We derive from the Maxwell tensor the forces and torques applied to a uniaxial anisotropic crystal when an extraordinary wave passes through it, and we show that the momentum to be associated with the wave in the crystal is collinear with the Poynting vector. Next, we present experimental results of torque measurements using, successively, two uniaxial anisotropic crystals placed inside a variable pressure container. We finally compare our results with those obtained by other authors and show that, according to the types of experiments, either Abraham's or Minkowski's momentum density will appear. [Translated by the journal]
Study of the Combined Effects of the Air-Gap Transfer for Maxwell Tensor and the Tooth Mechanical Modulation in Electrical Machines