Magnets were first used to indicate the direction and correct the time, which is what the "four acceptances" mentioned in Han Feizi Lun Heng written by Wang Chong in the Eastern Han Dynasty refers to.
Later, due to the development of navigation, China invented the compass in the 11th century.
In Shen Kuo's Talk on Meng Xi in the Song Dynasty, it is recorded that "the Fang family can be guided by a magnet grinding needle, but it is often slightly east, but not all south".
This not only shows the manufacture of the compass, but also finds the magnetic declination.
It was not until the 12 century that the compass was introduced to Europe.
2. From the end of18th century to the beginning of19th century, due to the needs of production development, the research work in electromagnetic phenomena developed rapidly.
Coulomb first determined the interaction force between charges from the laboratory in 1785, and the concept of charge began to have quantitative significance.
1820, Oster discovered the powerful effect of current on the magnetic needle from the experiment, which opened a new page of electrical theory.
In the same year, Ampere confirmed that the coil with current is similar to a magnet, and pointed out the essential problem of this phenomenon.
The famous ohm's law was obtained by ohm experiment in 1826.
Faraday made a special contribution to the study of electromagnetic phenomena. The electromagnetic induction phenomenon he discovered in 183 1 is an important theoretical basis for electronic technology in the future.
Cold words have played a great role in electromagnetic phenomena's theoretical and applied research. 1833, he established the law of determining the direction of induced current (cold rule).
Later, he devoted himself to the research of motor theory and expounded the principle of motor reversibility.
1844, Lengci and British physicist Joule independently confirmed the law of thermal effect of current (Joule-Lenz law).
Jacoby, who was engaged in electromagnetic phenomena research with Lengci, manufactured the world's first motor in 1834, thus proving the possibility of practical application of electric energy.
The rapid development of electrical engineering is inseparable from the work of Dorivo Dobro Volschi.
This outstanding Russian engineer is the founder of three-phase system. He invented and manufactured three-phase asynchronous motors and three-phase transformers, and adopted three-phase transmission lines for the first time.
On the basis of Faraday's research work, Maxwell put forward the electromagnetic wave theory from 1864 to 1873.
He predicted the existence of electromagnetic waves in theory, which laid a theoretical foundation for the development of radio technology.
1888, Hertz obtained electromagnetic waves through experiments, which confirmed Maxwell's theory.
However, the practical application of electromagnetic waves to serve mankind should also be attributed to Marconi and popov.
About seven years after Hertz experiment was successful, they independently conducted communication experiments in Italy and Russia, which opened the way for the development of radio technology.
3. In the process of struggling with nature, human beings constantly sum up and enrich their knowledge.
Electronic science and technology is developed in production struggle and scientific experiment.
Edison, an American inventor, discovered the thermionic effect in 1883, and then Fleming made an electronic diode by using this effect in 1904, and proved that the electron tube has the function of "valve". He was first used for radio detection.
1906, Dveress of the United States put the third electrode, the grid, into the Fleming diode, and invented the electronic triode, which made the most important milestone in early electronic technology.
For more than half a century, electron tubes have made great contributions to the neutrality of electronic technology; However, electron tubes are expensive, complicated to manufacture, bulky and consume a lot of electricity. Since 1948, several researchers at Bell Laboratories invented the transistor, which gradually replaced the electron tube in most fields.
However, we can't deny the unique advantages of electron tubes. In some devices, electron tubes are still needed in terms of stability, economy or power.
4. 1958 The world saw the first sample of integrated circuit.
The appearance and application of integrated circuits mark the development of electronic technology to a new stage.
It realizes the unification of materials, components and circuits; It is essentially different from the traditional design and production methods of electronic components and the structure of circuits.
With the development of integrated circuit manufacturing technology, the integration level is getting higher and higher, and large-scale and ultra-large-scale integrated circuits have appeared (for example, a complete computer can be made on a 6mm square silicon wafer), which further shows the advantages of integrated circuits.
With the development of semiconductor technology and the needs of scientific research, production and management, electronic computers came into being and became more and more perfect.
Since the birth of the first electronic computer in 1946, it has experienced four generations of electron tubes, transistors, integrated circuits and VLSI, and its operation speed has reached 65,438 billion times per second.
At present, the fifth generation computer (artificial intelligence computer) and the sixth generation computer (biological computer) are being studied and developed. They work through artificial intelligence rather than programs.
Especially since the advent of satellite computers in the 1970s, electronic computers have greatly accelerated their popularity because of their cheapness, convenience, reliability and compactness.
6. Digital control and digital measurement are constantly developing and widely used.
CNC machine tools and "adaptive" CNC machine tools have appeared one after another.
At present, the centralized control of dozens or even hundreds of CNC machine tools by electronic computers (so-called "group control") has been realized.
Thyristor (SCR) is also widely used in industry, which makes semiconductor technology enter the field of high voltage.
7. With the development of production and science and technology, electronic technology has been highly developed and widely used (such as space electronic technology, biomedical electronic technology, information processing and remote sensing technology, microwave application, etc.). ), which also played a revolutionary role in promoting the development of social productive forces.
Electronic level is an important symbol of modernization, and electronic industry is an important material and technical foundation to realize modernization.
The development speed and technical level of electronic industry, especially the high development of electronic computers and their wide application in production fields, directly affect the construction of industry, agriculture, science and technology and national defense, and are related to the development speed of socialist construction and national security; It also directly affects the material and cultural life of hundreds of millions of people and concerns the vital interests of the broad masses of the people.