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NCERT Exemplar Class 12 Physics solutions chapter 14 dives deep into the heart of microprocessors and transistors, something we cannot survive a day without. Class 12 Physics NCERT Exemplar solutions chapter 14 explores Semiconductors as devices whose properties lie between an insulator and a conductor. It possesses eccentric electrical properties and is mounted inside many electronics appliances that support our everyday lives. NCERT Exemplar solutions For Class 12 Physics chapter 14 provided here would help a student achieve academic success in both 12 boards and competitive exams. They would also help to understand and practice the concepts both theoretically and practically. Students can use NCERT Exemplar Class 12 Physics solutions chapter 14 PDF download to understand the best way to approach a problem.
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Question:1
The conductivity of a semiconductor increases with increase in temperature because
A. number density of free current carriers increases.
B. relaxation time increases.
C. both number density of carriers and relaxation time increase.
D. number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density.
Answer:
The answer is the option (d)Question:2
In Fig. 14.1, Vo is the potential barrier across a p-n junction, when no battery is connected across the junction
A. 1 and 3 both correspond to forward bias of junction
B. 3 corresponds to forward bias of junction and 1 corresponds to reverse bias of junction
C. 1 corresponds to forward bias and 3 corresponds to reverse bias of junction.
D. 3 and 1 both correspond to reverse bias of junction.
Answer:
Answer: The answer is the option (b)Question:3
In Fig. 14.2, 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. D1and 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:
The answer is the option (b)Question:4
A 220 V A.C. supply is connected between points A and B (Fig. 14.3). What will be the potential difference V across the resistor?
A. 220V
B. 110V
C. 0V
D.
Answer:
As p-n junction diode will conduct during positive half cycle only during the negative half cycle diode is reverse biases. during this diode will not give any output so potential difference across capacitor C-peak voltage of the given AC voltage
Question:5
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:
The answer is the option (b)Question:6
The output of the given circuit in Fig. 14.4.
A. would be zero at all times.
B. would be like a half wave rectifier with positive cycles in output.
C. would be like a half wave rectifier with negative cycles in output.
D. would be like that of a full wave rectifier.
Answer:
The answer is the option (c)
would be like a half wave rectifier with negative cycles in outpu
Question:7
In the circuit shown in Fig. 14.5, if the diode forward voltage drop is 0.3 V, the voltage difference between A and B is
A. 1.3 V
B. 2.3 V
C. 0
D. 0.5 V
Answer:
The answer is the option (b)Question:8
Truth table for the given circuit (Fig. 14.6) is
A.
A | B | C |
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 1 |
1 | 1 | 0 |
A | B | C |
0 | 0 | 1 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 1 |
A | B | C |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 0 |
1 | 1 | 1 |
A | B | C |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
Answer:
The answer is the option (c)A | B | C=A.B | d=.B | E=(C+D) | |
0 | 0 | 1 | 0 | 0 | 0 |
0 | 1 | 1 | 0 | 1 | 1 |
1 | 0 | 0 | 0 | 0 | 0 |
1 | 1 | 0 | 1 | 0 | 1 |
Question:9
When an electric field is applied across a semiconductor
A. electrons move from lower energy level to higher energy level in the conduction band.
B. electrons move from higher energy level to lower energy level in the conduction band.
C. holes in the valence band move from higher energy level to lower energy level.
D. holes in the valence band move from lower energy level to higher energy level.
Answer:
The answer is the option (a, c)Question:10
Consider an npn transistor with its base-emitter junction forward biased and collector base junction reverse biased. Which of the following statements are true?.
A. Electrons crossover from emitter to collector.
B. Holes move from base to collector.
C. Electrons move from emitter to base.
D. Electrons from emitter move out of base without going to the collector.
Answer:
The answer is the option (a, c)Question:11
Figure 14.7 shows the transfer characteristics of a base biased CE transistor. Which of the following statements are true?
A. At Vi = 0.4V, transistor is in active state.
B. At Vi = 1V, it can be used as an amplifier.
C. At Vi = 0.5V, it can be used as a switch turned off.
D. At Vi = 2.5V, it can be used as a switch turned on.
Answer:
The answer is the option (b, c, d)Question:12
In a npn transistor circuit, the collector current is 10mA. If 95 per cent of the electrons emitted reach the collector, which of the following statements are true?
