Materials and Components – Section 4
11. | The equation D = ∈_{0}∈_{r} E refers only to isotropic materials. | |||
Answer: Option A |
13. | Assertion (A): In some materials, ∈_{r} is independent of temperature while in others, ∈_{r} depends on temperature.
Reason (R): If permanent dipoles are absent, ∈_{r} varies with temperature. |
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Answer: Option C |
14. | An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves | |||||||
Answer: Option D |
15. | Spontaneous polarization occurs in ferroelectric materials. | |||
Answer: Option A |
16. | For a given value (n) of principle quantum number, the number of possible electronic states are | |||||||
Answer: Option B Explanation: The total number of states corresponding to a given value of n is equal to |
17. | Electrical conductivity of metals expressed in ohm^{-1} m^{-1} is of the order of | |||||||
Answer: Option B Explanation: Conductivity is reciprocal of resistivity. Since resistivity of metals is around 10^{-7} ohm-m, conductivity is about 10^{7} ohm^{-1} m^{-1}. So 10^{5} is the nearest value. |
18. | In a metal the probability of a state 0.1 eV below Fermi level being occupied | |||||||
Answer: Option A |
19. | An homogeneous dielectric material is subjected to an electric field E. If a small cavity is made inside the material, the electric field intensity inside and outside the cavity are different. | |||
Answer: Option B Explanation: The electric field intensity inside and outside the cavity are equal. |
20. | A dielectric is subjected to alternating field. The dielectric losses are potential to | |||||||
Answer: Option B Explanation: Absorption of energy is proportional to imaginary part of complex dielectric constant. |
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