Generation of electromagnetic fields

Electromagnetic field is a general term for the unity of electric and magnetic fields that are intrinsically linked and interdependent. The time-varying electric field produces a magnetic field, and the time-varying magnetic field produces an electric field. Electromagnetic fields can be caused by charged particles moving at a variable speed, or by currents with varying strengths. Regardless of the cause, the electromagnetic field always propagates around at the speed of light, forming electromagnetic waves. The electromagnetic field is the medium of electromagnetic action, has energy and momentum, and is a form of existence of matter. The properties, characteristics and the law of motion change of the electromagnetic field are determined by Maxwell's equations.

Time-varying electromagnetic field. Time-varying electromagnetic fields are significantly different from static electric and magnetic fields, and there are some effects due to time-varying. These effects have important applications and drive the development of electrotechnical technology.