81. Which of the following is quantized according to Bohr’s theory of atom ?
(a) linear momentum of electron
(b) linear velocity of electron
(c) angular momentum of electron
(d) angular velocity of electron
82. An electron in the conduction band –
(a) Has a lower energy than an electron in the valence band
(b) Has a higher energy than an electron in the valence band
(c) Is located near the surface of the solid
(d) Is bound to its parent atom
83. Covalent band exists in –
(a) Copper
(b) NaCl crystal
(c) Silicon
(d) Arsenic
84. In a good conductor, the energy gap between the conduction band and the valence band is –
(a) Infinity
(b) Wide
(c) Narrow
(d) Zero
85. The forbidden energy band gap in conductors, semiconductor and insulators are EG1, EG2 and EG3 respectively then –
(a) EG1 > EG2 > EG3
(b) EG1 < EG2 < EG3
(c) EG1 > EG2 = EG3
(d) EG1 = EG2 = EG3
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