Materials and Components problems
- 1. Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.
Reason (R): Thermionic emission current ? T2 e-Ew/kT.
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 and R is correct explanation of A
- 2. Assertion (A): Silicon is the most favoured semiconductor material.
Reason (R): PIV for silicon diode is more than that for germanium diode.
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: A is true but R is false
Explanation:
Higher PIV for silicon is a definite advantage.
- 3. Assertion (A): Magnetism can be explained by the theory of magnetic domains.
Reason (R): The existence of magnetic domains is evident from the Bitter powder patterns.
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. In crystalline solids, atoms are stacked in a regular manner.
Options- A. True
- B. False Discuss
Correct Answer: True
- 5. Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.
Options- A. True
- B. False Discuss
Correct Answer: True
- 6. In a piezoelectric crystal, the application of mechanical force will cause
Options- A. plastic deformation of crystal
- B. magnetic dipoles in the crystal
- C. electrical polarization in the crystal
- D. shift in Fermi level Discuss
Correct Answer: magnetic dipoles in the crystal
Explanation:
Piezoelectric materials permit conversion of mechanical force into electrical energy.
- 7. A piece of iron is placed in a magnetic field
Options- A. the magnetic field will not be affected
- B. the magnetic lines of force will bend to pass through the piece
- C. the magnetic lines of force will bend away from the piece
- D. any of the above depending on type of iron Discuss
Correct Answer: the magnetic lines of force will bend to pass through the piece
- 8. Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high.
Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions.
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 and R is correct explanation of A
- 9. Assertion (A): In Figure, the intercept of the line on y-axis is equal to N (ae + ai), where N is number of atoms/m3, ae is electronic polarizability and ai is ionic polarizability.
Reason (R): ae and ai are independent of temperature.
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 and R is correct explanation of A
Explanation:
The intercept on y-axis equals N (ae + ai).
This intercept is constant because ae and ai are independent of temperature.
- 10. Semi conducting materials are all
Options- A. elements
- B. compounds
- C. elements or compounds
- D. elements or mixtures Discuss
Correct Answer: elements or compounds
Explanation:
Many compounds also show semiconducting properties.
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