Electromagnetic stress and momentum in matter

We review Galilean Electromagnetism since the 1973 seminal paper of Jean-Marc Levy-Leblond and Michel Le Bellac and we explain for the first time all the historical experiments of Rowland, Vasilescu Karpen, Roentgen, Eichenwald, Wilson, Wilson and Wilson, which were previously interpreted in a Special Relativistic framework by showing the uselessness of the latter for setups involving slow motions of a part of the apparatus. Galilean Electromagnetism is not an alternative to Special Relavity but is precisely its low-velocity limit in Classical Electromagnetism.

http://www.pprime.fr/sites/default/files/pictures/pages-individuelles/D2/germain/EPJP2013.pdf

Forty years of Galilean Electromagnetism (1973–2013)

The eddy currents due to the motion of a thin conducting strip in the airgap of a d.c.-excited electromagnet are analysed. This permits determination of the braking force exerted on the sheet. A general method for this type of problem is outlined. The current streamlines are shown, and a specific numerical example is given. The results should be of interest in view of the widespread use of electromagnetic braking and damping in measuring instruments, relays etc.

Unipolar induction braking of thin metal sheets

Electromechanical braking is based on the interaction of eddy currents and a magnetic field, with the former usually induced in a moving part. Although, in many cases, the currents are constrained and restricted by preferred conduction paths (eg., a squirrel cage in the case of induction braking), on occasion the induced part is designed with uniform conductivity, in which case the currents are “free”: their paths depend on the geometrical configuration of the device and on its electromagnetic properties. In practice, eddy-current brakes are frequently used for motor testing since the braking force lends itself to continuous control through the current flowing in the excitation winding of the electromagnet. The present paper deals with the braking effect on a conducting sheet moving in the field of an electromagnet having poles of rectangular cross-section. Its practical objective is improved pole design, with a view to minimized material cost for a specific braking force. The analysis is undertaken for two cases: a) a conducting sheet of infinite horizontal dimensions; b) a conducting sheet of finite width but infinite in the direction of motion.

Optimal dimensions of rectangular electromagnet for braking purposes

This paper outlines an alternative exposition of the structure of quantum thermodynamics which is essentially based on Carnot’s theory where fluxes of caloric are identified with negative information fluxes. It is further assumed that the thermal energy evolved by thermal processes is identical with the electromagnetic zero-point background energy evolved by the destruction of information inscribed in a structural unit (qubit). Theoretical arguments on an elementary level are accompanied by illustrative examples.

W. G. V. Rosser

Papers

Classical electromagnetism via relativity