Discussion
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- Question
Lines of magnetic field attract each other.
Options- A. True
- B. False
- Correct Answer
- False
ExplanationLines of magnetic field repel each other.
Materials and Components problems
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- 1. The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300 K will be (in m2/s)
Options- A. 0.40
- B. 0.16
- C. 0.04
- D. 0.01 Discuss
Correct Answer: 0.01
- 2. The number of valence electrons in germanium atom is
Options- A. 4
- B. 2
- C. 1
- D. zero Discuss
Correct Answer: 4
- 3. The materials having low retentivity are suitable for making
Options- A. temporary smagnets
- B. weak magnets
- C. permanent magnets
- D. both temporary and permanent magnets Discuss
Correct Answer: temporary smagnets
- 4. Automobile ignition systems use the principle of
Options- A. resistance
- B. self inductance
- C. mutual inductance
- D. capacitance Discuss
Correct Answer: mutual inductance
Explanation:
A high voltage is induced due to mutual inductance because the number of turns in secondary coil is very high.- 5. If ?0 is the angular frequency of rotation of electron in the absence of magnetic field, the angular frequency ?, when a magnetic field B is acting is ? ? ?0 + (e/2m)B.
Options- A. True
- B. False Discuss
Correct Answer: True
- 6. If temperature is increased, the temperature coefficient of a metal
Options- A. increases
- B. decreases
- C. may increase or decrease
- D. remains constant Discuss
Correct Answer: decreases
- 7. In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ?0(?r - 1) E.
Options- A. True
- B. False Discuss
Correct Answer: True
- 8. The temperature at which some materials become superconductors is called
Options- A. Transition temperature
- B. Curie temperature
- C. Neel temperature
- D. Onnes temperature Discuss
Correct Answer: Transition temperature
- 9. A parallel plate capacitor having C = 200 x 10-12 F has loss dielectric having tan ? = 4 x 10-4. At an ac voltage of f = 106 Hz and peak value 2 V, the dielectric losses are
Options- A. 10-8 W
- B. 10-6 W
- C. 10-4 W
- D. 10-2 W Discuss
Correct Answer: 10-6 W
Explanation:
Dielectric losses = v2 ?C tan ?.- 10. When temperature is more than ferromagnetic curie temperature, the behaviour of a ferromagnetic material is similar to that of paramagnetic material.
Options- A. True
- B. False Discuss
Correct Answer: True
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