Company: Air India
AIR INDIA Electronics and Telecommunication Aptitude – I Material, Components and Devices – Multiple Choice Questions
1. The lowest temperature coefficient metal is
(A) Molybdenum. (B) Kantal. (C) Mangenin. (D) Nicrome
2. Density of gold is approximately equal to the density of
(A) Platinum (B) Tungstun (C) Nicrome (D) Kantal
3. For long- distance transmission lines which of the following is preferred
(A) Aluminium (B) Kantal (C) Copper (D) A mixture of Copper and Aluminium.
4. Resistivity range of semiconductors lies between the range of
(A) 10-3 to 103 ohm-m (B) 10-5 to 105 ohm-m (C) 10-3 to 105 ohm-m (D) 10-5 to 103 ohm-m
5. Which out of the following is a poorest insulator ?
(A) Bakelite (B) Lucite (C) Rubber (D) Polyethylene
6. Due to the free electrons moving in the metals the potential energy of the free electrons is
(A) Very high (B) Positive (C) Zero (D) Negative
7. Quantum states with the same energies are said to be
(A) Complementary states (B) degenerate states (C) equal energy states (D) None of these.
8. The probability of occupation P (E) of an energy level E by an electron is given by
(A) P (E) = 1/1+e(EF – E) / KT (B) P (E) = [1+e(E – EF)] / KT (C) (P (E) = 1/1+e(E – EF) / KT D) None of these
9. The wave number can take(A) only negative values. (B) only positive values (C) both Positive or negative values. (D) all real values possible
10. 7.18o K is the critical temperature of
(A) V (B) Ta (C) Po (D) V3Si.
11. At critical temperature T c the value of the critical magnetic field He is
(A) zero (B) some finite value, which depends upon the structure of the material. (C) infinity (D) None of these
12. Which of the following properties of the superconductor is a structure sensitive property ?
(A) Critical magnetic field strength H c (B) Critical temperature T c (C) Critical current density J c (D) None of these.
13. A quantum state has 19 for the sum of the squares of the quantum numbers n x, n y, n z. What is the degeneracy of state ?
(A) 22 (B)19 (C) 20 (D) 24
14. The order of energy gaps between the valance band and the conduction band in insulators and semi- conductors is
A) 10eV, 4eV (B) 6eV, 4eV (C) 6eV, 1eV (D) 1eV, 3eV
15. Mark the true statement.
A) Iron is greatly used for making permanent magnets. (B) Paper can’t affect magnetic lines of force or magnetic flux (C) ALNICO is commonly used for making electromagnets (D) Ferrites has lower permeability than air or vacuum.
16. A closed switch has ideally a resistance of
(A) zero ohm (B) infinite ohm (C) at least 100 ohm at any temperature (D) about 100 ohm at room temperature
17. If an electric flux density Do passes across a negatively charged surface the density of the flux
(A) remains same (B) decreases (C) increases (D) may increase or decrease
18.Which of the following is not an elemental semiconductor
(A) Te (B) C (C) B (D) Br
19. The potential energy of an electron is (A) constant and does not vary with the distance of electron from the atom (B) more when it is close to the positive ion(C) less it is close to the positive ion. (D) less when it is far from the positive ion
20. If the amplitude of the standing wave at a point is A, then the probability of finding an electron at that point is proportional to
(A) A3 (B) A2 (C) A (D) A1.732
21. In monovalent metals the outer most energy band is
(A) empty (B) full (C) half- filled (D) any of (A) or (B)
22.The Probability P (E) of an electron occupying energy level E becomes (A) P (E) = 1/1-exp[(E-EG) /kT] (B) P (E) = exp(-2 Eg/kT) (C) P (E) = exp (-2 EgkT) (D) None of these
23. A n-type semiconductor has excess of free electrons and a p-type semiconductor has deficiency of free electron. The semi- conductors are electrically
(A) positively charged and negatively charged respectively (B) negatively charged and positively charged respectively (C) both are electrically neutral (D) None of these
24.In zone refining section the purity achieved is better than
(A) 99.9% (B) 99.99% (C) 99.999% (D) 99.9999%
25.If the acceptor level is 0.16eV above the top of the valence band, the fractions of hole present at 300 K is
(A) 6.10 * 10-4 (B) 2.05 * 10-3 (C) 5.01 * 10-3 (D) 9.23 * 10-4