THE PHYSICS OF WIRELESS POWER TRANSFER

Surely WPT wasn't an act of pure sorcery and magic! So how is it possible to transfer electrical power from one source to another with out the any wires or other forms of direct physical contact? 

Ampere's law states that an electric current running though a wire generates a magnetic field. With the magnetic field generated, Faraday discovered that a electric current in a current carrying wire could induce another current in another wire, but only if the magnetic field produced was changing. This meant that in order for an EMF to be induced into another wire, the magnetic field must always be at a shifting state. EMF stands for electromotive force, which is what causes electrons to move to and from a current. 

Short distance WPT digraph

Photo form edgefxkits.com

For transmitting power over a short distance, a common model for WPT​ is demonstrated in the image above. A power supply puts a current through a curled wire, generating a short range magnetic field. Placing another coil, the receiver coil, with in the magnetic field will allow a flow of electric current from the source field to the receiver field. This process is called induction. The receiver coil then unloads that electric current to power a device. 

Long distance WPT digraph

Photo from witricity.com

For transmitting power over a longer distance, ​a rapidly oscillating electric current it applied to the coil at a specific resonant frequency which creates a magnetic field at the region around the coil. Tuning another coil with the same resonant frequency as the source coil and it will couple, resonating anywhere within that region and converting the oscillating magnetic field into an electrical current within the receiving coil. The space between two coils isn't affected by walls or any other common obstacles, so this process can work even if both coils are in different rooms. This response is called Highly Coupled Magnetic Resonance, which is a pretty new discovery. From there the receiving coil can now transfer is current and power a device or a battery.