COMEDK Exam 2018 Solved Paper

Drift velocity of the electron is given as
vd=‌

eEτ

m

where, e= charge on electron,
E= electric field
τ= relaxation time
and m= mass of the electron.
Since, ‌‌E=‌

V

l

∴‌‌vd=‌

eVτ

ml

Since, e,V,m and l are constant .
∴‌‌vd∝τ
On increasing the temperature of metal wire, relaxation time decreases, therefore drift velocity of electrons also decreases.
But on increasing temperature of metal wire, thermal velocity of electron increases.