Electrical hacking (was Re: [Techtalk] [OT] charging USB devicewithout a PC)

[Alvin Goats]

> Maria Blackmore said:
> > Electrons are perfect accountants, you never find any go missing, and
> > they will only flow if there is a completed circuit.
> Oooh ooh ooh........no they're not :-P
> 
> Just that if you're talking about "reasonable" currents, in the vast
> majority[0] of cases, not enough electrons will spontaneously make the
> journey concerned to do anything :)
> [0] I seem to recall a wonderful definition of "never", as applied to
> quantum mechanics - something along the lines of "expected to happen less
> than once in the lifetime of the universe" :^)


Ok, we have capacitors that are not connected to anything getting
charged by static electricity in air currents. The electrons move
without having a completed circuit.

Bismuth Telluride, Anitmony Telluride and Bismuth-Antimony-Telluride are
thermal electric materials, put a temperature difference on the two ends
of the material and electrons will move to one end and the 'holes' will
move to the opposite, without a closed circuit. These are used for
generating electricity, the only problem being that if the temperature
difference changes sides, the DC gets reversed.

Pyroelectric materials will do the same, as will piezoelectric and
electro-optical, the first is heat, the second with mechanical stress
and the last with light. Electrons can move all over the place and in
ordered directions WITHOUT a completed circuit. Piezo-speakers
(typically tweeters) and microphones will generate elecrical signals
based on the stress on the crystal due to the mechanical cone or ribbond
attached to them and do so whether they are connected to anything or
not. This is part of how people get hurt, they mistakenly think you have
to have a completed circuit to have current flow.

Alvin