"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
For a given length of fine copper wire of diameter 0.072 mm (2.9 mil) =
0.004 sq mm,
if it is squashed to cross-section dimensions of 0.02 * 0.2 mm (2 * 20 mil)
proportionally how much does the resistance change ?
and then to 0.01 * 0.4mm (1 * 40 mil) ?





AFAIK the resistance of wire is proportional to its Cross Sectional Area.
Period. If this remains unchanged, so does the resistance.



Gareth.



That is correct, but the length also has to remain unchanged The formula for
the resistance of a conductor is
R=r*L/A
where R= Resistance
r=Resistivity of the conductor (1.7x10^-8 for copper)
L=Length
A=cross section area

As you can see, the resistance remains constant as long as L and A remain the
same, or change in a manner that produces the same ratio.

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