Bihar Board - Class 12 Physics - Chapter 14: Semiconductor Electronics Short Answer Question
For Class 12 Bihar Board, the chapter Semiconductor Electronics in Physics covers the properties and applications of semiconductors and also including the working of diodes, transistors, and other semiconductor devices. You can find short-question answers that provide a clear understanding of these important concepts, aiding in better preparation for your exams on Vidyakul.
Short Answer Type Question
1. State the reason why GaAs is most commonly used in making of a solar cell.
Answer:
GaAs is most commonly used in making of a solar cell because :
(i) It has high optical absorption (~ 104 cm-1) .
(ii) It has high electrical conductivity.
2. Why should a photodiode be operated at a reverse bias?
Answer:
As fractional change in minority charge carriers is more than the fractional change in majority charge carriers, the variation in reverse saturation current is more prominent.
3. Give the logic symbol of NOR gate.
Answer:
4. Give the logic symbol of NAND gate.
Answer:
5. Give the logic symbol of AND gate.
Answer:
6. In a transistor, doping level in base is increased slightly. How will it affect
(i) collector current and
(ii) base current?
Answer:
Increasing base doping level will decrease base resistance and hence increasing base current, which results in a decrease in collector current.
7. What happens to the width of depletion layer of a p-n junction when it is
(i) forward biased,
(ii) reverse biased?
Answer:
(i) In forward biased, the width of the depletion layer of a p-n junction decreases.
(ii) In reverse biased, the width of depletion layer of a p-n junction increases
8. How does the depletion region of a p-n junction diode get affected under reverse bias?
Answer:
Depletion region widens under reverse bias.
9. How does the width of the depletion region of a p-n junction diode change under forward bias?
Answer:
The width of depletion region of a p-n junction
10. Write the truth table for a NAND gate as shown in the figure.
Answer:
Truth table for NAND gate:
11. What is the function of a photodiode?
Answer:
A photodiode is a special purpose p-n junction diode fabricated with a transparent window to allow light to fall on the diode. It is operated under reverse bias.
12. Write the truth table for a NOT gate connected A as shown in the figure.
Answer:
Truth Table
13. Write the truth table of a two point input NAND gate.
Answer:
14. Show variation of resistivity of Si with temperature in a graph.
Answer:
15. Plot a graph showing variation of current versus voltage for the material GaAs.
Answer:
A Graph showing variation of current versus voltage for GaAs
16. Draw the logic symbol of the NAND gate and give its Truth Table.
Answer:
17. Identify the logic gate whose output equals 1 when both of its inputs are 0 each.
Answer:
NAND gate or NOR gate.
18. If the output of a 2 input NOR gate is fed as both inputs A and B to another NOR gate, write down a truth table to find the final output, for all combinations of A, B.
Answer:
The truth table is:
19. The current in the forward bias is known to be more (~mA) than the current in the reverse bias (~µA). What is the reason, then, to operate the photodiode in reverse bias?
Answer:
The fractional increase in majority carriers is much less than the fractional increase in minority carriers. Consequently, the fractional change due to the photo-effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the majority carrier dominated forward bias current.
20. In the circuit shown in the figure, identify the equivalent gate of the circuit and make its truth table.
Answer:
Truth table of AND Gate :
21. In the circuit shown in the figure, identify the equivalent gate of the circuit and make its truth table.
Answer:
22. Assuming that the two diodes Dj and D2 used in the electric circuit shown in the figure are ideal, find out the value of the current flowing through 1Ω resistor.
Answer:
Since the diodes used are ideal, the diode Dj in forward bias will conduct the current in forward direction, while diode D2 in reverse bias will not allow any current to flow.
As such, 2Ωwith D1 and 1Ω are in series, the net resistance of the circuit will be
Hence the value of the current flowing through 1Ω resistor = 2A
23. Assuming that the two diodes D1 and D2 used in the electric circuit shown in the figure are ideal, find out the value of the current flowing through 2.5 Ω resistor.
Answer:
Value of the current flowing through 2.5 Ω resistor = 2.5 A
24. Write the truth table for the combination of the gates shown. Name the gates used.
Answer:
R gate = OR
S gate = AND
25. Identify the logic gates marked ‘P’ and ‘Q’ in the A given circuit. Write the B truth table for the combination.
Answer:
P gate = NAND
Q gate = OR
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