71. An intrinsic semiconductor at absolute zero temperature
A. has only a few holes and a few electrons
B. has very large number of holes and electrons
C. behaves like a good conductor
D. behaves like a good insulator

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72.  A germanium atom contains
A. four valence electrons
B. six valence electrons
C. four protons
D. six protons

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73. In Ge, an electron in the conduction band
A. is bound to its parent atom
B. has a higher energy than an electron ins the valence band
C. has zero charge
D. inlocated near the top of the crystal

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74. In Ge, when atoms are held together by the sharing of valence electrons
A. each shared atom leaves a hole
B. valence electrons are free to move away from the nucleus
C. velence electrons from irreversible covalent bands
D. valence electrons form reversible covalent bands

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75. A hole is the vacancy created when
A. a free electron moves on application of electric field
B. an electron breaks its covalent band
C. an atomic core moves
D. an electron reverts from conduction band to velence band

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76. When an electric field is applied to an intrinsic semiconductor at room temperature say from left to right
A. both electrons and holes drift to the right
B. both electrons and holes drift to the left
C. electrons drift to the right while the holes drift to the left
D. electrons drift to the left while holes drift to the right.

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77. Energy required to break a covalent bond in semiconductor is
A. always equal to 1.6 eV
B. greater in Ge than in Si
C. equal to the width of the forbidden energy gap
D. the same in Ge as in Si

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