NEET Physics: Logic Gates Practice Questions
14 free multiple-choice questions on Logic Gates for NEET Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more Logic Gates questions in the app →Q1. Which logic gate produces a HIGH output only if all its inputs are HIGH?
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Correct answer: C — AND
The AND gate requires all inputs to be true (HIGH) to produce a true (HIGH) output.
Q2. The expression (A AND B) is logically equivalent to which of the following operations?
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Correct answer: C — A NAND B
The expression (A AND B) is directly represented by the AND gate, and A NAND B is equivalent to NOT (A AND B).
Q3. The NAND gate is considered a universal gate because it can be used to construct which other gate?
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Correct answer: C — NOT gate
Any logic function (AND, OR, NOT) can be implemented using only NAND gates.
Q4. Which of the following gates is considered a universal gate?
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Correct answer: D — NAND
NAND and NOR gates are considered universal gates because any other logic function can be implemented using only NAND or only NOR gates.
Q5. Which logic gate is known as a universal gate because it can be used to implement any other logic function (AND, OR, NOT)?
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Correct answer: C — NAND
NAND and NOR gates are universal gates. Since NAND is a commonly cited universal gate, it is the correct answer.
Q6. A system requires a logic circuit that can detect if any one of its inputs is low (0). Which gate type is most efficiently used for this detection task across multiple inputs?
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Correct answer: C — NOR gate
The NOR gate is perfect for this task. If any input is 0, the output of the NOR gate becomes 1 (meaning the condition is met). This structure is fundamental for many multi-input detection schemes.
Q7. A system requires the output to be HIGH only if input P is HIGH OR input Q is HIGH. Which logic gate should be used to represent this condition?
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Correct answer: B — OR
The condition 'P is HIGH OR Q is HIGH' directly corresponds to the logical OR operation.
Q8. If an OR gate has inputs A=1 and B=1, what is the resulting output, and how does this relate to the NAND gate implementation?
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Correct answer: C — 0, equivalent to A OR B
For an OR gate, if inputs A=1 and B=1, the output is 1 (A OR B). The NAND gate operation (A AND B) followed by a NOT operation gives the same result as the OR gate (De Morgan's Law: (A+B)' = A' AND B').
Q9. A logic circuit uses an AND gate followed by a NOT gate. If the inputs are A and B, what is the simplified Boolean expression for the output of this combination?
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Correct answer: C — ô (A AND B)
The operation is (A AND B) then the result is inverted by NOT. This translates to NOT (A AND B), which is the definition of NAND operation.
Q10. Which of the following statements correctly describes the relationship between NAND and NOR gates?
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Correct answer: A — NAND gates are universal; any logic function can be implemented using only NAND gates.
Both NAND and NOR gates are universal gates, meaning any other logic function can be implemented using only NAND gates or only NOR gates.
Q11. In a 2-input NOR gate, if both inputs P and Q are HIGH (1), what is the output of the NOR gate?
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Correct answer: C — 0
The NOR operation (P OR Q) is 1, and NOR is the inverse of OR. P OR Q = 1. Therefore, NOR(1, 1) = 0.
Q12. A system requires an output that is HIGH only when input P is HIGH AND input Q is LOW. Which gate combination is required to implement this logic using only basic gates?
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Correct answer: C — P AND NOT Q
The required logic is P ∧ ¬Q. This is directly implemented by a NAND gate with inverted inputs (P and Q) or by using an AND gate with a NOT gate applied to Q. The expression P AND NOT Q is the direct implementation.
Q13. What is the simplified expression for the Boolean expression: (A NAND B) NAND (A NAND C)?
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Correct answer: B — A NAND B OR C
Using De Morgan's law and the property of NAND gate identity: (A' + B') NAND (A' + C') which simplifies to A' + (B' AND C'). Alternatively, using the property X NAND Y = (X AND Y)' and applying distribution rules simplifies this expression effectively to A NAND (B NAND C). Note: The expression is equivalent to A NAND (B NAND C).
Q14. If a circuit is constructed entirely using NOR gates, which of the following operations CANNOT be directly implemented using only NOR gates?
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Correct answer: D — XOR operation
NOR gates are functionally complete, meaning any Boolean function can be implemented. However, the XOR operation requires an additional gate or specific structure involving XOR gates themselves, as standard XOR operations cannot be directly derived solely from basic NOR gates without introducing additional gates or complex structures.
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