Wireless power demonstration 1937
A demonstration of wireless power transmission at the Franklin Institute, Philadelphia, USA in 1937. The device on the right is a radio transmitter that transmits power via shortwave radio waves to the receiver device at left, which lights the incandescent light shown. The transmitter consists of a triode vacuum tube oscillator, with the tank coil serving as an antenna. The simple receiver (left) is a tuned circuit consisting of an inductor coil and capacitor, tuned to the resonant frequency of the ocillator, with the light bulb in series. The inductor likewise serves as the receiving antenna. Visitors can adjust the inductor and capacitor with the two knobs visible on the left, and discover that if the receiver is brought out of resonance with the transmitter the light bulb will go out. The frequency may have been 60 MHz; the article is unclear.
Nikola Tesla discovered this resonant inductive coupling power transfer technique around 1900. It is currently being applied to many short range wireless power systems. As the source points out, the radio waves spread out in all directions, so this technique cannot be used to transmit power long distances.