A. The emitter current will be 8 mA.
B. The emitter current will be 10.53 mA.
C. The base current will be 0.53 mA.
D. The base current will be 2 mA.
Answer:
The answer is the option (b, c)Question:13
In the depletion region of a diode
A. there are no mobile charges
B. equal number of holes and electrons exist, making the region neutral.
C. recombination of holes and electrons has taken place.
D. immobile charged ions exist.
Answer:
The answer is the option (a, b, d)Question:14
What happens during regulation action of a Zener diode?
A. The current in and voltage across the Zenor remains fixed.
B. The current through the series Resistance (Rs) changes.
C. The Zener resistance is constant.
D. The resistance offered by the Zener changes.
Answer:
The answer is the option (b,d)Question:15
To reduce the ripples in a rectifier circuit with capacitor filter
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:
The answer is the option (a, c, d)Question:16
The breakdown in a reverse biased p–n junction diode is more likely to occur due to
A. large velocity of the minority charge carriers if the doping concentration is small.
B. large velocity of the minority charge carriers if the doping concentration is large.
C. strong electric field in a depletion region if the doping concentration is small.
D. strong electric field in the depletion region if the doping concentration is large.
Answer:
The answer is the option (a, d)Question:17
Why are elemental dopants for Silicon or Germanium usually chosen from group XIII or group XV?
Answer:
Silicon and germanium are chosen as a dopants because their size is compatible with the gaps in semiconductors. And they even are capable of forming covalent bonds.Question:18
Answer:
Sn is a conductor as it has an energy gap of 0 EV while C has an energy gap of 5.4 eV therefore, it is an insulator. Si and Ge have an energy gap of 1.1 eV and 0.7 eV, which makes them a semiconductor. The gaps in energy are related to their individual atomic size, which is responsible for making one insulator, conductor and semiconductor.Question:19
Answer:
We cannot measure the potential barrier of a PN-junction by connecting a sensitive voltmeter across its terminals because in the depletion region, there are no free electrons and holes and in the absence of forward biasing, PN- junction offers infinite resistance.Question:20
Draw the output waveform across the resistor (Fig.14.8).
Answer:
The diode act as a half wave rectifier, it offers low resistance when forward biased and high resistance when reverse biased.Question:21
The amplifiers X, Y and Z are connected in series. If the voltage gains of X, Y and Z are 10, 20 and 30, respectively and the input signal is 1 mV peak value, then what is the output signal voltage (peak value)
(i) if dc supply voltage is 10V?
(ii) if dc supply voltage is 5V?
Answer:
The ratio of output signal voltage to the input signal voltage is known as the total voltage amplification.Question:22
Answer:
Question:23
(a)
(b)
(i) Name the type of a diode whose characteristics are shown in Fig. 14.9 (A) and Fig. 14.9(B).
Answer:
i) Figure a) it represents the characteristics of Zener diode and figure b) represents a solar cell.Question:24
Answer:
Question:25
Answer:
IbR1 + Vbe = Vbb
Base current = Ib = Vbb – Vbe/R1
Ib is inversely proportional to R1
Hence, if R1 is increased, then Ib gets reduced.
Question:26
Answer:
Here, the OR gate is used to explain the situation:A | B | Y=A+B |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 1 |
Question:28
Explain why elemental semiconductor cannot be used to make visible LEDs.
Answer:
In an elemental semiconductor, the bandgap is such that the emission is in the infrared region and not in the visible region.Question:29
Write the truth table for the circuit shown in Fig.14.11. Name the gate that the circuit resembles.
Answer:
A | B | V0=A.B |
0 | 0 | 0 |
0 | 1 | 0 |
1 | 0 | 0 |
1 | 1 | 1 |
Question:30
Answer:
According to the problem Power=1 WattQuestion:31
Answer:
According to the problem forward biases resistance = and reverse biases resistance=Question:32
Answer:
According to the problem V1 =10V, Resistance RB=400k, VBE=0, VCE=0 and Rc=3kQuestion:33
Draw the output signals C1 and C2 in the given combination of gates (Fig. 14.15).
