How Does Wireless Charging Work? A Scientific Explanation – SlashGear

When using electric charging cables, you have to constantly insert and remove them from the device you want to charge. However, wireless chargers can be set up, synced with your device, and simply moved out of range when you’re ready to go. So, how far is too far away for a wireless charger? It all depends on the medium.

Wireless chargers are lumped into two categories: near-field and far-field. This name stems from the regions of an electromagnetic field near a wireless charge transmitter, which is typically referred to as an antenna. If the antenna produces a medium that weakens with distance, then the charger is considered a near-field device. If the distance has little to no effect on the power provided, then the device is considered far-field. 

However, since every medium vibrates at different wavelengths, what constitutes near” and “far changes from charger to charger. Generally speaking, If the receiver can be placed more than one wavelength away from the antenna, then the charger is considered far-field. Otherwise, it’s near-field.

Devices that use or convert currents to magnetic or electric fields generally fall under the near-field category. Meanwhile, wireless chargers that utilize microwaves, radio waves, lasers, and even plasma are considered far-field devices. These cover the majority of wireless charging gadgets out there, but some devices, such as resonant chargers, don’t fall into the above categories. These devices aren’t efficient at normal near-field or far-field distances, making them some of the only, for lack of a better term, mid-field wireless chargers around.