The valence of an impurity added to germanium crystal in order to convert it into a P-type semi conductor is

(a) 6                       (b) 5
(c) 4                       (d) 3

Concept Questions :-

Types of semiconductors
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In a semiconductor, the concentration of electrons is 8×1014 cm3 and that of the holes is 5×1012 cm3. The semiconductor is

(a) P-type                    (b) N-type
(c) Intrinsic                  (d) PNP-type

Concept Questions :-

Types of semiconductors
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The valency of the impurity atom that is to be added to germanium crystal so as to make it a N-type semiconductor, is

(a) 6                      (b) 5
(c) 4                      (d) 3

Concept Questions :-

Types of semiconductors
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Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity 
(a) Decreases                     (b) Increases
(c) Remains unchanged       (d) Becomes zero

Concept Questions :-

Types of semiconductors
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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

(a) Resistance of each increases

(b) Resistance of each decreases

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

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

Concept Questions :-

Types of semiconductors
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To obtain P-type Si semiconductor, we need to dope pure Si with 
(a) Aluminium                 (b) Phosphorous
(c) Oxygen                     (d) Germanium

Concept Questions :-

Types of semiconductors
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Electrical conductivity of a semiconductor

(a) Decreases with the rise in its temperature

(b) Increases with the rise in its temperature

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

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

Concept Questions :-

Types of semiconductors
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When a semiconductor is heated, its resistance

(a) Decreases                    (b) Increases
(c) Remains unchanged      (d) Nothing is definite

Concept Questions :-

Types of semiconductors
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In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of

(a) 1  MeV                  (b)  0.1 MeV
(c) 1 eV                      (d) 15 eV

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Energy band theory
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A N-type semiconductor is

(a) Negatively charged        (b) Positively charged
(c) Neutral                         (d) None of these

Concept Questions :-

Types of semiconductors
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