Multivibrators and 555 Timer MCQ & Objective Questions
Understanding "Multivibrators and 555 Timer" is crucial for students preparing for various exams. These topics not only form a significant part of the syllabus but also frequently appear in objective questions. Practicing MCQs related to these concepts can enhance your exam preparation and boost your confidence, helping you score better in important exams.
What You Will Practise Here
Types of multivibrators: astable, monostable, and bistable
Working principles of the 555 Timer
Key formulas related to timing intervals and frequency
Applications of multivibrators in real-world circuits
Diagrams illustrating circuit configurations
Definitions of important terms and concepts
Common troubleshooting techniques for 555 Timer circuits
Exam Relevance
The topics of Multivibrators and the 555 Timer are essential for students appearing in CBSE, State Boards, NEET, JEE, and other competitive exams. Questions often focus on the functionality of different types of multivibrators, the applications of the 555 Timer, and problem-solving based on circuit diagrams. Familiarity with these concepts can help you tackle both theoretical and practical questions effectively.
Common Mistakes Students Make
Confusing the types of multivibrators and their applications
Misunderstanding the timing calculations for the 555 Timer
Overlooking the significance of component values in circuit performance
Failing to interpret circuit diagrams accurately
FAQs
Question: What is the main function of a 555 Timer?Answer: The 555 Timer is primarily used for generating precise timing and oscillation in various electronic circuits.
Question: How do I calculate the frequency of an astable multivibrator?Answer: The frequency can be calculated using the formula: f = 1.44 / ((R1 + 2R2) * C1), where R1 and R2 are resistances and C1 is the capacitance.
Now is the time to enhance your understanding of "Multivibrators and 555 Timer". Dive into our practice MCQs and test your knowledge to excel in your exams!
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 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 monostable 555 timer circuit, what happens when the trigger pin is activated?
A.
The output goes high for a short duration
B.
The output remains low
C.
The output oscillates
D.
The timer resets
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Solution
When the trigger pin is activated, the output of a monostable 555 timer goes high for a short duration.
Correct Answer:
A
— The output goes high for a short duration
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Q. In a monostable 555 timer, what determines the duration of the output pulse?
A.
The supply voltage
B.
The value of the timing resistor and capacitor
C.
The trigger signal duration
D.
The output load
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Solution
The duration of the output pulse in a monostable 555 timer is determined by the values of the timing resistor and capacitor.
Correct Answer:
B
— The value of the timing resistor and capacitor
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Q. In an astable multivibrator, what determines the frequency of oscillation?
A.
The resistor values only
B.
The capacitor value only
C.
Both resistor and capacitor values
D.
The power supply voltage
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Solution
The frequency of oscillation in an astable multivibrator is determined by both the resistor and capacitor values.
Correct Answer:
C
— Both resistor and capacitor values
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Q. In astable mode, how many output states does a 555 timer have?
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Solution
In astable mode, the 555 timer continuously oscillates between two output states: high and low.
Correct Answer:
B
— 2
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Q. What happens when the trigger pin of a 555 timer is pulled low in monostable mode?
A.
The output goes high
B.
The output goes low
C.
The timer resets
D.
Nothing happens
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Solution
Pulling the trigger pin low causes the output to go high for the duration set by the timing components.
Correct Answer:
A
— The output goes high
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Q. What is the duty cycle of a 555 timer configured in astable mode?
A.
50%
B.
33%
C.
25%
D.
Depends on resistor values
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Solution
The duty cycle in astable mode depends on the resistor and capacitor values used in the circuit.
Correct Answer:
D
— Depends on resistor values
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Q. What is the effect of increasing the resistance in the timing circuit of an astable 555 timer?
A.
Increases the frequency
B.
Decreases the frequency
C.
No effect on frequency
D.
Increases the duty cycle
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Solution
Increasing the resistance in the timing circuit of an astable 555 timer decreases the frequency of the output waveform.
