Wang Zhonglin, director of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences, expanded Maxwell's equations

Chinese scientists have expanded the scope of application of Maxwell's equations.

On January 13, at the press conference of major original achievements of the Beijing Institute of Nanoenergy and Systems of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Nanoenergy), Wang Zhonglin, director and chief scientist of the Institute of Nanoenergy, said that after several years of research and experimental verification, his team successfully extended the electromagnetic field theory to the medium of motion, and expanded Maxwell's equations.

The extended Maxwell equation system established by Wang Zhonglin solves the problem of the scope of use of classical electromagnetism and is an important contribution made by Chinese scientific research institutions to the innovation of classical physics basic theory. His work was published in the international academic journal Materials Today under the title On the expanded Maxwell's equations for moving charged media system - general theory, mathematical solutions and applications in TENG.

Compared with Maxwell's equations for static media, Wang Zhonglin's expanded Maxwell equations not only contain all the connotations of the classical Maxwell equations, but also introduce the electromagnetic coupling effect due to the motion of the charged medium and the theoretical framework of the nano-generator.

Comparison of Maxwell's equations and Wang Zhonglin's extended Maxwell's equations

This system of equations can be applied to the detection of high-speed moving targets, such as high-speed rail in motion, high-speed flying aircraft, missiles, and even planetary operations, etc., to solve the problems of electromagnetic wave generation, emission, interaction, scattered electromagnetic wave detection and accurate extraction of target features.

More importantly, due to the introduction of velocity terms in the extended Maxwell equation system, not only the most common Doppler effect can be studied, but also the amplitude and phase changes of electromagnetic waves, and there are great application prospects in radar, antennas, aviation, aerospace and military fields that require wireless communication.

In 1861, Maxwell established a mechanical model of electromagnetic fields in his article "On the Lines of Force in Physics" and proposed the concept of displacement currents. Maxwell introduced displacement currents into ampere's law to satisfy the continuity equation for charge, thereby extending ampere's law to the time-varying case. This is the key to Maxwell's equations to elucidate the nature of electromagnetic phenomena, enabling Maxwell to recognize the electromagnetic properties of light and thus develop a systematic theory of electromagnetic fields.

Four years later, Maxwell published a paper on electromagnetic field dynamics at the Royal Society, proposing what we know today as Maxwell's equations. The publication of this article marks the initial establishment of the theory of electromagnetic field dynamics and lays a scientific foundation for the use of electromagnetic waves in modern human society.

Maxwell's system of equations unified electricity, magnetism, and optics, achieving a great unification of classical physics in history. Maxwell's research "paradigm" continues to influence the way we discover the laws of physics and explore the physical world today.

But Maxwell's equations describe the absence of dynamic media, and like other partial differential equations, Maxwell's equations are conditionally established. Equation (3) assumes that the shape, distribution, volume, and surface of the medium in the system do not change over time, i.e., they are stationary. If the medium is moving, its distribution changes with time, such as high-speed moving airplanes, running trains, etc., at which point equation (3) cannot be strictly true.

Wang Zhonglin was the first to realize this problem, in order to derive Maxwell's equation system in the case of a moving medium, he started from the integral form of the original equation system and combined with the correction of the equation (3) to establish an extended Maxwell equation system.

"The original motivation for expanding Maxwell's equations was to develop and improve the theoretical framework of the nano-generator", Wang Zhonglin said, the nano-generator uses displacement current as the driving force to effectively convert mechanical energy into electrical energy/electrical signal, which is another major application of Maxwell's equations in energy and sensing after electromagnetic wave theory and technology.

Wang Zhonglin is a leading scientist in the field of nanoscience and technology, inventing piezoelectric nano-generators, friction nano-generators and self-driving nano-system technologies, realizing the conversion of low-frequency mechanical energy collection scattered in the environment into electrical energy, providing a new way for the development of micro-nanoelectronic systems and the Internet of Things and sensor networks to achieve energy self-sufficiency and self-driving.