page_title: Wireless power transfer
section_title: Tesla
hierarchical_section_title: Wireless power transfer / History / Tesla
caption_attribution_description: English: Nikola Tesla demonstrating wireless transmission of power and high frequency energy at Columbia College, New York, in 1891. The two metal sheets were connected to his Tesla coil oscillator, which applied a high voltage oscillating at radio frequency. The electric field ionized the gas in the long, partially evacuated Geissler tubes he is holding (similar to modern neon lights), causing them to emit light without wires. Interlingua: Tesla demonstrante transmissiones sin filos durante su lection super alte frequentias e potential de 1891. Post ulterior recercas, Tesla presentava le fundamentos del radio in 1893. Esperanto: Nikola Tesla montras siajn eksperimentojn en Columbia College, Novjorko, en 1891. Post daŭraj esploroj li montris fundamentojn de radio en 1893. Italiano: Una dimostrazione di Tesla. ಕನ್ನಡ: ನಿಕೊಲಾ ಟೆಸ್ಲಾ ೧೮೯೧ರಲ್ಲಿ ತಮ್ಮ ರೇಡಿಯೊ ತಂತ್ರಜ್ಞಾನ ಪ್ರದರ್ಶಿಸುತ್ತಿರುವುದು. Norsk nynorsk: Nikola Tesla demonstrer trådlaus bølgjeoverføring i 1891. Русский: Никола Тесла демонстрирует передачу высокочастотной энергии на лекции в Колумбийском колледже Нью-Йорка, 1891 г. Basa Sunda: Tesla keur mintonkeun pangiriman informasi nirkabel dina kuliah ngeunaan frékuénsi luhur dina taun 1891. Saenggeus ngalakukeun risét anu sinambung, Tesla ngajelaskeun dasar-dasar ngeunaan radio dina taun 1893.
context_page_description: Wireless power transfer, wireless power transmission, wireless energy transmission, or electromagnetic power transfer is the transmission of electrical energy without wires as a physical link. In a wireless power transmission system, a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic field, which transmits power across space to a receiver device, which extracts power from the field and supplies it to an electrical load. The technology of wireless power transmission can eliminate the use of the wires and batteries, thus increasing the mobility, convenience, and safety of an electronic device for all users. Wireless power transfer is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible.
  Wireless power techniques mainly fall into two categories, near field and far-field. In near field or non-radiative techniques, power is transferred over short distances by magnetic fields using inductive coupling between coils of wire, or by electric fields using capacitive coupling between metal electrodes.
context_section_description: After 1890, inventor Nikola Tesla experimented with transmitting power by inductive and capacitive coupling using spark-excited radio frequency resonant transformers, now called Tesla coils, which generated high AC voltages.  Early on he attempted to develop a wireless lighting system based on near-field inductive and capacitive coupling and conducted a series of public demonstrations where he lit Geissler tubes and even incandescent light bulbs from across a stage. He found he could increase the distance at which he could light a lamp by using a receiving LC circuit tuned to resonance with the transmitter's LC circuit. using resonant inductive coupling. Tesla failed to make a commercial product out of his findings but his resonant inductive coupling method is now widely used in electronics and is currently being applied to short-range wireless power systems.
  Tesla went on to develop a wireless power distribution system that he hoped would be capable of transmitting power long distance directly into homes and factories. Early on he seemed to borrow from the ideas of Mahlon Loomis, proposing a system composed of balloons to suspend transmitting and receiving electrodes in the air above 30,000 feet (9,100 m) in altitude, where he thought the pressure would allow him to send high voltages (millions of volts) long distances. To further study the conductive nature of low pressure air he set up a test facility at high altitude in Colorado Springs during 1899. Experiments he conducted there with a large coil operating in the megavolts range, as well as observations he made of the electronic noise of lightning strikes, led him to conclude incorrectly that he could use the entire globe of the Earth to conduct electrical energy. The theory included driving alternating current pulses into the Earth at its resonant frequency from a grounded Tesla coil working against an elevated capacitance to make the potential of the Earth oscillate. Tesla thought this would allow alternating current to be received with a similar capacitive antenna tuned to resonance with it at any point on Earth with very little power loss. His observations also led him to believe a high voltage used in a coil at an elevation of a few hundred feet would "break the air stratum down", eliminating the need for miles of cable hanging on balloons to create his atmospheric return circuit. Tesla would go on the next year to propose a "World Wireless System" that was to broadcast both information and power worldwide. In 1901, at Shoreham, New York he attempted to construct a large high-voltage wireless power station, now called Wardenclyffe Tower, but by 1904 investment dried up and the facility was never completed.
caption: Tesla demonstrating wireless transmission by "electrostatic induction" during an 1891 lecture at Columbia College.  The two metal sheets are connected to a Tesla coil oscillator, which applies high-voltage radio frequency alternating current.  An oscillating electric field between the sheets ionizes the low-pressure gas in the two long Geissler tubes in his hands, causing them to glow in a manner similar to neon tubes.
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