In ECET 2026, the Digital Electronics subject is one of the most scoring areas for CSE students. Boolean Algebra & Logic Gates are core concepts that appear in almost every paper, often as direct and formula-based questions. Mastering this topic not only improves your accuracy but also boosts your confidence in solving logic-based problems quickly. Let’s understand the basics, followed by 10 practice MCQs.
📘 Concept Notes – Boolean Algebra & Logic Gates
🧮 Boolean Algebra
- Developed by George Boole.
- Deals with binary variables (0 and 1).
- Logical operations: AND, OR, NOT.
- Follows certain laws and theorems to simplify expressions.
📏 Basic Laws of Boolean Algebra
- Identity Law:
- A + 0 = A
- A · 1 = A
- Null Law:
- A + 1 = 1
- A · 0 = 0
- Idempotent Law:
- A + A = A
- A · A = A
- Complement Law:
- A + A’ = 1
- A · A’ = 0
- Double Negation:
- (A’)’ = A
🔌 Logic Gates
Logic gates perform logical operations on binary inputs.
1. AND Gate
- Output is 1 only if all inputs are 1.
- Boolean: Y = A · B
2. OR Gate
- Output is 1 if any input is 1.
- Boolean: Y = A + B
3. NOT Gate
- Output is opposite of input.
- Boolean: Y = A’
4. NAND Gate
- Output is NOT of AND result.
- Boolean: Y = (A · B)’
5. NOR Gate
- Output is NOT of OR result.
- Boolean: Y = (A + B)’
6. XOR Gate
- Output is 1 if inputs are different.
- Boolean: Y = A ⊕ B
7. XNOR Gate
- Output is 1 if inputs are same.
- Boolean: Y = (A ⊕ B)’
💡 Truth Table Example – AND Gate
| A | B | Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
🔟 10 Most Expected MCQs – ECET 2026 [Boolean Algebra & Logic Gates]
Q1. Who is known as the father of Boolean Algebra?
A) Isaac Newton
B) George Boole
C) Charles Babbage
D) Alan Turing
Q2. A + A’ equals:
A) 0
B) 1
C) A
D) A’
Q3. The output of an AND gate is 1 when:
A) Both inputs are 1
B) Any one input is 1
C) All inputs are 0
D) Inputs are different
Q4. Which gate is known as the universal gate?
A) XOR
B) AND
C) NAND
D) OR
Q5. What is the output of an OR gate if both inputs are 0?
A) 1
B) 0
C) A
D) Undefined
Q6. The complement of A · B is:
A) A + B
B) A’ + B’
C) A · B’
D) A’ · B’
Q7. Which logic gate outputs 1 when inputs are different?
A) NOR
B) XNOR
C) XOR
D) NAND
Q8. A + 0 is equal to:
A) 0
B) 1
C) A
D) A’
Q9. What is the Boolean expression for a NOR gate?
A) (A + B)’
B) (A · B)’
C) A ⊕ B
D) A + B
Q10. Which law states that A + A = A?
A) Complement Law
B) Idempotent Law
C) Identity Law
D) Double Negation
✅ Answer Key Table
| Q.No | Answer |
|---|---|
| Q1 | B |
| Q2 | B |
| Q3 | A |
| Q4 | C |
| Q5 | B |
| Q6 | B |
| Q7 | C |
| Q8 | C |
| Q9 | A |
| Q10 | B |
🧠 Explanations of All Answers
- Q1 → B: George Boole introduced Boolean Algebra.
- Q2 → B: Complement Law → A + A’ = 1.
- Q3 → A: AND gate outputs 1 only when both inputs are 1.
- Q4 → C: NAND can create all other logic gates.
- Q5 → B: OR gate with both 0 inputs gives 0.
- Q6 → B: De Morgan’s Law → (A · B)’ = A’ + B’.
- Q7 → C: XOR outputs 1 when inputs differ.
- Q8 → C: Identity Law → A + 0 = A.
- Q9 → A: NOR = NOT(OR) = (A + B)’.
- Q10 → B: Idempotent Law states A + A = A.
🎯 Why This Practice Matters for ECET 2026
Boolean Algebra & Logic Gates is a high-scoring and predictable topic in Digital Electronics. The formulas are fixed, and the questions are often repeated with slight changes. By practicing these MCQs, you can secure marks quickly without confusion during the exam. It also helps in solving K-map and circuit simplification questions efficiently.
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