Electrical Engineering Materials

71. The impurity atoms is semiconductors

1. inject more charge carriers
2. reduce the energy gap
3. increase the kinetic energy of valence electrons
4. all of the above

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72. The kinetic energy of a bounded electron is

1. less than that of unbounded electron
2. greater than that of unbounded electron
3. equal to that of unbounded electron
4. infinite

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73. The metal having the lowest temperature coefficient of resistance is

1. gold
2. copper
3. aluminium
4. kanthal

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74. The minority carrier concentration is largely a function of

1. forward biasing voltage
2. reverse biasing voltage
3. temperature
4. the amount of doping

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75. The number of atoms per unit cell in B.C.C. structure is

1. 1
2. 2
3. 4
4. 8

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76. The photo-electric effect occurs only when the incident light has more than a certain critical

1. intensity
2. speed
3. frequency
4. wave length

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77. The resistivity of a metal is a function of temperature because

1. the amplitude of vibration of the atoms varies with temperature
2. the electron density varies with temperature
3. the electron gas density varies with temperature
4. any of the above

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78. The structure sensitive property of a super conductor is

1. critical magnetic field
2. transition temperature
3. critical current density
4. none of the above

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79. The superconductivity is due to

1. the crystal structure having no atomic vibration at 0°K
2. all electrons interact in the super-conducting state
3. the electrons jump into nucleus at 0°K
4. none of the above

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80. The tiny block formed by the arrangement of a small group of atoms is called the

1. unit cell
2. space lattice
3. either (a) or (b)
4. none of the above

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