The resonant circuits were coils of copper wire which resonated with their internal capacitance dotted capacitors at 10 MHz. Power was coupled into the transmitter resonator, and out of the receiver resonator into the rectifier, by small coils which also served for impedance matching. Resonant inductive coupling electrodynamic coupling,  strongly coupled magnetic resonance  is a form of inductive coupling in which power is transferred by magnetic fields B, green between two resonant circuits tuned circuits , one in the transmitter and one in the receiver see diagram, right. The two are tuned to resonate at the same resonant frequency. The resonance between the coils can greatly increase coupling and power transfer, analogously to the way a vibrating tuning fork can induce sympathetic vibration in a distant fork tuned to the same pitch.
Wireless power transfer
Wireless Electricity? How the Tesla Coil Works
Nikola Tesla in his Colorado Laboratory with magnifying transmitter in action generating 20 million volts of electricity This technology can be used where conventional wires are unaffordable, inconvenient, expensive, hazardous, unwanted or impossible. It can also be used for applications where either an instantaneous amount or a continuous delivery of energy is needed. The power can be transmitted using microwaves, millimetre waves or lasers. WPT is a technology that can transport power to locations, which are practically impossible to reach. He produced an apparatus which produced and detected microwaves in the UHF region. In Tesla performed experiments in the field of pulsed wireless energy transfer.
Tesla's ideas about electrical conduction through the "natural media" fall into two categories: I also asked him if he is still at work on the project which he inaugurated in the '90's of transmitting power wirelessly anywhere on earth. He is at work on it, he said, and it could be put into operation. He at that time announced two principles which could be used in this project.
July 10, Fermilab Among his numerous innovations, Nikola Tesla dreamed of creating a way to supply power to the world without stringing wires across the globe. The inventor came close to accomplishing this when his "mad scientist" experiments with electricity led to his creation of the Tesla coil. The first system that could wirelessly transmit electricity, the Tesla coil was a truly revolutionary invention. Early radio antennas and telegraphy used the invention, but variations of the coil can also do things that are just plain cool — like shoot lightning bolts , send electric currents through the body and create electron winds.