The law of electromagnetic induction is a formula explaining the formation of an emf in a closed conductor loop with changes in the magnetic field. The postulate explains the operation of transformers, chokes and other products that ensure the development of technology today.
The story of Michael Faraday
Michael Faraday was taken from school with his elder brother, a reason for a speech defect. The discoverer of electromagnetic induction lisp, irritating the teacher. She gave money in order to buy a stick and carve out a potential client of a speech therapist. And the elder brother Michael.
The future star of science was truly the darling of fate. On the length of his life's journey, he, with due perseverance, found help. The brother with contempt returned the coin, reporting the incident to the mother. The family was not considered rich, and the father, a talented artisan, struggled to make ends meet. The brothers began to look for work early: the family lived on alms from 1801, Michael was ten years old at that time.
From thirteen Faraday enters the bookstore by a peddler of newspapers. Through the entire city, it barely manages to reach addresses at opposite ends of London. Due to diligence, the owner Ribot gives Faraday the place of the bookbinder's apprentice for seven years for free. For a long time, a man from the street paid the master for the process of acquiring a craft. Like Georg Omu the skill of a mechanic, Faraday in the future, the process of bookbinding was useful to the full. A big role was played by the fact that Michael carefully read the books that fall into his work.
Faraday writes that he equally willingly believed in the treatise of Mrs. Marset( Talk about Chemistry) and the tales of Thousand and One Nights. The desire to become a scientist has played an important role in this matter. Faraday chooses two directions: electricity and chemistry. In the first case, the main source of knowledge is the British Encyclopedia. Inquisitive mind requires confirmation of what has been written, the young bookbinder constantly checks knowledge in practice. Faraday becomes an experienced experimenter, which will play a leading role in the study of electromagnetic induction.
Recall that we are talking about a student without their own income. The elder brother and father assisted as much as possible. Starting with chemical reagents and ending with the assembly of an electrostatic generator: experiments require an energy source. At the same time, Faraday manages to attend paid lectures of natural science and meticulously puts knowledge in a notebook. Then she weaves the notes, using the acquired skills. The term of apprenticeship ends in 1812, Faraday begins to look for work. The new owner is not so docile, and, despite the prospect of becoming the heir to the cause, Michael is on his way to discovering electromagnetic induction.
The Faraday Scientific Path
In 1813, fate smiled upon a scientist who gave the world an idea of electromagnetic induction: he succeeds in taking the place of secretary to Sir Humphrey Davy, a brief acquaintance period in the future will play a role. Faraday is unbearable to perform longer than a binder, he writes a letter to Joseph Banks, then president of the Royal Society of Scientists. A fact will tell about the nature of the organization's activity: Faraday got a place called the senior minion: he helps the lecturers, wipes the dust from the equipment, and oversees the transportation. Joseph Banks ignores the message, Michael is not discouraged and writes Davy. After all, there are no other scientific organizations in England!
Davy is very attentive because he is personally acquainted with Michael. Without being naturally gifted with the ability to speak - remember the school experience - and express thoughts in writing, Faraday takes special lessons to develop the necessary skills. Experiments are carefully systematized in a notebook, he presents his thoughts in a circle of friends and like-minded people. By the time of his acquaintance with Sir Humphrey, Davy achieves remarkable skill, he is applying for a new scientist for the aforementioned position. Faraday is happy, but the idea to appoint a future genius to wash the dishes was originally set forth. ..
At the behest of rock, Michael is forced to listen to lectures on various topics. Assistance to professors was required only periodically, otherwise it was allowed to be in the classroom and listen. Given the cost of education at Harvard, this was a good leisure time. After six months of brilliant work( October 1813) Davy invites Faraday in a trip to Europe, the war is over, you need to look around. This became a good school for the discoverer of electromagnetic induction.
Upon returning to England( 1816), Faraday is promoted to laboratory assistant and publishes his first limestone research.
The phenomenon of electromagnetic induction consists in induction of an emf in a conductor under the action of a varying magnetic field. Today, on this principle, devices work, starting with transformers and ending with hobs. The championship in the region is given to Hans Oersted, on April 21, 1820, who noticed the effect of a closed circuit on the compass needle. Similar observations were published in the form of notes by Giovanni Domenico Romanosi in 1802.
The merit of a Danish scientist in attracting many prominent scientists to the cause. So, it is noticed that the arrow is deflected by a conductor with current, and in the fall of the aforementioned year the first galvanometer was born. The measuring device in the field of electricity has become a great help to many. Along the way, different points of view were expressed, in particular, Wollaston announced that it would be nice to make the conductor with a current rotate continuously under the influence of a magnet. In the 20s of the XIX century, euphoria reigned around this issue, until then magnetism and electricity were considered independent phenomena.
