Magnetic field resonance charging: consists of an energy sending device and an energy receiving device. When two devices are adjusted to the same frequency, or resonate at a specific frequency, they can exchange energy with each other. It is a technology that is currently under research. A team led by MIT Physics Professor Marin Soljacic used the technology to light up a 60-watt light bulb two meters away and named it WiTricity. The diameter of the coil used in this experiment reached 50 cm, and it could not be commercialized yet. If the coil size is to be reduced, the received power naturally decreases.