Revelando el signo de las cargas eléctricas usando un detector de polaridad entretenido

In this paper we will discuss the construction, use and operation of an electrostatic polarity detector that was designed with the purpose of making interesting and fun an introductory class about the existence of electric charges and their interactions. The polarity detector uses a simple circuit and a design that can be printed on a 3D printer. So the reader can easily build their own detector after buying and assembling some electronic components at low cost. The body of the detector has the form of a hammerhead shark whose eyes light up according to the sign of the charge of the object to be measured. This fun form of shark allows to build entertaining activities where students can investigate the fundamental properties of interactions between electrically charged objects.