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Logic Gates

Practice Questions:

Question 1: easy

Which of the gates is represented by above?

1. AND

2. NAND

3. OR

4. NOR

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Question 2: easy

In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table :

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Question 3: easy

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): A digital circuit that follows logical relationship between the input and output voltages are generally known as logic gates.

Reason (R): NOR and NAND gates are not considered as universal gates.

In the light of above statements, choose the correct answer from the options given below.

1. Both (A) and (R) are true and (R) is the correct explanation of (A)

2. Both (A) and (R) are true but (R) is not the correct explanation of (A)

3. (A) is true but (R) is false

4. Both (A) and (R) are false

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Assertion is true because logic gates process signals based on logical relationships. Reason is false because NAND and NOR gates can implement any Boolean function, meaning they are universal gates.

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Question 4: easy

Assertion (A): In an OR gate if any of the input is high the output is high.

Reason (R): OR gate is the basic gate.

1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)

2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

3. (A) is true but (R) is false

4. Both (A) and (R) are false

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Assertion (A) is the fundamental definition of an OR gate, which is true. Reason (R) is also true as an OR gate is a basic logic gate. However, (R) does not explain the functional behavior of the OR gate described in (A).

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Question 5: easy

Assertion (A): In an oscillator, the feedback is in the same phase which is called as positive feedback.

Reason (R): If the feedback voltage is in opposite phase the gain is greater than one.

1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)

2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

3. (A) is true but (R) is false

4. Both (A) and (R) are false

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Assertion (A) is true; for sustained oscillations, positive feedback (in-phase) is required. Reason (R) is false; opposite phase feedback, known as negative feedback, typically reduces the amplifier's gain, not increases it.

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Question 6: easy

Assertion (A): A NAND gate can be obtained by using NOR gates.

Reason (R): NOR, NAND and XOR gates are called universal gates.

1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)

2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

3. (A) is true but (R) is false

4. Both (A) and (R) are false

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NAND and NOR gates are universal gates, meaning any other logic gate (including NAND) can be constructed using only NOR gates. Hence, Assertion (A) is true. However, while NAND and NOR are universal gates, XOR is not. Therefore, Reason (R) is false.

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