81. In a superconductor the value of critical density depends upon
82. In scintillation coating applications, shields of which material are generally placed around the photomultiplier tube to overcome interference effects of electrons deflected from their normal path?
83. In a variable type carbon resistor the carbon track is formed of a mixture of a carbon, resin and
84. Consider the following statement : Extrinsic semiconductors show high electrical conductivity because the impurities are
1. of high conductivity
2. highly mobile
3. highly charged
Which of these statements are NOT correct?
1. of high conductivity
2. highly mobile
3. highly charged
Which of these statements are NOT correct?
85. Match List-I with List-II and select the correct answer using the options given below:
List-I
List-II
a. Hexagonal crystal
1. a = b = c; γ = α = β ≠ 90º
b. Rhombohedral crystal
2. a = b ≠ c; α = β = 90º; γ = 120º
c. Triclinic crystal
3. a ≠ b ≠ c; α = β ≠ γ ≠ 90º
d. Monoclinic crystal
4. a ≠ b ≠ c; α ≠ γ ≠ 90º ≠ β
| List-I | List-II |
| a. Hexagonal crystal | 1. a = b = c; γ = α = β ≠ 90º |
| b. Rhombohedral crystal | 2. a = b ≠ c; α = β = 90º; γ = 120º |
| c. Triclinic crystal | 3. a ≠ b ≠ c; α = β ≠ γ ≠ 90º |
| d. Monoclinic crystal | 4. a ≠ b ≠ c; α ≠ γ ≠ 90º ≠ β |
86. A resistance thermometer has a temperature coefficient of resistance 10-3 per degree and its resistance at 0°C is 1.0 Ω. At what temperature is its resistance 1.1 Ω?
87. Ceramic insulators undergo a glazing process to reduce the possibility of electric breakdown. What is the effect of this process?
88. Piezoelectric materials serve as a source of
89. The materials having permanent electric moment are called
90. The Electrical susceptibility and relative permittivity are related as:
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