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JEE Main Last 10 Years Question Papers with Solutions PDF 2024 to 2014

Drift Velocity - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Drift Velocity is considered one of the most asked concept.

  • 16 Questions around this concept.

Solve by difficulty

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

A electric current of 16 A exists in a metal wire of cross section \mathrm{10^{-6}\, m^{2}} and length 1m. Assuming one free electrons per atom. The drift speed of the free electrons in the wire will be
( Density of metal \mathrm{=5 \times 10^3 \mathrm{~kg} / \mathrm{m}^3,}  atomic weight \mathrm{=60} )

If E denotes electric field in a uniform conductor and \mathrm{Vd} the corresponding drift velocity of free electrons in the conductor then which of the following graph is correct ?

At room temperature, copper has free electron density of 8.4\times 10^{28}m^{-3}. The electron drift velocity in a copper conductor of cross-sectional area 10^{-6}m^{2} and carrying a current of 5.4 A, will be 

Two wires A and B of the same material, having radii in the ratio 1:2 and carry currents in the ratio 4 :1. The ratio of drift speed of electrons in A and B is 

Concepts Covered - 1

Drift Velocity

Relaxation time (\tau): The time interval between two successive collisions of electron with the Positive ions.

Mean Free path: The path between two consecutive collisions is called free path. The average length of these free paths is called “Mean Free Path”. 

Drift velocity

Drift velocity is the average velocity that a particle such as an electron attains in a material due to an electric field.

v_{d}=\frac{-e \vec{E}}{m} \tau

Where v_d is the drift velocity, E is the electric field applied, e and m are the charge and mass of electrons respectively and \tauis the relaxation time.

  • Vd is directly proportional to E: v_{d} \alpha E when the temperature is constant , the greater the electric field larger will be the drift velocity

Drift velocity and current

J=\frac{I}{A}=\frac{neA\upsilon _{d}}{A}

J=ne\upsilon_{d}

  • Current independent of Area: Current does not change with change in cross-sectional area

  • Vd is inversely proportional to area: v_{d}  \alpha  \frac{1}{A}  :

  • Drift velocity varies inversely with the area of cross-section

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Drift Velocity

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