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ECE :: Materials and Components

  1. For a paramagnetic material, susceptiblity increases with increasing temperature.

  2. A.
    True
    B.
    False

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  3. Hydrogen is used in

  4. A.
    large size transformers
    B.
    MCB
    C.
    large size generators
    D.
    circuit breakers

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  5. Assertion (A): Ferroelectric materials have spontaneous polarization.

    Reason (R): Above curie temperature, ∈ = for ferro-electric materials.

  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. If e is the charge of an electron, R is the radius of its orbit and ω is the angular velocity of electron, the magnetic dipole moment μm of the orbit is |μm| = eωR2.

  8. A.
    True
    B.
    False

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  9. If ∈r' and ∈r" are the real and imaginary parts of complex dielectric constant ∈r, and δ is the loss angle. Then

  10. A.
    B.
    C.
    tan δ = ∈'"
    D.
    tan δ = 1 - ∈'

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  11. Assertion (A): At a temperature of 1000 K, thermionic emission current is about 0.1 A/cm2 of surface.

    Reason (R): Thermionic emission current is given by Ith = SA0 T2 e-Ew/kT.

  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. At room temperature, the current in intrinsic semiconductor is due to

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

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  15. Ferroelectric materials are those which

  16. A.
    cannot be polarized
    B.
    have a permanent polarization
    C.
    have ae equal to zero
    D.
    have μp = 0

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  17. Assertion (A): Power loss in a conductor of resistance P = I2R.

    Reason (R): When a conductor is carrying current with current density J as a result of applied field E, then heat developed/m3/ second = JE.

  18. 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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  19. Assertion (A): For Diamond, μr = 1

    Reason (R): Diamond is a diamagnetic material.

  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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