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# Problem: What is the mean free time between collisions for electrons in an iron wire and an aluminum wire?

###### FREE Expert Solution

The mean free time between collisions for electrons ina wire is expressed as:

$\overline{){\mathbf{\tau }}{\mathbf{=}}\frac{\mathbf{m}\mathbf{\sigma }}{{\mathbf{n}}_{\mathbf{e}}{\mathbf{e}}^{\mathbf{2}}}}$

For electrons in an iron wire:

$\begin{array}{rcl}\mathbf{\tau }& \mathbf{=}& \frac{\mathbf{\left(}\mathbf{9}\mathbf{.}\mathbf{11}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{31}}\mathbf{\right)}\mathbf{\left(}\mathbf{1}\mathbf{×}{\mathbf{10}}^{\mathbf{7}}\mathbf{\right)}}{\mathbf{\left(}\mathbf{8}\mathbf{.}\mathbf{5}\mathbf{×}{\mathbf{10}}^{\mathbf{28}}\mathbf{\right)}\mathbf{\left[}{\mathbf{\left(}\mathbf{1}\mathbf{.}\mathbf{6}\mathbf{×}\mathbf{10}\mathbf{-}\mathbf{19}\mathbf{\right)}}^{\mathbf{2}}\mathbf{\right]}}\end{array}$

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###### Problem Details
What is the mean free time between collisions for electrons in an iron wire and an aluminum wire?