Regarding a semiconductor which one of the following is wrong 

(a) There are no free electrons at room temperature

(b) There are no free electrons at 0 K

(c) The number of free electrons increases with rise of temperature

(d) The charge carriers are electrons and holes

Concept Questions :-

Types of semiconductors
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Which of the following statements is true for an N-type semi-conductor 

(a) The donor level lies closely below the bottom of the conduction band

(b) The donor level lies closely above the top of the valence band

(c) The donor level lies at the halfway mark of the forbidden energy gap

(d) None of above

Concept Questions :-

Types of semiconductors
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Choose the correct statement

(a) When we heat a semiconductor its resistance increases
(b) When we heat a semiconductor its resistance decreases
(c) When we cool a semiconductor to 0 K then it becomes super conductor
(d) Resistance of a semiconductor is independent of temperature

Concept Questions :-

Types of semiconductors
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Intrinsic semiconductor is electrically neutral. Extrinsic semiconductor having large number of current carriers would be 

(a) Positively charged

(b) Negatively charged

(c) Positively charged or negatively charged depending upon the type of impurity that has been added

(d) Electrically neutral

Concept Questions :-

Types of semiconductors
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If ne and vd be the number of electrons and drift velocity in a semiconductor. When the temperature is increased

(a) ne increases and vd decreases
(b) ne decreases and vd increases
(c) Both ne and vd increases
(d) Both ne and vd decreases

Concept Questions :-

Types of semiconductors
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The energy gap of silicon is 1.14 eV. The maximum wavelength at which silicon will begin absorbing energy is

(a) 10888 Å                    (b) 1088.8 Å
(c) 108.88 Å                   (d) 10.888 Å

Concept Questions :-

Energy band theory
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Which of the following energy band diagram shows the N-type semiconductor

Concept Questions :-

Energy band theory
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The mobility of free electrons is greater than that of free holes because

1. They carry negative charge

2. They are light

3. They mutually collide less

4. They require low energy to continue their motion

Concept Questions :-

Types of semiconductors
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Which of the energy band diagrams shown in the figure corresponds to that of a semiconductor

Concept Questions :-

Energy band theory
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The energy band diagrams for three semiconductor samples of silicon are as shown. We can then assert that

(a) Sample X is undoped while samples Y and Z have been doped with a third group and a fifth group impurity respectively
(b) Sample X is undoped while both samples Y and Z have been doped with a fifth group impurity
(c) Sample X has been doped with equal amounts of third and fifth group impurities while samples Y and Z are undoped
(d) Sample X is undoped while samples Y and Z have been doped with a fifth group and a third group impurity respectively

Concept Questions :-

Energy band theory
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