Q4Electrical Materials
Question
Q.4. Define relaxation time of electrons in a conductor.
Answer
Relaxation time (τ) is the mean time between successive scattering collisions of a conduction electron, determining mobility (μ = eτ/m) and conductivity (σ = ne²τ/m).
The relaxation time τ of electrons in a conductor is the average time between two successive collisions of a drifting conduction electron with lattice vibrations, impurities, or defects — the interval during which the applied field freely accelerates the electron before scattering randomizes its momentum. It represents the time constant with which the electron distribution relaxes to equilibrium after a disturbing field is removed, and it sets the conductivity through σ = ne²τ/m in the free-electron model; typical values in good metals at room temperature are of order 10⁻¹⁴ seconds.