To recharge portable electronics, scientists hope to perfect a method for transmitting electrical energy wirelessly. The effect, which has not yet been demonstrated, would take advantage of induction, in which a varying magnetic field can induce electrical flow in a nearby conductor. To boost the range and power, Massachusetts Institute of Technology researchers propose introducing a short gap in a metal loop and attaching two small disks at each end. When electrified, such an object has a natural frequency that results from current flowing back and forth along the loop from one disk to the other. If a second loop has the same frequency, it should be able to receive energy from the other through the magnetic field. From a few meters away, the rate of energy transferred might reach tens of watts, or enough to power a laptop, according to simulations presented November 14 at a meeting of the American Institute of Physics.
This article was originally published with the title "Cordless Charging" in Scientific American 296, 2, 25 (February 2007)