부산대학교 도서관

The Ball Bearing High Voltage generator is a fairly simple and transparent apparatus that can serve as a tool to motivate conceptual descriptions and calculations in electrostatics that are normally presented to our students in a rather dry and matter-of-fact fashion. For example, instead of posing a problem in the typical textbook form of "Calculate the electric field of a point charge q located a distance d in front of an infinite conducting plane," and having the students wonder, "Why would we have to know that?" or "Why would anyone be interested in that?" we can simply demonstrate the eye-catching and curiosity-awakening Ball Bearing High Voltage (BBHV) generator, and then sit back and wait until our students start asking questions of their own. This way, the students have a genuine interest in answering their own questions--they have taken ownership and are far more motivated to arrive at an answer that is satisfactory to them. In this article I will illustrate how the BBHV generator is a demonstration apparatus capable of illustrating electrostatic concepts at multiple levels, ranging in difficulty from the middle school to the advanced graduate school level, from using concepts such as electric field, induced charges, surface charge distribution, and equipotential surfaces, to applications of Gauss's law and techniques such as the method of image charges. In this article I will not explicitly do all the calculations that are required to answer all the questions that the BBHV generator poses as most of them are quite familiar to us. Working out the answers to all questions surrounding the BBHV generator would fill half of a textbook. Instead, I will illustrate how the BBHV apparatus serves as a demonstration tool that motivates the necessity for the numerous calculations we do in electrostatics and electrodynamics, and how this one apparatus can tie together the different methods, approaches, and "tricks" we employ as we encounter electrostatics again and again in our journey from middle school to graduate school. In the following sections I will briefly describe the apparatus, present some questions that arise naturally when studying this apparatus, and illustrate various electrostatics concepts that can be motivated using the BBHV generator. To help the reader to quickly find a suitable question or homework assignment for their course, each of the following segments are marked with an icon approximately indicating the appropriate skill level and mathematical sophistication {MS = Middle School; HS = High School; IC = Introductory College level; AU = Advanced Undergraduate level; GS = Graduate School level} required to solve the question at hand. As many of the questions and problems that arise here are solved in the literature, I will provide only some of the answers here.