In April 1820, Danish physicist Oersted discovered that a current-carrying wire could cause a nearby small magnetic needle to swing.
Oersted's discovery of the interaction between electricity and magnetism - that is, the magnetic effect of electric current - immediately shocked Europe. Many people started experiments. The purpose of the experiment was to find the inverse phenomenon of Oersted's experiment - ----Magnet generates electricity.
In 1825, Swiss physicist Coladon conducted such an experiment. He inserted a magnet into a spiral coil connected to a sensitive galvanometer to observe whether there was any current generated in the coil.
However, during the experiment, in order to eliminate the influence of the moving magnet on the sensitive galvanometer, Colaton placed the sensitive galvanometer connected to the spiral coil in another room through a long wire. .
He thought that the current generated should be "stable" anyway (at that time, the scientific community believed that the electricity generated by magnetic fields should be "stable"). After inserting the magnet, if there is current, it will run to another place. It’s not too late to observe in one room.
In this way, Colaton began the experiment. However, no matter how fast he ran, the galvanometer pointer he saw was pointing at the "0" scale.
Colaton failed. What kind of failure is Colaton's failure?
Later generations have various opinions. Some say it was a "successful failure." Because Colaton's experimental device was designed completely correctly. If the magnet is strong enough, the wire resistance is not large, and the galvanometer is very sensitive, then when Colaton inserts the magnet into the spiral coil, the pointer of the galvanometer will indeed swing.
In other words, the electromagnetic induction experiment was successful, but Colaton didn't see it. He ran "too slowly" and didn't even see the galvanometer pointer swing back. Some people said, It was a "regrettable failure."
Because if Colaton had an assistant in another room, or if Colaton had placed the galvanometer in a visible place in the same room, then the laurels of the discovery of electromagnetic induction would definitely be It belongs to Colaton.
The first person to discover electromagnetic induction was D.F.J. Arago of France.
Oersted discovered the experiment of electric current affecting a small magnetic needle. French physicist Arago was very excited to report this matter to the French Academy of Sciences. The French scientific community immediately launched electromagnetic experiments. Among them, Ampere, Bid Austria-Saval and others have made significant achievements. Arago himself also actively carried out electromagnetic experiments.
In 1822, D.F.J. Arago and A.von Humboldt accidentally discovered that metal has a damping effect on the oscillation of a nearby magnetic needle when measuring the geomagnetic intensity. In 1824, Arago conducted a copper plate experiment based on this phenomenon and found that the rotating copper plate would drive the freely suspended magnetic needle above to rotate, but the rotation of the magnetic needle was out of sync with the copper plate and lagged slightly behind.
Electromagnetic damping and electromagnetic drive are the earliest electromagnetic induction phenomena discovered. However, because they did not directly manifest themselves as induced currents, they could not be explained at the time and did not attract enough attention.
Faraday strongly realized that nature is symmetrical. Since electricity can turn into magnetism due to changes, magnetism should be able to turn into electricity. Not only did Arago not have this profound understanding, he also did not realize that once the magnetoelectric experiment was successful, it could have a drastic impact on mankind, and Faraday knew this very well.
When others laughed at him about the bullshit use of studying magnetism and electricity, Faraday bluntly retorted: What is the use of having a son?
Henry Joseph, a physics professor at Albany College in the United States, improved the electromagnet in 1829. He used insulated wires densely wound around an iron core to create an electromagnet that could lift nearly a ton. of strong electromagnets.
In the same year, Henry discovered the self-induction phenomenon of current when using experiments to prove the effect of wires of different lengths on the lifting force of electromagnets: breaking a long wire carrying current can produce bright sparks.
In 1832, he announced the discovery of the phenomenon of self-induction in a published paper. In January 1835, Henry introduced the results of his research to the American Philosophical Society. He used 14 experiments to qualitatively determine the relative sizes of the inductances of conductors of various shapes.
He also discovered the fundamental laws of transformer operation.
In August 1830, Henry had observed the phenomenon of electromagnetic induction in his experiment, one year before Faraday discovered the phenomenon of electromagnetic induction. However, Henry was concentrating on making larger electromagnets at the time and did not publish the experimental results in time, thus losing the right to discovery. Some people say that he was busy traveling and getting married at the time, while others say that because of his professorship, he could not spend too much time on research.
Henry's electromagnet contributed to the invention of the telegraph. Morse and Wheatstone, the inventors of practical telegraphs, both used the relay invented by Henry.
Henry made many inventions in his life, but he never applied for patents and always announced them to the society for free. Henry died in Washington on May 13, 1878.
The world recognizes the British Faraday as the discoverer of electromagnetic induction. The main reason is that he realized that the key to electromagnetic induction is the relative motion between the coil and the magnetic field.
Faraday proposed five phenomena of electromagnetic induction, namely five scenarios in which electromagnetic induction occurs: changing current, changing magnetic field, moving constant current, moving magnet, and conductor moving in a magnetic field.
Later Weber and Newman summarized these five situations as changes in magnetic flux, collectively known as Faraday's law of electromagnetic induction.
In August 1831, Faraday wound two coils on both sides of a soft iron ring. One of them was a closed loop, with a magnetic needle placed in parallel near the lower end of the wire, and the other was connected to the battery pack and connected to the switch. A closed loop with power is formed. The experiment found that when the switch is turned on, the magnetic needle deflects; when the switch is turned off, the magnetic needle deflects in the opposite direction, which indicates that an induced current occurs in the coil without a battery pack.
Faraday immediately realized that this was a non-constant transient effect. Then he conducted dozens of experiments and summarized the situations that produce induced current into five categories: changing current, changing magnetic field, moving constant current, moving magnet, and conductor moving in the magnetic field, and formalized these phenomena. Named electromagnetic induction.
Faraday also discovered that the induced current generated in loops of different metal conductors under the same conditions is proportional to the conductive ability of the conductor. From this, he realized that the induced current is generated by an induced electromotive force that has nothing to do with the properties of the conductor. Yes, even if there is no loop and no induced current, the induced electromotive force still exists.
Later, Lenz's law, which determines the direction of induced current, and Faraday's law of electromagnetic induction, which describes the quantitative law of electromagnetic induction, were given. (The formula was not given by Faraday himself) And according to the different causes, the induced electromotive force is divided into two types: kinetic electromotive force and induced electromotive force. The former originates from the Lorentz force, and the latter originates from the rotating electric field generated by the changing magnetic field. .
Faraday always believed that various natural forces are closely related and can transform into each other. After nearly 10 years, until 1831, he finally discovered that although the magnetic force generated by an energized coil cannot cause an energizing current in another coil, when the current of the energized coil is turned on or interrupted, the magnetic force in the other coil will The galvanometer pointer deflected slightly.
Faraday seized this discovery and conducted repeated experiments, and the experimental results verified this phenomenon. He also designed various other experiments, and changes in magnetic force could also produce electric current. This is the famous principle of electromagnetic induction. Faraday's discovery finally opened a new way to generate large amounts of electric current outside of batteries.
The principle of electromagnetic induction discovered by Faraday gave mankind the golden key to open the treasure house of electrical energy. It took a big step forward on the road of conquering and utilizing nature. It was an epoch-making great scientific achievement.
Using this principle, Faraday created the prototype of the world's first induction generator. Later, on this basis, people made practical electric motors, generators, transformers and other electrical equipment, and established thermal and hydroelectric power stations, making electricity widely used in all aspects of society. All of this is inseparable from Faraday's great contribution