Materials and Components problems
- 1. The maximum temperature limit of class B insulation is
Options- A. 90°C
- B. 105°C
- C. 120°C
- D. 130°C Discuss
Correct Answer: 130°C
- 2. Resistivity of metals consists of two parts, one part constant and the other temperature dependent.
Options- A. True
- B. False Discuss
Correct Answer: True
- 3. Assertion (A): The regular or irregular stacking of atoms has importanteffect on properties of materials.
Reason (R): The arrangement of atoms in a given material can be studied using X-rays.
Options- 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 Discuss
Correct Answer: Both A and R are true but R is not correct explanation of A
- 4. Assertion (A): Both sodium and ferrous are ferromagnetic.
Reason (R): Both sodium and ferrous have body centred cubic structure.
Options- 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 Discuss
Correct Answer: Both A and R are true but R is not correct explanation of A
- 5. Assertion (A): ?0 has the dimensions of farad per meter.
Reason (R): D = ?0?r E.
Options- 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 Discuss
Correct Answer: Both A and R are true but R is not correct explanation of A
Explanation:
The dimensions of ?0 can be derived from the expression D = ?0?r E.
- 6. Assertion (A): Drift velocity of electrons is proportional to the applied electric field E.
Reason (R): The average drift velocity per unit field is called mobility.
Options- 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 Discuss
Correct Answer: Both A and R are true but R is not correct explanation of A
- 7. For iron, the ferromagnetic Curie temperature is
Options- A. about 20 K
- B. about 100°C
- C. about -20°C
- D. about 1000 K Discuss
Correct Answer: about 1000 K
- 8. In a valence crystal, the valence electrons
Options- A. are not shared
- B. are shared between neighbouring atoms
- C. are shared by all atoms
- D. any of the above Discuss
Correct Answer: are shared between neighbouring atoms
Explanation:
In true valence crystals the binding between the atoms is accomplished by the sharing of valence electrons.
This sharing can only be between neighbouring atoms only.
- 9. The probability of recombination of electrons and holes in a semiconductor is proportional to
Options- A. density of electrons
- B. density of holes
- C. density of electrons and holes
- D. none of the above Discuss
Correct Answer: density of electrons and holes
- 10. A photoconductor is a
Options- A. conductor
- B. semiconductor
- C. insulator
- D. superconductor Discuss
Correct Answer: semiconductor
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