What is the basic process of Max's electromagnetic theory?

1. Faraday's law of electromagnetic induction and Maxwell's development of electromagnetic theory. Faraday's law of electromagnetic induction, discovered in 183 1 year, initially revealed the internal relationship between electricity and magnetism. Maxwell established a magnificent building of electromagnetic field theory on the basis of Gauss theorem, Ampere loop theorem and Faraday's law of electromagnetic induction, and the cornerstone of this building is the beautiful Maxwell equation. It is no exaggeration to say that Faraday's discovery and Maxwell's contribution are milestones in the process of human science and have epoch-making significance. Faraday brought mankind into the era of electrification, while Maxwell brought mankind a revolution in communication and information technology. They not only connect the past with the future in scientific research, but also have epoch-making encounters and cooperation. This is vividly described in the following article. Faraday, Maxwell and electromagnetic theory (reading 1) Weber walked through one ohm after another, which brought me an echo ── "I am your loyal and sincere Farah, charging to one volt to show my love for you." -Maxwell Faraday discovered the phenomenon of electromagnetic induction through experiments, and put forward the hypothesis of magnetic lines and magnetic fields from intuitive conjecture, but it could not be proved by experiments at the moment, so he kept this prediction in the filing cabinet in the basement of the Royal College 1832, waiting for friends to come to the door. He waited for twenty-three years, but no one came to the door and didn't hear a word that could understand him. On the contrary, many people, including some famous physicists at that time, often satirized him. Only by working hard can he get rid of these troubles. When he is tired from work, he leans back in his chair and closes his eyes. Sometimes he can't help but think of what Kepler said after discovering the three laws: I discovered it anyway, and it may take a hundred years for someone to understand it. It seems that no one will share the joy of discovery with me in my life. I can only bear the loneliness of this discovery. One day, he was sighing in a pile of periodicals he received every day, and suddenly his eyes lit up. The title of a paper suddenly came into view: On Faraday's Line of Force. It's like a hungry person picking up a piece of sweet bread and sweeping away punctuated words in one breath. This is indeed a good paper, which expounds his findings and thoughts in detail. The beauty lies in comparing Faraday's field full of force lines to a fluid field, which can be explained by the results of fluid mechanics. The force line is summarized as a vector differential equation, which can be described mathematically. Faraday has been out of school since he was a child and has not been trained in a regular school. What he lacks most is mathematics. Now suddenly someone comes to help him from a mathematical point of view. It's a blessing in disguise. He was busy looking at the author, but it was a strange name: james clerk maxwell. Since then, he has been asking about the author everywhere. Just when this article suddenly appeared, the author suddenly disappeared without a trace. Just when Faraday was looking forward to seeing Maxwell, but he couldn't find him, a young man was walking on his way to Edinburgh, the ancient capital of Scotland. This man is Maxwell (183 1 year ~ 1879). He used to work at Cambridge University in London, but a few days ago, he suddenly received a letter from home saying that his father was seriously ill, so he left work and rushed back to his hometown. Maxwell was born in 183 1 year1month 13. It happened to be the 33rd day after Faraday discovered electromagnetic induction. It seems that God sent him to earth instead of Faraday. Maxwell's mother died of lung disease when he was nine years old, so he lived alone with his father since childhood. His father is an extremely clever engineer, and he doesn't want to be bound by tradition. Once, he put a bottle of flowers on the table and taught his son to sketch. What I don't want to hand in after painting is all geometric figures: flowers are large and small circles, leaves are triangles, and vases are big trapezoid. The father touched his son's childish face and said, "It seems that you are a genius in mathematics, and you will achieve something in this field in the future." So he began to teach him geometry and algebra. Maxwell is really a child prodigy. He won two first prizes in the math and poetry competitions held in middle schools. /kloc-at the age of 0/5, he wrote a paper on conic curves before graduating from middle school and published it in the Journal of the Royal Society of Edinburgh. Maxwell was admitted to Edinburgh University when he was sixteen. Once in class, he suddenly raised his hand and stood up, saying that an equation deduced by the teacher on the blackboard was wrong. The lecturer also said angrily, "If you are right, I will call him Maxwell formula!" " "I don't want the teacher to make a careful calculation after class, and the results prove that the students are right. 