A wireless electrical outlet works by using the magnetic fields that occur naturally in a current moving through the wires in a outlet to create a current and voltage in the wires of the device receiving power in a process known as inductive coupling. Typically, the outlet only works within short distances. Transmitting power over longer distances requires the use of resonance to prevent a waste of energy.
The wires are typically bent into a coil to amplify the magnetic field. Resonance occurs when the magnetic coil is working at the frequency in which it naturally wants to work, determined by its material properties. The frequency is created by attaching a capacitor, which stores energy, to the ends of the coils. The properties of the capacitor and the coil determines its resonant frequency, and only two coils within a few meters with the same resonant frequency will have power transmitted between them. The wire coil in the outlet receives current from the power source. The wire coil in the device has current that flows through it that is induced by the magnetic field from the outlet's coils. The devices need either a built-in or a plug-in receiver to work, as a normal charge port doesn't contain the compatible coil and circuitry necessary to transmit power to the device's battery.