physics problem?

Question

Given rho = 1.08 [ohm mm^2/m], what is sigma? ____ [m/mm^2/ohm]

how would I do this?? please help, thanks

Answer 1

rho = 1.08 [ohm mm^2/m]
the dimensions of RHO clearly indicate that it is "specific resistance" or resistivity of the material.
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R (Resistance) = RHO [L / A]
so RHO = R*A(crossection area)/L (length)
= ohm*mm^2/meter
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conductivity of material (sigma) will be = [1 / RHO]
sigma = [1/1.08] {meter /ohm*mm^2}
sigma = [1/1.08] {meter /ohm*(10^-3 meter)^2}
sigma = [1/1.08] {10^6 /ohm*meter}
sigma = [1/1.08] {10^6 /ohm*meter}
sigma = 925925.925 {ohm*meter}^-1
====================
1 siemen = 1/ohm
----------------------------
sigma = 925925.925 siemen * {meter}^-1

http://en.wikipedia.org/wiki/Siemens_(unit)
http://en.wikipedia.org/wiki/Electrical_conductivity

Answer 2

What do rho and sigma stand for and what are the physical meanings of those quantities? Understanding the underlying concepts makes this problem very simple.