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Logic Gates

Practice Questions:

Question 1: 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

View Answer

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 2: 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

View Answer

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 3: 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

View Answer

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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