🚀 go-pugleaf

zowie@daedalus.stanford.edu (Craig "Powderkeg" DeForest) writes:
>You hit the nail on the head.  There are two good reasons for AC
>rather than DC: it's easier to generate (no make-and-break brushes in
>the generator); and it's much easier to step voltage up and down.  That's
>crucial because resistive losses go like the current you're transporting.

To be precise, the (heat) loss goes like the square of the current which 
Joule proved a few centuries ago : dQ/dt = R*I^2  where dQ/dt is the heat
dissipated per unit time and unit length and R is the resistance of the wire 
per unit length. This makes it extremely important to transport electricity
at low current and high voltage.
	
	DC power lines (in Europe) are in use where the cable is under water
or under earth. This is because the sea acts like a giant capacitor which
would cause big losses if you used AC because the sea 'shorts' the cable.
(capacitors don't transport DC current)

And about the claim that the magnetic field from AC power lines should give
a cancer risk. I doubt it. If you have read either the swedish or the danish
examination of this and you understand statistics you would doubt it too !
The danish paper concluded that extremely low frequency EMF might lead to 
cancer on a basis of 3 (three) cancer incidents over a test period of 18 years.
Noone has yet been able to point out a physical mechanism that via EMF turns
human cells into cancer cells as well as experiment with animals has not shown
that such a thing is possible. I just wonder why people always wants to fear 
what is not worth worrying about instead of thinking about what is really a 
threat to us humans - but I'll pass that over to alt.psycology .....

Sven ..... snil@daimi.aau.dk