If $n,\,e,\,\tau $ and $m$ respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length $l$ and area of cross-section $A$ will be
A$\frac{{ml}}{{n{e^2}\tau A}}$
B$\frac{{m{\tau ^2}A}}{{n{e^2}l}}$
C$\frac{{n{e^2}\tau A}}{{2ml}}$
D$\frac{{n{e^2}A}}{{2m\tau l}}$
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A$\frac{{ml}}{{n{e^2}\tau A}}$
a (a) $R = \rho \frac{l}{A} = \frac{n}{{n{e^2}\tau }}.\frac{l}{A}$
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