In  recent years, technologies related to smartphones have become more and  more mature, and the technological achievements they have brought are  constantly attracting attention. Just recently, a technology called  "wireless charging" that was first used by the famous Nokia lumia920 has  widely aroused people's curiosity and attention, and people think it is  a very magical function and technology. In fact, after I searched for  relevant information, I found that wireless charging technology actually  appeared a long time ago, but after recent years of development, it has  only become mature and easy to use now. Expanded to the field of smart  phones.

Wireless  charging technology, as the name suggests,is to transmit energy to  electronic devices through the air to achieve the purpose of charging.  The realization of wireless charging technology is mainly through three  methods: electromagnetic induction charging, magnetic field resonance  charging and radio wave charging. The wireless charging of the Nokia  lumia920 uses electromagnetic induction charging.

First,  the electromagnetic induction charging is introduced. We have learned  the principle in high school, that is to say, when the current flows  through the coil, a magnetic field will be generated around it. This is  the electromagnetic effect discovered by the Danish physicist Oster; and  when other coils without electricity are close to the magnetic field,  the current will be generated, which is the phenomenon of  electromagnetic induction discovered by the British physicist Faraday.  Electromagnetic induction wireless charging technology combines these  two ideas and uses the principle of electromagnetic induction for  charging: there is a coil at the sending end and a receiving end, and  the coil at the sending end is connected to a wired power supply, and  electromagnetic signals are generated through electromagnetic phenomena.  The coil at the receiving end induces the electromagnetic signal  generated at the sending end and generates electricity through  electromagnetic induction to generate current to charge the battery. Of  course, there is a certain distance between the sending end and the  receiving end to show the convenience of wireless charging. This power  transmission distance is about a few millimeters to ten centimeters,  which is relatively short, but this distance   for the smartphones we  usually use is enough, we only need to put the battery and the receiving  device on the charging platform to charge it, eliminating the trouble  of wiring.   Its principle and production are relatively simple, so  there are many posts on the Internet that convert mobile phones charged  by wire into wireless charging.

There  is also magnetic resonance charging，whose basic principle is the  principle of magnetic field coupling resonance, and that is similar to  the resonance of sound. It is not difficult to imagine that if the  tuning forks with the same vibration frequency are arranged, one will  sound and the other will resonate; in the same way, when there is  current in one of the two coils adjusted to the same frequency in the  magnetic field, the other one will exchange energy with it, thereby  generating an electric current. According to the working principle of  the wireless charger, there is a sending end and a receiving end, and  the sending end is connected to a direct current, which is converted  into a high-frequency AC signal through a resonant converter, so that  the sending end coil generates a certain distance around it.An  electromagnetic field with large high-frequency changes, and when the  receiving coil is located in this electromagnetic field, the  high-frequency change of the magnetic flux of the transmitting coil will  generate a certain high-frequency induced electromotive force in the  receiving coil, and then pass through the device at the receiving coil  end , the receiving end can generate DC current to charge the battery.  Magnetic field resonance charging is different from electromagnetic  induction charging.It does not emit electromagnetic waves, but only  forms a magnetic field around it, and consumes less power than inductive  charging, and the transmission distance is longer, ranging from tens of  centimeters to several meters. This technology has been applied to  vehicles, maglev trains and other means of transportation, but it is  only in the experimental stage.

Finally,  wireless charging. Its basic principle is similar to that of early  mineral radios. According to physical principles, changes in the  strength of the current in the conductor at the sending end will  generate radio waves, and radio waves can carry energy and transfer  energy. At the same time, when radio waves are transmitted to the  receiving end through space, the electromagnetic field changes caused by  the radio waves will produce a resonance effect, and will generate  current in the conductor at the receiving end, thereby realizing  wireless charging using radio waves. At present, there are technological  products that can use this principle to capture and convert the radio  waves emitted by the transmitter on the socket, including the radio  waves bounced by objects, into direct current, and charge low-voltage  electronic products within an effective range of one meter.

Wireless  charging technology still has some shortcomings, such as large energy  loss, inability to support high-power charging, inability to support  long-distance, large electromagnetic radiation, and potential safety  hazards. But none of these can stop it from showing its charm. Just  imagine, if in the future our mobile phones, computers, etc. no longer  need the shackles of wires, if we no longer have to carry a lot of data  cables with us when traveling far away, if electric vehicles and other  traffic Tools can be charged while walking, such a life will be  infinitely convenient and beautiful. I believe that in the near future,  scientists will be able to solve each of these technical difficulties,  change life with physics, and make life better with technology!