WBJEE: Important Questions and Preparation Tips – Electronic Devices

Find chapter notes of chapter Electronic Devices including important topics like classification of solids, intrinsic semiconductor, extrinsic semiconductor, p-n junction, photodiode, Light Emitting Diode(LED), solar cell etc. About 1-2 questions are always asked from this chapter in the examination.

After the detailed analysis of the latest syllabus and the pattern of the few last year papers of WBJEE entrance examination, Subject Experts of Physics have prepared the chapter notes of chapter Electronic Devices.

In these notes, they have also included some previous year solved questions which will help aspirants to get to know about the difficulty level of the questions which are asked in previous year WBJEE examination.

About the Exam:

West Bengal Joint Entrance Examination (WBJEE) is a state level common entrance test organized by West Bengal Joint Entrance Examinations Board for admission to the Undergraduate Level Engineering and Medical Courses through a common entrance test in the State of West Bengal.

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Important Concepts:

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Some previous years solved questions are given below:

Question 1:

The inputs to the digital circuit are shown below. The output Y is

Solution 1:

Hence, the correct option is (C).

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Question 2:

Solution 2:

Hence, the correct option is (D).

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Question 3:

In a p-n junction diode not connected to any circuit

(A) the potential is the same everywhere

(B) the p-type side is at a higher potential than the n-type side

(C) there is an electric field at the junction directed from the n-side to the p-type side

(D) there is an electric field at the junction directed from the p-type side to the n-type side

Solution 3:

There is an electric field at the junction directed from the n-side to the p-type side

Hence, the correct option is (C).

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Question 4:

Which of the following statements is not true ?

(A) The resistance of intrinsic semiconductors decreases with increase of temperature

(B) Doping pure Si with trivalent impurities give p-type semiconductors

(C) The majority carriers in n-type semiconductors are holes

(D) A p-n junction can act as a semiconductor diode

Solution 4:

The majority carriers in n-type semiconductors are holes

Hence, the correct option is (C).

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Question 5:

If a semiconductor has an intrinsic carrier concentration of 1.41 × 10¹⁶/m³, when doped with 10²¹/m³ phosphorous atoms, then the concentration of holes/m³ at room temperature will be

(A)  2 × 10²¹                      

(B)  2 × 10¹¹              

(C)  1.41 × 10¹⁰       

(D) 1.41 × 10¹⁶

Solution 5:

Doping will increase the number of electrons only and not the holes.

So, number of holes will be equal to number of intrinsic carrier concentration = 1.41 × 10¹⁶/m³

Hence, the correct option is (D).

WBJEE WBJEE 2014 Solved Physics Question Paper

WBJEE 2018: Notification, Application, Dates, Eligibility, Exam Pattern, Syllabus