Digital Circuits Questions and Answers – Boolean Logic Operations

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Boolean Logic Operations”.

1. In boolean algebra, the OR operation is performed by which properties?
a) Associative properties
b) Commutative properties
c) Distributive properties
d) All of the Mentioned
View Answer

Answer: d
Explanation: The expression for Associative property is given by A+(B+C) = (A+B)+C & A*(B*C) = (A*B)*C.
The expression for Commutative property is given by A+B = B+A & A*B = B*A.
The expression for Distributive property is given by A+BC=(A+B)(A+C) & A(B+C) = AB+AC.

2. The expression for Absorption law is given by _________
a) A + AB = A
b) A + AB = B
c) AB + AA’ = A
d) A + B = B + A
View Answer

Answer: a
Explanation: The expression for Absorption Law is given by: A+AB = A.
Proof: A + AB = A(1+B) = A (Since 1 + B = 1 as per 1’s Property).

3. According to boolean law: A + 1 = ?
a) 1
b) A
c) 0
d) A’
View Answer

Answer: a
Explanation: A + 1 = 1, as per 1’s Property.
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4. The involution of A is equal to _________
a) A
b) A’
c) 1
d) 0
View Answer

Answer: a
Explanation: The involution of A means double inversion of A (i.e. A”) and is equal to A.
Proof: ((A)’)’ = A

5. A(A + B) = ?
a) AB
b) 1
c) (1 + AB)
d) A
View Answer

Answer: d
Explanation: A(A + B) = AA + AB (By Distributive Property) = A + AB (A.A = A By Commutative Property) = A(1 + B) = A*1 (1 + B = 1 by 1’s Property) = A.
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6. DeMorgan’s theorem states that _________
a) (AB)’ = A’ + B’
b) (A + B)’ = A’ * B
c) A’ + B’ = A’B’
d) (AB)’ = A’ + B
View Answer

Answer: a
Explanation: The DeMorgan’s law states that (AB)’ = A’ + B’ & (A + B)’ = A’ * B’, as per the Dual Property.

7. (A + B)(A’ * B’) = ?
a) 1
b) 0
c) AB
d) AB’
View Answer

Answer: b
Explanation: The DeMorgan’s law states that (AB)’ = A’ + B’ & (A + B)’ = A’ * B’, as per the Dual Property.
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8. Complement of the expression A’B + CD’ is _________
a) (A’ + B)(C’ + D)
b) (A + B’)(C’ + D)
c) (A’ + B)(C’ + D)
d) (A + B’)(C + D’)
View Answer

Answer: b
Explanation: (A’B + CD’)’ = (A’B)'(CD’)’ (By DeMorgan’s Theorem) = (A” + B’)(C’ + D”) (By DeMorgan’s Theorem) = (A + B’)(C’ + D).

9. Simplify Y = AB’ + (A’ + B)C.
a) AB’ + C
b) AB + AC
c) A’B + AC’
d) AB + A
View Answer

Answer: a
Explanation: Y = AB’ + (A’ + B)C = AB’ + (AB’)’C = (AB’ + C)( AB’ + AB’) = (AB’ + C).1 = (AB’ + C).
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10. The boolean function A + BC is a reduced form of ____________
a) AB + BC
b) (A + B)(A + C)
c) A’B + AB’C
d) (A + C)B
View Answer

Answer: b
Explanation: (A + B)(A + C) = AA + AC + AB + BC = A + AC + AB + BC (By Commutative Property) = A(1 + C + B) + BC = A + BC (1 + B + C =1 By 1’s Property).

Sanfoundry Global Education & Learning Series – Digital Circuits.

To practice all areas of Digital Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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