Question

In metals, the time of relaxation of electrons

• A. increases with increasing temperature
• B. decreases with increasing temperature
• C. does not depend on temperature
• D. changes suddenly at $400K$

Answer 1

The correct option is B decreases with increasing temperature

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

where $m=$mass of electron, $n=$ electron density, $e=$ electronic charge and $\tau =$ relaxation time.

Resistance $R=\frac{\rho l}{A}=\frac{ml}{n{e}^2\tau A}$ or $R\propto \frac{1}{\tau }$

Since in metals Resistance increases with temperature so the relaxation of electrons decreases with increasing temperature.