Exam-style question
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In an astable multivibrator using a 555 timer, what happens to the duty cycle if R2 is increased while R1 and C remain constant?.
- A.It increases
- B.It decreases
- C.It stays the same
- D.It becomes 50 %
Model answer
What a good answer should say
- It decreases
Explanation
Why this works
Formula: D = (R1+R2)/(R1+2R2). Substitution: R1 constant, R2 increases.
Working: As R2 grows, the numerator grows slower than the denominator, so D decreases. Answer: It decreases.
Units: None. Conclusion: The duty cycle falls when R2 is increased.
Common mistake
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