Q8Electrical Materials
Question
Q.8. Define relaxation time of electrons in a conductors.
Answer
Relaxation time (τ) is the average time between successive collisions of a conduction electron with the lattice, during which the electron is accelerated by the applied field; it directly determines mobility and conductivity (σ = ne²τ/m).
The relaxation time (τ) of electrons in a conductor is the mean time interval between two successive collisions of a conduction electron with lattice ions, impurities, or defects, during which the electron is freely accelerated by the applied electric field before being scattered and losing its drift momentum. It is the characteristic time over which the electron distribution 'relaxes' back to equilibrium after the field is removed, and it directly determines the drift mobility (μ = eτ/m) and hence electrical conductivity via σ = ne²τ/m, where n is the free-electron density and m the electron mass, making τ the central microscopic parameter of the free-electron (Drude) conduction model.