Experiment for teaching a fundamental principle in electrostatics

According to the theory of electrostatics, the potential difference, or simply “voltage” between two given points in an electrostatic field is a measure of the energy required to move a unit charge between those points. This fundamental principle is usually taught to engineering and physics students in introductory electricity and magnetism (E&M) courses. Unfortunately, experience has shown that students usually have great difficulty grasping that voltage in electrical circuits and systems is actually a measure of energy. This paper describes an advanced experiment that was designed at the University of West Florida for demonstrating the concept practically. In the experiment, a programmable robot arm moves a charged metal plate between two electrodes connected to a voltage source, while a control computer (connected to interface circuitry and a force sensor) directly provides a measurement of the energy exerted in moving the plate. Assessment of the students' understanding of the concept after they perform the experiment has shown an improvement from about 10% (of the total number of students) to nearly 98%.