Given below are two statements: Statement I: An n-type semiconductor carries a net negative charge. Statement II: In a p-type semiconductor, electrons are the majority carriers. Choose the correct answer.

Both Statement I and Statement II are incorrect

Both Statement I and Statement II are correct

Statement I is incorrect but Statement II is correct

Statement I is correct but Statement II is incorrect

Inputs A and B feed a NOR gate. The NOR output and input A then feed a NAND gate, whose output is Y. How does Y behave?

Y is 1 for every input combination

Y is 0 for every input combination

Semiconductor Electronics

11 NEET-UG practice questions on Semiconductor Electronics, part of Physics. The first 11 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Match List-I with List-II. List-I (behaviour of a two-input gate) A. Output is 1 only when both inputs are 1 B. Output is 0 only when both inputs are 0 C. Output is 0 only when both inputs are 1 D. Output is 1 only when both inputs are 0 List-II (gate) I. OR II. NOR III. AND IV. NAND
1. AA-I, B-III, C-II, D-IV
2. BA-III, B-II, C-IV, D-I
3. CA-III, B-I, C-IV, D-II
4. DA-IV, B-I, C-III, D-II
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Answer: C · A-III, B-I, C-IV, D-II
AND is 1 only for inputs 11, and OR is 0 only for inputs 00. NAND inverts AND, so it is 0 only for 11, and NOR inverts OR, so it is 1 only for 00.
- A: AND and OR tables are interchanged, and so are NAND and NOR.
- B: The OR and NOR outputs have been interchanged.
- D: The AND and NAND outputs have been interchanged.
Remember this
NAND inverts AND and NOR inverts OR, so each pair of truth tables is complementary row by row.
Question 2 · Medium
A silicon diode with a forward drop of 0.7 V is connected in forward bias in series with a 430 Ω resistor and a 5 V battery. What is the current in the circuit?
1. A11.6 mA
2. B10 mA
3. C0 mA
4. D13.3 mA
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Answer: B · 10 mA
The resistor takes 5 - 0.7 = 4.3 V, so I = 4.3/430 = 0.01 A = 10 mA.
- A: The diode's 0.7 V drop was ignored.
- C: This treats the diode as if reverse biased.
- D: The drop was added to the battery voltage.
Remember this
Subtract the diode's forward drop from the battery voltage before applying Ohm's law to the resistor.
Question 3 · Medium
A voltage regulator uses a 20 V source, a 200 Ω series resistor and an 8 V Zener diode, with a 1 kΩ load across the Zener. The Zener is in breakdown. What current flows through the Zener?
1. A52 mA
2. B68 mA
3. C60 mA
4. D8 mA
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Answer: A · 52 mA
The series resistor takes 20 - 8 = 12 V, so its current is 12/200 = 60 mA. The load takes 8/1000 = 8 mA. The Zener carries the rest, 60 - 8 = 52 mA.
- B: The load current was added to the series current.
- C: This is the series current, without subtracting the load current.
- D: This is the load current, not the Zener current.
Remember this
Series current divides between Zener and load, and the load voltage stays fixed at the Zener voltage.
Question 4 · Medium
Given below are two statements: Statement I: An n-type semiconductor carries a net negative charge. Statement II: In a p-type semiconductor, electrons are the majority carriers. Choose the correct answer.
1. ABoth Statement I and Statement II are correct
2. BBoth Statement I and Statement II are incorrect
3. CStatement I is incorrect but Statement II is correct
4. DStatement I is correct but Statement II is incorrect
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Answer: B · Both Statement I and Statement II are incorrect
Dopant atoms are electrically neutral, so a doped crystal stays neutral overall, and I is wrong. In p-type material, the trivalent dopant creates holes, which are the majority carriers, so II is wrong.
- A: Doped crystals remain neutral, and holes are the majority carriers in p-type.
- C: Holes are the majority carriers in p-type, so II is wrong.
- D: The crystal stays neutral, so I is wrong.
Remember this
Doping changes carrier numbers, not overall charge; electrons are majority in n-type, holes in p-type.
Question 5 · Hard
Inputs A and B feed a NOR gate. The NOR output and input A then feed a NAND gate, whose output is Y. How does Y behave?
1. AY is the same as A NAND B
2. BY is the same as A OR B
3. CY is 0 for every input combination
4. DY is 1 for every input combination
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Answer: D · Y is 1 for every input combination
If A = 0, the NAND gate has a 0 input, so Y = 1. If A = 1, the NOR output is 0, so the NAND gate again has a 0 input and Y = 1. Thus the NAND inputs are never both 1. Check with AB = 11: NOR gives 0, NAND(1, 0) = 1.
- A: For AB = 11, A NAND B is 0, but Y is 1.
- B: For AB = 00, A OR B is 0, but Y is 1.
- C: This would need both NAND inputs to be 1 every time.
Remember this
A NAND gate gives 0 only when all inputs are 1, so test whether that state can occur.
Question 6 · Easy
A p-n junction diode is forward biased. What happens to its depletion region and barrier height?
1. AThe depletion width increases and the barrier height decreases
2. BThe depletion width and the barrier height both decrease
3. CThe depletion width and the barrier height both increase
4. DThe depletion width decreases and the barrier height increases
Answer and explanation in LearnFree account
Question 7 · Easy
A full-wave rectifier is fed from a 50 Hz ac supply. What is the fundamental frequency of the ripple in its output?
1. A50 Hz
2. B200 Hz
3. C100 Hz
4. D25 Hz
Answer and explanation in LearnFree account
Question 8 · Medium
Given below are two statements about the circuit drawn, with a p-n junction connected to a cell: Statement I: The depletion layer here is wider than in the same junction with no cell connected. Statement II: The very small current in this circuit, below breakdown, is mainly due to minority carriers. Choose the correct answer.
Figure: MedExams
1. ABoth Statement I and Statement II are incorrect
2. BStatement I is correct but Statement II is incorrect
3. CStatement I is incorrect but Statement II is correct
4. DBoth Statement I and Statement II are correct
Answer and explanation in LearnFree account
Question 9 · Medium
Match List-I with List-II. List-I (circuit in the figure, with output Z) A. Circuit A B. Circuit B C. Circuit C D. Circuit D List-II (equivalent gate) I. OR II. NOT III. NOR IV. AND
Figure: MedExams
1. AA-IV, B-I, C-II, D-III
2. BA-I, B-IV, C-II, D-III
3. CA-IV, B-III, C-II, D-I
4. DA-II, B-I, C-IV, D-III
Answer and explanation in LearnFree account
Question 10 · Easy
An ideal full-wave rectifier is fed with a 50 Hz sine wave. Which graph shows its output voltage over 40 ms?
Figure: MedExams
1. AGraph C
2. BGraph A
3. CGraph B
4. DGraph D
Answer and explanation in LearnFree account
Question 11 · Hard
A Zener diode of the rating marked regulates the voltage across a load in the circuit shown, fed by an ideal cell. How much power does the Zener dissipate?
Figure: MedExams
1. A0.8 W
2. B0.4 W
3. C0.1 W
4. D0.5 W
Answer and explanation in LearnFree account

