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ECE :: Materials and Components

  1. When the atom of rare gas is placed in an electric field the nucleus shifts from the centre of electron cloud by an amount x. If the radius of electron cloud is R, then

  2. A.
    x << R
    B.
    x 0.5 R
    C.
    x ≅ 0.75 R
    D.
    x ≅ R

  3. Macroscopic quantities of a given material

  4. A.
    are absolutely constant
    B.
    are a function of temperature
    C.
    are a function of temperature, pressure field
    D.
    none of the above

  5. For a superconductor, the relative permeability is

  6. A.
    zero
    B.
    high
    C.
    low
    D.
    either low or high

  7. The relative permeability of a ferromagnetic material is

  8. A.
    1
    B.
    less than 1
    C.
    about 10
    D.
    1000 or more

  9. If v is velocity of electron, ε0 is absolute permittivity, m is mass of electron, e is charge on electron and r is the radius of orbit of electron in hydrogen atom, the stability of orbit requires the following equation to be satisfied


  10. Assertion (A): The equation D = ∈0rE is applicable only to isotropic materials.

    Reason (R): In polycrystalline materials, the directional effects are absent.

  11. 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

  12. Assertion (A): For a dielectric, P = ∈0(∈r - 1) E.

    Reason (R): Dipole moment per unit volume is called polarization of dielectric.

  13. 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

  14. Assertion (A): Ferrites are very useful at very high frequencies.

    Reason (R): Ferrites have high permeability and high resistivity.

  15. 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

  16. In a conductor the current flow is due to

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