Basic science courses, such as physics, are fundamental to precollege studies. For instance, in different engineering applications, electricity and magnetism require comprehending subjects such as electrical circuits and power electronics. However, abstract concepts such as electric or magnetic fields are often difficult to explain without visual tools. Computer programs designed for learning physics fundamentals are useful in this area because they allow the visualization, interaction and reinforcement of main concepts in a better way than using only blackboard. In this work, an interactive MATLAB based program to visualize a magnetic field in 3D was presented. The measurements were sampled by a computer-controlled Cartesian robot with a Hall effect sensor. The magnetic field was generated by an energized electromagnet to show the relationship between electricity and magnetism. The designed graphical user interface aims to stimulate interest in electromagnetism in precollege students.