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- Question
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
- Correct Answer
- motion of domain walls and domain rotation
- 1. 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
- 2. The units for ?r are
Options- A. Farads
- B. Farads/m
- C.
- D. no units Discuss
- 3. 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 Discuss
- 4. 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
- 5. 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
- 6. The relative permeability of a ferromagnetic material is
Options- A. 1
- B. less than 1
- C. about 10
- D. 1000 or more Discuss
- 7. 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
- 8. As the temperature of semiconductor is increased
Options- A. the average number of free charge carriers decreases
- B. the average number of free charge carriers increases
- C. the average number of free charge carriers remains the same
- D. the average number of free charge carriers may increase or decrease Discuss
- 9. For an insulating material, dielectric strength and dielectric losses should be
Options- A. high and high
- B. low and high
- C. high and low
- D. low and low Discuss
- 10. Macroscopic quantities of a given material
Options- A. are absolutely constant
- B. are a function of temperature
- C. are a function of temperature, pressure field
- D. none of the above Discuss
Materials and Components problems
Search Results
Correct Answer: copper decreases and germanium increases
Explanation:
As temperature is decreased, resistance of conductors decreases and resistance of semiconductors increases.
Correct Answer: no units
Explanation:
?r is only a numeric. Hence no units.
Correct Answer: 1, 2, 3 and 4 are correct
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: 1000 or more
Correct Answer: below liquid helium temperature
Correct Answer: the average number of free charge carriers increases
Explanation:
As temperature increases, conductivity of semi- conductors increases.
Correct Answer: high and low
Explanation:
An insulating material should have high dielectric strength and low losses.
Correct Answer: none of the above
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