Then Faraday's life ushered in another good luck. A customer gave Faraday some tickets, which were four speeches by David of the Royal Academy. Faraday was so happy that he made a detailed record of all the contents of the four lectures. He bound these records and sent them to David with an application to be an assistant in the graduate school. A few months later, David really gave Faraday the job. One of David's colleagues said, "Let him wash the bottle. If he is really good, he will accept the job. " If he refuses, he can do nothing. "The salary of this job is less than Faraday's subscription salary, but he is eager for this opportunity.
Soon, David visited Europe in 18 13 and took Faraday with him as a secretary and scientific assistant. Although David's wife regarded Faraday as a servant, the young man never complained, but took this opportunity to meet key figures in the scientific community, including Volta, Impert (André-Marie, 1775- 1836) and Josep Louis GayLussac. 1778- 1850), arago (1786- 1853), Alexander von Humbokit (1769- 1859) and They traveled all over Europe, from one laboratory to another, completing various experiments and attending various lectures. In this process, Faraday received an education that he had never had before.
18 15, they returned to England, and Faraday officially became a laboratory assistant, in charge of mineral collection and instrument director of the Royal Institute. He became David's right-hand man in the laboratory, because he was smart, expert and dedicated, and often worked from 9 am to 1 1 pm. A few months later, his salary increased to the annual salary of 100, and remained at 1853.
Faraday was as excited as the rest of the scientific community when he read the experiment that Oster did in 1820. Oster's magnetic needle shows that the current does not flow from one end of the wire to the other in a straight line, but flows around the wire. Ampere in Paris confirmed this idea. He proved that if two current-carrying wires are placed in parallel, and one of them is in voluntary movement state, when the two wires have the same current direction, they attract each other; If the currents are in opposite directions, they will repel each other.
Faraday made a simple experiment by himself. 182 1 in September, he demonstrated "electromagnetic rotation", which made the current-carrying wire rotate around the fixed magnet and at the same time made the magnet rotate around the fixed current-carrying wire. This is the first original motor.
Unfortunately, David was angry with Faraday for this. He claimed that Faraday had eavesdropped on the conversation between David and wollaston (William Hyde Woaston, 1766- 1828) because the conversation involved similar experiments. Faraday admits that he may have been inspired by the conversation, but his devices are essentially different, and wollaston and history also admit this.
In any case, this is perhaps Faraday's most insignificant discovery, and he is brewing a bigger discovery. 1822, Faraday wrote in his notebook: "Transform magnetism into electricity." Oster uses electricity to generate magnetic force (magnetic needle reflects magnetic force). Why can't the opposite process happen?
Faraday started with the idea put forward by Ampere and another physicist William sturgeon (1783- 1850). He first prepared an iron ring, a part of which was wound with a coil, and closed the key to introduce current. Another part of the iron ring is also wound on the coil and then connected to the galvanometer. He thinks that the current in the first coil may produce a current in the second coil. The galvanometer can measure the second current and display the result.
The idea really succeeded-this is the first transformer-but the result was a bit surprising. Although there is a stable magnetic force in the iron ring, there is no stable current in the second coil. On the contrary, only when Faraday closes the line will there be an instantaneous current in the second coil-ammeter jump. Then when he cut off the line again, an instantaneous current was generated, marked by the galvanometer jumping again.
Because Faraday doesn't know mathematics, he can only explain this phenomenon vividly and put forward the concept of magnetic field lines. He noticed that if iron filings were scattered on paper, a strong magnet was placed on the paper and tapped lightly, the iron filings would show a certain pattern along the direction he called the magnetic field lines. He imagined that the current formed some kind of magnetic field, radiating in all directions from the source. When he closed the circuit in the experiment, the magnetic field lines radiated outward and the second coil cut them off. At this point, there is an induced current in the second coil. When he disconnected the line, the magnetic field lines "contracted", and the second coil cut off the magnetic field lines again, thus generating an induced current. He also studied the magnetic field lines of bar magnets, spherical magnets like the earth and current-carrying wires. This is the first time to look at the universe with a more creative new vision since Galileo and Newton put forward the mechanistic universe. This is the emergence of field theory.
183 1 year, Faraday demonstrated the force line in another way in a large-scale popularization lecture at the Royal College. He picked up a coil and inserted a magnet into it. The galvanometer pointer connected to the coil began to shake, and when the movement of the magnet stopped, the shaking stopped. When he took out the magnet, the galvanometer showed up again. The magnet moves in the coil and is also displayed. If you move the coil past the magnet, the galvanometer will also show it. But if the magnet is stationary in the coil, the galvanometer has no current. Faraday discovered the principle of electromagnetic induction. In other words, he found that the combination of mechanical motion and magnetic force can produce electric current. This is the basic principle of the generator. [Another physicist, joseph henry of the United States (1797-1878) also brilliantly demonstrated this same idea, but he did not publish it in time. Therefore, Faraday, who was absorbed in his work, won the honor of "discovery right", and Henry readily accepted this honor]
Of course, Faraday's next goal is to build a generator that can generate continuous current, rather than intermittent induced current in the experiment. To this end, he made a copper plate and let its edge pass between the poles of the permanent magnet. When the copper disk rotates, it will generate current, and the induced current can come in handy. The wheel is driven to rotate by a water wheel or a steam engine, and the kinetic energy of running water or the energy after fuel combustion is converted into electric energy. Today's generators are very different from Faraday's original devices. It was put into practical use after more than 50 years of improvement, but this is undoubtedly the most important electrical discovery so far.
From childhood, Faraday was convinced of the relationship and unity between natural forces and natural phenomena. He admitted that his field theory published in 1844, as well as the discussion on the interrelationship between magnetism, electricity and motion, all revolved around this belief. 1845165438+1October 5th, he wrote at the beginning of the paper on the magnetization of light and the revelation of magnetic field lines:
"I have held this view for a long time, which is almost a belief, just like the knowledge of many nature fans: I believe that although the forms of material forces are different, they are homologous; Or in other words, they are so directly related and interdependent that they can all be converted to each other and have the same ability in function. "
Not many people paid attention to Faraday's field theory at first, but Faraday's belief in the unity of nature was confirmed by Joule, Thomson, Helmholtz, Clausius and Maxwell in various ways in the work of the following decades.
At the same time, the relationship between Faraday and David continued to deteriorate. As time went on, David had to admit that Faraday was surpassing himself, so he began to become jealous and bitter. When Faraday's name was reported to the Royal Society and he was ready to be accepted as a member, David objected. Although David voted against it alone, Faraday was elected as a member of the Royal Society on 1824. 1825, Faraday became the director of the laboratory, 1833, he became the professor of chemistry at the Royal College. Faraday is a gentle and loyal man. He would rather spend time in the laboratory or stay at home with his wife Sarah Barnard than respond to David's behavior. He still has a lot of things to do. John tyndall (1820-1893), as Faraday's successor in the Royal Institute, once described Faraday as "an excitable and grumpy person, but after a high degree of self-discipline, he has turned this popularity into a flash and motivation in life instead of wasting it in unnecessary excitement".
We have deep respect for the great experimenter Faraday, as ernest rutherford (187 1- 1937) said in 193 1:
"Looking back, the more we study Faraday's work, the more we can feel his unparalleled talent as an experimenter and natural philosopher. When we consider his discovery and its influence on scientific and industrial progress, we really can't find a commensurate honor to commemorate Faraday, one of the greatest discoverers of all time. "