# Semiconductor Device MCQs for NEET

Semiconductors are those substances whose conductivity lies between that of a conductor and an insulator.

On the basis of purity, semiconductors are divided into two types as:

1. Intrinsic semiconductor
2. Extrinsic semiconductor

Further, extrinsic semiconductors are divided into two types as:

1. n-type semiconductors
2. p-type semiconductors

Question and Answer

1. Which among the following is the most commonly used semiconductor?

1. Silicon
2. Carbon
3. Germanium
4. Sulphur

Answer: (a) Silicon

2. What happens to the resistance of a pure semiconductor when heated?

1. The resistance increases
2. The resistance decreases
3. The temperature remains the same
4. Can’t say

Answer: (b) The resistance decreases

3. How many valence electrons does a pentavalent impurity have?

1. 3
2. 4
3. 5
4. 6

Answer: (c) 5

4. How many valence electrons do trivalent impurities have?

1. 2
2. 3
3. 4
4. 5

Answer: (b) 3

5. Which of the following is created when trivalent impurities are added to a semiconductor?

1. Free electrons
2. Holes
3. Bound electrons
4. Valence electrons

Answer: (b) Holes

6. Which of the following does a hole in the semiconductor define?

1. A free proton
2. A free neutron
3. A free-electron
4. An incomplete part of an electron pair bond

Answer: (d) An incomplete part of an electron pair bond

7. An electron and a hole in close proximity would tend to _____.

1. attract each other
2. repel each other
3. have no effect on each other
4. destroy each other

Answer: (a) attract each other

8. What is the random motion of free electrons and holes due to thermal agitation called?

1. Pressure
2. Diffusion
3. Ionisation
4. None of the above

Answer: (b) Diffusion

9. Why is the mobility of free electrons greater than that of holes?

1. They are light
2. They mutually collide less
3. They require low energy to continue the motion
4. They carry negative energy

Answer: (c) They require low energy to continue the motion

10. The relation between the number of free electrons in semiconductor and its temperature is given as

1. $n\propto T$
2. $n\propto T^2$
3. $n\propto T^{3/2}$
4. $n\propto \sqrt{T}$

Answer: (c) $n\propto T^{3/2}$

11. Which of the following does the resistivity of a semiconductor depend upon?

1. Length of the semiconductor
2. Atomic nature of the semiconductor
3. Shape and atomic nature of the semiconductor
4. Shape of semiconductor

Answer: (b) Atomic nature of the semiconductor

12. Which of the following statements is true about extrinsic semiconductors?

1. The gap between the conduction band and the valence bond is more than 16 eV
2. The gap between the conduction band and the valence bond is about 1 eV
3. The gap between the conduction band and valence band is 100 eV and more
4. The conduction band and the valence band overlap.

Answer: (b) The gap between the conduction band and the valence bond is about 1 eV

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