Electricity Without Wires
The idea of transmitting electricity without wires was first explored by Thomas Edison and Nicola Tesla in the nineteenth century (Nicola Tesla led a really interesting life, and is the subject of several conspiracy theories. He was played by David Bowie in the movie “The Prestige”). The recent systems have included the use of microwaves (concerns regarding health) and lasers (requires line of sight). One company has been gaining a lot of interest, perhaps for the silly name – Witricity. Their system relies upon resonance. with a recent demonstration showing how an Apple iPhone could be charged without wires.
When two objects have the same resonant frequency, they can exchange energy without having an effect on objects around them. Witricity’s approach exploits the resonance of low frequency electromagnetic waves. Two coils, with the same resonant frequency are used. One is plugged in to the mains, and the other in to the object which is to be charged. As each cycle of energy arrives at the second coil, it builds up a voltage which is used to charge the device. Charging begins automaticaly, as soon as the object is brought in to range.