Materials And Components MCQ Questions & Answers

21

At what temperatures domains lose their ferromagnetic properties?

A) Above ferromagnetic Curie temperature B) Below paramagnetic Curie temperature C) Above 4°K D) At room temperature

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Answer & Solution

Answer: Option A

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22

Resistivity of Ge is

A) 230 kΩcm B) 230 Ωcm C) 44.54 Ωcm D) 44.5 kΩcm

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Answer & Solution

Answer: Option C

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23

Superconductivity is destroyed

A) At high temperature B) At high magnetic field C) In presence of magnetic impurity D) In all the above cases

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Answer & Solution

Answer: Option D

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24

Which one of the following is the best definition of a superconductor?

A) It is a material showing perfect conductivity and meissner effect below a critical temperature B) It is a conductor having zero resistance C) It is a perfect conductor with highest diamagnetic susceptibility D) It is a perfect conductor but becomes resistive when the current density through it exceeds a critical value

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Answer & Solution

Answer: Option A

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25

Match List-I with List-II and select the correct answer:

List-I	List-II
a. Ferro-magnetism	1. d.c. electrical resistivity vanishes at the critical temperature T_C
b. Semiconductor	2. Doping with impurity increases the electrical conductivity
c. Optical property of solid	3. An internal molecular field B_M which is proportional to magnetization M exists at each dipole and aligns it parallel to other dipoles
d. Superconductivity	4. Above the Neel temperature the dipoles become randomly oriented
	5. The conductivity of crystalline semiconductors and dielectrics increases by radiation incident

A) a-3, b-5, c-2, d-1 B) a-3, b-2, c-5, d-1 C) a-4, b-5, c-2, d-3 D) a-4, b-2, c-5, d-3

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Answer & Solution

Answer: Option B

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26

Which of the following statements in NOT true?

A) Superconductors show perfect diamagnetism B) Superconductors have almost zero resistivity C) The external magnetic field has no effect on superconductors D) Entropy increase on going from superconducting state to normal state

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Answer & Solution

Answer: Option C

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27

Which one of the following materials is a ceramic material?

A) Mica B) Zinc sulphide C) Antimony D) Copper

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Answer & Solution

Answer: Option B

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28

Consider the following statements:
The conductivity of a metal has negative temperature coefficient since:
1. The electron concentration increase with temperature.
2. The electron mobility decreases with temperature.
3. The electron-lattice scattering rate increases with temperature.
Which of the above statements is/are correct?

A) 1 only B) 1 and 2 C) 2 and 3 D) 3 only

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Answer & Solution

Answer: Option C

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29

Piezoelectricity is the reverse effect of

A) Electroluminescence B) Electrostriction C) Peltier effects D) Hall effect

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Answer & Solution

Answer: Option B

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30

Consider the following statements:
He-Ne laser
1. gives continuous output
2. emits red light
3. requires a DC magnet
4. can be voice modulated by using a Kerr cell
Which of these statements are correct?

A) 1, 2 and 3 B) 1, 3 and 4 C) 1, 2 and 4 D) 2, 3 and 4

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Answer & Solution

Answer: Option C

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Materials And Components MCQ Questions & Answers | ECE