Answer:
A | B | C | D | E | F | G | H | I | C1 |
0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 1 |
1 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 0 |
0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 0 |
1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 |
A | B | C | D | E | F | G | C2 |
0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 |
1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 |
0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 |
1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 |
Question:34
Consider the circuit arrangement shown in Fig 14.16 (a) for studying input and output characteristics of n-p-n transistor in CE configuration.
Select the values of RB and RC for a transistor whose VBE = 0.7 V, so that the transistor is operating at point Q as shown in the characteristics shown in Fig. 14.16 (b).
Given that the input impedance of the transistor is very small and VCC = VBB = 16 V, also find the voltage gain and power gain of circuit making appropriate assumptions.
Answer:
According to the problem at point Q, from graph andQuestion:35
Answer:
The waveform obtained from the circuit will be a sine wave with a little dip in the input wave.Question:36
Answer:
Question:37
An X-OR gate has following truth table:
A | B | Y |
0 | 0 | 0 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
Answer:
XOR can be obtained by combining two NOT gates, two AND gates and one OR gate. The logic relation for the given table is as follows:Question:38
Consider a box with three terminals on top of it as shown in Fig.14.18 (a):
Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement.
A student performs an experiment in which any two of these three terminals are connected in the circuit shown in Fig. 14.18 (b).
The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit.
The graphs are
(i) when A is positive and B is negative
(ii) when A is negative and B is positive
(iii) When B is negative and C is positive
(iv) When B is positive and C is negative
(v) When A is positive and C is negative
(vi) When A is negative and C is positive
From these graphs of current – voltage characteristic shown in Fig. 14.18 (c) to (h), determine the arrangement of components between A, B and C.
Answer:
a) n-side of the PN junction is connected to the A terminals while B is connected to the top-side of PN junction.Question:39
Answer:
Question:40
In the circuit shown in Fig.14.20, find the value of RC.
Answer:
Let us consider the ciruit diagram to solve this problemThe topics and subtopics covered in this chapter are as follows:
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Semiconductors help in equipment control in a variety of fields, such as contributing to road safety by improving automobile efficiency, operating air conditioners, and smoothly changing temperature and in medical centres for laser treatments. In addition to this, semiconductor technology has successfully achieved efficient techniques of energy-saving, system efficiency, miniaturisation of global warming, which in turn helps to conserve the global environment and to live a safe and comfortable life. A popular semiconductor is silicon. It is an important component of the IC, which is an integrated circuit of transistors. Different types of transistors are used as fundamental working concepts behind logic gates, which in turn are used to draft and design electrical and digital circuits. The transistors in analogue circuits, which use semiconductors as a protagonist in building their structure, work as responders to a range of input and output. Some Analog circuits include amplifiers and oscillators. So Class 12 Physics solutions NCERT Exemplar chapter 14 is an important part of Class 12 curriculum
· The devices that use semiconductors have assembled a wide area of usage because of their reliability, compactness, accuracy, and power efficiency, with considerably cheaper costs. As individual operating components, they have found use in optical sensors, power devices, light emitters, and lasers.
· By using NCERT Exemplar Class 12 Physics solutions chapter 14, students will be able to demonstrate the movement of electrons and holes inside a semiconductor, study the idea of doping, the types of doping, the formation of diodes and their applications, and the setting up of LEDs' in a circuit.
· Through NCERT Exemplar Class 12 Physics chapter 14 solutions, we would learn about the materials used as semiconductors, common types of semiconductors used in a wide array of fields, their working principles, junction formats, transistors, and a variety of digital applications of the same.
Also read NCERT Solution subject wise
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Also Check NCERT Books and NCERT Syllabus here:
This chapter covers everything related to semiconductors like types, properties, junction transistors, diodes, logic gates, etc.
In NEET exam 2 to 3 questions are asked every year from the chapter Semiconductor Electronics. Mostly questions from both analog and digital electronics are included.
Students can get a better understanding of the concepts discussed in the chapter using NCERT Exemplar Solutions For Class 12 Physics Chapter 14, which in turn will be helpful for exams
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