ICT Revision MCQ Series (AL Grade 12) . 4 Logic Gates to design basic digital circuits and devices

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Introduction In today’s fast-paced learning environment, multiple-choice questions (MCQs) have become a powerful tool for quick revision and self-assessment. Our Revision MCQ Series is designed to help students reinforce their understanding of key concepts through well-structured MCQs.

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ICT Revision MCQ Series AL lesson 4 . Logic Gates to design basic digital circuits
This quiz assesses your knowledge of Grade 12 ICT lessons and serves as a revision test for your A/L examination preparation. It helps reinforce key concepts and improve your understanding of important ICT topics.
Perfect for:
Sri Lankan AL ICT students revising core concepts.
Building a strong foundation for exams and practical applications.
Good luck! 🖥️📊

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Category: Revision MCQ AL Grade 12 Lesion 4
Select Your Preferred Language 😊
Match the following gates with their truth table characteristics: (a) NAND (1) Outputs 0 only if all inputs are 1 (b) NOR (2) Outputs 1 only if all inputs are 0 (c) XNOR (3) Outputs 1 if inputs are equal (d) XOR (4) Outputs 1 if inputs differ
a-1, b-2, c-3, d-4
a-2, b-1, c-4, d-3
a-3, b-4, c-1, d-2
a-1, b-3, c-2, d-4
a-4, b-2, c-3, d-1

NAND is NOT AND, NOR is NOT OR, XNOR outputs 1 for equal inputs, and XOR outputs 1 for differing inputs.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which expression represents the carry output of a full adder?
AB + BCin + ACin
A XOR B XOR Cin
A AND B AND Cin
A OR B OR Cin
A NAND B NAND Cin

The full adder’s carry is derived from its truth table: AB + BCin + ACin.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which Boolean expression is equivalent to (A OR B)’ using De Morgan’s Laws?
A’ AND B’
A’ OR B’
A AND B
A XOR B
A NAND B

De Morgan’s Law states (A OR B)’ = A’ AND B’. This transforms the negated OR into an AND of negated inputs.
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Category: Revision MCQ AL Grade 12 Lesion 4
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A vending machine dispenses a product if a coin is inserted (C = 1) and the button is pressed (B = 1). Which gate combination represents this?
AND gate
OR gate
XOR gate
NAND gate
NOR gate

The machine requires C = 1 AND B = 1, directly implemented by an AND gate.
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Category: Revision MCQ AL Grade 12 Lesion 4
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(a) Half adder: Outputs sum and carry for two bits. (b) Full adder: Outputs sum only for three bits. (c) Flip-flops: Used in sequential circuits. (d) NAND gate: Used in combinational circuits. (e) Boolean algebra: Simplifies sequential circuits. Choose the correct statements.
(a), (c), and (d)
(a), (b), and (c)
(b) and (d) only
All of the above
(a), (c), and (e)

(a), (c), and (d) are correct. Full adder outputs sum and carry (b is incorrect). Boolean algebra simplifies combinational circuits (e is incorrect).
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Category: Revision MCQ AL Grade 12 Lesion 4
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For a classroom system that turns on the projector (output = 1) only when the teacher is present (T = 1) and the room is dark (D = 1), which represents the input, process, and output?
Input: T, D; Process: AND operation; Output: Projector on
Input: T; Process: NOT operation; Output: Projector off
Input: D; Process: OR operation; Output: Projector on
Input: T, D; Process: XOR operation; Output: Projector on
Input: T; Process: Check T = 0; Output: Projector off

The projector requires T = 1 AND D = 1, processed by an AND gate.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which statements correctly describe Boolean algebra? (a) Commutative law: A + B = B + A (b) Don’t law: (A AND B)’ = A’ OR B’ (c) SOP form: Product of sums (d) Karnaugh map: Simplifies expressions
(a) and (b) only
(a), (b), and (d)
(a), (c), and (d)
All of the above
(b) and (d) only

