A hydrometer is used to measure:
Try it first: pick an option, then read the explanation.
Correct answer: D. Specific gravity of liquids
Asked in SSC JE 2011
Detailed Explanation
The hydrometer is a standard laboratory and field instrument that operates on Archimedes' principle of flotation.
Why “Specific gravity of liquids” Is Correct
A hydrometer is a calibrated sealed glass instrument designed to float vertically in a liquid; the depth of immersion on its graduated stem directly indicates the specific gravity of the liquid.
Why the Other Options Are Wrong
- A. Velocity of fluids: Velocity of fluids is measured using Pitot tubes, current meters, or hot-wire anemometers.
- B. Velocity of gases: Velocity of gases is measured using anemometers.
- C. Flow of fluids: Flow of fluids (discharge) is measured using venturimeters, orifice meters, or flow nozzles.
Key Point
A hydrometer measures the specific gravity (relative density) of liquids.
Key Concepts for Students
- Hydrometer sinks deeper in less dense liquids and floats higher in denser liquids.
- Lactometer is a specialized hydrometer for testing milk purity.
- Do not confuse hydrometer (specific gravity) with hygrometer (humidity).
Practice more: this is question 62 in Properties of Fluid MCQs – Part 5. Try the whole set and check every answer instantly.