estat1 - Physics 54 Electrostatics 1 The covers of this...

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Electrostatics 1 The covers of this book are too far apart — Ambrose Bierce Overview In the previous course the description of physical phenomena was based on what might be called the “mechanical” model. The material universe was assumed to consist of small objects (particles) interacting with each other through forces, according to the three laws of Newton. Things of ordinary (macroscopic) size were modeled as made up of large numbers of particles; they were divided into solids, liquids and gases according to how tightly the particles making up the system were bound to each other by the forces. By applying the program of Newtonian mechanics, we were able to give at least an approximate description of a very wide range of phenomena. To be sure, there were loose ends, some of which were apparent to scientists of the 18th century. Newton’s theory of gravity provided an excellent description of many phenomena, but the question of how two objects separated by empty space could interact was left as a mystery. Electric and magnetic phenomena, known since ancient times, were almost totally unexplained. And the nature of light was the subject of heated debate: is it a wave phenomenon, or is it in the nature of a stream of particles? This course take up those questions and discusses the answers discovered by scientists of the 18th and 19th centuries. It turns out that the questions are all related to one another. Like gravity, electric and magnetic interactions also involve acting “at a distance” without any intervening medium. And in the 19th century the description of these phenomena turned away from the mechanical point of view, becoming centered instead on the idea of felds . In the last half of that century it became clear that light is in fact a phenomenon in which the Felds by themselves transfer energy from source to observer, often through space completely devoid of particles. This is a course about the Felds. While we will continue to regard solids, liquids and gases as consisting of particles (atoms and molecules, and their constituents), and while we will still often analyze the motion of those particles under the in±uence of interaction forces, much of our attention will be on the Felds themselves, their sources and their properties. One can see (perhaps with the help of instruments) the effects of the Felds, but one cannot see the Felds themselves, so the description is necessarily a bit abstract and mathematical. Of course any kind of “seeing” involves light, which is just a particular conFguration of Felds. Besides, our modern style of life depends heavily on devices based on our understanding of the electromagnetic Feld. It is surely worth the effort to gain some understanding of how these Felds behave. PHY 54
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This note was uploaded on 10/19/2011 for the course PHYSICS 54L taught by Professor Thomas during the Summer '09 term at Duke.

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estat1 - Physics 54 Electrostatics 1 The covers of this...

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