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ECE :: Materials and Components

  1. Assertion (A): Rochelle salt and Barium titanate are both ferroelectric.

    Reason (R): Ferroelectric materials exhibit hysteresis effect.

  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

  3. The units for electric dipole moment are

  4. A.
    coulombs
    B.
    colomb-metre
    C.
    coulomb/metre
    D.
    coulomb/m2

  5. The temperature coefficient of resistivity of semiconductors is

  6. A.
    positive
    B.
    negative
    C.
    may be positive or negative
    D.
    very low

  7. Which of the following is used in automatic control of street lights?

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

  9. A leaky dielectric has ∈r = ∈r' - jr". If a field E is applied, the current component in phase with E is proportional to ∈r".

  10. A.
    True
    B.
    False

  11. Assertion (A): In ionic dielectrics, P = Pe + Pi.

    Reason (R): In ionic crystals, permanent electric dipole moment is zero.

  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

  13. The current flow in a semiconductor is due to

  14. A.
    holes
    B.
    electrons
    C.
    holes and electrons
    D.
    holes, electrons and ions

  15. Assertion (A): Relative permittivity is determined by the atomic structure of the material.

    Reason (R): Absolute permittivity is determined by the atomic structure of the material.

  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

  17. Eddy current loss is

  18. A.
    proportional to frequency
    B.
    independent of frequency
    C.
    proportional to (frequency)2
    D.
    proportional to (frequency)3

  19. The dipole moment per unit volume P as a function of E for an insulator is

  20. A.
    P = ∈0 E(∈r)
    B.
    P = ∈0 E
    C.
    P = ∈0(∈r - 1) E
    D.
    P =