Semiconductor Electronics: Class 12 Previous Year Questions

Semiconductor Electronics questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. When a p-n junction diode is forward biased (A) the barrier height and the depletion layer width both increase. (B) the barrier height increases and the depletion layer width decreases. (C) the barrier height and the depletionlayer widthboth decrease. (D) the …
   Board 20251 markAssertion-ReasonRepeated: 2024,2025
2. When a p-n junction diode is subjected to reverse biasing : (A) the barrier height decreases and the depletion region widens. (B) the barrier height increases and the depletion region widens. (C) the barrier height decreases and the depletion region shrinks. (…
   Board 20241 markAssertion-ReasonRepeated: 2024,2025
3. With the help of a circuit diagram, explain the working of a p-n junction diode as a full wave rectifier. Draw its input and output waveforms.
   Board 20243 marksshort answerRepeated: 2022,2024
4. In an unbiased p-n junction, at equilibrium, which of the following statements is true ? 1 (A) Diffusion current is zero but drift current exists. (B) Diffusion current exists but drift current is zero. (C) Diffusion and drift currents are equal and opposite. …
   Board 20261 markAssertion-Reason
5.  11. Two heaters rated as (P1, V) and (P2, V) are connected in series across a dc source of V 2 volt. The power consumed by the combination will be – 1 (A) (P1 + P2) (B) P1 + P2 2 (C) P1 P2 2(P1 + P2) (D) P1 P2 4(P1 + P2) { } 10  12.     p-n …
   Board 20261 markMCQ
6.  26. Briefly explain the two important processes that occur during the formation of a p-n junction. 3 { } 18  27. (a)          -                (…
   Board 20263 marksshort answer
7. SECTION – B 17. Write two points of difference between intrinsic and extrinsic semiconductors.
   Board 20262 marksshort answer
8. Assertion (A) : On forward biasing a p-n junction diode, the height of the barrier potential increases. 1 Reason (R) : In forward biasing of a p-n junction diode, the direction of the applied voltage is in the same direction as the built-in potential.
   Board 20261 markAssertion-Reason
9.  27. (a) Explain the statement : “Current is a scalar although we represent current with an arrow”. 3 (b) Use Kirchhoff’s rules to find the current through 3  resistor in the circuit shown in the figure : { } 16  28.  r   N     …
   Board 20263 marksshort answer
10.  g p g p q 29. A p-type or n-type semiconductor can be converted into a p-n junction by doping it with suitable impurity. The motion of majority charge carriers causes diffusion current across the junction while the barrier electric field causes motion of min…
    Board 20264 markscase-based
11. An ac voltage Vi = 12 sin (100 t)V is applied between points A and B in a network of two ideal diodes and three resistors as shown in figure. During the positive half-cycle of the input voltage Vi supplied to the network. 3 (a) Identify which of the two diode…
    Board 20263 marksshort answer
12. When the resistance measured between p and n ends of a p-n junction diode is high, it can act as a/an - (B) (A) resistor inductor (C) capacitor (D) switch For Questions 13 to 16, two statements are given - one labelled Assertion (A) and other labelled Reason (…
    Board 20251 markAssertion-Reason
13. (a) Draw circuit arrangement for studying V-I characteristics of a p-n junction diode. (b) Show the shape of the characteristics of a diode. (c) Mention two information that you can get from these characteristics.
    Board 20253 marksshort answer
14. ( ) p q gy p gy 28. (a) semiconductor ? (b) A p-n junction is forward biased. Describe the movement of the charge carriers which produce current in it. (c) The graph shows the variation of current with voltage for a p-n junction diode. I (mA) 30- 20- Reverse F…
    Board 20253 marksshort answer
15. A p-type Si semiconductor is made by doping an average of one dopant atom per 5 × 1o7 silicon atoms. If the number density of silicon atoms in the specimen is 5 × 1028 atoms m-3, find the number of holes created per cubic centimetre in the specimen due to dopi…
    Board 20252 marksshort answer
16. The threshold voltage of a silicon diode is O.7 V. It is operated at this point by connecting the diode in series with a battery of V volt and a resistor of 1000 Q. Find the value of V when the current drawn is 15 mA.
    Board 20252 marksshort answer
17. A beaker is filled with water (refractive index upto a height H. A coin is placed at its bottom. The depth of the coin, when viewed along the near normal direction, will be 3H (A) (B) 4H (C) (D)
    Board 20251 markMCQ
18. Assertion (A) : It is difficult to move a magnet into a coil of large number of turns when the circuit of the coil is closed. Reason (R) : The direction of induced current in a coil with its circuit closed, due to motion of a magnet, is such that it opposes th…
    Board 20251 markAssertion-Reason
19. Assertion (A) : We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of a n-type semiconductor. Reason (R) : In a p-type semiconductor ne >> nn while in a n-type semiconductor nn >> ne
    Board 20251 markAssertion-Reason
20. A tub is filled with a transparent liquid to a height of 30.0 cm. The apparent depth of a coin lying at the bottom of the tub is found to be 16.0 cm. The speed of light in the liquid will be (A) 1.6 × 108 m s-1 (B) 2.0 × 108 m s-1 (C) 3.0 × 108 m s-1 (D) 2.5 ×…
    Board 20251 markMCQ

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