Scientists have<!-- angga_r1409 here --> known for nearly two centuries how to transmitelectricity without wires, and the phenomenon has been demonstratedseveral times before. But it wasn't until the rise of personalelectronic devices that the demand for wireless power materialized. Inthe past few years, at least three companies have debuted prototypes ofwireless power devices, though their distance range is relativelylimited [see "Power Brokers," next page]. Then last year, a team at theMassachusetts Institute of Technology set the stage for wireless powerthat works from across a room.

The key to wireless power isresonance. Think of a wineglass that shatters when an opera singer hitsjust the right note. When the voice matches the glass's resonantfrequency—the tone you hear when you tap the glass—the glassefficiently absorbs the singer's energy and cracks. Using magneticinduction and two identical copper coils that resonate at the samefrequency, the MIT scientists successfully powered a 60-watt lightbulbfrom a power source seven feet away. The team called their inventionWiTricity, short for "wireless electricity." Next up: sending the juiceeven farther and more efficiently.