Abstract

This article discusses experiments which enable the identification of the seat of mechanical forces in homopolar-machines reported earlier in this journal [J. Guala-Valverde and P. Mazzoni, Am. J. Phys. 63, 228-229 (1995); J. Guala-Valverde, P. Mazzoni, and K. Blas, ibid. 65, 147-148 (1997)]. We provide a suitable variation on a recent work "The Unipolar Dynamotor: A Genuine Relational Engine'' [J. Guala-Valverde and P. Mazzoni, Apeiron 8, 41-52 (2001)], where "relational'' implies "absolutely relativistic.'' Our view agrees with both Weber's recognition in the 19th century of the importance of relative motion in electromagnetic phenomena [A. K. T. Assis, Electrodynamics (Kluwer, Dordrecht, 1994)] and Einstein's 1905 statement concerning electromagnetism [Ann. Phys. 17, 891-921 (1905)].