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ECE :: Materials and Components

  1. The number of valence electrons in pentavalent impurity is

  2. A.
    5
    B.
    4
    C.
    3
    D.
    1

  3. If the diameter of a wire is doubled, its current carrying capacity becomes

  4. A.
    one-fourth
    B.
    half
    C.
    twice
    D.
    four times

  5. The law J = σE, where J is current density, σ is electrical conductivity and E is field strength is

  6. A.
    Ohm's law
    B.
    Gauss law
    C.
    Ampere's law
    D.
    Biot-Savart law

  7. Assertion (A): Silicon is less sensitive to changes in temperature than germanium.

    Reason (R): Cut in voltage in silicon is less than that in germanium.

  8. 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

  9. Material which lack permanent magnetic dipoles are known as

  10. A.
    paramagnetic
    B.
    diamagnetic
    C.
    ferromagnetic
    D.
    ferrimagnetic

  11. A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neglected, to keep the capacitance same, the dielectric constant must be

  12. A.
    halved
    B.
    kept the same
    C.
    doubled
    D.
    made 4 times

  13. Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.

    Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈'r - j"r.

  14. 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

  15. In atomic physics, a state with l = 0 is called p state.

  16. A.
    True
    B.
    False

  17. If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature

  18. A.
    both will have equal value of resistivity
    B.
    both will have equal negative resistivity
    C.
    resistivity of germanium will be higher than that of silicon
    D.
    resistivity of silicon will be higher than that of germanium

  19. When an electric field E is applied to solid and liquid insulating materials, the internal field Ei acting at the location of atom is such that

  20. A.
    Ei = E
    B.
    Ei > E
    C.
    Ei < E
    D.
    Ei may be equal to or less than E