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. How many 16-bit timers/counters are available in the 8051 microcontroller?
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Solution
The 8051 microcontroller has 2 available 16-bit timers/counters.
Correct Answer:
B
— 2
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Q. How many 8-bit registers does the 8051 microcontroller have?
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Solution
The 8051 microcontroller has 32 general-purpose 8-bit registers.
Correct Answer:
C
— 32
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Q. How many bits are in a byte?
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Solution
A byte consists of 8 bits.
Correct Answer:
B
— 8
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Q. How many external interrupts does the 8051 support?
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Solution
The 8051 microcontroller supports 2 external interrupts.
Correct Answer:
B
— 2
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Q. How many inputs can an Ex-OR gate have?
A.
1
B.
2
C.
3
D.
Any number
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Solution
An Ex-OR gate can have any number of inputs, but it is commonly used with 2 inputs.
Correct Answer:
D
— Any number
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Q. How many outputs does an 8-to-1 multiplexer have?
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Solution
An 8-to-1 multiplexer has 1 output, which is selected from 8 different input lines.
Correct Answer:
A
— 1
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Q. How many select lines are needed for a 16-to-1 multiplexer?
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Solution
A 16-to-1 multiplexer requires 4 select lines because 2^4 = 16.
Correct Answer:
C
— 4
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Q. How many states does a 3-bit counter have?
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Solution
A 3-bit counter can represent 2^3 = 8 different states.
Correct Answer:
C
— 8
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Q. If A = 1 and B = 0, what is the output of A XOR B?
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Solution
The output of A XOR B is 1 when A = 1 and B = 0.
Correct Answer:
B
— 1
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Q. If A is true and B is true, what is the output of A OR B?
A.
True
B.
False
C.
1
D.
0
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Solution
An OR gate outputs true if at least one input is true; since both are true, the output is true.
Correct Answer:
A
— True
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Q. If A=0 and B=1, what is the output of an Ex-NOR gate?
A.
1
B.
0
C.
Undefined
D.
Both 0 and 1
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Solution
The Ex-NOR gate outputs 0 when the inputs are different (A=0, B=1).
Correct Answer:
B
— 0
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Q. In a 4-bit binary counter, what is the maximum count it can reach?
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Solution
A 4-bit binary counter can represent values from 0 to 15, making the maximum count 15.
Correct Answer:
A
— 15
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Q. In a 4-bit binary number, what is the maximum decimal value it can represent?
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Solution
A 4-bit binary number can represent values from 0 to 15, so the maximum is 15.
Correct Answer:
A
— 15
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Q. In a 4-bit shift register, how many bits can it hold?
A.
2 bits
B.
4 bits
C.
8 bits
D.
16 bits
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Solution
A 4-bit shift register can hold exactly 4 bits of data.
Correct Answer:
B
— 4 bits
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Q. In a 4-to-1 multiplexer, how many select lines are required?
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Solution
A 4-to-1 multiplexer requires 2 select lines to choose one of the four input lines.
Correct Answer:
B
— 2
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Q. In a 555 timer circuit, what does the threshold pin do?
A.
Resets the timer
B.
Sets the output high
C.
Detects when the capacitor voltage exceeds a certain level
D.
Controls the timing interval
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Solution
The threshold pin detects when the capacitor voltage exceeds 2/3 of the supply voltage, which affects the output state.
Correct Answer:
C
— Detects when the capacitor voltage exceeds a certain level
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Q. In a 555 timer configured as a monostable multivibrator, what triggers the output pulse?
A.
A high signal
B.
A low signal
C.
A falling edge
D.
A rising edge
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Solution
A monostable 555 timer is triggered by a falling edge on the trigger pin, which causes the output to go high for a specified duration.
Correct Answer:
D
— A rising edge
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Q. In a 555 timer, what is the purpose of the discharge pin (Pin 7)?
A.
To trigger the timer
B.
To reset the timer
C.
