A conducting wire of length L, uniform area of cross-section A of a material having n free electrons per unit volume offers a resistance R to flow of current through itself. (m and e respectively denote the mass and charge of electron). If $τ$ is mean free time of free electrons in the conductor, the correct formula for resistance R is:

$R=\frac{mL}{e^2nAτ}$

The correct answer is Option (1) → $R=\frac{mL}{e^2nAτ}$

The formula for the resistance R is,

$R=ρ\frac{L}{A}$

and

Resistivity, $ρ\frac{m}{ne^2τ}$

$⇒R=\frac{mL}{ne^2τA}$