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by aidenn0 3411 days ago
A varying magnetic field produces an electrical field.

A varying electrical field produces a magnetic field.

Therefore if you produce either a varying electrical field or a varying magnetic field, you will generate the other, which will then propagate out; this is EM radiation.

I only did a quick read of the paper, but this looks like they are generating a standing wave (think like a guitar string, where the amplitude of motion is fixed at any point along the string) with a wavelength much larger than the size of the room; this lets them capture the electrical field in capacitors in the center of the room while still having a moving magnetic field throughout the room, thus effectively separating the two, which allows for a moving magnetic field (which the receivers can convert to an electric field) without having a high-magnitude electrical field in the free space of the room.

1 comments

Seems to me more like they used the big copper tube in the center of the room and the aluminum walls of the room itself to guide the current flow. It's as if the copper tube and the room are a big conductor through which electricity flows (actually oscillates) - this changing electric field in the conductor creates a magnetic field in the space around it, i.e., the room. So the electric field is contained and guided through the conducting walls of the room, while the magnetic field permeates the space in the room itself.
Yes, the walls and ceiling conducting are important to this (otherwise there would be a large induced electric field outside the room).

There are capacitive elements in the pole which is important for allowing it to be resonant at a wavelength much larger than the room (the wavelength used is over 200 meters).

The very long wavelength means that, in theory, one cuold design a room with less of the perimeter conductive (a wire mesh would certainly work; they suggest that doors and windows, or even conductive panels that are connected could work).