Electrical Engineering Materials MCQ

1. The tiny block formed by the arrangement of a small group of atoms is called the

(a) space lattice.
(b) unit cell.
(c) cubic cell.
(d) primitive cell.

2. A unit cell is

(a) a unit cube containing the smallest number of atoms.
(b) a group of atoms which forms the cubic structure.
(c) the smallest group of atoms which when regularly repeated forms the crystal.
(d) none of the above.

3. The coordination number of a cubic structure is

(a) 8
(b) 6
(c) 4
(d) 2

4. Most of the common metals have………..structures.

(a) cubic
(b) linear
(c) hexagonal
(d) none of these.

5. The number of crystal systems is

(a) 3
(b) 4
(c) 7
(d) 14

6. A primitive cell is

(a) a unit cell in which lattice points are only at its corners.
(b) a unit cell of a simple cubic crystal.
(c) the cell that contains smallest group of atoms.
(d) a basic building block of a crystal.

7. An atom in a crystal vibrates at a frequency determined by

(a) crystal temperature.
(b) crystal heat content.
(c) the stiffness of the bonds it makes with neighbours.
(d) none of the above.

8. Phonons (Quanta of lattice vibration) obey

(a) Maxwell distribution.
(b) Maxwell-Boltzmann distribution.
(c) Fermi-Dirac distribution.
(d) Bose-Einstein distribution. [I.E.S. E.E.-I, 2011]

9. A closed packed hexagonal space lattice is found in

(a) calcium and magnesium.
(b) cobalt, antimony and bismuth.
(c) aluminum, copper and lead.
(d) chromium, tungsten and molybdenum.

10. The Rutherford’s atomic model based on experimental observations could not be accepted. This is because

(a) it does not take into account the quantization condition of angular momentum of an electron.
(b) it does not consider orbital motion of an electron.
(c) it does not explain hydrogen spectrum.
(d) the statement is false.

11. Total number of electrons that can be accommodated in various electron states in a valence band of a given solid is equal to

(a) atomic number of the solid.
(b) half the number of atoms in the solid.
(c) the number of atoms in the solid.
(d) twice the number of atoms in the solid. [I.E.S. E.E.-I, 2001]

12. Consider the following in relation to the orbital motion of an electron:

1. State of energy momentum.
2. Orbital angular level.
3. Angle between the applied magnetic field and angular momentum.

The quantum numbers l, m and n of an electron in orbit represent respectively
(a) 1, 2 and 3
(b) 2, 3 and 1
(c) 3, 2 and 1
(d) 3, 1 and 2 [I.E.S. E.E.-I, 1998]

13. Consider the following statements: Secondary (or molecular) bonds are

1. the attraction forces exist between atoms or molecules.
2. stronger than primary bonds.
3. can be divided as electrostatic bonds.
4. weaker than primary bonds.

Which of the above statements is/are correct?
(a) 1 only.
(b) 2 and 3 only.
(c) 1 and 4 only
(d) 1, 2, 3 and 4. [I.E.S. E.E.-I, 2010]

14. Ionic bonding in solids depends primarily on

(a) transfer of electrons.
(b) sharing of electrons.
(c) electrical dipoles.
(d) all of the above.

15. The velocity of an electron at the Fermi level 5.0 eV is

(a) 1.33 x 10⁴ m/s.
(b) 1.33 x 10⁶ m/s.
(c) 1.33 x 10⁸ m/s.
(d) 4 x 10⁶ m/s.

17. The drift velocity of an electron under the action of applied electric field is of the order of

(a) 10^-14
(b) 10^-11
(c) 10^-7
(d) 10⁷

18. Forbidden band is largest in

(a) conductor.
(b) semiconductor.
(c) insulator.

19. Width of energy bands depends on which of the following?

(a) Temperature.
(b) Pressure.
(c) Relative freedom of electrons in the crystal.
(d) Mass of atom in the material. [I.E.S. E.E.-1. 2006]

20. Packing fraction of simple cube is

(a) 0.48
(b) 0.52
(c) 0.65
(d) 0.89 [A.M.I.E. 1994]