Discussion
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- Question
Consider the following statements
- An iron cored choke is non linear and passive device.
- A carbon resistor kept in sunlight is a time invariant and passive device.
- A dry cell is a time varying and active device.
- An air capacitor is time invariant and passive device.
Options- A. 1, 2, 3 and 4 are correct
- B. 1, 2, 3 are correct
- C. 1, 2, 4 are correct
- D. 2 and 4 are correct
- Correct Answer
- 1, 2, 3 and 4 are correct
- 1. As per Matthiessen's rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures
Options- A. aT = 0
- B. aT > ri
- C. aT ? ri
- D. aT < ri Discuss
- 2. A dielectric of relative permittivity ?r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by
Options- A. P = constant
- B. P = ?0 E
- C. P = ?0(?r - 1) E
- D. P = ?r E Discuss
- 3. Assertion (A): The equation D = ?0?rE is applicable only to isotropic materials.
Reason (R): In polycrystalline materials, the directional effects are absent.
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
- 4. In a conductor the current flow is due to
Options- A. holes
- B. electrons
- C. ions
- D. electrons and ions Discuss
- 5. Assertion (A): Intrinsic resistivity of silicon is lower than that of germanium.
Reason (R): Magnitude of free electron concentration in germanium is more than that of silicon.
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
- 6. The units for ?r are
Options- A. Farads
- B. Farads/m
- C.
- D. no units Discuss
- 7. A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of
Options- A. copper decreases and germanium increases
- B. both decreases
- C. both increases
- D. copper increases and germanium decreases Discuss
- 8. Magnetic hysteresis phenomenon is explained by
Options- A. motion of domain walls
- B. motion of domain walls and domain rotation
- C. domain rotation
- D. none of the above Discuss
- 9. The relative permeability of a ferromagnetic material is
Options- A. 1
- B. less than 1
- C. about 10
- D. 1000 or more Discuss
- 10. Some ceramic materials become superconducting
Options- A. below liquid helium temperature
- B. between liquid helium and liquid nitrogen temperature
- C. above liquid nitrogen but below room temperature
- D. at room temperature Discuss
Materials and Components problems
Search Results
Correct Answer: aT < ri
Explanation:
At very low temperatures a T ? 0. Since resistivity has a finite value even at low temperature, a T < ri.
Correct Answer: P = ?0(?r - 1) E
Correct Answer: Both A and R are true but R is not correct explanation of A
Correct Answer: electrons
Correct Answer: A is false but R is true
Correct Answer: no units
Explanation:
?r is only a numeric. Hence no units.
Correct Answer: copper decreases and germanium increases
Explanation:
As temperature is decreased, resistance of conductors decreases and resistance of semiconductors increases.
Correct Answer: motion of domain walls and domain rotation
Correct Answer: 1000 or more
Correct Answer: below liquid helium temperature
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