Define mobility of electron.

The drift velocity of an electron for a unit electric field is referred to as the mobility of the electron. The mobility of an electron can be calculated by the formula:

μ = Vd/E

where, Vd refers to the drift velocity of an electron

E is the external electric field

The SI unit of electron mobility is m2s-1V-1


Related Questions

  1. Give two examples of drift velocity.
  2. What is the relation between drift velocity and electric field?
  3. Explain the relation between current and drift velocity.
  4. Define the drift velocity of electrons in a conductor?
  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.
  7. 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.

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CBSE CLASS XII Related Questions

  • 1.
    Suppose a pure Si crystal has \( 5 \times 10^{28} \) atoms per \( \text{m}^3 \). It is doped with \( 5 \times 10^{22} \) atoms per \( \text{m}^3 \) of Arsenic. Calculate majority and minority carrier concentration in the doped silicon. (Given: \( n_i = 1.5 \times 10^{16} \, \text{m}^{-3} \))


      • 2.
        Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.


          • 3.
            Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.


              • 4.
                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 \( F \)

                • 5.
                  Write any two features of nuclear forces.


                    • 6.
                      Two thin lenses of focal length \( f_1 \) and \( f_2 \) are placed in contact with each other coaxially. Prove that the focal length \( f \) of the combination is given by \[ f = \frac{f_1 f_2}{f_1 + f_2}. \]

                        CBSE CLASS XII Previous Year Papers

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