Magnetic levitation is one of the mechanisms that is at the forefront of technology. It is used in its most basic form in educational teaching, where the principles of physics converge that have as their principle electromagnetism and the fields created by existing poles that repel according to a quantity of initial current, giving instructive ideas of how the theoretical formulas work, giving life to a practical visual system. The current use on a large scale are the Maglev trains of Japan or superconductivity, being the realization of the quantum effects visualized at the moment of cooling the sample. The electronic circuit tends to be stable because, when using a high-power current, a Triac is needed to compensate the electrical flow provided by the operational amplifier and, therefore, stabilize with the photodiode when activated with the Led diode. Our purpose is to create a circuit...

One of the first subjects studied in Electricity and Magnetism classes is how one can make an electrically neutral object be an electrically charged object. There are three ways to do it: charging by friction, charging by contact and charging by induction. Induction charging is a method used to charge an object without actually touching the object to any other charged object. In order to illustrate the explanation of how the process of charging an electrically neutral body by induction, a 3D model was built using the finite elements method to show the increasing of the surface charge density in a initially neutral sphere when the distance between this sphere and a negatively charged bar decreases.