Another look at the current-carrying wire in special relativity

Abstract

In this paper we examine two models for a current-carrying wire in special relativity. The first model assumes an infinitely long wire and does not specify the source or return path for the current. This model is simple and easy to analyze, so it is often used in introductory textbooks to show the significance of special relativity for electromagnetism. The second model is a coaxial line with a battery at one end and a short circuit at the other. The center conductor of the line represents the wire of interest, and the outer conductor forms the return path for the current. The analysis for this model is more involved than that of the first model, but it provides information not available from that model. This new information answers questions a student might have when first encountering the simpler model.