Triboelectric Series Using a Simple Charge Sign Checker

Prompt determination of the positive or negative signs of charged objects promotes students’ understanding of electrostatics and motivates them to learn more about this field of physics. We developed a low-cost (about US$5) and easy-to-use device for checking the signs of the static charges in objects. It consists of two easy-to-build circuits, one for positive- and another for negative-charge detection. Both are composed of a metal–oxide–semiconductor field-effect transistor (MOSFET), an LED indicator, a tactile switch (momentary contact switch), and a jumper wire. In this paper, we provide instruction on how to build this device. Junior high school students who used it successfully created a triboelectric series by testing various daily-life materials. A free-response questionnaire revealed that the device is highly useful for consolidating students’ understanding of static electricity.