E=IxR and Vanner [RE-wrenches]

[hugh piggott]

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>At 11:08 PM 9/10/01 -0400, you wrote:
>>Actually, isn't it "resistivity" that stays constant? Actual resistance
>>decreases (i.e. at less current flow there is less voltage drop.) And yes,
>>environmental factors do need to remain constant....
>>
>
>Resistivity, that's a new one on me.  I've spent a good deal of my career
>working Ohm's law and it's my experience that resistance is a physical
>attribute that does not change except with physical changes to the device
>(heat or dimensions).

Resistivity is the resistance per unit of the substance (ohms per 
metre for a metre squared conductor for instance).  It's the inverse 
of conductivity.

If there is a change of temperature the resistivity changes, and 
therefore so does the resistance.  Resistivity of copper changes by 
about 3% for every ten degrees C rise.

-- 
Hugh

http://www.ScoraigWind.co.uk

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