# MCQ Questions for Class 12 Physics Chapter 14 Semiconductor Electronics: Materials, Devices and Simple Circuits with Answers

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## Semiconductor Electronics: Materials, Devices and Simple Circuits Class 12 MCQs Questions with Answers

Solve these Semiconductor Electronics: Materials, Devices and Simple Circuits Multiple Choice Questions of Class 12 Physics Chapter 14 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
In the figure, assuming the diodes to be ideal, (a) D1 is forward biased and D2 is reverse biased and hence current flows from A to B.
(b) D2 is forward biased and D1 is reverse biased and hence no current flows from B to A and vice versa.
(c) D1 and D2 are both forward biased and hence current flows from A to B.
(d) D1 and D2 are both reverse biased and hence no current flows from A to B and vice versa.

Answer: (b) D2 is forward biased and D1 is reverse biased and hence no current flows from B to A and vice versa.

Question 2.
Hole is
(a) an anti-particle of electron.
(b) a vacancy created when an electron leaves a covalent bond.
(c) absence of free electrons.
(d) an artificially created particle.

Answer: (b) a vacancy created when an electron leaves a covalent bond.

Question 3.
For the depletion region of a diode which one is incorrect?
(a) There are no mobile charges.
(b) Equal number of holes and electrons exists, making the region neutral.
(c) Recombination of holes and electrons has taken place.
(d) Immobile charged ions exist.

Answer: (a) There are no mobile charges.

Question 4.
To reduce the ripples in a rectifier circuit with capacitor filter which one is false?
(a) RL should be increased.
(b) Input frequency should be decreased.
(c) Input frequency should be increased.
(d) Capacitors with high capacitance should be used.

Answer: (b) Input frequency should be decreased.

Question 5.
Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to (Eg)C, (Eg)Si and (Eg) Ge. Which of the following statements is true?
(a) (Eg)Si < (Eg)Ge < (Eg)C
(b) (Eg)C < (Eg)Ge > (Eg)Si
(c) (Eg)C > (Eg)Si > (Eg)Ge
(d) (Eg)C = (Eg)Si = (Eg)Ge

Answer: (c) (Eg)C > (Eg)Si > (Eg)Ge

Question 6.
In an unbiased p-n junction, holes diffuse from the p-region to n-region because
(a) free electrons in the n-region attract them.
(b) they move across the junction by the potential difference.
(c) hole concentration in p-region is more as compared to n-region.
(d) All the above.

Answer: (c) hole concentration in p-region is more as compared to n-region.

Question 7.
In a p-n junction diode, change in temperature due to heating:
(a) affects only reverse resistance
(b) affects only forward resistance
(c) Does not affect resistance of p-n junction
(d) affects the overall V-I characteristics of p-n junction

Answer: (d) affects the overall V-I characteristics of p-n junction

Question 8.
A specimen of silicon is to be made p-type semiconductor for this one atom of indium, on an average, is doped in 5 × 107 silicon atoms. If the number density of silicon is 5 × 1022 atoms m-3, then the number of acceptor atoms per cm³ will be
(a) 2.5 × 1030
(b) 1.0 × 1013
(c) 1.0 × 1015
(d) 2.5 × 1036

Question 9.
The given circuit has two ideal diodes connected as shown in the figure below. The current flowing through the resistance R1 will be: (a) 1.43 A
(b) 3.13 A
(c) 2.5 A
(d) 10.0 A

Question 10.
Consider the junction diode as ideal. The value of current flowing through AB is: (a) 0 A
(b) 10-2A
(c) 10-1 A
(d) 10-3 A

II. Fill in the blanks

Question 1.
At room temperature …………………… is the energy gap for silicon.

Question 2.
A pure semiconductor which is free of impurity is called …………………… semiconductor.

Question 3.
When an impurity is added to a pure semiconductor it becomes …………………… semiconductor.

Question 4.
There are …………………… types of extrinsic semiconductors.

Question 5.
Mobility of hole is …………………… than that of electrons.

Question 6.
…………………… is deliberate addition of desirable impurity atoms into an intrinsic semiconductor to increase its electrical conductivity.

Question 7.
…………………… type is obtained by doping an intrinsic semiconductor with a pentavalent impurity.

Question 8.
…………………… type is obtained by doping an intrinsic semiconductor with a trivalent impurity.

Question 9.
…………………… are the majority carriers in N-type semiconductor.

Question 10.
…………………… are the majority carriers in P-type semiconductor.

Question 11.
Two important processes that occur during the formation of a p-n junction are …………………… and ……………………

Question 12.
The …………………… is the fictitious battery, which seems to be connected across the junction with its positive terminal in the n-region and the negative terminal in the p-region.

Question 13.
The region around the junction, which is devoid of any mobile charge carriers, is called the ……………………

Question 14.
In p-n junction diode there is a …………………… of majority carriers across the junction in forward bias.

Question 15.
A p-n junction is said to be …………………… based if the p-type semiconductor is connected to the positive terminal and the n-type semiconductor is connected to the negative terminal of an external battery.

Question 16.
The resistance of p-n junction is …………………… when reverse biased.

Question 17.
A …………………… is a device, which converts ac into pulsating dc, i.e. unidirectional current.

Question 18.
The output frequency of the half wave rectifier is …………………… as the input frequency.

Question 19.
LED works under …………………… bias.

Question 20.
The Zener diode is always …………………… biased.

Question 21.
A photo diode is always …………………… biased.