1850, his father sent him to Cambridge university to study. /kloc-graduated with the second place in mathematics in 0/854. After graduation, he became interested in electromagnetism. The following year, he published "On Faraday's Line of Force". Just as his talent began to emerge in a new field, he suddenly received a letter from home and hurried back. As soon as Maxwell entered the house, he saw his father haggard and bedridden, and he was very sad to think of the hardships of losing his mother when he was a child and his father pulling himself. He waited in front of the medicine bed all day and was docile everywhere. In order to take care of his father nearby, he wrote to Cambridge University and resigned, preparing to teach at maryse Kyle College in Aberdeen Port, not far from home. The following year, my father died suddenly. He went to the deceitful Kyle College in Mari and gave a lecture on "natural philosophy". When winter goes and spring comes, it is 1860 in a blink of an eye. Maxwell has been here for four years. Although he has made important achievements in the study of Saturn's rings and gas mechanics, he has no time to take care of electromagnetism, which he has always cared about. At this time, maryse Kyle College merged with another college, and his lecture was cancelled. I wonder where the new rice bowl is. But at this time, his alma mater, Edinburgh University, was about to recruit a professor of natural philosophy, and he quickly signed up. There are three people in the same exam. On the basis of knowledge and reputation, he was naturally admitted. When I don't want to have an oral exam, I feel nervous unconsciously when I face the senior teachers of my alma mater in front of me. He speaks fast and slow, and his sentences are intermittent. In the end, due to "poor oral expression", I lost the election, so I had to take my wife to London again and take refuge in the Royal College. But it's a blessing in disguise. He didn't expect that it was because he lost the election in Edinburgh that he achieved his career. Faraday, since reading Maxwell's article, has been paying attention to whether there are any similar articles published every day, and is also asking about McVeigh everywhere. Who knows, like a comet crossing the sky, there is no news from now on. He is getting older every day. At 1860, he is a 79-year-old man, and his only worry is that his discovery is unknown. Is it really a hundred years before the file in that basement can be realized? One morning, when he was walking on the lawn in front of his house with crutches, a man and a woman came in the distance. The man is young and chic, and the woman is quiet and beautiful. This man and a woman came to Faraday's eyes. This woman is carrying many colorful gifts. The man leaned down and asked respectfully, "Are you the respected Mr. Faraday?" "Yes, I am michael faraday, a very ordinary person. "Faraday is most afraid of compliments, so he always adds this attribute." I am your loyal student Maxwell. ""Are you Mr. Maxwell who wrote a paper about my force line? " "yes. I am just a child in front of you and your knowledge. "Maxwell is forty years younger than Faraday. When Faraday confirmed that Maxwell was standing in front of him, he put down his crutch and his eyes suddenly lit up. Maxwell jumped up too, and they hugged each other tightly. One is an experimental master, and the other is a mathematical genius. This is the embrace of physics and mathematics, and it is a great blessing for physics. Faraday said, "I've been waiting for you for too long. You finally returned to London. It was your strong magnetic field that finally attracted me back. This time, I not only returned to London, but also returned to the Royal College and returned to your side. Faraday smiled modestly and said, "It's a pity that I am old, but there is still time. When Tycho gave it to Kepler, he had only one year left in his life. God can give me a year is enough. " "Teacher, you will live a long life." "I wish our new theory a long life!" Both of them burst out laughing with joy. After several years of research, Faraday proved that magnetic energy can produce electricity, current and electric field. Electric current is different from electric field. Current can obviously heat wires and electrolyze water, which is called conduction current. Although the changing electric field has some properties of current, it is not obvious. Smart Maxwell named it "displacement current". Conducted current can excite a magnetic field and affect the deflection of the needle. Can this displacement current (changing the electric field) excite a magnetic field? This is nothing more than a specific thermal effect, which can shock people, and it is nothing more than obvious magnetism that can attract iron. They are too obscure and mysterious. Faraday has been experimenting for many years, but he still hasn't found the connection between them. Just as some micro-sculptors can carve a poem on their hair, he has long used his feelings instead of his eyes to operate. At the most critical time, problems are often not solved by experiments, but can only be decided by reasoning. This problem was really deduced by Maxwell with mathematical formula. In the scientific history of 1865, the unified electromagnetic field theory was finally born. Maxwell published a set of equations describing