555 timer in monostable mode — compute R1 for a target pulse width A 555 timer is configured as a monostable multivibrator with timing capacitor C1 = 0.01 µF. Determine the resistor R1 required to obtain a pulse width of 2 ms (use T = 1.1 * R1 * C1).

Introduction / Context:The 555 timer in monostable mode generates a single pulse whose duration depends on an external resistor and capacitor. The standard timing relation is T = 1.1 * R * C for the high output interval. This question tests your ability to rearrange the formula and select a practical resistor value for a specified pulse width and known capacitance, a frequent task in embedded timing and pulse-generation circuits.

Given Data / Assumptions:

• Monostable mode (one-shot) using a 555 timer IC.
• Target pulse width T = 2 ms.
• Timing capacitor C1 = 0.01 µF = 10 nF = 10 * 10^-9 F.
• Timing relation: T = 1.1 * R1 * C1.

Concept / Approach:Rearrange the timing equation to solve for R1. Ensure unit consistency (seconds, farads, ohms). After computing R1, compare the result to the offered options, rounding to a standard resistor value where appropriate.

Step-by-Step Solution:

Verification / Alternative check:Back-calculate the pulse: T_est = 1.1 * 182,000 * 10e-9 ≈ 1.1 * 0.00182 ≈ 0.002002 s ≈ 2.00 ms, matching the requirement.

Why Other Options Are Wrong:

• 200 kΩ: gives T ≈ 2.2 ms (too long).
• 91 kΩ: gives T ≈ 1.0 ms (half the target).
• 182 Ω: off by three orders of magnitude; pulse would be microseconds.

Common Pitfalls:Confusing microfarads with nanofarads, omitting the 1.1 constant, or rounding to a non-standard value that misses timing by a wide margin.

Final Answer:182 kΩ