Define the drift velocity of electrons in a conductor?

Drift Velocity is the average velocity attained by electrons, the charged particles, in a material due to an electric field. The drift velocity can be calculated using the following formula:

I = nAvQ

where,

  • v is the drift velocity of electrons
  • n is the number of electrons
  • A is the area of cross-section of a conductor
  • Q is the charge of an electron
  • I is the current flowing through the conductor.

Related Questions

  1. What is the relation between drift velocity and electric field?
  2. Two conducting wires X and Y of the same diameter but different materials are joined in series across a battery. If the number density of electrons in X is twice that in Y, find the ratio of the drift velocity of electrons in the two wires.
  3. Give two examples of drift velocity.
  4. Explain the relation between current and drift velocity.
  5. 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.
  6. It is known that the drift velocity of electrons is only a few mm/s for a current of a few amperes. How is it possible that a current is established almost instantaneously when a circuit is closed? For example, a bulb glows as soon as the connection is switched on. Explain.

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CBSE CLASS XII Related Questions

  • 1.
    A long solenoid of length \( L \) and radius \( r_1 \) having \( N_1 \) turns is surrounded symmetrically by a coil of radius \( r_2 \, (r_2>r_1) \) having \( N_2 \) turns (\( N_2 \ll N_1 \)) around its mid-point. Derive an expression for the mutual inductance of solenoid and coil. Is \( M_{12} = M_{21} \) valid in this case?


      • 2.
        Assertion (A) : The mass of a nucleus is less than the sum of the masses of the constituent nucleons. Reason (R) : Energy is absorbed when the nucleons are bound together to form a nucleus.

          • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
          • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
          • Assertion (A) is true, but Reason (R) is false.
          • Both Assertion (A) and Reason (R) are false.

        • 3.
          If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.


            • 4.
              Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

                • (i) and (iii) only
                • (iii) and (iv) only
                • (i), (iii) and (iv) only
                • All of them

              • 5.
                Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

                  • attract with a force \( \frac{F}{2} \)
                  • repel with a force \( \frac{F}{2} \)
                  • repel with a force \( F \)
                  • attract with a force \( F \)

                • 6.
                  If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.

                    CBSE CLASS XII Previous Year Papers

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