3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item The influence of high school physics teachers' beliefs about physics and physics education on alternative conceptions in electromagnetism: a Lesotho study(1996) Qhobela, MakomoselaThis study was designed to investigate beliefs of Physics Teachers, in Lesotho, about Physics and Physics teaching and their awareness of students' alternative conceptions. The study used three questionnaires as its research tools. The first questionnaire investigated beliefs of teachers about Physics concepts, particularly electromagnetism, and the teaching of those concepts. An 'index of agreement' was calculated to determine the tendency of responses. The second queatlonnalre investigated teachers' awareness of students' alternative conceptions, while the third investigated Students' alternative conceptlons. Teachers' predictions are compared with the students' answers. The study shows some teachers having beliefs which can be grouped into two categories, namely constructlvlsts and empiricists. There is however no clear separation between the two categories. The study also shows that some teachers are not aware of students' alternative conceptlons, while some teachers had the same alternative conceptions as students,Item Lightning return stroke electromagnetics - time domain evaluation and application(2016) McAfee, Carson William IanThe work presented extends and contributes to the research of modelling lightning return stroke (RS) electromagnetic (EM) fields in the time domain. Although previous work in this area has focused on individual lightning electromagnetic pulse (LEMP) modelling techniques, there has not been an investigation into the strengths and weaknesses of different methods, as well as the implementation considerations of the models. This work critically compares three unique techniques (Finite Antenna, FDTD, and Single Cell FDTD) under the same ideal simulation parameters. The research presented will evaluate the EM fields in the range of 50m to 500m from the lightning channel. This range, often referred to as the near field distance, has a significant effect on lightning induced overvoltages on distribution lines, which are primarily created by the horizontal EM fields of the RS channel. These close distances have a significant effect on the model implementations, especially with the FDTD method. Each of these modelling methods is explained and tested through examples. The models are implemented in C++ and have been included in the Appendix to aid in future implementation. From the model simulations it is clear that the FDTD method is the most comprehensive model available. It allows for non-ideal ground planes, as well as complex simulation environments. However, FDTD has a number of numerical related errors that the Finite Antenna method does not suffer from. The Single Cell FDTD method is simple to implement and does not suffer from the same numerical errors as a full FDTD implementation, but is limited to simple simulation environments. This work contributes to the research field by comparing and evaluating three techniques and giving consideration to the implementation and the applicability to lightning EM simulations.Item On the sixth mechanism of lightning injury(2015-04-30) Blumenthal, RyanThe work presented in this thesis extends and contributes to research in the field of lightning injury mechanisms. Six mechanisms have been described in the literature about lightning injury. This thesis takes an in-depth look at the sixth injury mechanism. The sixth mechanism may be thought of as a ‘pressure-shock wave’ which is directly proportional to the current of the lightning discharge, and which is present immediately surrounding lightning’s luminous channel. A literature review, case studies and two novel experiments helped confirm the sixth mechanism’s existence. The medical data and the lightning data were then aligned. Two main questions were addressed, namely within what range is a human at risk; and what is the risk of lightning’s pressure shock wave. This ‘pressure-shock wave’ may explain some of the more curious lightning injury patterns seen on lightning-strike victims. Knowledge and insight into the sixth mechanism may have direct and indirect applications to those working in the fields of lightning injury and lightning protection. This thesis represents a contribution to the literature in both medicine and engineering.