Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity 

(1) Decreases

(2) Increases

(3) Remains unchanged

(4) Becomes zero

Subtopic:  Types of Semiconductors |
 88%
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A piece of copper and the other of germanium are cooled from the room temperature to 80 K, then which of the following would be a correct statement

(1) Resistance of each increases

(2) Resistance of each decreases

(3) Resistance of copper increases while that of germanium decreases

(4) Resistance of copper decreases while that of germanium increases

Subtopic:  Types of Semiconductors |
 65%
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To obtain a P-type Si semiconductor, we need to dope pure Si with 

(1) Aluminium

(2) Phosphorous

(3) Oxygen

(4) Germanium

Subtopic:  Types of Semiconductors |
 82%
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The electrical conductivity of a semiconductor

(1) Decreases with the rise in its temperature

(2) Increases with the rise in its temperature

(3) Does not change with the rise in its temperature

(4) First increases and then decreases with the rise in its temperature

Subtopic:  Types of Semiconductors |
 76%
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When a semiconductor is heated, its resistance

(1) Decreases

(2) Increases

(3) Remains unchanged

(4) Nothing is definite

Subtopic:  Types of Semiconductors |
 83%
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In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of

(1) 1  MeV

(2)  0.1 MeV

(3) 1 eV 

(4) 15 eV

Subtopic:  Energy Band theory |
 63%
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An N-type semiconductor is

(1) Negatively charged

(2) Positively charged

(3) Neutral

(4) None of these

Subtopic:  Types of Semiconductors |
 64%
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The energy band gap of Si is

(1) 0.70 eV

(2) 1.1 eV

(3) Between 0.70 eV to 1.1 eV

(4) 5 eV

Subtopic:  Energy Band theory |
 56%
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The forbidden energy bandgap in conductors, semiconductors, and insulators are EG1,EG2 and EG3 and respectively. The relation among them is

(1) EG1=EG2 =EG3

(2) EG1<EG2 <EG3

(3) EG1>EG2 >EG3 

(4) EG1<EG2 >EG3

Subtopic:  Energy Band theory |
 90%
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When Ge crystals are doped with phosphorus atom, then it becomes 

(1) Insulator

(2) P-type

(3) N-type

(4) Superconductor

Subtopic:  Types of Semiconductors |
 86%
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