Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Edward B. Thornton, Timothy Stanton. Includes bibliographical references (p. 59-62). Also available online.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Curtis A. Collins, Mary L. Batteen. Includes bibliographical references (p. 79-80). Also available online.

published_or_final_version / Physics / Master / Master of Philosophy

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The present thesis is devoted to an analysis of the possibility of Bose condensates supporting persistent currents in the ring geometry. Our analysis is based on an approach developed by F. Bloch which focuses on the ground state energy of the condensate as a function of its angular momentum L. According to this approach, persistent currents are stable if the energy exhibits a local minimum at some nonzero angular momentum. We have used this approach for a single-species gas within a mean- eld approximation to show that persistent currents are stable at integral multiples of N*hbar, where N is the number of atoms in the system, provided a certain interaction parameter exceeds some critical value. These results are extended to a binary mixture of bosonic atoms and we show that the system is still capable of supporting persistent currents under certain conditions. Some of our conclusions contradict those appearing in the earlier literature. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-03-27 10:05:21.831

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The thesis is mainly concerned with experimental studies of the heating effects of eddy currents. Sinusoidal and non-sinusoidal eddy current heating losses in non-magnetic conducting discs and spheres, subjected to a uniform field, are studied both theoretically and experimentally. The theory uses two different methods to calculate the power dissipation in the objects, and it employs Fourler series for the non-sinusoidal case. Some approximations for the losses at low frequency have been derived. The experimental study has three main sections. The first deals with the generation of uniform field for inducing eddy currents. Square Helmholtz coils have been designed, constructed and calibrated for this purpose. The second part is concerned with the measurement of the heat generated by eddy currents. A differential thermometer, using two matched therrnistors in a Blumlein bridge circuit, has been designed, built and calibrated. Operating close to balance, with a phase sensitive detector, the thermometer detects differences of 10-5 degrees C. In the third part, the experiment arranged for the eddy current heating measurements is described. The measured and the calculated results are compared, and the agreement was found to be about 2%. In foil wound inductors excited by alternating current, eddy currents together with proximity effect cause a redistribution of the current density across the width of the inductors. The current flow is increased along the edges of the foil and decreased along the centre portion. A thermal demonstration of this phenomenon, which is known as width effect, is described and studied by using the differential thermometer.

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