# Look no wires

My wife was complaining this morning about the mass of knitting that is underneath our home computer. Not knitting of the woollen jersey kind, but knitting of the wire kind, that is needed to supply power to the computer, printer, modem, etc etc etc and to allow the computer to talk to the printer, etc. Our house doesn’t come close to having enough power outlets for all the electrical things that are commonplace, so it is loaded with those multisocket strips that make me feel just slightly uneasy sometimes.

But help is at hand. Communicating between a computer and a printer doesn’t necessarily need wires; protocols such as bluetooth for wireless transfer of data have been around for years now. This problem is an easy one because the amount of power required to transfer data is pretty minimal – you are primarily interested in transmitting 1’s and 0’s, not many joules of energy.

But what about powering the computer in the first place? Surely that needs a lead to the socket in the wall. (Even if you run on battery, you still are left with recharging the battery sometimes.) This is possible too, without wires. Essentially there are two ways to do it.

One is to use very directional antennas, and beam energy in the direction you want it. That works just fine. but your receiver has to be in line-of-sight of the transmitter, and that’s not often possible in a house laden with furniture, walls, people etc. Plus, if we are talking about high power, you don’t want to stand in the way of it.

An alternative approach is a tuned induction loop. This transfers the energy from one electrical circuit, e.g. in the floor of your house, to another (in your appliance) through electromagnetic induction. That is, the alternating currents in the first circuit create magnetic fields; these alternating magnetic fields then create currents in the second. Hey presto, you have power transfer. The phenomenon has been known to physics for a very long time now, but still it hasn’t really been much use of it, certainly not domestically.  But with so much wiring needed these days, maybe its time is approaching.  Aristeidis Karalis does a nice discussion of this in PhysicsWorld magazine.