555 Timer (Monostable) — Compute Output Pulse Width A 555 monostable circuit uses R1 = 4.7 kΩ and C1 = 47 µF. Using t = 1.1 * R1 * C1, determine the output pulse width and choose the closest option.

Difficulty: Easy

Correct Answer: 243 ms

Explanation:


Introduction / Context:
The 555 timer in monostable mode generates a single pulse each time it is triggered. Pulse width depends on the external timing resistor and capacitor. Accurate calculation is essential for timing, control, and pulse-shaping tasks.



Given Data / Assumptions:

  • R1 = 4.7 kΩ = 4700 Ω.
  • C1 = 47 µF = 47 × 10^-6 F.
  • Formula: t = 1.1 * R1 * C1.


Concept / Approach:
Apply the standard monostable timing relation directly and express the result in milliseconds for readability.



Step-by-Step Solution:
Compute t = 1.1 * 4700 * 47×10^-6.First multiply R1 * C1 = 4700 * 47×10^-6 ≈ 0.2209.Multiply by 1.1: 0.2209 * 1.1 ≈ 0.243 s.Convert to milliseconds: 0.243 s ≈ 243 ms.



Verification / Alternative check:
Dimensional check: Ω * F yields seconds; numerical value aligns with typical 555 timing ranges for kΩ and tens of µF.



Why Other Options Are Wrong:

  • 24 s: Off by three orders of magnitude.
  • 24 ms: Off by approximately a factor of 10.
  • 243 µs: Off by a factor of 1000.


Common Pitfalls:
Misplacing metric prefixes (µF vs nF) or forgetting the 1.1 factor.


Final Answer:
243 ms

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