Semiconductor Electronics

Match List-I with List-II. List-I (behaviour of a two-input gate) A. Output is 1 only when both inputs are 1 B. Output is 0 only when both inputs are 0 C. Output is 0 only when both inputs are 1 D. Output is 1 only when both inputs are 0 List-II (gate) I. OR II. NOR III. AND IV. NAND

A silicon diode with a forward drop of 0.7 V is connected in forward bias in series with a 430 Ω resistor and a 5 V battery. What is the current in the circuit?

A voltage regulator uses a 20 V source, a 200 Ω series resistor and an 8 V Zener diode, with a 1 kΩ load across the Zener. The Zener is in breakdown. What current flows through the Zener?

Given below are two statements: Statement I: An n-type semiconductor carries a net negative charge. Statement II: In a p-type semiconductor, electrons are the majority carriers. Choose the correct answer.

Inputs A and B feed a NOR gate. The NOR output and input A then feed a NAND gate, whose output is Y. How does Y behave?

A p-n junction diode is forward biased. What happens to its depletion region and barrier height?

A full-wave rectifier is fed from a 50 Hz ac supply. What is the fundamental frequency of the ripple in its output?

Match List-I with List-II. List-I (circuit in the figure, with output Z) A. Circuit A B. Circuit B C. Circuit C D. Circuit D List-II (equivalent gate) I. OR II. NOT III. NOR IV. AND

An ideal full-wave rectifier is fed with a 50 Hz sine wave. Which graph shows its output voltage over 40 ms?

A Zener diode of the rating marked regulates the voltage across a load in the circuit shown, fed by an ideal cell. How much power does the Zener dissipate?