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Question

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

The correct answer is

0.1 Ω/°C

The question asks us to calculate the sensitivity of a platinum thermometer based on the provided table of resistance values at various temperatures. Understanding the sensitivity of an instrument is crucial for accurate measurement.

Sensitivity of Platinum Thermometer Measurement

The sensitivity of a measuring instrument, like a platinum thermometer, tells us how much the output changes for a given change in the input. In this context, the output is resistance (in Ohms, Ω) and the input is temperature (in degrees Celsius, °C). Therefore, the sensitivity will be expressed in Ω/°C.

The fundamental formula to calculate sensitivity (S) is:

\[S = \frac{\text{Change in Output}}{\text{Change in Input}}\]

For a platinum thermometer, this translates to:

\[S = \frac{\Delta \text{Resistance}}{\Delta \text{Temperature}} = \frac{\Delta R}{\Delta T}\]

Resistance and Temperature Data Analysis

Let's examine the provided data for the platinum thermometer, which lists corresponding resistance and temperature values:

Resistance (Ω) Temperature (°C)
200 100
205 150
210 200
215 250

To determine the sensitivity, we can select any two data points from this table. As observed from the table, the resistance increases consistently by 5 Ω for every 50 °C increase in temperature. This indicates a linear relationship, meaning the sensitivity should be constant across the given measurement range.

Calculating Instrument Sensitivity

Let's use the first two data points from the table to perform the calculation for the sensitivity of the measurement instrument:

  • First data point: Resistance (\(R_1\)) = 200 Ω, Temperature (\(T_1\)) = 100 °C
  • Second data point: Resistance (\(R_2\)) = 205 Ω, Temperature (\(T_2\)) = 150 °C

Next, we calculate the change in resistance ($\Delta R$) and the change in temperature ($\Delta T$):

  • Change in Resistance ($\Delta R$) = \(R_2 - R_1 = 205\, \Omega - 200\, \Omega = 5\, \Omega\)
  • Change in Temperature ($\Delta T$) = \(T_2 - T_1 = 150\, ^\circ\text{C} - 100\, ^\circ\text{C} = 50\, ^\circ\text{C}\)

Finally, we calculate the sensitivity (S) of the platinum thermometer instrument using the formula:

\[S = \frac{\Delta R}{\Delta T} = \frac{5\, \Omega}{50\, ^\circ\text{C}}\]

\[S = 0.1\, \Omega/^\circ\text{C}\]

This result implies that for every one degree Celsius change in temperature, the resistance of the platinum thermometer changes by 0.1 Ω. This consistent and predictable change is a key characteristic demonstrating the responsiveness and reliability of the instrument's measurement.

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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. 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?

  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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