Digital Electronics MCQ & Objective Questions
Digital Electronics is a crucial subject for students preparing for school and competitive exams in India. Mastering this topic not only enhances your understanding of electronic systems but also significantly boosts your exam scores. Practicing MCQs and objective questions in Digital Electronics helps you identify important concepts and improves your problem-solving skills, making it an essential part of your exam preparation.
What You Will Practise Here
Fundamentals of digital logic design
Binary number systems and conversions
Logic gates and their truth tables
Combinational circuits and their applications
Sequential circuits and flip-flops
Boolean algebra and simplification techniques
Key definitions and important formulas
Exam Relevance
Digital Electronics is a significant topic in various examinations, including CBSE, State Boards, NEET, and JEE. Students can expect questions related to logic gates, number systems, and circuit design. Common patterns include multiple-choice questions that test both theoretical knowledge and practical applications, making it vital to be well-prepared with important Digital Electronics questions for exams.
Common Mistakes Students Make
Confusing between different types of logic gates and their functions.
Misunderstanding the conversion processes between binary and decimal systems.
Overlooking the importance of truth tables in combinational circuits.
Failing to apply Boolean algebra correctly in simplification problems.
Neglecting the timing diagrams in sequential circuits.
FAQs
Question: What are the key topics I should focus on in Digital Electronics for exams?Answer: Focus on logic gates, number systems, combinational and sequential circuits, and Boolean algebra.
Question: How can I improve my performance in Digital Electronics MCQs?Answer: Regular practice of MCQs and understanding the underlying concepts will greatly enhance your performance.
Start solving practice MCQs today to test your understanding and solidify your knowledge in Digital Electronics. Remember, consistent practice is the key to success in your exams!
Q. What is the result of the expression A AND NOT A?
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Solution
The expression A AND NOT A is always false, which is represented by 0.
Correct Answer:
C
— 0
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Q. What is the result of the expression A OR (A AND B) when A is true?
A.
True
B.
False
C.
Undefined
D.
A AND B
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Solution
If A is true, A OR (A AND B) evaluates to true regardless of B.
Correct Answer:
A
— True
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Q. What is the result of the expression A OR A?
A.
A
B.
0
C.
1
D.
A AND A
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Solution
The expression A OR A simplifies to A, as it is idempotent.
Correct Answer:
A
— A
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Q. What is the result of the expression A OR NOT A?
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Solution
The expression A OR NOT A is always true, which is represented by 1.
Correct Answer:
D
— 1
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Q. What is the result of the expression NOT (A AND B)?
A.
A OR B
B.
A AND B
C.
NOT A AND NOT B
D.
NOT A OR NOT B
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Solution
This is an application of De Morgan's Theorem, which states NOT (A AND B) = NOT A OR NOT B.
Correct Answer:
D
— NOT A OR NOT B
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Q. What is the role of a capacitor in an integrated circuit?
A.
To amplify signals
B.
To store electrical energy
C.
To provide a path for current
D.
To regulate voltage
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Solution
Capacitors in integrated circuits are used to store electrical energy temporarily, smoothing out voltage fluctuations.
Correct Answer:
B
— To store electrical energy
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Q. What is the role of a multiplexer in MSI circuits?
A.
To perform addition
B.
To select data from multiple sources
C.
To store data
D.
To amplify signals
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Solution
A multiplexer selects data from multiple input sources and forwards it to a single output line.
Correct Answer:
B
— To select data from multiple sources
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Q. What is the role of a voltage divider in interfacing?
A.
To increase voltage levels
B.
To decrease voltage levels
C.
To filter noise
D.
To convert AC to DC
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Solution
A voltage divider is used to decrease voltage levels to a desired value suitable for interfacing with other components.
Correct Answer:
B
— To decrease voltage levels
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Q. What is the role of the discharge pin in a 555 timer?
A.
To charge the timing capacitor
B.
To reset the timer
C.
To discharge the timing capacitor
D.
To control the output frequency
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Solution
The discharge pin is used to discharge the timing capacitor when the output goes low.
Correct Answer:
C
— To discharge the timing capacitor
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Q. What is the role of the instruction register in a microprocessor?
A.
To store the next instruction to be executed
B.
To hold data temporarily
C.
To manage input/output operations
D.
To control the clock speed
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Solution
The instruction register holds the current instruction that is being executed by the microprocessor.
Correct Answer:
A
— To store the next instruction to be executed
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Q. What is the simplified form of A AND A?
A.
A
B.
0
C.
1
D.
A AND 1
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Solution
According to the Idempotent Law, A AND A simplifies to A.
Correct Answer:
A
— A
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Q. What is the simplified form of the expression A AND (A OR B)?
A.
A
B.
B
C.
A OR B
D.
A AND B
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Solution
Using the Absorption Law, A AND (A OR B) simplifies to A.
Correct Answer:
A
— A
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Q. What is the simplified form of the expression A AND (B OR C)?