Correct Answer:
B
— Decreases the frequency
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Q. What is the maximum output current of a standard 555 timer?
A.
10 mA
B.
20 mA
C.
200 mA
D.
500 mA
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Solution
The maximum output current of a standard 555 timer is typically around 20 mA.
Correct Answer:
B
— 20 mA
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Q. What is the primary function of a 555 timer in monostable mode?
A.
Generate a continuous square wave
B.
Generate a single pulse of a specific duration
C.
Act as a voltage comparator
D.
Control the brightness of an LED
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Solution
In monostable mode, the 555 timer generates a single pulse of a specific duration when triggered.
Correct Answer:
B
— Generate a single pulse of a specific duration
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Q. What is the primary function of a bistable multivibrator?
A.
To generate a continuous waveform
B.
To store a binary state
C.
To convert analog signals to digital
D.
To amplify signals
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Solution
A bistable multivibrator has two stable states and can store a binary state (0 or 1) until it is triggered to change states.
Correct Answer:
B
— To store a binary state
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Q. What is the purpose of the discharge pin in a 555 timer?
A.
To charge the timing capacitor
B.
To discharge the timing capacitor
C.
To control the output frequency
D.
To set the timer mode
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Solution
The discharge pin is used to discharge the timing capacitor when the output goes low.
Correct Answer:
B
— To discharge the timing capacitor
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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 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 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 supply voltage range for a standard 555 timer?
A.
1.5V to 5V
B.
4.5V to 15V
C.
5V to 20V
D.
10V to 30V
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Solution
The typical supply voltage range for a standard 555 timer is 4.5V to 15V.
Correct Answer:
B
— 4.5V to 15V
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Q. What type of multivibrator is used to generate a square wave output?
A.
Astable multivibrator
B.
Monostable multivibrator
C.
Bistable multivibrator
D.
None of the above
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Solution
An astable multivibrator continuously switches between its high and low states, generating a square wave output.
Correct Answer:
A
— Astable multivibrator
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Q. Which component is essential for setting the timing interval in a 555 timer?
A.
Inductor
B.
Resistor
C.
Diode
D.
Transistor
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Solution
Resistors and capacitors are essential for setting the timing interval in a 555 timer.
Correct Answer:
B
— Resistor
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Q. Which component is used to set the timing interval in a 555 timer circuit?
A.
Resistor
B.
Capacitor
C.
Inductor
D.
Diode
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Solution
The timing interval in a 555 timer circuit is set by a resistor and a capacitor.
Correct Answer:
B
— Capacitor
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Q. Which configuration of the 555 timer is used for pulse width modulation (PWM)?
A.
Astable mode
B.
Monostable mode
C.
Bistable mode
D.
None of the above
Show solution
Solution
Astable mode of the 555 timer is commonly used for generating pulse width modulation (PWM) signals.
Correct Answer:
A
— Astable mode
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Q. Which of the following configurations can a 555 timer be used in?
A.
Astable
B.
Monostable
C.
Bistable
D.
All of the above
Show solution
Solution
A 555 timer can be configured in astable, monostable, and bistable modes.
Correct Answer:
D
— All of the above
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Q. Which of the following configurations can a 555 timer NOT be used in?
A.
Monostable
B.
Astable
C.
Bistable
D.
Quadrastable
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Solution
The 555 timer can be used in monostable, astable, and bistable configurations, but not quadrastable.
Correct Answer:
D
— Quadrastable
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Q. Which pins of the 555 timer are used to set the timing interval in astable mode?
A.
Pin 1 and Pin 2
B.
Pin 2 and Pin 6
C.
Pin 6 and Pin 3
D.
Pin 4 and Pin 8
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Solution
In astable mode, the timing interval is set by the resistors connected to pins 2 (trigger) and 6 (threshold) along with the capacitor connected to pin 6.
Correct Answer:
B
— Pin 2 and Pin 6
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