Questions and answers for exam Preparation

MCQs

Total Questions : 500 | Page 50 of 50 pages

Question 491. 9. Consider the following materials :1. Pure silicon 2. Aluminium 3. Doped silicon 4. Mica. The correct sequence in the order of their increasing electrical resistivity is

1-2-3-4
2-3-4-1
2-3-1-4
1-3-4-2

Discuss Question

Answer: Option C. -> 2-3-1-4

Question 492. 0. There are four contributors to total polarization of a material. These contributions are electronic, ionic, dipolar and space-charge polarization. At optical frequencies the only major contribution to polarization is from

electronic polarization
ionic polarization
dipolar polarization
space-charge polarization

Discuss Question

Answer: Option A. -> electronic polarization

Question 493. 2. In semiconductor wafer cleaning, trichloroethylene is used to remove

Dust particles from the surface
Grease from the surface
Impurities from within the crystal
Moisture from the surface

Discuss Question

Answer: Option C. -> Impurities from within the crystal

Question 494. 3. Consider the following statements about ferrites :1. Ferrites have high resistivity.2. Ferrites have low eddy current losses.3. Ferrites are used as core materials in high frequency (MHz) transformers. Which of the statements given above are correct?

1, 2 and 3
1 and 2
1 and 3
2 and 3

Discuss Question

Answer: Option A. -> 1, 2 and 3

Question 495. 1. For electrons and holes, the Hall I +Er coefficients are

both positive
both negative
positive and negative, respectively
negative and positive, respectively

Discuss Question

Answer: Option D. -> negative and positive, respectively

Question 496. 5. In a dielectric material there are four contributions to the total polarisation. Out of these only one is dependent on temperature and this contribution is

electric polarization
space-charge polarization
ionic polarization
orientational polarisation

Discuss Question

Answer: Option D. -> orientational polarisation

Question 497. 4. Anecessary but not a sufficient condition for a crystal to show ferro-electricity is

absence of centre of symmetry
presence of centre of symmetry
presence of both translational and rotational symmetry
absence of both translational and rotational symmetry

Discuss Question

Answer: Option A. -> absence of centre of symmetry

Question 498. 6. If m = permanent dipole moment, k = Boltzmann constant and T= absolute temperature, then orientational polarisability is equal to

3kT
3kT
3kTm
3kTm2

Discuss Question

Answer: Option B. -> 3kT

Question 499. 7. Which one of the following statements is correct? Copper and silicon are forming a junction; at thermal equilibrium

the Fermi levels in the two materials are at the same energy level irrespective of the number of free electrons in copper and silicon
the Fermi level of copper is at a higher energy level compared to that of silicon as copper has more free electrons.
the Fermi levle of silicon is at a higher energy level compared to that of copper as silicon has more free electrons.
copper and silicon, being in thermal equilibrium, will have the same pecific heat and Fermi levels have no relation to thermal equilibrium

Discuss Question

Answer: Option D. -> copper and silicon, being in thermal equilibrium, will have the same pecific heat and Fermi levels have no relation to thermal equilibrium

Question 500. 4. Which one of the following statements is correct? Copper and silicon are forming a junction; at thermal equilibrium

the Fermi levels in the two materials are at the same energy level irrespective of the number of free electrons in copper and silicon
the Fermi level of copper is at a higher energy level compared to that of silicon as copper has more free electrons.
the Fermi levle of silicon is at a higher energy level compared to that of copper as silicon has more free electrons.
copper and silicon, being in thermal equilibrium, will have the same pecific heat and Fermi levels have no relation to thermal equilibrium

Discuss Question

Answer: Option D. -> copper and silicon, being in thermal equilibrium, will have the same pecific heat and Fermi levels have no relation to thermal equilibrium