A.
A AND B
B.
A AND C
C.
A AND (B AND C)
D.
A AND B OR A AND C
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Solution
This follows the Distributive Law, which states A AND (B OR C) = A AND B OR A AND C.
Correct Answer:
D
— A AND B OR A AND C
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Q. What is the size of the internal RAM in the 8051 microcontroller?
A.
128 bytes
B.
256 bytes
C.
512 bytes
D.
64 bytes
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Solution
The internal RAM size of the 8051 microcontroller is 128 bytes.
Correct Answer:
A
— 128 bytes
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Q. What is the truth table output for a 2-input NAND gate when both inputs are high?
A.
0
B.
1
C.
Both 0 and 1
D.
Undefined
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Solution
A NAND gate outputs low (0) only when both inputs are high (1); otherwise, it outputs high (1).
Correct Answer:
A
— 0
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Q. What is the truth table output for a 2-input XOR gate when both inputs are the same?
A.
0
B.
1
C.
Both 0 and 1
D.
Undefined
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Solution
A 2-input XOR gate outputs 0 when both inputs are the same (either both 0 or both 1).
Correct Answer:
A
— 0
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Q. What is the truth table output for a NAND gate when both inputs are low?
A.
0
B.
1
C.
Both 0 and 1
D.
Undefined
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Solution
A NAND gate outputs high (1) when at least one input is low; thus, it outputs 1 when both inputs are low.
Correct Answer:
B
— 1
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Q. What is the truth table output for an Ex-NOR gate when both inputs are different?
A.
0
B.
1
C.
Both 0 and 1
D.
Undefined
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Solution
An Ex-NOR gate outputs 0 when both inputs are different.
Correct Answer:
A
— 0
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Q. What is the truth value of A AND B if A is true and B is false?
A.
True
B.
False
C.
Undefined
D.
Both True and False
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Solution
The AND operation outputs true only if both A and B are true; otherwise, it outputs false.
Correct Answer:
B
— False
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Q. What is the truth value of an Ex-OR gate when the inputs are A=1 and B=0?
A.
0
B.
1
C.
Undefined
D.
Both 0 and 1
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Solution
The Ex-OR gate outputs 1 when the inputs are different (A=1, B=0).
Correct Answer:
B
— 1
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Q. What is the truth value of an OR gate with inputs 0 and 0?
A.
0
B.
1
C.
undefined
D.
error
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Solution
An OR gate outputs 0 only when both inputs are 0.
Correct Answer:
A
— 0
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Q. What is the two's complement of the binary number 0110?
A.
1001
B.
1010
C.
1100
D.
1110
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Solution
The two's complement of 0110 is 1010.
Correct Answer:
B
— 1010
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Q. What is the typical duty cycle of a 555 timer configured in astable mode?
A.
50%
B.
33%
C.
25%
D.
Varies based on resistor values
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Solution
The duty cycle in astable mode varies based on the resistor and capacitor values used in the circuit.
Correct Answer:
D
— Varies based on resistor values
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Q. What is the typical duty cycle of an astable 555 timer when both resistors are equal?
A.
25%
B.
50%
C.
75%
D.
100%
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Solution
When both resistors in an astable 555 timer are equal, the duty cycle is typically 50%.
Correct Answer:
B
— 50%
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Q. What is the typical input impedance of a CMOS gate?
A.
Low
B.
Medium
C.
High
D.
Variable
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Solution
CMOS gates have a high input impedance, which allows them to draw very little current from the input signal.
Correct Answer:
C
— High
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Q. What is the typical input impedance of CMOS logic gates?
A.
Low
B.
Medium
C.
High
D.
Variable
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Solution
CMOS logic gates have a high input impedance, which allows them to draw very little current.
Correct Answer:
C
— High
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Q. What is the typical output of a 2-to-4 line decoder?
A.
2 outputs active
B.
4 outputs active
C.
1 output active
D.
All outputs active
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Solution
A 2-to-4 line decoder typically has 4 outputs, with one output active based on the 2-bit input.
Correct Answer:
B
— 4 outputs active
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Q. What is the typical output voltage level for a logic high in TTL?
A.
0V
B.
2.5V
C.
5V
D.
12V
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Solution
In TTL logic families, the typical output voltage level for a logic high is around 5V.
Correct Answer:
C
— 5V
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Q. What is the typical output voltage level of a 555 timer in high state?
A.
0V
B.
1.5V
C.
Vcc
D.
0.7V
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Solution
The output voltage level of a 555 timer in high state is typically equal to the supply voltage (Vcc).
Correct Answer:
C
— Vcc
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Q. What is the typical output voltage range of a standard 10-bit ADC?
A.
0 to 5V
B.
0 to 10V
C.
0 to 255V
D.
0 to 1023V
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Solution
A standard 10-bit ADC typically has an output voltage range of 0 to 5V, representing values from 0 to 1023.
Correct Answer:
A
— 0 to 5V
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