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CHAPTER 3: ELECTRIC FLUX DENSITY, GAUSS'S LAW, AND DIVERGENCE

Tài liệu tham khảo về giáo trình vật lí bằng tiếng anh về điện trường, từ trường. dành cho các bạn yêu thích môn vật lí. | CHAPTER 3 ELECTRIC FLUX DENSITY GAUSS S LAW AND DIVERGENCE After drawing a lew OÍ the fields described in the previoLIS C hapter and becoming familiar with the concept of the streamlines which show the direction of the force on a test charge at every point it is difficult to avoid giving these lines a physical significance and thinking of them as flux lines. No physical particle is projected radially outward from the point charge and there are no steel tentacles reaching out to attract or repel an unwary test charge but as soon as the streamlines are drawn on paper there seems to be a picture showing something is present. It is very helpful to invent an electric flux which streams away symmetrically from a point charge and is coincident with the streamlines and to visualize this flux wherever an electric field is present. This chapter introduces and uses the concept of electric flux and electric flux density to solve again several of the problems presented in the last chapter. The work here turns out to be much easier and this is due to the extremely symmetrical problems which we are solving. 53 I e-Text Main Menu Textbook Table of Contents 54 ENGINEERING ELECTROMAGNETICS 3.1 ELECTRIC FLUX DENSITY About 1837 the Director of the Royal Society in London Michael Faraday became very interested in static electric fields and the effect of various insulating materials on these fields. This problem had been bothering him during the past ten years when he was experimenting in his now Run OLIS work on i nduced electromotive force which we shall discuss in Chap. 10. With that subject completed he had a pair of concentric metallic spheres constructed the outer one consisting of two hemispheres that could be firmly clamped together. He also prepared shells of insulating material or dielectric material or simply dielectric which would occupy the entire volume between the concentric spheres. We shall not make immediate use of his findings about dielectric materials for we are .