Materials and Components - Section 1 (3)
Materials and Components - Section 1
| 17. | If e is the charge of an electron, R is the radius of its orbit and ω is the angular velocity of electron, the magnetic dipole moment μm of the orbit is |μm| = eωR2. |
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Answer: Option B Explanation: 1 μm 1 = 0.5 eωr2. |
| 18. | Assertion (A): Ferroelectric materials have spontaneous polarization. Reason (R): Above curie temperature, ∈ = |
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Answer: Option B Explanation: Both A and R are correct. Spontaneous polarization vanishes above ferroelectric curie temperature. |
for ferro-electric materials.| 19. | Hydrogen is used in |
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Answer: Option C Explanation: Modem large size generators have hydrogen cooling. |
| 20. | For a paramagnetic material, susceptiblity increases with increasing temperature. |
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| 21. | In metals the valence electron wave functions are strongly perturbed by the presence of neighbouring atoms. |
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Answer: Option A Explanation: In a metal valence electrons are shared by all atoms. |
| 22. | The units of μ0 and μr are |
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Answer: Option C Explanation: μr is only a numeric. |
| 23. | There is no hysteresis phenomenon is any dielectric material. |
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Answer: Option B Explanation: Hysteresis phenomenon exists in dielectic materials. |
| 24. | If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then |
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Answer: Option D Explanation: As the intrinsic carrier concentration is doubled, the concentration of both electrons and holes is doubled. |