Ampere tension in electric conductors

Abstract

It is shown that the application of the Ampere and Lorentz force laws to a closed current in a metallic circuit results in two different mechanical force distributions around the circuit. In addition to the transverse forces, which both laws predict, the Ampere electrodynamics requires a set of longitudinal forces that subject the conductor to tension. These longitudinal forces explain electromagnetic jet propulsion and the recoil mechanism in a railgun. Pulse current experiments are described in which Ampere tension shattered solid aluminum wires. Electrons moving through the metal lattice are the basic current-elements of the Lorentz force theory. But Ampere assumed his current-elements to be infinitely divisible. With the help of computer-aided analysis and experiment, it is demonstrated that the amperian current-element must also be of finite size and involve at least one lattice ion in addition to the conduction electron. Calculations with Ampere's formula have been found to give reasonable results when the atom, or unit atomic cell, is taken to be the smallest possible current-element. Some technological consequences of Ampere tension are discussed briefly with regard to pulse currents in normal conductors and steady currents in superconductors. The use of large macroscopic current-elements of unit length-to-width ratio gives rough approximations to the Ampere tension. The accuracy of the calculations can be improved by resolving the conductor into a number of parallel filaments, each filament being subdivided into cubic current-elements.