This is the third in a series of four volumes, all written at an elementary calculus level. The complete course covers the most important areas of classical physics, such as mechanics, thermodynamics, statistical mechanics, electromagnetism, waves and optics. The volumes are the result of a translation, an in-depth revision, and an update of the Italian version published by Decibel-Zanichelli. This third volume deals with classical electromagnetism.
The vast majority of physics phenomena naturally taking place around us originate in electromagnetic forces. The largest portion of the technology that holds sway over so much of our lives and our civilization is the result of our knowledge and control of electromagnetic forces.
The forces that keep atoms together internally, binding electrons to nuclei, and externally, binding those atoms within molecules, are electromagnetic. As a consequence, the energies developed in all chemical reactions are electromagnetic, including the biochemical ones, which are the basis of life itself. Contact forces, such as friction, between solid surfaces are electromagnetic, and so is the drag force acting on a body moving in a fluid. Elastic forces, cohesion forces, and the force that results from the earth’s magnetism are all electromagnetic. Light itself is an electromagnetic wave, whose wavelength is in the range to which our eyes are sensitive. The radio waves we use in telecommunications, radio, television, and cellular phones are electromagnetic as well, utilizing much greater wavelengths. As a matter of fact, all the phenomena on scales larger than those of the atomic and molecular have a gravitational or electromagnetic origin.
Modern technology is more than 99 % reliant on electromagnetism. In hydroelectric power stations, for example, big turbines are moved by water falling on them through large pipes under pressure. The turbines move electromagnetic generators, made of massive copper coils rotating between the poles of an electromagnet. The generators produce an electromotive force that is then distributed through a network of thousands of copper wires across distances of hundreds of kilometers to factories, offices, and houses. Here, the electric power is used by electric motors to produce all types of objects, to control chemical processes, or simply to light our rooms or wash our dishes. All of these are electromagnetic processes. Cellular phones emit and receive electromagnetic waves, which are produced or detected and amplified by electronic circuits. Our computers store, process, and transmit information using electronic circuits of ever-increasing complexity and miniaturization.
However, the electromagnetic nature of natural phenomena does not appear at first sight and remained substantially unknown until roughly two centuries ago. Lighting is the phenomenon with the most evident (to us) electric nature, but it was not the genesis of the study of electric and magnetic phenomena. On the contrary, the first observations were in regard to the curious properties of amber, which, when rubbed, attracted small pieces of papyrus, and of magnetite, a stone capable of attracting pieces of iron. These phenomena were reported by the Greek philosopher Thales from Miletus in the sixth century BC. Twenty-two centuries had to pass before the first systematic observations and the first attempts at interpretation of electric and magnetic phenomena would occur, with William Gilbert’s publication of his work in the book De magnete in 1600. Still, almost two more centuries would go by before Charles Augustin de Coulomb would make the fundamental measurement of the electric force between two charges and its dependence on their distance in 1785, finally paving the way for electric and magnetic research.
1. Electrostatic Field in a Vacuum
2. Conductors in Equilibrium
3. Electrostatic Energy
5. Electric Currents
7. Electromagnetic Induction
8. Magnetic Energy
9. Magnetic Properties of Matter
10. Maxwell Equations
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