JEE Physics 2025 Question with Solution

Given: A logic circuit with inputs $A$ and $B$, intermediate NOT and AND gates, an unknown gate $G$, and a truth table for output $Y$.

Find: Which logic gate must be placed at $G$ to obtain the given truth table.

Step 1: Analyze the circuit structure.

• The circuit consists of two NOT gates applied to $A$ and $B$, followed by two AND gates whose outputs feed into gate $G$.
• From the given truth table, $Y$ is high for $(A,B)=(0,0)$ and $(1,1)$, but low otherwise.

Step 2: Identify the logical expression. Observing the output pattern, the solution identifies the output as

Step 3: Match with the gate. The gate that gives

is the NOR gate.

Therefore, the correct option is C.

Given: The unknown gate $G$ must produce the shown output truth table.

Find: The name of the gate at $G$.

Step 1: Recall the behavior of a NOR gate. A NOR gate gives output $1$ only when all inputs are $0$. Otherwise, the output is $0$.

Step 2: Compare with the standard NOR truth table:

• $A=0, B=0 \Rightarrow Y=1$
• $A=0, B=1 \Rightarrow Y=0$
• $A=1, B=0 \Rightarrow Y=0$
• $A=1, B=1 \Rightarrow Y=0$

This matches the NOR pattern stated in the solution approach.

Therefore, the required gate is the NOR Gate, so the correct option is C.