On the occasion of 1821, Michael Faraday put the idea into practice. It is claimed that the first electric motor was then born. On September 12, 1821, in a letter to Gasparu de la Riva, Faraday wrote:
“I found out that the attraction and repulsion of a magnetic needle with a wire with current is child's play. A certain force will continuously rotate the magnet under the action of electric current. I built theoretical calculations and managed to put it into practice. ”
A letter to de la Reeve did not become an accident. As he became a scientist, Faraday gained quite a few supporters and the only implacable opponent. .. Sir Humpfrey Davy. Experimental installation declared plagiarism ideas Wollaston. Sample construction:
- Silver bowl filled with mercury. Liquid metal has good electrical conductivity and serves as a moving contact.
- At the bottom of the bowl is a cake of wax, where a rod magnet is stuck with one pole. The second rises above the surface of mercury.
- A wire connected to a source is hanging from a height. The end of it is immersed in mercury. The second wire is near the edge of the bowl.
- If a constant electric current is passed through a closed circuit, the wire begins to describe circles on mercury. The center of rotation becomes a permanent magnet.
The design is called the world's first electric motor. But the effect of electromagnetic induction has not yet manifested. There is an interaction of two fields, no more. Faraday, by the way, did not stop, and made a bowl where the wire is stationary, and the magnet moves( forming a surface of rotation - a cone).Proved that there is no fundamental difference between the sources of the field. Therefore, induction is called electromagnetic.
Immediately, Faraday was accused of plagiarism and poisoned for several months, which he bitterly wrote to trusted friends. In December 1821, a conversation with Wollaston took place, the incident seemed to be settled, but. .. a little later the group of scientists resumed the attacks, Sir Humpfrey Devi became the head of the opposition. The meaning of the main claims was to oppose the idea of accepting Faraday as members of the Royal Society. This put heavy pressure on the future discoverer of the law of electromagnetic induction.
The discovery of the law of electromagnetic induction
For the time being, Faraday seemed to abandon the idea of research in the field of electricity. Sir Humphrey Davy was the only one who threw the ball against Michael's candidacy. Perhaps the former student did not want to upset the patron who was the then president of society. But the idea of the unity of natural processes was constantly tormented: if electricity could be turned into magnetism, one should try to do the opposite.
This idea was born - according to some information - in 1822, and Faraday constantly carried with him a piece of iron ore that looked like it served as a “memory knot”.Since 1825, being a full member of the Royal Society, Michael receives the position of head of the laboratory and immediately makes innovations. The staff now meets once a week at a lecture with visual demonstrations of instruments. Gradually, the entrance becomes open, even children are given the opportunity to try new things. This tradition marked the beginning of the famous Friday nights.
For five years, Faraday was engaged in optical glass, the group did not achieve great success, but there were practical results. There was a key event - Humphrey Davy’s life, which was constantly opposed to experiments with electricity, ends. Faraday rejects the proposal for a new five-year contract and begins now openly research that led straight to magnetic induction. According to the literature, the series lasted 10 days, unevenly scattered in the period from August 29 to November 4, 1831.Faraday describes his own laboratory setup:
I made a ring with an outer radius of 3 inches from a soft( with strong magnetic properties) circular metal of 7/8 inch diameter. In fact, it turned out the core. The three primary windings were separated from each other by cotton cloth and tailoring cord, so that they could be combined into one or used separately. The length of the copper wire in each is 24 feet. The quality of insulation is checked with the help of batteries. The secondary winding consisted of two segments, each 60 feet long, separated from the primary one by a distance.
From the source( presumably an element of Wollaston), which had 10 plates, each 4 square inches in area, was fed to the primary winding. The ends of the secondary are shorted by a piece of wire, a compass needle was placed three feet from the ring along the chain. When the power source was closed, the magnetized needle immediately began to move, and after an interval returned to its original place. Obviously, the primary winding causes a response in the secondary. Now I would say that the magnetic field propagates through the core and induces an emf at the output of the transformer.
With a power failure, the effect was repeated. There is a parasitic counter-EMF, which Nikola Tesla fought with, creating spiral coils. The next day( August 30), Faraday analyzes the result of experiments and tries to compare what he has seen with facts already known to science. The experience of Arago in 1822 comes to mind, showing the interrelation of the rotation of the magnetic needle and the copper disk. Readers have already guessed that the needle interacted with the field of induction currents. So the law of electromagnetic induction was discovered.