Question

When the output of an OR gate is applied as input to a NOT gate, then the combination acts as a

• A. NAND gate
• B. NOR gate
• C. AND gate
• D. OR gate

Answer 1

The Correct Option is B

The given question describes a combination of logic gates and asks what kind of gate is formed when the output of an OR gate is fed into a NOT gate. Let's break down the operation step-by-step:

1. Understand the Operation of an OR Gate:
   • An OR gate outputs a high signal (1) if at least one of its inputs is high (1).
   • The truth table for a two-input OR gate is as follows:

Input A	Input B	Output (A OR B)
0	0	0
0	1	1
1	0	1
1	1	1

1. Understand the Operation of a NOT Gate:
   • A NOT gate, or inverter, outputs the opposite of its input. 
   • If the input is high (1), the output will be low (0), and vice versa.
2. Combining the OR Gate and NOT Gate:
   • The output of the OR gate is fed into the NOT gate. This combination is equivalent to a NOR gate.
   • The truth table for a NOR gate can be derived by inverting the output of the OR gate:

Input A	Input B	Output (A OR B)'
0	0	1
0	1	0
1	0	0
1	1	0

The truth table shows that the output is high only when both inputs are low, which defines a NOR gate. Hence, when the output of an OR gate is connected to the input of a NOT gate, the combination acts as a NOR gate.