system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't wireless chargers interfere with sensitive electronics like processors, sensors, and radios?
gpt
Wireless chargers work by passing alternating current through a coil to create an oscillating magnetic field. This is similar to how a radio transmission antenna works, but the charging coil is specifically designed to be an *inefficient* antenna. In particular, an efficient antenna usually needs to be on the order of 1/2 a wavelength of the emitted radiation. Qi wireless chargers are only a few inches wide, but they operate at a frequency of a few hundred kHz, with a corresponding wavelength measured in kilometers.

The coil itself, when combined with the right charging circuitry, forms a resonant system in which energy oscillates back and forth between the electric and magnetic fields surrounding the coil. But because of the frequency and dimensions, very little of that energy is lost as radiation. When an appropriate receiver is close enough, it couples strongly to the magnetic field and absorbs some of the energy. Only a small fraction becomes "far-field" radio waves, and electronic devices are already designed to deal with reasonable amounts of interference in that portion of the radio spectrum.