Basic Digital Logic Gates and Circuits MCQs

What is the primary function of a logic gate?
A) To perform logical operations on one or more inputs
B) To amplify electrical signals
C) To store data
D) To convert analog signals to digital
Answer: A

Which logic gate outputs true only when all inputs are true?
A) AND gate
B) OR gate
C) NOT gate
D) XOR gate
Answer: A

What is the output of an OR gate if both inputs are false?
A) False
B) True
C) Indeterminate
D) High
Answer: A

Which gate is known as the inverter?
A) NOT gate
B) AND gate
C) OR gate
D) NAND gate
Answer: A

What is the output of a NAND gate when both inputs are true?
A) False
B) True
C) High
D) Low
Answer: A

Which logic gate outputs true only when an odd number of inputs are true?
A) XOR gate
B) AND gate
C) OR gate
D) NOR gate
Answer: A

What is the function of a NOR gate?
A) Outputs true only when all inputs are false
B) Outputs true when at least one input is true
C) Outputs true when an odd number of inputs are true
D) Outputs the inverse of the AND gate
Answer: A

How many inputs can a basic logic gate have?
A) One or more
B) Two only
C) Three only
D) None
Answer: A

Which of the following represents the logical expression for an AND gate?
A) A · B
B) A + B
C) A’
D) A ⊕ B
Answer: A

What is the truth value of A AND B if A is true and B is false?
A) False
B) True
C) High
D) Low
Answer: A

Which circuit combines multiple logic gates?
A) Logic circuit
B) Series circuit
C) Parallel circuit
D) Capacitor circuit
Answer: A

What is the output of an XOR gate when both inputs are true?
A) False
B) True
C) High
D) Low
Answer: A

Which logic gate can be used to create a NOT function using an AND gate?
A) NAND gate
B) NOR gate
C) OR gate
D) XOR gate
Answer: A

What does a truth table represent?
A) All possible input combinations and their corresponding outputs
B) The physical layout of a circuit
C) The flow of current in a circuit
D) The design of a logic gate
Answer: A

Which gate has the truth table that produces true when both inputs are false?
A) NOR gate
B) AND gate
C) OR gate
D) NAND gate
Answer: A

What is the result of combining an AND gate and a NOT gate?
A) NAND gate
B) NOR gate
C) XOR gate
D) AND gate
Answer: A

Which of the following logic gates is considered universal?
A) NAND gate
B) AND gate
C) OR gate
D) NOT gate
Answer: A

What is the main advantage of using NAND and NOR gates?
A) They can create any other type of logic gate
B) They require fewer resources
C) They have a lower power consumption
D) They are easier to design
Answer: A

Which type of gate is represented by the following truth table: 00->0, 01->1, 10->1, 11->1?
A) OR gate
B) AND gate
C) XOR gate
D) NOT gate
Answer: A

What is the output of a three-input AND gate when one input is false?
A) False
B) True
C) High
D) Low
Answer: A

In digital circuits, what is the binary value of logic low?
A) 0
B) 1
C) 2
D) 3
Answer: A

What is the Boolean expression for an OR gate with inputs A and B?
A) A + B
B) A · B
C) A’
D) A ⊕ B
Answer: A

What type of logic gate is a multiplexer?
A) Combinational circuit
B) Sequential circuit
C) Feedback circuit
D) Oscillator circuit
Answer: A

How does a digital circuit perform an arithmetic operation?
A) By using logic gates to manipulate binary numbers
B) By converting binary to decimal
C) By using physical counting
D) By converting analog signals to digital
Answer: A

What is the primary purpose of a flip-flop in digital circuits?
A) To store binary data
B) To perform arithmetic operations
C) To amplify signals
D) To manage input/output operations
Answer: A

Which gate produces an output of false only when all inputs are true?
A) NOR gate
B) NAND gate
C) AND gate
D) OR gate
Answer: A

What is the output of a NOT gate if the input is true?
A) False
B) True
C) High
D) Low
Answer: A

Which logic gate is often used to perform addition in digital circuits?
A) XOR gate
B) AND gate
C) OR gate
D) NOT gate
Answer: A

Which gate’s output is true when at least one input is true?
A) OR gate
B) AND gate
C) NOT gate
D) NAND gate
Answer: A

What is a common application of a logic gate?
A) Implementing digital circuits
B) Storing data
C) Transmitting signals
D) Amplifying audio
Answer: A

Which component is essential for creating a simple digital circuit?
A) Logic gates
B) Resistors
C) Capacitors
D) Inductors
Answer: A

How many output states does a two-input AND gate have?
A) Four
B) Three
C) Two
D) One
Answer: A

What is a half-adder?
A) A circuit that adds two binary digits
B) A circuit that subtracts two binary digits
C) A circuit that divides two binary digits
D) A circuit that multiplies two binary digits
Answer: A

Which Boolean operation is represented by the following expression: A + A’ ?
A) True
B) False
C) A
D) A’
Answer: A

What does the term “propagation delay” refer to in digital circuits?
A) The time it takes for a signal to travel through a gate
B) The time it takes for a circuit to power on
C) The time it takes to reset a flip-flop
D) The time it takes for data to transfer
Answer: A

Which of the following statements about logic gates is true?
A) They operate on binary values
B) They can only have one input
C) They can only produce one output
D) They are only used in computers
Answer: A

What is the output of a NAND gate if both inputs are false?
A) True
B) False
C) Low
D) High
Answer: A

Which of the following gates can be combined to create any digital circuit?
A) NAND and NOR gates
B) AND and OR gates
C) NOT gates only
D) XOR gates only
Answer: A

Which of the following best describes a digital circuit?
A) A circuit that processes discrete values
B) A circuit that processes continuous signals
C) A circuit that amplifies sound
D) A circuit that generates heat
Answer: A

What does a two-input XOR gate produce when both inputs are the same?
A) False
B) True
C) High
D) Low
Answer: A

Which logic gate’s output is always the opposite of the input?
A) NOT gate
B) AND gate
C) OR gate
D) NAND gate
Answer: A

What is the main characteristic of combinational logic circuits?
A) Their output depends only on current inputs
B) Their output depends on past inputs
C) They have memory elements
D) They are always sequential
Answer: A

Which operation does a full adder perform?
A) Adds three binary digits and accounts for carry
B) Subtracts two binary digits
C) Multiplies two binary digits
D) Divides two binary digits
Answer: A

In digital logic, what does the symbol ‘·’ represent?
A) AND operation
B) OR operation
C) NOT operation
D) XOR operation
Answer: A