OPSC OAS 2022 PrelimsScience & TechnologyQuestion 4
Solved previous year question from the OPSC OAS/OCS 2022 Preliminary Examination (General Studies), with the official answer key and a detailed explanation.
Question
Meniscus rise in glass thermometer is due to the change in
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Answer & Explanation
Correct answer: (A) Density
- In a glass thermometer, the liquid (mercury or alcohol) rises in the narrow capillary tube when temperature increases. This meniscus rise is due to the change in density of the liquid.
Key Principle
The working of a thermometer is based on thermal expansion of liquids. When a liquid is heated:
- Its volume increases
- Its mass remains constant
- Therefore its density decreases (density = mass/volume)
- The decreased density causes the liquid to rise in the capillary tube.
