Q63 / 270 · NDA 2025 (Phase 2) · General Ability
Which one of the following instruments can be used to measure −250°C temperature?
- ABy using a mercury based thermometer
- BBy using an alcohol based thermometer
- CBy using a clinical thermometer
- Correct answerDBy using thermocouple based thermometer
Solution
Mercury freezes at $-39^\circ\text{C}$, so a mercury-based thermometer cannot be used to measure $-250^\circ\text{C}$.
Alcohol freezes at $-115^\circ\text{C}$, so an alcohol-based thermometer is also unsuitable for measuring $-250^\circ\text{C}$.
A clinical thermometer is designed to measure human body temperature, typically in the narrow range of $35^\circ\text{C}$ to $42^\circ\text{C}$.
A thermocouple-based thermometer can measure a very wide range of temperatures, typically from $-270^\circ\text{C}$ to over $2000^\circ\text{C}$ depending on the metals used. Therefore, it can be used to measure $-250^\circ\text{C}$.
Answer: By using thermocouple based thermometer
Alcohol freezes at $-115^\circ\text{C}$, so an alcohol-based thermometer is also unsuitable for measuring $-250^\circ\text{C}$.
A clinical thermometer is designed to measure human body temperature, typically in the narrow range of $35^\circ\text{C}$ to $42^\circ\text{C}$.
A thermocouple-based thermometer can measure a very wide range of temperatures, typically from $-270^\circ\text{C}$ to over $2000^\circ\text{C}$ depending on the metals used. Therefore, it can be used to measure $-250^\circ\text{C}$.
Answer: By using thermocouple based thermometer
Hence, the correct answer is option: 'D'.