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Q.12 Physics · Section A ⭐ 360° Option Elimination Active
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NEET 2024 Physics Question 12 Solution

Topic: Semiconductor Electronics · Official NTA Booklet Code T1
NEET 2024 Physics Question 12: Deriving Boolean Expression from a Truth Table

Question

A logic circuit provides the output Y as per the following truth table. The expression for the output Y is:

✓
Verified Against NTA Final Answer Key
Option (1) : B̄
📚 Semiconductor Electronics Easy
📋 Given Parameters & Problem Setup
Input A 0, 0, 1, 1
Input B 0, 1, 0, 1
Output Y 1, 0, 1, 0
⚡

The 30-Second Exam Hall Shortcut: ⚡ Independent Variable Inspection

⏱️ Save ~40 seconds

Notice Y is 1 when B=0, and Y is 0 when B=1 regardless of A -> Y = NOT(B) = B̄!

1 Inspect Row 1 and Row 3: When B = 0, Y = 1 (both for A=0 and A=1).
2 Inspect Row 2 and Row 4: When B = 1, Y = 0 (both for A=0 and A=1).
3 Output Y depends ONLY on input B, and is always the inverse of B.
4 Therefore, Y = B̄.
5 Option (1) in 3 seconds!
🛡️
Why You Can 100% Trust This Shortcut: Boolean Algebra Principles & Truth Table Analysis.
📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Tabulation and Pattern Analysis

Examine the given truth table row by row: - Row 1: A = 0, B = 0 -> Y = 1 - Row 2: A = 0, B = 1 -> Y = 0 - Row 3: A = 1, B = 0 -> Y = 1 - Row 4: A = 1, B = 1 -> Y = 0

Y(A,B)=B‾Y(A, B) = \overline{B}
Step 2

Sum-of-Products (SOP) Formulation

Writing the canonical minterms for the rows where the output Y is 1 (Row 1 and Row 3):

Y=A‾B‾+AB‾Y = \overline{A}\overline{B} + A\overline{B}
Step 3

Boolean Factoring and Simplification

Factor out the common term B̄ using the distributive law:

Y=B‾(A‾+A)=B‾(1)=B‾Y = \overline{B}(\overline{A} + A) = \overline{B}(1) = \overline{B}
⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan
1 (1)
✓ 100% Correct
Verdict & Scientific Reason:

Rigorous SOP Boolean reduction confirms Y = B̄.

💡
Why this is airtight: None.
2 (2)
✗ Incorrect
Verdict & Scientific Reason:

Inverts the output; when B=0, Y=1, not 0.

⚠️
Student Fallacy (Why candidates pick this trap): Assuming direct proportionality instead of inversion.
3 (3)
✗ Incorrect
Verdict & Scientific Reason:

For A=1, B=1, this expression gives 1 · 1 + 0 = 1, but truth table specifies Y=0.

⚠️
Student Fallacy (Why candidates pick this trap): Attempting algebraic expansion without verifying all truth table rows.
4 (4)
✗ Incorrect
Verdict & Scientific Reason:

For A=0, B=1, this expression gives 0 · 0 + 1 = 1, whereas the truth table gives Y=0.

⚠️
Student Fallacy (Why candidates pick this trap): Guessing multi-variable expressions.
⚠️

NTA Trap Alert: Over-Complicating with Both Variables

Students spend time setting up complex Karnaugh maps without noticing that A is a "don’t care" redundant variable.

🛡️ How to avoid the -1 mark: Always compare the output column directly against individual input columns first!
📖

Core NEET Syllabus Standard

Physics Core Digital Electronics · Semiconductor Electronics: Materials, Devices and Simple Circuits Standard Benchmark
Core Scientific Principle Tested:

"When an output is high whenever a specific input is low and vice-versa regardless of other inputs, the function reduces to the single-variable NOT operation (Y = X̄)."

Syllabus Focus: Boolean Algebra and Logic Functions
✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗
A changes but Y ignores; Y is NOT B and nothing more!

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