Extracting Energy from an External Magnetic Field
  In this paper we describe the theory of a device that is able to extract energy from an external magnetic field. The device is a cylindrical magnetic insulator that once put in rotation makes electromagnetic angular momentum to be stored in the electromagnetic field in contrary direction to the mechanical angular momentum of the device. As a consequence due to total angular momentum conservation the device increases its angular velocity (when {\epsilon}{\mu}>1) Natural units are used in the paper and all conservation laws are rigorously satisfied. The voltage generated by the device is found solving explicitly Maxwell equations for rotating magnetic insulators in external fields, a subject that have provoked lots of polemics in the literature and which we hope to be here clarified due to our pedagogical presentation. 
Waldyr A. Rodrigues Jr. and Edmundo Capelas de Oliveira
math-ph gr-qc math.MP