169. A semiconductor has ____ temperature coefficient of resistance
A. positive
B. zero
C. negative
D. none of the above

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170. The most commonly used semiconductor is
A. germanium
B. silicon
C. carbon
D. sulphur

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171. A semiconductor has generally _____ valence electrons.
A.2
B.3
C.6
D.4

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172. The resistivity of pure germanium under standard conditions is about
A. 6 x 104 L2 cm
B. 3 x 104 Sr2 cm
C. 3 x 106 SI cm
D. 6 x 10-4 LI cm

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173. When a pure semiconductor is heated, its 3V
A. goes up
B. goes down
C. remains the same
D. cannot say

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174. The strength of a semiconductor crystal resistance comes from
A. forces between nuclei
B. forces between protons
C. electron-pair bonds
D. none of the above

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175. When a penta valent impurity is added to a pure semiconductor, it becomes
A. an insulator
B. an intrinsic semiconductor
C. p-type semiconductor
D. n-type semiconductor

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