Question

What is the microscopic expression for conductivity?

Options

• \[\sigma=\frac{m}{ne^2\tau}\]

• \[\sigma=\frac{ne^2\tau}{m}\]

• \[\sigma=\frac{I}{A}\]

• \[\sigma=-\frac{eE\tau}{m}\]

Answer 1

Comparing \[j=\sigma E\] with \[j=\frac{ne^2\tau}{m}E\] gives \[\sigma=\frac{ne^2\tau}{m}\]. Conductivity therefore increases with free electron density and relaxation time.