Question

The circuit diagram shown here corresponds to the logic gate

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

Answer 1

The correct option is C

NOR Gate

Explanation for correct option:

In case of option C

1. A NOR gate is a digital logic gate that gives output $0$ if any one of its inputs are $1$, otherwise gives the output $1$.
2. From the circuit diagram, $A$ and $B$ can have two outputs that are either $0$ or $1$. For the LED bulb to glow the current must flow through the circuit in the LED bulb, otherwise, the bulb will be off.
3. When the input in $A$ is $0$ and $B$ is $0$, current will flow towards the LED and it will glow.
4. When the input in $A$ is $1$ and $B$ is $0$, current will flow through $A$ and will be grounded, no current will go towards LED and it won't glow.
5. When the input in $A$ is $0$ and $B$ is $1$, no current will flow through $A$ but will go towards $B$ and eventually be grounded, no current will go towards LED and it won't glow.
6. When the input in $A$ is $1$ and $B$ is $1$, all the current will flow towards $A$ and then $B$ and eventually be grounded, no current will go towards LED and it won't glow.
7. Given below is the truth table for the circuit. And it can easily be observed that it is NOR gate.

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	0

Explanation for incorrect option:

In the case of option A

1. An AND gate is a digital logic gate that gives output $0$ if any one of its inputs are $0$, otherwise gives the output $1$.
2. From the truth table, it is clear that it is not AND gate.
3. Thus, this option is incorrect.

In the case of option B

1. An OR gate is a digital logic gate that gives output $1$ if at least any one of its inputs is $1$, otherwise gives the output $0$.
2. From the truth table, it is clear that it is not an OR gate.
3. Thus, this option is incorrect.

In the case of option D

1. An NAND gate is a digital logic gate that gives output $0$ only when both the inputs are $1$, otherwise gives the output $1$.
2. From the truth table, it is clear that it is not NAND gate.
3. Thus, this option is incorrect.

Hence, option C is correct.