(a), (b), and (d) are correct. SOP is sum of products, not product of sums (c is incorrect).
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Category: Revision MCQ AL Grade 12 Lesion 4
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What is the primary tool used to simplify Boolean expressions visually?
Boolean algebra
Karnaugh map
Logic gate
Flip-flop
Boolean algebra

Karnaugh maps provide a visual method to group minterms and simplify expressions efficiently.
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Category: Revision MCQ AL Grade 12 Lesion 4
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A circuit needs to output 1 only when inputs A and B are the same. Which gate is best?
XNOR gate
XOR gate
AND gate
OR gate
NAND gate

The XNOR gate outputs 1 when inputs are equal (A = B), matching the requirement.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Match the gates with their negated equivalents: (a) NAND (1) NOT OR (b) NOR (2) NOT AND (c) AND (3) NOT XOR (d) OR (4) NOT NOR
a-2, b-1, c-4, d-3
a-1, b-2, c-3, d-4
a-2, b-1, c-3, d-4
a-3, b-4, c-1, d-2
a-4, b-3, c-2, d-1

NAND is NOT AND, NOR is NOT OR, AND is not XOR, and OR is not NOR.
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Category: Revision MCQ AL Grade 12 Lesion 4
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What is the primary method to represent a digital circuit’s behavior before implementation?
Boolean algebra
Truth table
Karnaugh map
Logic gates
Flip-flops

Truth tables define a circuit’s input-output behavior, serving as the foundation for design.
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Category: Revision MCQ AL Grade 12 Lesion 4
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In digital circuits, _______ is used to simplify expressions. In CPUs, _______ circuits add bits. In memory, _______ store data. For circuit design, _______ gates are universal.
Boolean algebra, half adder, flip-flops, NAND
Truth tables, sequential, registers, NOR
De Morgan’s Laws, multiplexers, latches, AND
SOP forms, adders, RAM, OR
Karnaugh maps, combinational, counters, XOR

Boolean algebra simplifies, half adders add bits, flip-flops store data, and NAND is universal.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which Boolean expression is equivalent to A’ AND (B OR C)?
(A’ AND B) OR (A’ AND C)
(A OR B) AND (A OR C)
A AND (B’ OR C’)
A’ OR (B AND C)
(A’ OR B) AND (A’ OR C)

Using the distributive law, A’ AND (B OR C) = (A’ AND B) OR (A’ AND C).
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Category: Revision MCQ AL Grade 12 Lesion 4
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For a traffic light system that allows traffic to pass (output = 1) only when the pedestrian signal is off (P = 0) and the vehicle signal is green (V = 1), which correctly represents the input, process, and output?
Input: P, V; Process: Check P = 0, V = 1; Output: Allow traffic
Input: P; Process: Invert P; Output: Allow traffic
Input: V; Process: Check V = 0; Output: Stop traffic
Input: P, V; Process: OR operation; Output: Allow traffic
Input: P; Process: Check P = 1; Output: Allow traffic

The system requires P = 0 and V = 1, processed as NOT P AND V, outputting 1 to allow traffic.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which logic gate is considered a universal gate?
AND gate
OR gate
XOR gate
NAND gate
NOT gate

NAND gates can implement any logic function (e.g., NOT, AND, OR), making them universal.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which expression represents a NOT gate using a NAND gate?
A NAND A
A NAND B
(A NAND B) NAND (A NAND B)
A OR A
A AND A

A NAND A = NOT (A AND A) = NOT A, implementing a NOT gate using a NAND gate.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which of the following cannot be directly implemented by a flip-flop in a digital circuit?
Storing a single bit
Maintaining circuit state
Adding two binary digits
Forming a register
Supporting sequential logic

Flip-flops store bits and support sequential logic, but addition requires combinational circuits like half adders.
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Category: Revision MCQ AL Grade 12 Lesion 4
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(a) Half adder: Used in CPU arithmetic. (b) Full adder: Handles carry-in. (c) Flip-flops: Store bits in memory. (d) XOR gate: Not a sequential circuit. (e) NAND gate: Not a CPU building block. Choose the correct statements.
(a), (b), (c), and (d)
(a), (b), and (c)
(b) and (d) only
All of the above
(a), (c), and (e)

All are correct except (e), as NAND is not a direct CPU building block like adders.
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Category: Revision MCQ AL Grade 12 Lesion 4
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For a circuit that outputs 1 only when inputs A and B are different, which represents the input, process, and output?
Input: A, B; Process: XOR operation; Output: 1 if A ≠ B
Input: A, B; Process: AND operation; Output: 1 if A = B
Input: A; Process: NOT operation; Output: Inverted A
Input: A, B; Process: OR operation; Output: 1 if A or B is 1
Input: A, B; Process: NAND operation; Output: 1 if A = B

The XOR gate outputs 1 when inputs differ (A ≠ B), matching the described process.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which statements correctly describe Karnaugh maps? (a) Used to simplify Boolean expressions. (b) Groups minterms to reduce terms. (c) Limited to two variables. (d) Converts SOP to POS directly.
(a) and (b) only
(a), (b), and (d)
(a), (c), and (d)
All of the above
(b) and (d) only

Karnaugh maps simplify expressions by grouping minterms. They handle multiple variables (c is incorrect) and don’t directly convert SOP to POS (d is incorrect).
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Category: Revision MCQ AL Grade 12 Lesion 4
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Match the following logic gates with their functions: (a) NOT (1) Outputs 1 if inputs differ (b) AND (2) Inverts the input (c) XOR (3) Outputs 1 if all inputs are 1 (d) OR (4) Outputs 1 if any input is 1
a-2, b-3, c-1, d-4
a-1, b-3, c-4, d-2
a-3, b-2, c-1, d-4
a-2, b-1, c-3, d-4
a-4, b-2, c-3, d-1

NOT inverts, AND requires all 1s, XOR outputs 1 for differing inputs, and OR outputs 1 for any 1.
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Category: Revision MCQ AL Grade 12 Lesion 4
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(a) Half adder: Uses XOR and AND gates for sum and carry. (b) Full adder: Includes carry-in for three-bit addition. (c) Flip-flops: Store multiple bits in registers. (d) NAND gate: Can implement any logic function. (e) Karnaugh map: Used for sequential circuit design. Choose the correct statements.
(a), (b), and (d)
(a), (b), and (c)
(b) and (d) only
All of the above
(a), (b), (d), and (e)

(a), (b), and (d) are correct. Flip-flops store one bit, not multiple (c is incorrect). Karnaugh maps are for combinational, not sequential circuits (e is incorrect).
23 / 30
Category: Revision MCQ AL Grade 12 Lesion 4
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Which expression represents the sum output of a half adder?
A XOR B
A AND B
A OR B
A NAND B
A NOR B

The sum of a half adder is A XOR B, as it outputs 1 when inputs differ.
24 / 30
Category: Revision MCQ AL Grade 12 Lesion 4
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Which statements correctly describe logic gates? (a) NOT gate has one input and inverts it. (b) AND gate outputs 1 if any input is 1. (c) XOR gate outputs 1 if inputs differ. (d) NAND gate is a universal gate.
(a) and (c) only
(a), (b), and (d)
(a), (c), and (d)
All of the above
(b) and (d) only

NOT inverts, XOR outputs 1 for differing inputs, and NAND is universal. AND outputs 1 only if all inputs are 1, so (b) is incorrect.
25 / 30
Category: Revision MCQ AL Grade 12 Lesion 4
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A CPU requires a circuit to add two bits without considering a carry-in. Which logic gate combination best represents this system?
XOR and AND gates
OR and NOT gates
NAND and NOR gates
AND and OR gates
XOR and NOR gates

A half adder uses XOR for the sum (A XOR B) and AND for the carry (A AND B), suitable for adding two bits.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which of the following is not a combinational logic gate?
NAND gate
NOR gate
XNOR gate
Flip-flop
XOR gate

Flip-flops are sequential circuits, while NAND, NOR, XNOR, and XOR are combinational gates.
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Category: Revision MCQ AL Grade 12 Lesion 4
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A home security system activates an alarm if the door is open (D = 1) or the window is open (W = 1). Which gate best represents this?
OR gate
AND gate
XOR gate
NAND gate
NOR gate

The alarm activates if D = 1 OR W = 1, directly represented by an OR gate.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Digital circuit design uses Boolean algebra for simplification. In circuit optimization, _______ is used to reduce gate count. In CPU design, _______ circuits perform arithmetic. In memory systems, _______ store bits. For universal gates, _______ can implement any logic function.
Karnaugh map, combinational, flip-flops, NAND
De Morgan’s Laws, sequential, registers, NOR
Truth tables, adders, latches, AND
Boolean theorems, flip-flops, RAM, OR
SOP forms, multiplexers, counters, XOR

Karnaugh maps simplify expressions, combinational circuits (e.g., adders) perform arithmetic, flip-flops store bits, and NAND is a universal gate.
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Category: Revision MCQ AL Grade 12 Lesion 4
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What is the primary logic gate used to invert an input signal in a digital circuit?
AND gate
OR gate
NOT gate
XOR gate
NAND gate

The NOT gate takes a single input and produces its inverse (0 to 1, or 1 to 0), making it the primary gate for signal inversion.
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Category: Revision MCQ AL Grade 12 Lesion 4
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Which of the following cannot be achieved using a single basic logic gate?
Inverting a signal
Outputting 1 when both inputs are 1
Outputting 1 when at least one input is 1
Adding two binary digits with carry
Outputting 1 when inputs differ

Basic logic gates (NOT, AND, OR, XOR) perform simple operations. Adding two binary digits with a carry requires a combinational circuit (e.g., half adder), not a single gate.
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Table of Contents

Why Use MCQs for Learning? MCQs are a great way to evaluate your understanding of a subject in a structured manner. Here’s why they are effective:

Quick and Efficient – MCQs allow for rapid assessment of knowledge.
Engaging and Interactive – They keep learning interesting and encourage active participation.
Memory Retention – Answering questions enhances recall and reinforces concepts.
Instant Feedback – You can immediately check your answers and improve your understanding.

Tips MCQ-Based Exams

To score well in MCQ exams, follow these strategies:

Understand the Concepts – Don’t just memorize answers; understand the logic behind them.
Eliminate Wrong Options – Narrow down choices by eliminating incorrect answers.
Time Management – Avoid spending too much time on one question.
Practice Regularly – Consistent practice improves accuracy and speed.
Read Carefully – Pay attention to tricky words like not, always, and except.

Conclusion

The Revision MCQ Series is your go-to resource for mastering concepts efficiently. Keep practicing with Lesson 1 questions and stay tuned for upcoming lessons. Your success starts with consistent revision and smart study techniques!

FAQs

1. How can MCQs help in learning? MCQs improve retention, provide quick assessment, and make learning engaging.

2. Can I find more lessons in this series? Yes! We regularly update the Revision MCQ Series with new lessons. Stay tuned!

3. How should I prepare for MCQ-based exams? Understand concepts, practice regularly, manage time well, and eliminate wrong answers.

4. Where can I access more MCQs? You can find additional MCQs on our website or in upcoming blog posts.

5. Is this MCQ series suitable for all students? Yes! Whether you’re a beg

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ICT Revision MCQ Series (AL Grade 12) . 4 Logic Gates to design basic digital circuits and devices

Why Use MCQs for Learning? MCQs are a great way to evaluate your understanding of a subject in a structured manner. Here’s why they are effective:

Tips MCQ-Based Exams

Conclusion

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