Electronic – Resistivity unit conversions


I am a plant eco-physiologist working with leaf venation networks. I want to calculate the resistance of a vein segment in units of Ohms, using the formula Resistance = (resistivity * segment length)/ cross sectional area. I have the vein length in m, the vein cross-sectional area in cm2 and I calculated the vein resistivity using the Sack and Frole 2006 formula (DOI: 10.1890/05-0710) which gives the resistivity in units of MPa mmol-1 s m. How could I convert this resistivity in MPa mmol-1 s m to units of Ohm m (Ohms per meter)?

Best Answer

The Sack and Frole formula is for hydraulic resistivity, which is related to fluidics, not electrical resistivity. They're different things so you can't convert.

In basic SI units, electrical resistivity \$\rho\$ is in units of:

\$\text{kg}\cdot \text{m}^2\cdot A^{-2} \cdot s^{-2}\$ or in derived units \$\Omega\cdot \text{m}\$ or \$V\cdot A^{-1}\cdot \text{m}\$

The hydraulic resistivity is analogous in that the pressure (analogous to voltage) is in Pascals, the length in m and the flow rate (analogous to current flow in A = coulombs/s) in mmol/s but they are completely different physical things.