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1. When a pure semiconductor is heated, its resistance
A. Goes down.
B. Goes up.
C. Remains the same.
D. None of the above.
3. The densities of electrons and holes in an extrinsic semiconductor are 8 x 1015 cm-3 and 5 x 1012 cm-3 respectively. The mobilities of electrons and holes are respectively 23 x 103 cm3 / Vs and 102 cm3 / Vs. Which type of semiconductor is it?
A. p-type only
B. n-type only
C. either n or p type
D. both n and p type
4. A semiconductor is formed by
A. Covalent bonds
B. Electrovalent bonds
C. Coordinate bonds
D. None of above
5. Arrange the materials in ascending order of energy band gaps
A. conductor, semiconductor, insulator
B. insulator, semiconductor, conductor
C. semiconductor, conductor, insulator
D. insulator, conductor, semiconductor
6. In a semiconductor, current conduction is due
A. Only to holes.
B. Only to electrons
C. To holes and electrons
D. None of the above
7. Electrons moving like molecules of a gas exist in:
A. all solids
B. covalent solids
C. metallic solids
D. ionic solids
8. An n-type semiconductor is
A. Not charged at all
B. Positively charged
C. Electrically neutral
D. Negatively charged
10. In a semiconductor, the energy gap between valence band and conduction band is about
A. 10 eV
B. 5 eV
C. 1 eV
D. 15 eV
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