Which device is used for measuring the specific gravity of liquids?

Which device is used for measuring the specific gravity of liquids?

• A. Hydrometer
• B. Thermometer
• C. Barometer
• D. Hydraulic gauge

Answer: (A)

Measuring how dense a liquid is compared to water uses a device designed for buoyancy-based comparison. A hydrometer floats in the liquid, and the depth it sinks depends on the liquid’s density. The denser the liquid, the less it sinks, so the reading on the calibrated stem gives the specific gravity directly. This works because buoyant force equals the weight of the displaced liquid, so denser liquids displace less volume for the same weight. The other devices are for temperature, atmospheric pressure, or hydraulic pressure, none of which directly measure how heavy a liquid is relative to water.

Measuring how dense a liquid is compared to water uses a device designed for buoyancy-based comparison. A hydrometer floats in the liquid, and the depth it sinks depends on the liquid’s density. The denser the liquid, the less it sinks, so the reading on the calibrated stem gives the specific gravity directly. This works because buoyant force equals the weight of the displaced liquid, so denser liquids displace less volume for the same weight. The other devices are for temperature, atmospheric pressure, or hydraulic pressure, none of which directly measure how heavy a liquid is relative to water.