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Home ‣ Electronics and Communication Engineering ‣ Materials and Components Comments
  • Question

  • Electrical contact materials used in switches, brushes, relay must possess


  • Options
  • A. high thermal conductivity and high melting point
  • B. low thermal conductivity and low melting point
  • C. high thermal conductivity and low melting point
  • D. low thermal conductivity and high melting point

  • Correct Answer
  • high thermal conductivity and high melting point 

    Explanation
    Heat generated at contact should be dissipated quickly and contact should not melt.

    Materials and Components problems

    Search Results

    • 1. Curie Weiss law is .

    • Options
    • A. True
    • B. False
      • Discuss
    • 2. In an intrinsic semiconductor, at a given temperature T

    • Options
    • A. the number of electrons-hole pairs generated per second due to thermal motion are equal to the number of electron-hole pairs lost per second due to recombination
    • B. the number of electron-hole pairs generated per second due to thermal motion is always less than the number of electron-hole pairs lost per second due to recombination
    • C. the number of electron hole pairs generated per second due to thermal motion is always more than the number of electron-hole pairs lost per second due to recombination
    • D. any of the above
      • Discuss
    • 3. The magnetic quantum number determines the component of angular momentum along a prescribed direction.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. Wood is a diamagnetic material.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. The phenomenon of dielectric hysteresis occurs with

    • Options
    • A. dc
    • B. ac
    • C. both ac and dc
    • D. none of the above
      • Discuss
    • 6. The unit for mmf is

    • Options
    • A. A
    • B. Wb
    • C. T
    • D. V
      • Discuss
    • 7. If a small amount of Cu is added to Ni conductor, then

    • Options
    • A. resistivity of Ni will decrease at all temperatures because Cu is a better conductor than Ni
    • B. residual resistivity of Ni at low temperature will increase as Cu atoms act as defect centres
    • C. resistivity of Ni will increase at all temperatures as Cu destroys the periodicity of Ni and acts as defects
    • D. resistivity of Ni remains the same
      • Discuss
    • 8. A conductor carries 10 A current in + x direction and is lying in a field having a flux density 0.2 T directed along + z direction. The magnitude of force per metre length and direction are

    • Options
    • A. 2 N, + y direction
    • B. 2 N, - y direction
    • C. 0.02 N, + y direction
    • D. 0.02 N, - y direction
      • Discuss
    • 9. The core of a solenoid is made of material of relative permeability ?r. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0

    • Options
    • A. the fields inside and outside the cavity must be equal
    • B. the field inside the cavity must be made stronger than field outside the cavity
    • C. the field inside the cavity must be made weaker than the field outside the cavity
    • D. none of the above
      • Discuss
    • 10. Assertion (A): Hall effect is used to determine whether the semi- conductor is p or n type.

      Reason (R): Under the influence of field, holes and electrons move in opposite direction.


    • 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
      • Discuss

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