176. Which of the following is not a semiconductor –
(a) Silicon
(b) Germanium
(c) Arsenic
(d) Selenium
177. A Silicon crystal becomes p- type when –
(a) Code to very low temperature
(b) Alloyed with germanium
(c) Doped with boron atoms
(d) Doped with arsenic atom
178. Carbon is said to be semiconductor. But –
(a) Graphite and diamond are good conductor
(b) Graphite and diamond are also semiconductor
(c) Graphite is good conductor but diamond is bad conductor
(d) Graphite is bad conductor but diamond is good conductor
179. In case of semiconductors the width of forbidden gap is about –
(a) 0.01 eV
(b) 10 eV
(c) 100 eV
(d) 1 eV
180. Arrange different materials in ascending order of their resistivity –
(a) Insulators – Semiconductors – Metals
(b) Semiconductors – insulators – metals
(c) Metals – semiconductors – insulators
(d) Insulators ndash; Metals – semiconductors
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