Wireless charging technology in electric toothbrushes, razors, cell phones already have some applications, wireless charging of electric vehicles have also preliminary tests. If wireless charging can be achieved, then we can not save high-voltage transmission lines to achieve wireless transmission, and even can receive space solar cell power to completely solve the problem of human transmission and energy use Xiaobian try to talk about wireless transmission Rely on unreliable Wireless transmission In the cracked wireless transmission problems, let us first expand the scope of wireless transmission about it - "wireless transmission." The concept of energy includes a broader, the sun is the most common "wireless energy", but it is more than 150 million kilometers, 4.5 billion years of wireless energy transmission. First look at what forms of energy, look at them can "wireless" transmission. We are already familiar with the forms of energy in the world. Four kinds of high school physics have been learned: power, heat, light and electricity. Coupled with nuclear energy and chemical energy, probably in these six forms of energy (where the force is mechanical energy, electricity refers to electromagnetic energy). Nuclear energy and chemical energy from the atomic force and chemical bond force can not be long-distance transmission, so we only consider the mechanical energy, thermal energy, light energy and electromagnetic energy transfer of four energy. First, there are four common ways of wired transmission: the transmission of mechanical energy corresponds to the transmission of rigid rod, which is the carrier of mechanical energy, for example, the transmission shaft of a car; the optical energy transmission corresponds to an optical fiber and the optical fiber is a carrier of light; Conductor, such as a variety of metals; electromagnetic energy corresponding to the wire or core, are good conductors of electricity or magnetism. The characteristic of wired transmission is that the resistance of this channel is very low: the steel rod has no loss of mechanical energy, the optical fiber has little loss of light energy, the thermal resistance of a good conductor is small, the resistance of a wire is small, and the reluctance of an iron core is small. That way we can harvest the less lost energy on the far side. There is no such "low impedance path" as to what energy can be wirelessly transmitted wirelessly, only air or nothing vacuum. The four kinds of energy in the air or vacuum propagation effect how? First of all, mechanical and thermal energy, both must have the media to spread, the vacuum can not spread, and the air of the two kinds of energy will be dispersed around, resulting in poor propagation. Light energy transmission does not require media, humans can use the laser for high-power light energy transmission, the laser can even be made into a laser cannon. But the laser on topography and weather requirements, the light can only go straight, and can not be diffuse particles in the air, or loss too much. Even if it can be transmitted, both the transmitting and the receiving ends are less expensive and costly to convert from light to electricity and from light, and the cost is high. Perhaps in the future only space energy through laser transmission to the ground there is a certain feasibility. The only remaining energy, and we usually come into contact with only 50 or 60 hertz of electric energy, is a very low frequency, the wavelength of electromagnetic waves of up to five thousand six thousand kilometers, such a long wavelength for the general transmission distance is no electromagnetic wave characteristics (Earth Of the equator about 40,000 km), so electromagnetic induction is the main way of energy transmission. We are now using wireless charging technology, as well as laboratory wireless transmission technology, are the use of electromagnetic induction principle. Appendix I explains the difference between electromagnetic induction and electromagnetic waves. The essence of wireless energy transmission Since the air or vacuum is a "high-resistance channel" for energy transmission, you want the energy to pass smoothly and not spread diffusely due to "high resistance". There is only one way - resonance! The laser is a resonant Light source, the radio by resonance to receive the signal, the same power transmission also need the help of resonance. Details of the resonance can be found in Appendix II below, detailing the concept of resonance and examples of resonance of various energies. Wireless transmission of electrical energy We need to establish a loop with a resonant frequency of 50 Hz so that energy can be transmitted. Having said that, it is not easy to implement. The real environment is too complicated, the electric field and the magnetic field will meet various obstacles in the sky, and the iron or steel in the building will be absorbed by the electromagnetic field. The jargon is called "shielding" (similar to putting the phone in No signal in a closed tin box, all the signals are absorbed by the tin box). When we design the loop parameters, it is too difficult to fully consider the capacitance inductance of all steel along the road. (Capacitance and inductance are the most common but also the most difficult to understand the concept of electricity, a small opportunity to write a description of the physical nature of the capacitor and inductor is what) there are wireless transmission applications, such as wireless charging toothbrush, mobile phone One of the common features of these cases is the short distance. Toothbrushes and cell phones are placed in the charging seat, wireless charging car chassis and floor stickers are also very close (within 30cm). Only one near the goal of reducing the ambient stray capacitance inductance, so that we can design the circuit to maximize the transmission of energy. Of course, from another perspective, this is also to improve the transmission efficiency of energy. The longer the distance, the more stray capacitance inductors, the more they absorb the energy, the less energy it can reach its destination and the lower the energy transfer efficiency. So from the point of view of stray parameters, it is almost impossible to complete wireless transmission over long distances because stray parameters and the effects of various shields are almost impossible to remove.