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- Question
Which of the following are true for relative dielectric constant?
- It is dimensionless.
- It is equal to 1 for vacuum.
- It is equal to 1 for all substances.
Options- A. 1 and 2 only
- B. 2 and 3 only
- C. 1 and 3 only
- D. 1, 2 and 3
- Correct Answer
- 1 and 2 only
Explanation?r has no units and equal to 1 for vacuum. For other substances it has different value.
Materials and Components problems
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- 1. The residual resistivity of a binary alloy at 0 K is
Options- A. sum of residual resistivities of component metals
- B. difference of residual resistivities of component metals
- C. product of residual resistivities of component metals
- D. dependent on the concentration of minor component in the alloy Discuss
Correct Answer: dependent on the concentration of minor component in the alloy
- 2. If the number of atoms per unit volume of a monoatomic gas changes, the dielectric constant still remains constant.
Options- A. True
- B. False Discuss
Correct Answer: True
Explanation:
The dielectric constant changes as it is proportional to the number of atoms per unit volume.- 3. When a dielectric material is subjected to alternating field, the absorption of energy by the material from the field is given by the imaginary part of polarizability.
Options- A. True
- B. False Discuss
Correct Answer: True
- 4. The merger of hole and free electron is called
Options- A. covalent bonding
- B. recombination
- C. thermal energy
- D. free electrons Discuss
Correct Answer: recombination
- 5. Assertion (A): Resistivity of a perfect single crystal of a metal goes to zero as T approaches zero.
Reason (R): Scattering of electrons is due to deviations from perfect periodicity of lattice.
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
- 6. The elements which become superconducting at extremely low temperatures are
Options- A. good conductors at room temperature
- B. ferromagnetic at room temperature
- C. relatively poor conductors at room temperature
- D. insulators at room temperature Discuss
Correct Answer: relatively poor conductors at room temperature
- 7. The phenomenon of dielectric hysteresis occurs with
Options- A. dc
- B. ac
- C. both ac and dc
- D. none of the above Discuss
Correct Answer: ac
Explanation:
Hysteresis phenomenon occurs when direction of electric field is changed. This can happen only with ac.- 8. Wood is a diamagnetic material.
Options- A. True
- B. False Discuss
Correct Answer: False
- 9. The magnetic quantum number determines the component of angular momentum along a prescribed direction.
Options- A. True
- B. False Discuss
Correct Answer: True
- 10. In an intrinsic semiconductor, at a given temperature T
Options- A. the number of electrons-hole pairs generated per second due to thermal motion are equal to the number of electron-hole pairs lost per second due to recombination
- B. the number of electron-hole pairs generated per second due to thermal motion is always less than the number of electron-hole pairs lost per second due to recombination
- C. the number of electron hole pairs generated per second due to thermal motion is always more than the number of electron-hole pairs lost per second due to recombination
- D. any of the above Discuss
Correct Answer: the number of electrons-hole pairs generated per second due to thermal motion are equal to the number of electron-hole pairs lost per second due to recombination
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