Define relaxation time of the free electrons drifting in a conductor. How is it related to the drift velocity of free electrons? Use this relation to deduce the expression for the electrical resistivity of the material. Share with your friends Share 0 Vipra Mishra answered this Solution 1) Relaxation time is defined as the average time taken by an electron to in between the two successive collisions.The distance travelled during this relaxation time is known as mean free path.Drift velocity of free electrons vd=mean free path of electronrelaxation time vd = lτ.But when electrons are subjected to electric field E, the move withacceleration a, so ma = eE, where m and e are mass and electronic charge. therefore a=eEm, since the electrons move from the position of rest, so vd= aτ = eEmτ.Let there are n number of electrons per unit volume, so total number ofelectrons q=neA vd and the corresponding current i is given by, i =q/τ = neA vd or i = neA×eEτm=ne2AτmE.But E = Vl, where V is potential difference.So i = ne2AτmVlor R = Vi=l mne2Aτ= constant. 0 View Full Answer
