Inaug.-diss.--Marburg. / Lebenslauf.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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(1) Developments in a.c. conductance techniques during the past ninety years have been reviewed, and a brief outline is given of the older theories regarding electrolytic polarisation. (2) A conductance bridge - incorporating the double heterodyne principle - has been constructed, capable of giving resistance readings to an accuracy of 0.01% over a range of frequencies covering the best part of 100 kc/s. It has also been found possible to calibrate the oscillator so that frequency settings can be guaranteed to an accuracy of , at least, 0.1% in the range: 2 kc/S to 50 kc/S. (3) The Wheatstone Bridge Network has been slightly modified to enable measurements at the high frequencies. (4) Resistances in the measuring arm of the bridge have been calibrated 'in situ' by the method of intercomparison. (5) A brief description is given of the modern theories regarding electrode processes and modern methods of eliminating electrode effects. (6) Two types of conductance cells, with bright Pt electrodes, have been used to carry out measurements on potassium chloride solutions: (a) Thomas- Gledhill Cell (b) Nichol-Fuoss Cell. The latter incorporates concentric, cylindrical electrodes with the lead to the outer electrode acting as an electrical shield for the lead to the inner electrode. This cell was constructed and used for the first time in this laboratory. (7) From resistance-frequency graphs plotted, it is shown that the Jones and Christian extrapolation procedure cannot be applied (with any degree of confidence) to obtain the true resistance, when measurements are effected over an extended range of frequencies. (8) The method of resistance-reactance diagrams is discussed and applied to various networks of resistances and capacitances. (9) By drawing resistance-reactance diagrams for the experimental readings obtained, equivalent circuits have been derived - for all the solutions investigated in the N-F cell, and for the approx. O.OlD solution in the T-G cell - which approximate to cell behaviour in the range: 500 c/s to 75 kc/s. The less concentrated solutions in the T-G cell show peculiar behaviour at the high frequencies. (10) Probable reasons are advanced for deviations from linearity on resistance-frequency graphs. (11) A new method is proposed for determining the true resistance of solutions measured in cells of the N-F type. Summary, p. 166-167.

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This study was undertaken in order to investigate the possible occurrence of horizontal variations in the electrical conductivity of the Earth’s upper mantle in southwestern Canada, using a series of simultaneous magnetic variograph recordings. Until recently no variation in the conductivity in a horizontal direction had been anticipated nor observed. During the past five years Parkinson in Australia, Rikitake in Japan, Schmucker in Germany and others have observed marked differences in the magnetograms at closely spaced stations. Secondary magnetic fields produced by induction in high conductivity regions in the Earth’s upper mantle have been suggested as the cause of these differences. The profile described in this thesis indicates conductivity inhomogeneities in southwestern British Columbia and southwestern Alberta. The vertical magnetic fields produced by induction in these inhomogeneities for magnetic variations with periods from 10 to 120 minutes have magnitudes of about 30 to 60 percent of the normal horizontal component. The normal vertical component is about 20 percent of the horizontal. These regions appear to be essentially two dimensional with anomalous induction resulting only from that component of the incident magnetic variations which is perpendicular to their strike. This strike and the intensity of the induced field have been estimated at each station. A pronounced difference has also been found between the vertical component of the diurnal geomagnetic variations at a station In the Rocky Mountains and those at the rest of the stations along the profile. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A general analytical method to derive the distributed circuit parameters and mode propagation constants for an n-conductor transmission line is developed. The analysis uses electromagnetic field concepts and the results are interpreted in terms of distributed circuit parameters. The procedure involves transforming the problem of the n-conductor line above a ground with finite conductivity into that of an n-conductor above a ground with infinite conductivity. Correction factors are added to account for the finite conductivity of the ground. The distributed circuit parameters thus calculated are used to calculate the mode propagation constants over a frequency range from 10 Hz to 1 MHz for values of ground conductivity varying between 1 mho/m and 10⁻⁵ mho/m and relative permittivity varying between 10 and 50. Numerical results for the distributed circuit parameters and mode propagation constants for a typical 500 kV single circuit transmission line and various ground conditions are given. The results show that one mode has a higher attenuation and a lower velocity than either of the other two modes, suggesting the zero sequence mode for a completely balanced system. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The critical, currents and magnetic fields required to destroy superconductivity have been measured for thin films of indium and tin in the thickness range of 585 Å to 3600 Å, The measurements were made in the region close to the transition temperature, T[subscript c] . The critical current measurements on a 585 Å thick indium film are the first reported which combine the use of a compensated geometry avoiding the difficulties associated with specimen edges, and fast rising current pulses in which the transition is not obscured by specimen heating. The fast current pulses used had a rise time of 7 nanoseconds. It was found that the temperature dependence of the critical currents in the region near the transition temperature, 0 ⋜ ΔT ⋜ 0.15°K is in. agreement with the Ginzburg-Landau theory. For a number of films the critical currents were measured using pulses having a rise time of 1.2 microseconds. The critical currents have been found to vary linear 1 with the film thickness, in agreement with the G-L theory. Measurements with fast pulses seem to indicate the existence of a transition delay of about 7 nanoseconds, independent of the current amplitudes. The transition from the superconducting to the normal state immediately following the transition delay appears to be very fast. For the critical field data, the temperature dependence is in accordance with the G-L theory in the range 0⋜ΔT ⋜ 0.3°K for both indium and tin films. The effective penetration depth calculated in the manner of Ittner, and Douglass and Blumberg was found to be dependent on the thickness and the mean free path. The critical magnetic fields were found to be inversely proportional to the film thickness in agreement with G-L theory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate