Semiconductor Electronics is a high-scoring and application-based chapter in Class 12 Physics that explains the working of electronic materials and devices used in everyday technology. This chapter covers important topics such as energy bands, intrinsic and extrinsic semiconductors, p–n junction diode, Zener diode, rectifiers, transistors, logic gates, and simple electronic circuits, which are frequently asked in CBSE board exams and competitive exams like JEE and NEET.
NCERT Solutions for Class 12 Physics Chapter 14 – Semiconductor Electronics are prepared strictly according to the latest CBSE syllabus and exam pattern. The solutions are written in simple, clear, and exam-oriented language with well-labelled diagrams, circuit symbols, and step-by-step explanations, helping students understand electronics concepts easily and score well in board examinations.
NCERT Solutions for Class 12 Physics Chapter 14 – Semiconductor Electronics: Materials, Devices and Simple Circuits
Q.
In n-type silicon, which of the following statement is true:
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are dopants.
Q.
Which of the statement given is true for p-type semiconductors?
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are dopants.
Q.
Carbon, silicon and germanium have four valence electrons each. These are characterized 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?
Q.
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 the above.
Q.
When a forward bias is applied to a p-n junction, it
(a) raises the potential barrier.
(b) reduces the majority carrier current to zero.
(c) lowers the potential barrier.
(d) None of the above.
Q.
In half-wave rectification, what is the output frequency if the input frequency is 50 Hz. What is the output frequency of a full-wave rectifier for the same input frequency?
Q.
A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm?
Q.
The number of silicon atoms per m3 is 5 × 1028. This is doped simultaneously with 5 × 1022 atoms per m3 of Arsenic and 5 × 1020 per m3 atoms of Indium. Calculate the number of electrons and holes. Given that ni = 1.5 × 1016 m-3. Is the material n-type or p-type?
Q.
In an intrinsic semiconductor the energy gap Eg is 1.2 eV. Its hole mobility is much smaller than electron mobility and independent of temperature. What is the ratio between conductivity at 600 K and that at 300 K? Assume that the temperature dependence of intrinsic carrier concentration ni is given by
where n0 is a constant.
Q.
In a p-n junction diode, the current I can be expressed as
where I
0 is called reverse saturation current. V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, k
B is the Boltzmann constant 8.62 × 10
-5 eV/K and T is the absolute temperature. If for a given diode I
0 = 5 × 10
-12 A and T = 300 K, then
(a) What will be the forward current at forward voltage of 0.6 V?
(b) What will be the increase in the current if voltage across the diode is increased to 0.7 V?
(c) What is the dynamic resistance?
(d) What will be the current if reverse bias voltage changes from 1 V to 2 V?
Q.
You are given the two circuits as shown in Fig. 14.36. Show that circuit (a) acts as OR gate while the circuit (b) acts as AND gate.
Q.
Write the truth table for a NAND gate connected as given in Fig. 14.37.
Hence identify the exact logic operation carried out by this circuit
Q.
You are given two circuits as shown in figure, which consist of NAND gates. Identify the logic operation carried out by the two circuits.
Q.
Write the truth table for circuit given in figure 14.39 below consisting of NOR gates and identify the logic operation (OR, AND, NOT) which this circuit is performing.
(Hint: A = 0, B = 1 then A and B inputs of second NOR gate will be 0 and hence Y = 1. Similarly work out the values of Y for other combinations of A and B. Compare with the truth table of OR, AND, NOT gates and find the correct one.)
Q.
Write the truth table for the circuits given in the figure 14.40, consisting of NOR gates only. Identify the logic operations (OR, AND, NOT) performed by the two circuits.
NCERT Solutions for Class 12 Physics Chapter 14 – Semiconductor Electronics: Materials, Devices and Simple Circuits
Q. 1) In n-type silicon, which of the following statement is true?
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are dopants.
Ans: (c)
Q. 2) Which statement is true for p-type semiconductors?
(a) Electrons are majority carriers and trivalent atoms are the dopants.
(b) Electrons are minority carriers and pentavalent atoms are the dopants.
(c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are dopants.
Ans: (d)
Q. 3) In an unbiased p–n junction, holes diffuse from p-region to n-region because
Ans: (c) hole concentration in p-region is more as compared to n-region.
Q. 4) When a forward bias is applied to a p–n junction, it
Ans: (c) lowers the potential barrier.
Q. 5) Output frequency of rectifiers
Ans:
Half wave rectifier → 50 Hz
Full wave rectifier → 100 Hz
Note: Q&A containing MathML or Latex or Katex code cannot be rendered in pdf document.
FAQs: Class 12 Physics Chapter 14 – Semiconductor Electronics
Q1. Is Semiconductor Electronics important for exams?
Yes, it is a high-weightage and scoring chapter for CBSE and competitive exams.
Q2. Which topics are most important in this chapter?
p–n junction diode, rectifiers, transistors, and logic gates.
Q3. Are numericals asked from this chapter?
Yes, diode and transistor-based numericals are common.
Q4. Are diagrams important in this chapter?
Yes, circuit diagrams and logic gate symbols are frequently asked.
Q5. How do NCERT Solutions help?
They provide NCERT-aligned, exam-ready explanations with diagrams and solved questions.