Identify the logic operation carried out by the following circuit.

The correct answer is Option (4) → OR

A NAND gate with its two inputs joined gives \( Y = \overline{A\cdot A} = \overline{A} \), so it acts as a NOT gate. Each of the two input gates therefore gives the complement of its input, and these feed the last NAND gate.

    \( Y_1 = \overline{A},\quad Y_2 = \overline{B} \)

    \( Y = \overline{Y_1\cdot Y_2} = \overline{\overline{A}\cdot\overline{B}} \)

By De Morgan's theorem, \( \overline{P\cdot Q} = \overline{P} + \overline{Q} \):

    \( Y = \overline{\overline{A}} + \overline{\overline{B}} = A + B \)

This is the OR operation.

Note: A similar question was also asked in CUET (UG) 2022 on 23-08-2022 (Slot 1).

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Additional Exercises – …