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NDA 2 2025 GAT, question 63

Topic: Physics

Q63

Which one of the following instruments can be used to measure −250∘C-250^{\circ}C temperature ?

  1. (a) By using a mercury based thermometer
  2. (b) By using an alcohol based thermometer
  3. (c) By using a clinical thermometer
  4. (d) By using thermocouple based thermometerCorrect answer

Solution.

Answer: (d) By using thermocouple based thermometer

  1. −250°C is about 23 K.
  2. Mercury and ordinary alcohol thermometers cannot work there because their liquids freeze.
  3. A suitably chosen and calibrated cryogenic thermocouple can operate at such temperatures; not every thermocouple type has this range.