Materials and Components – Section 2
21. | In molecules of ionic crystals, orientation polarization is zero. | |||
Answer: Option A |
23. | For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in | |||||||
Answer: Option C Explanation: It is the characteristic of a photoconductor that its resistance decreases with increase in illumination. |
24. | A permeable substance is one | |||||||
Answer: Option D |
25. | When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ∈‘r – j∈“r . In such materials, the dielectric losses under alternating stress is proportional | |||||||
Answer: Option A Explanation: The imaginary part of ∈r gives rise to absorption of energy. |
26. | The classes of solid dielectrics are | |||||||
Answer: Option C |
27. | A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be | |||||||
Answer: Option D Explanation: Inductance is proportional to square of number of turns. |
28. | A material which is lightly repelled by a magnetic field is known as | |||||||
Answer: Option A |
29. | Which of the following is the poorest conductor of electricity? | |||||||
Answer: Option B |
30. | The magnetic moment in units of Bohr magneton of a ferrous ion in any ferrite is | |||||||
Answer: Option C |