🚀 go-pugleaf

In article <13404@creare.COM> kwg@creare.UUCP (Kent Goeking) writes:
>
>   I would like to know if there are any materials that demonstrate negative
>   resistance on the macroscopic scale.  I am aware of this behavior in tunnel
>   diodes but I wonder if it might not occur in other structures. 
<stuff deleted>
>   A plot of V vs I in this case
>   would have negative slope and thus Ohms law would be rewritten V=-IR.

Pedant's corner: dV/DI = -R -> (V-Vo) = -IR.  We don't need to add an extra 
                 sign stripe to resistors and all battery manufacturors can
                 breathe easy.

>   Anyone know of such a material?

Low pressure neon - like in a bulb or plasma pannel, or other similar stuff.
A gap of 1cm in vacuum has a very high resistance, but apply enough voltage
to get a discharge and it can go to less than 0.1 ohm.

Some pure superconductors can do funny things with flux lines.  I have
measured potential profiles along a conductor where the voltage gradient
along a specimen seems to change sign, though the overall trend is positive.
The flux lines due to the imposed magnetic field and those generated by the
current get driven about by the current, and this can lead to them busting 
out wherever they can.




-- 
Richard Kirk         Image Processing Group    Crosfield Electronics Ltd. U.K.
rak@crosfield.co.uk  0442-230000 x3361/3591    Hemel Hempstead, Herts, HP2 7RH