the law of electromagnetic field motion. He proved that changing magnetic field can produce electric field, and changing electric field can produce magnetic field. This is better than Faraday's "magnetism" that can generate current and current that can generate "magnetism". Magnetic field, electric field, magnetic field and electric field, the action of these two fields (electromagnetic waves) is constantly changing under certain conditions, unlike the "vacuum action at a distance" described by Newtonian mechanics. Faraday's prediction has been perfectly expounded and rigorously demonstrated mathematically. What's even better is that Maxwell used his own equation to deduce that the speed of electromagnetic waves is exactly equal to the speed of light, which proves that light is also an electromagnetic wave. Optics and electromagnetism are also fused here. The emotional opposition of Newton, Hooke and Huygens to the essence of light is truly unified today. Faraday is luckier than Tycho after all. He saw the perfection of his theory and the performance of his successor. The second year after the theory of electromagnetism was established-1867, the founder of electromagnetism passed away with satisfaction. After Maxwell published the formula in 1865, he immediately went back to his hometown in the countryside, closed the door, and devoted himself to writing the General Theory of Electromagnetism, expounding this theory in detail. Eight years later, this masterpiece, which can be compared with the Philosophy of Nature published by Newton 1687, was finally published. Newton built a magnificent building of classical mechanics, and Maxwell built a skyscraper of classical electromagnetism. After 186 years of hard climbing, physics finally jumped to the second peak. Maxwell's electromagnetic theory unifies the essence of electromagnetic phenomena and light phenomenon, and completes a great fusion of physics, which is a great event in the history of science in the19th century. But at that time, because the mathematical methods used in the book were abstruse and abstract, and electromagnetic waves were not found for a long time after the book was published. Therefore, few people supported his theory, but doubts and objections followed. In this way, whether electromagnetic waves really exist has become the key to test Maxwell's theory. Although Maxwell made great contributions to modern physics, he was not happy at that time. No one understands his theory, and his wife needs to be taken care of after a long illness. His lecture on electromagnetic theory was ignored. Sometimes, only two students sit in an empty classroom. All kinds of unpleasant things made him exhausted and his health became worse and worse. 1879165438+1October 5th, the great scientist Maxwell finally died of lung disease. 2. Maxwell's two hypotheses (1). Vortex electric field hypothesis Faraday's law of electromagnetic induction: Analysis of the non-electrostatic field of induced electromotive force from the perspective of power supply Since induced electromotive force can make the charge in the closed wire form a closed current, there must be a "rotating field" to drive the charge to move. Maxwell boldly assumed along this line that this field is a "vortex electric field" and an "alternating electric field" which is different from both static electric field and steady electric field. The following is the mathematical derivation of this idea: However, Maxwell's hypothesis (vortex electric field hypothesis), plus electrostatic field, can be extended and converted into a differential form, indicating that "changing magnetic field can excite vortex electric field", electrostatic field, steady electric field and other fields excited by charges are called Coulomb field, so any electric field can be considered to be composed of Coulomb field and vortex field, that is, Among them: (2) The circuit (Figure 1-3) considering capacitor charging in displacement current assumption diagram 1-3 is unstable, so it is obvious that the Ampere Loop Theorem is not valid everywhere in the circuit when all wires take out the capacitor and close the Gaussian surface to take in the capacitor. Is there any way to extend it to such an unstable circuit? Maxwell assumes that the interrupted conduction current in the capacitor is connected by the displacement current under the unsteady condition, that is, the connection between the conduction current and the displacement current is closed at the same time, so that the equation in the loop theorem can change under the steady condition, so it can be expanded into and its corresponding differential formula can be expanded into expansion, indicating that "the changing electric field can also excite the eddy current magnetic field". In addition, the corresponding differential equation of the total "current" expression is or 3. The "4,3,2, 1" of Maxwell's electromagnetic field theory framework is briefly described. Maxwell's electromagnetic field theory framework can be summarized by "4,3,2, 1", and there are 4-4 equations: Maxwell's equation and the basic equation of electrodynamics. 3- three relationships:,,; 2- Two hypotheses: eddy current field and displacement current; 1-A prediction: the electromagnetic field propagates in the form of waves at the speed of light.