If n, e, tau and m represent electron density | vedclass

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(A) The resistance $R$ of a conductor is given by the formula $R = \rho \frac{l}{A}$,where $\rho$ is the resistivity of the material.The resistivity $

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$\frac{m l}{n e^2 	au A}$

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(A) The resistance $R$ of a conductor is given by the formula $R = ho \frac{l}{A}$,where $ho$ is the resistivity of the material.The resistivity $ho$ in terms of microscopic parameters is given by $ho = \frac{m}{n e^2 	au}$,where $m$ is the mass of the electron,$n$ is the electron density,$e$ is the charge of an electron,and $	au$ is the relaxation time.Substituting the expression for $ho$ into the resistance formula:$R = \left( \frac{m}{n e^2 	au} ight) \frac{l}{A} = \frac{m l}{n e^2 	au A}$.Therefore,the correct option is $A$.

If $n, e, \tau$ and $m$ represent electron density,charge,relaxation time,and mass of an electron respectively,then the resistance of a wire of length $l$ and cross-sectional area $A$ is given by:

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