Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

R. G. Hussey


This dissertation describes an investigation into students' understanding of the interaction between two charged conductors. The study consists of two parts. The first part is based on interviews and written tests conducted with students in an algebra-trigonometry-based physics course. Results from several tasks are reported. Two of the tasks involve a pair of identical conductors that are given an initial charge, are made to touch each other, and are then separated. In the first task, students were asked to predict the final charges on each conductor. In the second, they were asked to predict the final positions of the charges on the conductors and whether the conductors attract, repel or do not affect each other. Some students did not correctly predict the final charges on the conductors because they failed to consider all of the electrostatic forces on the charges. Others did not consider forces at all. Still others did not conserve charge. In addition, students were also asked ancillary questions to complement the ideas covered in the two tasks. One of these questions involved the distance dependence of the interaction between two suspended charged conductors. Student responses to this question indicate that most of them know that the electrostatic force decreases with distance but many believe that the smaller force will cause the suspended conductor to oscillate in the presence of the fixed conductor. In another question, many students predict that a thin plastic sheet can block the interaction between two conductors. In yet another question, virtually none of them could explain completely why a neutral conductor is attracted to a charged conductor. In order to determine how these ideas evolve among students at different levels, tests were administered to populations as varied as fifth graders to graduate students. This forms the second part of the dissertation. It was found that the main ideas on electrostatics recur through the various populations in varying degrees. However, there is a progression, albeit small, from the fifth grader to the graduate student both in their ideas and the way they express these ideas.