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ECE :: Materials and Components

  1. If the number of atoms per unit volume of a monoatomic gas changes, the dielectric constant still remains constant.

  2. A.
    True
    B.
    False

  3. The number of protons in a copper atom are

  4. A.
    2
    B.
    9
    C.
    11
    D.
    29

  5. When a material is in superconducting state and a magnetic field is applied

  6. A.
    the superconducting property is not affected
    B.
    the superconducting property may be affected and resistivity may increase from zero to a low value
    C.
    the superconducting property may be destroyed
    D.
    the material may become an insulator

  7. For a diamagnetic material, μr = 1.

  8. A.
    True
    B.
    False

  9. We can know the arrangement of atom in a material by studying electron diffraction pattern.

  10. A.
    True
    B.
    False

  11. The elements which become superconducting at extremely low temperatures are

  12. A.
    good conductors at room temperature
    B.
    ferromagnetic at room temperature
    C.
    relatively poor conductors at room temperature
    D.
    insulators at room temperature

  13. Electrical contact materials used in switches, brushes, relay must possess

  14. 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

  15. If μp is permanent dipole moment and T is absolute temperature, the orientation polarization of polyatomic gases is

  16. A.
    proportional to μp2T
    B.
    proportional to
    C.
    proportional to μp T
    D.
    proportional to

  17. The phenomenon of dielectric hysteresis occurs with

  18. A.
    dc
    B.
    ac
    C.
    both ac and dc
    D.
    none of the above

  19. The induced magnetic dipole moment is independent of the permanent magnetic dipole moment.

  20. A.
    True
    B.
    False