دانلود کتاب الکترومغناطیس و اندازه‌گیری تاثیر آن بر پوست

Although there is a very large literature on theoretical electromagnetism, there is much less on experimental measurements, particularly for the skin effect at low frequencies. The author has found that of several recent papers he has written in this field, the one which received the most attention concerned experimental measurements of the skin effect at low frequencies [1,7]. For this reason, this monograph emphasizes the experimental measurements and results obtained for the skin effect, particularly at low frequencies. For a review of the subject, the article https://en.wikipedia.org/wiki/Skin_effect in Wikipedia is suggested. [2]. Presumably, in the case of AI, it must employ someone, perhaps like CERN, to conduct the experiments necessary to validate its conclusions. However, to begin with, we need to establish the theoretical background necessary to understand the results obtained from measurements. The book therefore begins with an introductory Chapter 1 on the derivation of the equations of time-dependent electromagnetic disturbances, in which we compare James Clerk Maxwell’s original approach [3] with the present-day approach. The remaining chapters mainly concern the solution of Maxwell’s equations in the frequency domain. The importance of Maxwell’s discoveries has been widely recognized. The following quote from the introductory chapter may serve to encourage the reader. As Roger Penrose points out, “Maxwell’s equations were the first of the relativistic equations” and “the theory of electromagnetism plays an important part in quantum theory, providing the archetypical field of quantum field theory” [4]. Also, Albert Einstein, stressed “The Special Theory of relativity has crystallized out from the Maxwell-Lorentz theory of electromagnetic phenomena”, “which in no way opposes the theory of relativity” [5]. The book does not necessarily assume that the reader has a detailed knowledge of electromagnetism. It may therefore also be of interest to those involved in other disciplines where electromagnetism is not a major subject but includes fairly advanced mathematics at a level, say, of Arfken [6]. Other disciplines include geophysics, mechanical engineering, and mining engineering, where electromagnetic techniques are widely employed. Although there are other textbooks and papers directed towards this goal, the approach employed here follows Maxwell’s original analysis [3], which is not usually the case. This approach also does not require a detailed knowledge of electrical engineering, but it does lead to the fundamental equations of electromagnetism; the diffusion equations in conductors and the wave equations in non-conductors, leading to the electromagnetic theory of light and the pressure exerted by electromagnetic radiation. Chapter 2 introduces Maxwell’s four vector equations (all based on experimental measurements) with solutions, initially for free space, leading to the wave equations for electric and magnetic fields, travelling waves, and the relationship between the electric and magnetic fields, plane waves with two components, and the constants of propagation for free space. This is followed by a section on the solutions of Maxwell’s equations for lossy materials. This again leads to wave equations but with additional diffusion terms – the Helmholtz Wave Equations or Equations of Telegraphy, details of the propagation constants in lossy materials, complex refractive index, optical constants, Debye equations, dissipation factor, and circuit parameters. Chapter 3 concerns steady state and time-dependent power dissipation, including power dissipation in circuits, power dissipation in the time and frequency domain, power factor, instantaneous power, oscillatory power (important in inductive circuits), power flow, poynting theorem, superconductivity, complex poynting theorem, relaxation effect, impedance, dissipation in circuits. This chapter and Chapter 2 also briefly discuss superconductors. Chapter 4 is an Introductory chapter to the skin effect, including approximate methods of analysis for various conductor geometries. It begins with a general explanation about the decrease of the electromagnetic fields with depth as the frequency increases, the use of high conductivity films on conductors, hollow conductors at low frequencies, and high permeability materials. This chapter also includes a brief history of the skin effect, which was very important to the pioneers of radio communications. In recent times, the large development of wind turbines and the extension of the electrical transmission lines to the many remote sites have led to increased energy losses due to the low-frequency skin effect. This is followed by chapters covering more detailed theory and experimental measurements of the skin effect in solid and hollow cylindrical tube conductors. Copper or aluminium tube busbars are used in electricity substations and have many advantages over solid copper busbars. These busbars must withstand very high current and voltage switching transients. The final chapter describes methods of measuring the skin effect over a wide range of frequencies. In addition to the dedicated techniques used to measure L, C, and R, a Gain Phase-Meter (GPM) technique was also employed here to measure the amplitude and phase to determine the impedance as a function of frequency. This was particularly useful for the low-frequency skin effect, where the resistance may be less than a milliohm. The book finishes with an Appendix containing Bessel’s modified equation, Kelvin functions, properties of Bessel functions, power integral and orthogonality, and finally, a reference section and index.