Question

If n, e, t and m are respectively the density, charge, relaxation time and mass of an electron then the resistance of wire of length / and cross-sectional area 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. $\frac{n{e}^{2}A}{2m\tau l}$

Answer 1

Answer: (A)

$\frac{ml}{n{e}^2\tau A}$

The resistivity of a material is given by $\rho =\frac{m}{n{e}^2\tau }$

The resistance of the material is $R=\frac{\rho l}{A}=\frac{ml}{n{e}^2\tau A}$