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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumDiagram reading

JEE Main 25 February 2021, Shift 2, Physics Q20

Question 20 of 90 in this shift, Physics question 20 of 30, Section A.

The truth table for the following logic circuit is :

The figure, in words

Logic circuit with inputs A (top) and B (bottom). A goes to the top AND gate directly and also through a NOT gate (inverter, drawn vertically) whose output crosses over to the bottom AND gate; B goes to the bottom AND gate directly and also through a NOT gate whose output crosses over to the top AND gate. The outputs of the two AND gates feed a single OR gate with a small circle (bubble) at its output, giving output Y. Options 1-4 are truth tables (A, B, Y).
  1. (1)[table with columns A, B, Y: A=0 B=0 Y=0; A=0 B=1 Y=1; A=1 B=0 Y=1; A=1 B=1 Y=0]
  2. (2)[table with columns A, B, Y: A=0 B=0 Y=1; A=0 B=1 Y=0; A=1 B=0 Y=0; A=1 B=1 Y=1]Official answer
  3. (3)[table with columns A, B, Y: A=0 B=0 Y=1; A=0 B=1 Y=0; A=1 B=0 Y=1; A=1 B=1 Y=0]
  4. (4)[table with columns A, B, Y: A=0 B=0 Y=0; A=0 B=1 Y=1; A=1 B=0 Y=0; A=1 B=1 Y=1]

Official answer

Option 2

NTA final key.

Chapter
Semiconductor Electronics: Materials, Devices and Simple Circuits
Topic
Logic Gates
Idea tested
Combinational Logic Circuits

Same idea in other shifts

Asked 31× in all
  1. 2 Apr 2026, Shift 2 · Q30If X and Y are the inputs, the given circuit works asMediumDiagram basedHas a figure
  2. 4 Apr 2026, Shift 1 · Q38Two 44 bits binary numbers, A=1101A=1101 and B=1010B=1010 are given in the inputs of a logic circuit shown in figure below. The output (YY) will…EasyDiagram basedHas a figure
  3. 5 Apr 2026, Shift 1 · Q45For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow?EasyDiagram basedHas a figure
  4. 6 Apr 2026, Shift 2 · Q43Refer to the logic circuit given below. For two inputs (A=1A=1, B=1B=1) and (A=0A=0, B=1B=1), output (YY) will be __________.EasyDiagram basedHas a figure
  5. 2 Apr 2025, Shift 2 · Q39In the digital circuit shown in the figure, for the given inputs the P and Q values are :MediumDiagram basedHas a figure
  6. 3 Apr 2025, Shift 1 · Q45Choose the correct logic circuit for the given truth table having inputs A and B. Inputs A, B / Output Y: A=0,B=0: Y=0 A=0,B=1: Y=0…MediumDiagram basedHas a figure
  7. 3 Apr 2025, Shift 2 · Q45The truth table corresponding to the circuit given below is :EasyDiagram basedHas a figure
  8. 7 Apr 2025, Shift 2 · Q45Consider the following logic circuit. The output is Y=0Y=0 when :EasyDiagram basedHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.