In This Post we are providing Chapter- 14 SEMICONDUCTOR ELECTRONIC : MATERIAL, DEVICES AND SIMPLE CIRCUITS NCERT MOST IMPORTANT QUESTIONS for Class 12PHYSICS which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter
NCERT MOST IMPORTANT QUESTIONS ON SEMICONDUCTOR ELECTRONIC : MATERIAL, DEVICES AND SIMPLE CIRCUITS
1.Draw a pn junction with reverse bias? Which biasing will make the resistance of a
p-n-junction high?
Ans.
Reverse biasing will make the resistance high as it will not allow the current to pass.
2.Write the truth table for the following combination of gates?
Ans.
| A | B | Y’ | Y |
| 0 1 1 | 0 1 1 | 0 1 1 1 | 0 1 1 |
3.Draw the voltage current characteristics of a zener diode?
Ans.
4.For a extrinsic semiconductor, indicate on the energy band diagram the donor and
acceptor levels?
Ans. N-type Extrinsic Semiconductor P-type Extrinsic Semiconductor
5.What do you mean by depletion region and potential barrier in junction diode?
Ans.A layer around the junction between p and n-sections of a junction diode where charge carriers electrons and holes are less in number is called depletion region. The potential difference created across the junction due to the diffusion of charge carriers across the junction is called potential barrier.
6.A transistor has a current gain of 30. If the collector resistance is 6k, input resistance is 1k, calculate its voltage gain?
Ans.Given 
Voltage gain = current gain 
Rgain
Voltage gain = 306 = 180
7. What are the advantages and disadvantages of semiconductor devices over vacuum tubes?
Ans.Advantages – Semiconductor devices are very small in size as compared to the vacuum tubes. It requires low voltage for their operation
Disadvantage – Due to the rise in temperature and by applying high voltage it can be damaged.
8.The base of a transistor is lightly doped. Explain why?
Ans.In a transistor, the majority carries form emitter region moves towards the collector region through base. If base is made thick and highly doped, majority carriers will combine with the other carriers within the base and only few is collected by the collector which leads to small output collector current. Thus in order to have large output collector current, base is made thin and lightly doped.
9. Determine the currents through resistance R of the circuits (i) and (ii) when similar diodes are connected as shown in the figure.
Ans.In figure (i) 
are forward biased
In figure (ii) 
is forward biased but 
is reverse biased due to which offers infinite resistance
10.What do you mean by hole in a circuit? Write its two characteristics?
Ans.A vacancy created in a covalent bond in a semiconductor due to the release of electron is known as hole in a semiconductor.
Characteristics of hole
(i) Hole is equivalent to a positive electronic charge.
(ii) Mobility of hole is less than that of an electron
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