Current Electricity

JEE Main level, single correct, medium

14 of 380

Question 14 of 380

The drift velocity of electrons for a conductor connected in an electrical circuit is Vd{V}_{d}. The conductor is now replaced by another conductor with same material and same length but double the area of cross-section. The applied voltage remains same. The new drift velocity of electrons will be

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Answer: (A) Vd{V}_{d}

Drift velocity of electrons through a conductor kept in an external electric field is given by Vd=−eEmτ=−eVmlτ{V}_{d}=-\dfrac{eE}{m}\tau =-\dfrac{eV}{ml}\tau
Where, e=e=magnitude of charge on electron, m=m=mass of electron, E=E=external electric field and τ=\tau =average relaxation time.
As, drift velocity is independent of area. So, the new drift velocity of electrons will be Vd{V}_{d}.

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