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ECE :: Materials and Components

  1. Assertion (A): Dielectric losses are proportional to tan δ.

    Reason (R): tan δ = where ∈r' and ∈r" denote the real and imaginary parts of ∈r.

  2. 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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  3. In a polyatomic gas, the types of polarization which exist together are

  4. A.
    electronic and orientational
    B.
    electronic and ionic
    C.
    ionic and orientational
    D.
    electronic, orientational and ionic

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  5. Assertion (A): Metals are better heat conductors than insulators.

    Reason (R): If is temperature gradient, Q is heat flow density and K is thermal conductivity, then Q = - K (dT/dx).

  6. 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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  7. The number of tightly bound electrons in silicon atom are

  8. A.
    14
    B.
    10
    C.
    6
    D.
    4

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  9. Electric dipole moment is usually expressed in debye units. Here, 1 debye unit equals

  10. A.
    3.33 x 10-30 C-m
    B.
    3.33 x 10-30 C-m2
    C.
    3.30 x 10-10 C-m
    D.
    3.33 x 10-10 C-m2

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  11. A particle of charge Q coulombs is bound elastically to an equilibrium position with a force constant of f newton per metre. The polarizability of the system is

  12. A.
    B.
    C.
    D.
    Qf

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  13. 1 Bohr magneton = .

  14. A.
    True
    B.
    False

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  15. An electron (charge -e) is rotating in a circular orbit of radius R, around a proton with charge +e at a constant angular velocity ω. The orbital magnetic dipole moment is

  16. A.
    0.5 eω R2
    B.
    eω R2
    C.
    2 eω R2
    D.
    0.5 eω R3

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  17. In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain.

  18. A.
    True
    B.
    False

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  19. Which of the following is used in lightning arresters?

  20. A.
    Thermistor
    B.
    Photoconductor
    C.
    Transistor
    D.
    Varistor

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