Electronic Devices — DPP 1

20 NEET questions from Electronic Devices, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

Attempt this test free 20 questions · 30 minutes · +80 marks
1
In a p-type semiconductor, there are mainly :-
  1. A free electrons
  2. B holes
  3. C both (A) and (B)
  4. D none of these
Show answer

Correct answer: B

2
Carbon, Silicon and Germanium atoms have four valence electrons each. Their valence and conduction bonds are separated by energy band gaps represented by $\left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { C } } , \left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { Si } }$ and $\left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { Ge } }$ respectively. Which one of the following relationships is true in their case :-
  1. A $\left( \mathrm { Eg } _ { \mathrm { g } } \ll \left( \mathrm { Eg } _ { \mathrm { Ge } } \right. \right.$
  2. B $\left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { C } } > \left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { Si } }$
  3. C $\left( \mathrm { Eg } _ { \mathrm { g } } \right) _ { \mathrm { C } } = \left( \mathrm { Eg } _ { \mathrm { g } } \right) _ { \mathrm { Si } }$
  4. D $\left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { C } } < \left( \mathrm { E } _ { \mathrm { g } } \right) _ { \mathrm { Si } }$
Show answer

Correct answer: B

3
Two wires P and Q made up of different materials have same resistance at room temperature. When heated, resistance of P increases and that of Q decreases. We conclude that:-
  1. A P and Q both are conductors but because of being made of different materials it happens so.
  2. B P is n-type semiconductor and Q is p-type semiconductor.
  3. C P is semiconductor and Q is conductor.
  4. D P is conductor and Q is semiconductor.
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Correct answer: D

4
Choose the false statement from the following :-
  1. A the resistivity of a semiconductor increases with increase in temperature.
  2. B substances with energy gap of the order of 10 eV are insulators.
  3. C in conductors the valence and conduction bands may overlap.
  4. D the conductivity of a semiconductor increases with increases in temperature.
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Correct answer: A

5
In semiconducting material the mobilities of electrons and holes are μ$_{e}$ and μ$_{h}$ respectively. Which of the following is true :-
  1. A $\mu _ { \mathrm { e } } > \mu _ { \mathrm { h } }$
  2. B $\mu _ { e } < \mu _ { h }$
  3. C $\mu _ { e } = \mu _ { h }$
  4. D $\mu _ { \mathrm { e } } < 0 ; \mu _ { \mathrm { h } } > 0$
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Correct answer: A

6
When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor:
  1. A increases
  2. B decreases
  3. C remains the same
  4. D become zero
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Correct answer: A

7
A conducting wire of Copper and Germanium are cooled from room temperature to temperature 80 K, then their resistance will :-
  1. A increase
  2. B decrease
  3. C copper's increase and Germanium's decrease
  4. D copper's decrease and Germanium's increase
Show answer

Correct answer: D

8
When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called :-
  1. A intrinsic
  2. B extrinsic
  3. C p-type
  4. D n-types
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Correct answer: A

9
If $n _ { e }$ and $n _ { h }$ are the number of electrons and holes in a semiconductor heavily doped with phosphorus, then :-
  1. A $n _ { e } \gg n _ { h }$
  2. B $\mathrm { n } _ { \mathrm { e } } \ll \mathrm { n } _ { \mathrm { h } }$
  3. C $n _ { e } \leq n _ { h }$
  4. D $n _ { e } = n _ { h }$
Show answer

Correct answer: A

10
Let n$_{p}$ and n$_{e}$ be the numbers of holes and conduction electrons in an extrinsic semiconductor.
  1. A $n _ { p } > n _ { e }$
  2. B $n _ { p } = n _ { e }$
  3. C $n _ { p } < n _ { e }$
  4. D $n _ { p } \neq n _ { e }$
Show answer

Correct answer: D

11
Platinum and silicon are cooled after heating up to $25 ^ { \circ } \mathrm { C }$ then :-
  1. A resistance of platinum will increase and that of silicon decreases.
  2. B resistance of silicon will increase and that of platinum decreases.
  3. C resistance of both will decrease.
  4. D resistance of both increases.
Show answer

Correct answer: B

12
Which statement is correct for p-type semiconductor
  1. A the number of electrons in conduction band is more than the number of holes in valence band at room temperature
  2. B the number of holes in valence band is more than the number of electrons in conduction band at room temperature
  3. C there are no holes and electrons at room temperature
  4. D number of holes and electrons is equal in valence and conduction band
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Correct answer: B

13
A semiconductor wire is connected in an electric circuit in series and temperature of semiconductor increased then the current in the circuit :-
  1. A decreases
  2. B constant
  3. C increases
  4. D will not flow
Show answer

Correct answer: C

14
A semiconductor is damaged by a strong current, because :-
  1. A lack of free electrons
  2. B decrease in electrons
  3. C excess of electrons
  4. D none of these
Show answer

Correct answer: C

15
The atomic bonding is same for which of the following pairs :-
  1. A Ag and Si
  2. B Ge and Si
  3. C Ne and Ge
  4. D NaCl and Ge
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Correct answer: B

16
Electric conduction in a semiconductor takes place due to :-
  1. A electrons only
  2. B holes only
  3. C both electrons and holes
  4. D neither electrons nor holes
Show answer

Correct answer: C

17
A p-type semiconductor is :-
  1. A positively charged
  2. B negatively charged
  3. C uncharged
  4. D uncharged at 0 K but charged at higher temperatures
Show answer

Correct answer: C

18
In semiconductor, at room temperature :-
  1. A valence band are partially empty and conduction band are partially filled
  2. B valence band are fully filled and conduction band are partially empty
  3. C valence band are fully filled
  4. D conduction band are fully empty
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Correct answer: A

19
In an intrinsic semiconductor, number of electrons and holes at room temperature are :-
  1. A equal
  2. B zero
  3. C unequal
  4. D infinity
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Correct answer: A

20
The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature :-
  1. A decreases exponentially with increasing band gap.
  2. B increases exponentially with increasing band gap.
  3. C decrease with increasing temperature.
  4. D is independent of the temperature and the band gap.
Show answer & explanation

Correct answer: A

$\mathrm{n}=\mathrm{AT}^{3 / 2} \mathrm{e} \frac{-\Delta \mathrm{Eg}}{2 \mathrm{kT}}$

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