2. 183 1 year, Faraday in Britain discovered electromagnetic induction. Maxwell further expounded the research results of Faraday and others with mathematical formulas, and extended the theory of electromagnetic induction to space.
3. 1973, a man stood on the street of new york, pulled out a wireless phone about the size of two bricks and started talking. This man is marty cooper, the inventor of mobile phone. At that time, he was an engineer at Motorola. This was the first mobile phone in the world at that time.
4. The first generation of mobile phones (1G) refers to analog mobile phones, which appeared in Hong Kong, the United States and other film and television works in the 1980s and 1990s. The first person to develop a mobile phone was Dr. Cooper from Motorola, USA.
The second generation mobile phone (2G) is also the most common mobile phone. Usually, these mobile phones use very mature standards such as PHS, GSM or CDMA, with stable call quality and appropriate standby time.
Extended data:
1, a modern mobile phone, was born in 1987. Its weight is still about 750 grams, which is like a big brick compared with today's mobile phone with only 60 grams.
Since then, the slimming of mobile phones has become more and more rapid. 199 1 year, and the weight of the mobile phone is about 250g. 1in the autumn of 996, a mobile phone with a volume of 100 cubic centimeter and a weight of 100 gram appeared. Since then, it has been further miniaturized and lightweight, and 1999 has been lighter than 60 grams.
3. 1973 In April, marty cooper, a famous engineer and technician of Motorola Company in the United States, invented the world's first civil mobile phone. When Cooper made the world's first mobile phone, he could use any electromagnetic frequency band.
4. The first generation of analog mobile phones actually distinguish different mobile phones of different users through different frequencies. The second generation mobile phone -GSM system distinguishes users with a very small time difference. Today, the frequency resources are obviously insufficient, and the number of mobile phone users is also growing rapidly in geometric series.
5. Thus, a relatively new CDMA technology to distinguish different computers by different codes came into being. The mobile phone using this technology not only has better call quality and confidentiality, but also can reduce radiation, which is called "green mobile phone".
Baidu encyclopedia-mobile phone