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  • Question

  • Assertion (A): For most metals, Fermi energy EF is less than 10 eV.

    Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.


  • Options
  • A. Both A and R are true and R is correct explanation of A
  • B. Both A and R are true but R is not correct explanation of A
  • C. A is true but R is false
  • D. A is false but R is true

  • Correct Answer
  • Both A and R are true and R is correct explanation of A 

    • More questions

    • 1. Performance of a PIN diode switch is represented by

    • Options
    • A. insertion loss when switch is off
    • B. insertion loss when switch is on
    • C. insertion loss when switch is on and isolation loss when switch is off
    • D. insertion loss when switch is off and isolation loss when switch is on
      • Discuss
    • 2. In a single phase full wave converter (M-2 connection) feeding on R - L load, the input voltage is v = Vm sin ?t. The expression for dc output voltage is

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 3. The relation between thermal conductivity K (W/m/°C), heat flow density Q (watt/m2) and dT/dx (°C per metre) is

    • Options
    • A. Q = K(dT/dx)
    • B. Q = - K(dT/dx)
    • C. K = Q(dT/dx)
    • D. dT/dx = - QK
      • Discuss
    • 4. If f is the frequency of electromagnetic wave, fc is cutoff frequency, then in a rectangular waveguide

    • Options
    • A. attenuation is low when f > fc
    • B. attenuation is low when f < fc
    • C. attenuation is high when f < fc
    • D. either (b) or (c)
      • Discuss
    • 5. A parallel polarized wave is incident from air into paraffin having relative permittivity 3, the value of its Brewster angle is

    • Options
    • A. 0°
    • B. 30°
    • C. 45°
    • D. 60°
      • Discuss
    • 6. For a permanent magnetic material

    • Options
    • A. the residual induction and coercive field should be large
    • B. the residual induction and coercive field should be small
    • C. area of hysteresis loop should be small
    • D. initial relative permeability should be high
      • Discuss
    • 7. The sensitivity of a superheterodyne receiver is determined by

    • Options
    • A. the gain IF amplifier
    • B. the gain of RF amplifier
    • C. the noise figure
    • D. all of the above
      • Discuss
    • 8. In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain.

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. A material which is lightly repelled by a magnetic field is known as

    • Options
    • A. diamagnetic material
    • B. non-magnetic material
    • C. ferromagnetic material
    • D. paramagnetic material
      • Discuss
    • 10. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will

    • Options
    • A. increase
    • B. decrease
    • C. first decrease then increase
    • D. first increase then decrease
      • Discuss

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