DIRECT MEASUREMENT OF LONGITUDINAL ELECTROMAGNETIC (EM) FORCES IN WIRES

Electromagnetic (EM) force is presently described by the magnetic component of the Lorentz force and predicts the acceleration of a charged particle in a direction purely perpendicular to its motion, consequently dismissing any EM force aligned with its velocity. Although not generally known nor accepted, a longitudinal EM force component, parallel to the current, has been experimentally researched since 1822, however until now, completely unambiguous evidence of this non Lorentzian component has proved elusive. Here we show a simple experiment that, for the first time, provides an explicit direct measurement of longitudinal EM force. This research investigated the axial expansion force in a wire when passing direct current (DC). Any non superconducting wire that passes current is heated due to its resistance, and warming is typically known to cause expansion in all dimensions. The experimental method reported here therefore carefully distinguished between expansion due to heat and any other mechanisms. It specifically measured force in the direction of electric current and by eliminating alternative theories, revealed a longitudinal EM force in a range of metals, wire lengths and diameters and initial conditions that is not accounted for by thermal expansion, magnetic pinch or electromigration. This experiment is both simple and inexpensive enough to be repeated and enhanced in most university laboratories and supports the search for a novel and more accurate law of EM force.