To discharge the timing capacitor
D.
To provide power to the timer
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Solution
The discharge pin (Pin 7) is used to discharge the timing capacitor when the output goes low, allowing the timer to reset for the next cycle.
Correct Answer:
C
— To discharge the timing capacitor
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Q. In a binary counter, what is the maximum count for a 3-bit counter?
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Solution
A 3-bit counter can represent values from 0 to 7, which is a total of 8 states.
Correct Answer:
A
— 7
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Q. In a binary counter, what is the maximum count for a 4-bit counter?
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Solution
The maximum count for a 4-bit counter is 2^4 - 1 = 15.
Correct Answer:
A
— 15
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Q. In a binary to decimal converter, what is the decimal equivalent of the binary number 1011?
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Solution
The binary number 1011 is equal to 1*2^3 + 0*2^2 + 1*2^1 + 1*2^0 = 8 + 0 + 2 + 1 = 11.
Correct Answer:
C
— 11
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Q. In a bistable multivibrator using a 555 timer, how is the output state changed?
A.
By changing the power supply
B.
By triggering the reset pin
C.
By applying a trigger to the trigger pin
D.
By connecting a capacitor
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Solution
In a bistable multivibrator, the output state is changed by applying a trigger to the trigger pin.
Correct Answer:
C
— By applying a trigger to the trigger pin
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Q. In a circuit with an Ex-OR gate, if both inputs are 0, what is the output?
A.
1
B.
0
C.
Undefined
D.
Both 0 and 1
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Solution
The output of an Ex-OR gate is 0 when both inputs are 0.
Correct Answer:
B
— 0
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Q. In a circuit, if the Ex-OR gate has inputs A=1 and B=1, what will be the output?
A.
1
B.
0
C.
Undefined
D.
Both 0 and 1
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Solution
The Ex-OR gate outputs 0 when both inputs are the same, which is 1 in this case.
Correct Answer:
B
— 0
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Q. In a circuit, if the inputs to an Ex-NOR gate are both 1, what is the output?
A.
0
B.
1
C.
Depends on the circuit
D.
Undefined
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Solution
The output of an Ex-NOR gate is 1 when both inputs are 1.
Correct Answer:
B
— 1
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Q. In a circuit, what is the purpose of a signal?
A.
To provide power
B.
To indicate a state or condition
C.
To store data
D.
To increase resistance
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Solution
A signal is used to indicate a state or condition within a circuit, such as on/off or high/low.
Correct Answer:
B
— To indicate a state or condition
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Q. In a combinational circuit, what does the term 'propagation delay' refer to?
A.
Time taken for the output to stabilize
B.
Time taken for the input to change
C.
Time taken for the circuit to power on
D.
Time taken for the circuit to reset
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Solution
Propagation delay is the time taken for the output to stabilize after the input has changed.
Correct Answer:
A
— Time taken for the output to stabilize
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Q. In a combinational circuit, what is the primary function of multiplexers?
A.
To perform arithmetic operations
B.
To select one of many inputs
C.
To store data
D.
To invert signals
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Solution
Multiplexers are used to select one of many input signals and forward the selected input to a single output line.
Correct Answer:
B
— To select one of many inputs
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Q. In a combinational logic circuit, what is the primary function of multiplexers?
A.
To perform arithmetic operations
B.
To select one of many inputs
C.
To store data
D.
To invert signals
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Solution
Multiplexers are used to select one of many input signals and forward the selected input to a single output line.
Correct Answer:
B
— To select one of many inputs
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Q. In a discrete-time signal, what does the term 'aliasing' refer to?
A.
Loss of signal strength
B.
Distortion of the signal due to insufficient sampling
C.
The process of filtering a signal
D.
The conversion of a signal from analog to digital
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Solution
Aliasing occurs when a signal is sampled at a rate lower than twice its highest frequency, causing different signals to become indistinguishable.
Correct Answer:
B
— Distortion of the signal due to insufficient sampling
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