# Assertion Reason Physics Chapter 14 Semiconductor Electronics

Questions of Assertion Reason of Physics Chapter 14 Semiconductor Electronics CBSE Class 12 are very simple to understand as this chapter deals with Semiconductor Electronics. To solve assertion reason type questions of Physics, a deeper understanding of concept about Classification of Metals, Conductors and Semiconductors, Intrinsic Semiconductor, Extrinsic Semiconductor, p-n Junction, Semiconductor Diode and Application of Junction Diode as a Rectifier is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.

How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.

How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.

In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:

Assertion (A)Reason (R)MCQ Options (Fixed for all questions)
If TrueTrue(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
If TrueTrue(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
If TrueFalse(c) Assertion (A) is true but reason (R) is false.
If FalseTrue(d) Assertion (A) is false but reason (R) is true.
If FalseFalse(e) Both Assertion and Reason are false.

Now, lets practice some Assertion Reason Questions of Physics: Chapter 14 Semiconductor Electronics

For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.

Question.1.
Assertion: A pure semiconductor has negative temperature coefficient of resistance.
Reason: In a semiconductor on raising the temperature, more charge carriers are released, conductance increases and resistance decreases.

Ans.1. (a)
In semiconductors, by increasing temperature, covalent bond breaks and conduction hole and electrons increase.

Question.2.
Assertion: If the temperature of a semiconductor is increased then its resistance decreases.
Reason: The energy gap between conduction band and valence band is very small.

Ans.2. (a)
In semiconductors the energy gap between conduction band and valence band is small (1 eV). Due to temperature rise, electron in the valence band gain thermal energy and may jumpy across the small energy gap, (to the conduction band). Thus conductivity increases and hence resistance decreases.

Question.3.
Assertion: In semiconductors, thermal collisions are responsible for taking a valence electron to the conduction band.
Reason: The number of conduction electrons go on increasing with time as thermal collisions continuously take place.

Ans.3. (c)
Both The Assertion is correct but Reason is incorrect.

Question.4.
Assertion: A p-type semiconductors is a positive type crystal.
Reason: A p-type semiconductor is an uncharged crystal.

Ans.4. (d)
There is no charge on P-type semiconductor, because each atom of semiconductor is itself neutral.

Question.5.
Assertion: Silicon is preferred over germanium for making semiconductor devices.
Reason: The energy gap in germanium is more than the energy gap in silicon.

Ans.5. (c)
Silicon is cheaper than germanium, so it is preferred over germanium. But energy gap in germanium is smaller than silicon.

Question.6.
Assertion: Electron has higher mobility than hole in a semiconductor.
Reason: The mass of electron is less than the mass of the hole.

Ans.6. (a)
Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

Question.7.
Assertion: The number of electrons in a p-type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature.
Reason: It is due to law of mass action.

Ans.7. (a)
Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

Question.8.
Assertion: When two semi conductor of p and n type are brought in contact, they form p-n junction which act like a rectifier.
Reason: A rectifier is used to convent alternating current into direct current.

Ans.8. (b)
Study of junction diode characteristics shows that the junction diode offers a low resistance path, when forward biased and high resistance path when reverse biased. This feature of the junction diode enables it to be used as a rectifier.

Question.9.
Assertion: Diode lasers are used as optical sources in optical communication.
Reason: Diode lasers consume less energy.

Ans.9. (c)
Statement – 1 is True, Statement- 2 is False

Question.10.
Assertion: The diffusion current in a p-n junction is from the p-side to the n-side.
Reason: The diffusion current in a p-n junction is greater than the drift current when the junction is in forward biased.

Ans.10. (d)
Diffusion current is due to the migration of holes and electrons into opposite regions, so it will be from p-side to n-side. Also in forward bias it will increases.

Question.11.
Assertion: The drift current in a p-n junction is from the n-side to the p-side.
Reason: It is due to free electrons only.

Ans.11. (a)
Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

Question.12.
Assertion: A p-n junction with reverse bias can be used as a photo-diode to measure light intensity.
Reason: In a reverse bias condition the current is small but it is more sensitive to changes in incident light intensity.

Ans.12. (a)
Both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.