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ECE :: Materials and Components

  1. Which of these has the highest dielectric strength?

  2. A.
    Mica
    B.
    Air
    C.
    Cotton
    D.
    Rubber

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  3. An electron in a metal suffers collision and if the probability of it being scattered over an angle dθ is 2p P(θ) sin θ dθ where P(θ) is an arbitrary function of scattering angle θ, then

  4. A.
    2pP(θ) sin θ dθ = 0
    B.
    2pP(θ) sin θ dθ = 2
    C.
    2pP(θ) sin θ dθ = -1
    D.
    2pP(θ) sin θ dθ = 1

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  5. For an insulating material, dielectric strength and dielectric losses should be

  6. A.
    high and high
    B.
    low and high
    C.
    high and low
    D.
    low and low

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  7. Consider the following statements

    1. An iron cored choke is non linear and passive device.
    2. A carbon resistor kept in sunlight is a time invariant and passive device.
    3. A dry cell is a time varying and active device.
    4. An air capacitor is time invariant and passive device.
    Of these statements

  8. A.
    1, 2, 3 and 4 are correct
    B.
    1, 2, 3 are correct
    C.
    1, 2, 4 are correct
    D.
    2 and 4 are correct

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  9. Some ceramic materials become superconducting

  10. A.
    below liquid helium temperature
    B.
    between liquid helium and liquid nitrogen temperature
    C.
    above liquid nitrogen but below room temperature
    D.
    at room temperature

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  11. Assertion (A): Doping level in extrinsic semiconductors is very small.

    Reason (R): Additional of impurity in the ratio of 1 part in 108 parts increases the number of charge carriers by about 20.

  12. 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

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  13. The core of an atom consists of

  14. A.
    nucleus
    B.
    nucleus and all orbits
    C.
    nucleus and inner orbits
    D.
    none of the above

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  15. Assertion (A): Copper is a good conductor of electricity.

    Reason (R): Copper has a face centred cubic lattice.

  16. 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

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  17. When a dielectric is subjected to an electric field E, each volume element of dielectric can be considered to be carrying an electric dipole moment.

  18. A.
    True
    B.
    False

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  19. Assertion (A): In an intrinsic semiconductor J = (μn x μp)eni.

    Reason (R): Intrinsic charge concentration ni at temperature T is given by ni2 = A0 T3 e-EG0/kT.

  20. 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

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