on refrigerator doors), a 20 cm long school rule, a paper, and a free
application (app) that needs to be downloaded and installed that measures magnetic fields using the
smartphone’s magnetic field sensor or magnetometer. The apps we have used are: Magnetometer (iOS),
Magnetometer Metal Detector, and Physics Toolbox Magnetometer (Android). Nothing else is needed.
Cost of this practice: free. The main purpose of the practice is that students determine the
dependence of the component x of the magnetic field produced by different magnets (including ring
magnets and sphere magnets). We obtained that the dependency of the magnetic field with the distance
is of the form