DC Pandey Solutions: Semiconductor

# DC Pandey Solutions: Semiconductor | Physics Class 12 - NEET PDF Download

Introductory Exercise 32.1

Ques 1: 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)< (Eg)Ge > (Eg)Si
(c) (Eg)> (Eg)Si > (Eg)Ge
(d) (Eg)= (Eg)S= (Eg)Ge
Ans:
(c)

Introductory Exercise 32.2

Ques 1: 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 of the above
Sol:
(c)

Ques 2: When a forward bias is applied to a p-n junction. lt
(a) raises the potential barrier
(b) reduces the majority carrier current to zero
(c) lowers the potential barrier
(d) All o f the above
Sol: (c)

Introductory Exercise 32.3

Ques 1: For transistor action, which of the following statements are correct?
(a) Base, emitter and collector regions should have similar size and doping concentrations
(b) The base region must be very thin and lightly doped
(c) The emitter junction is forward biased and collector junction is reverse biased
(d) Both the emitter junction as well as the collector junction are forward biased
Ans:
(b,c)

Ques 2: For a transistor amplifier, the voltage gain
(a) remains constant for all frequencies
(b) is high at high and low frequencies and constant in the middle frequency range
(c) is low at high and low frequencies and constant at mid frequencies
(d) None of the above
Ans:
(c)

Ques 3: For a CE-transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. Suppose the current amplification factor of the transistor is 100. Find the input signal voltage and base current, if the base resistance is 1 kΩ.
Ans:
Vi = 0.01 V, ib = 10 μA

Introductory Exercise 32.4

Ques 1: Make the output waveform Y of the NAND gate for the following inputs A and B.

Ans:

Ques 2: You are given two circuits. Identify the logic operation carried out by the two circuits.

Ans:
(a) AND (b) OR

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## Physics Class 12

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## FAQs on DC Pandey Solutions: Semiconductor - Physics Class 12 - NEET

 1. What are semiconductors and how do they function?
Ans. Semiconductors are materials with electrical conductivity between that of a conductor and an insulator. They are typically made of silicon or germanium. Semiconductors work by having a controlled number of impurities or dopants added to them, which creates extra charge carriers. These charge carriers can be manipulated to control the flow of current through the semiconductor.
 2. What are the applications of semiconductors in everyday life?
Ans. Semiconductors have numerous applications in everyday life. They are used in electronic devices such as computers, mobile phones, televisions, and radios. They are also used in solar cells to convert sunlight into electricity, in LED lights for energy-efficient lighting, and in transistors for amplifying and switching electronic signals.
 3. How are semiconductors manufactured?
Ans. Semiconductors are manufactured through a process called semiconductor fabrication or semiconductor manufacturing. This involves several steps, including crystal growth, wafer fabrication, doping, lithography, etching, and packaging. The process requires cleanroom environments and precise control over temperature, pressure, and chemical reactions to ensure the quality and reliability of the semiconductor devices.
 4. What is the band gap in semiconductors?
Ans. The band gap in semiconductors refers to the energy difference between the valence band (the highest energy level that electrons occupy) and the conduction band (the lowest energy level that electrons can move into and conduct electricity). This band gap determines the conductivity properties of the semiconductor. A larger band gap indicates a wider range of energy needed for electrons to move, making the material more insulating, while a smaller band gap allows for easier movement of electrons, making the material more conducting.
 5. What are the different types of semiconductors?
Ans. There are two main types of semiconductors: intrinsic and extrinsic. Intrinsic semiconductors are pure semiconducting materials, such as silicon or germanium, with no intentional impurities added. Extrinsic semiconductors, on the other hand, have controlled impurities added to alter their electrical properties. These impurities are called dopants and can be of two types: n-type (donor dopants) or p-type (acceptor dopants). The addition of these dopants allows for the manipulation of the semiconductor's conductivity and makes it suitable for various electronic applications.

## Physics Class 12

105 videos|425 docs|114 tests

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