Q 12-14-215JEE MainJEE Main 2025 (7 Apr, Shift 2)Medium
Consider the logic circuit shown in the figure: A and B feed an AND gate; NOT A and B feed an OR gate; the outputs of the AND and OR gates feed a NAND gate whose output is Y. The output is $Y = 0$ when:
Answer: (A) $A = 1$ and $B = 1$
$Y_1 = A\cdot B$, $Y_2 = \overline A + B$, and $Y = \overline{Y_1\cdot Y_2}$.
A NAND gate gives 0 only when both its inputs are 1. $Y_1 = 1$ needs $A = B = 1$, and then $Y_2 = 0 + 1 = 1$ as well, so $Y = 0$.
For every other input $Y_1 = 0$, so $Y = 1$. Hence $Y = 0$ only for $A = 1$, $B = 1$.
Solution by Sreeraj P, M.Sc Physics