[LINK] Some shocking news about wireless electricity

[Stewart Fist]

Glen says:
> 
> Oh dear. A electromagnetic field in a wire versus in free space isn't
> "transforming one form of energy to another". Both are electromagnetic.

Both are, but one is in the form of a field, and the other is in the form of
a current - which is why a transformer current always lags behind the field
changes.

It is also why objects in the near-field of a transmitter are effected in a
different way (separately with right-angle electrical and magnetic fields)
to objects in the far-field (beyond one wavelength - where we regard it as
radiated EMF).  

I guess we are just arguing here over he use of the word "transformed".
Inductive coupling is a near-field phenomena.

> 
> In fact, inductive coupling is efficient. Plugpack rectification and
> DC current over thin wires has its own losses and I feel comfortable
> that you could build an inductive charging system with less
> loss. Particularly since the source is a medium voltage AC.

Such systems have been in use for years to power pace-makers, etc.  What is
being claimed here is something different - something that doesn't require
close coupling.

Inductive coupling is efficient when the two sides of the couple are closely
spaced and perfectly matched -- but not when they are deliberately separated
or mismatched, as they are here. That's the whole purpose of the idea.

You point out in relationship to mismatching (but not separation) in

> The problem is that the size and weight required for the inductive
> coils to be efficient is incompatible with the desired handheld form
> for phones, iPods, etc.

I totally agree.

Adams claim that ...

> Then the idea of turning the TV of instead of Standby no longer is
> relevant because it's charging the phone, laptop, shaver, watch, pace
> maker, and other devices :)

...just emphasises the sheer wastage and inefficiencies  of such a system,
because every other metal object within range will also be experiencing
electrical effects, resulting in heat.