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Question

There are 2 systems:

a. An automatic washing machine

b. An automatic intensity adjustable light bulb

Which of these systems will be more sensitive to the variation in system's gain?

The correct answer is

Automatic washing machine

System Gain Sensitivity Overview

Understanding system gain sensitivity is crucial in control systems. It refers to how much the output or performance of a system changes in response to variations in its internal gain parameters. Gain, in this context, can be thought of as the amplification factor or efficiency of a component within the system. Systems can generally be categorized into two main types based on their control mechanism: open-loop and closed-loop (feedback) systems.

Washing Machine System Analysis

An automatic washing machine typically operates as an open-loop control system for its primary washing cycle. While it has automated steps (filling, washing, rinsing, spinning), it generally does not continuously measure the cleanliness of clothes and adjust the wash intensity or duration based on real-time feedback during the wash cycle itself. Its performance, such as how clean the clothes get, is directly dependent on the efficiency and power of its internal components like the motor, water pump, and heating element. These internal components contribute to the system's overall "gain."

  • If the motor's efficiency (its gain) decreases due to wear and tear or manufacturing variations, the washing action might become less effective, and the clothes might not get as clean.
  • There is no immediate feedback mechanism during the wash to compensate for this decrease in gain. The machine simply proceeds with its pre-programmed cycle.

Therefore, an automatic washing machine, being largely an open-loop system in its core operation, will be more sensitive to the variation in system's gain. Any change in the gain of its internal components directly affects its output performance without automatic correction.

Adjustable Light Bulb System Analysis

An automatic intensity adjustable light bulb, by its very nature, implies a continuous measurement of ambient light and an adjustment of its own output to maintain a desired illumination level. This is a classic example of a closed-loop feedback control system.

  • It uses a light sensor (the feedback element) to measure the actual light intensity in the room.
  • This measured value is compared to a desired set-point (the reference illumination level).
  • Any difference (error) between the desired and actual light levels is used by the controller to adjust the power supplied to the light bulb, thereby changing its intensity.

In such a closed-loop system, negative feedback is employed to reduce the sensitivity of the overall system to variations in its internal components. If the "gain" of the light bulb itself (i.e., its efficiency in converting electrical power to light, which might decrease over time) changes:

  • The light sensor will detect a deviation from the desired light level.
  • The control system will automatically increase or decrease the power to the bulb to compensate for this change and maintain the desired light intensity.

This feedback mechanism makes the automatic intensity adjustable light bulb system significantly less sensitive to the variation in system's gain of its components.

Comparison of System Sensitivity

To summarize the sensitivity of the two systems:

System Type Description Sensitivity to Gain Variation
Automatic Washing Machine Mostly Open-Loop Control More Sensitive (no continuous feedback to correct for component changes)
Automatic Intensity Adjustable Light Bulb Closed-Loop Feedback Control Less Sensitive (feedback mechanism compensates for component changes)

Therefore, the automatic washing machine will be more sensitive to variations in the system's gain because it lacks the continuous feedback mechanism present in the automatic intensity adjustable light bulb to actively compensate for such changes.

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Important Questions from Sensitivity

  1. An ammeter requires a change of 3 A in its coil to produce a change in deflection of the pointer by 12 mm. Its sensitivity is

  2. During the measurement of voltage, the voltmeter responded with a 0.18-V change when the input was varied by 0.2 V. Find the sensitivity of the instrument.

  3. If the value of (1 + GH) is less than 1, then sensitivity is/has _____.
  4. Study the given table for resistance values of a platinum thermometer measured at a range of temperatures. Calculate the sensitivity of the measurement of the instrument.

    Resistance (Ω) Temperature (°C)
    200100
    205150
    210200
    215250
  5. If meter A requires 100 mA to give full-scale deflection, meter B requires 50 mA to give scale deflection and meter C requires 80 mA to give full-scale deflection, then the

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