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The specific gravity of electrolyte is measured by
manometer
hygrometer
hydrometer
psychrometer
hydrometer
Quick Summary: The specific gravity of a lead-acid battery electrolyte (sulfuric acid) is measured using a hydrometer. It serves as a direct indicator of the battery's state of charge, as the density of the electrolyte changes due to the chemical reaction involving sulfuric acid during charging and discharging.
The specific gravity of a lead-acid battery electrolyte (sulfuric acid) is measured using a hydrometer. It serves as a direct indicator of the battery's state of charge, as the density of the electrolyte changes due to the chemical reaction involving sulfuric acid during charging and discharging.
SG=Density┬аof┬аPure┬аWaterDensity┬аof┬аElectrolyteтАЛ тАФ Definition of Specific Gravity
The hydrometer operates on Archimedes' Principle, where a floating body displaces a volume of fluid equal to its own weight. A calibrated glass float (spindle) inside the hydrometer sinks deeper in less dense (discharged) electrolyte and floats higher in more dense (fully charged) electrolyte. By observing the scale reading at the liquid surface level, the relative density (specific gravity) is determined.
A fully charged lead-acid battery typically has a specific gravity between 1.250 and 1.280.
A discharged battery typically shows a specific gravity near 1.100 to 1.150.
Temperature affects the reading, so corrections are often applied if the electrolyte is not at standard temperature (usually 27┬░C).
Sulfuric acid is consumed during discharge, reducing the density of the solution.
Simple, low-cost device
Provides immediate, real-time indication of charge state
Does not require an external power source
Requires manual sampling of potentially corrosive acid
Accuracy is temperature-dependent
Cannot be used on sealed (VRLA/AGM) batteries
Lead-acid battery health monitoring
Automotive battery maintenance
Industrial UPS systems with wet-cell batteries
Hydrometer readings are a primary diagnostic tool in industrial maintenance.
Option B (Hygrometer) measures humidity, Option A (Manometer) measures pressure, and Option D (Psychrometer) measures relative humidity using dry/wet bulb thermometers.
C is correct тАФ The hydrometer measures specific gravity based on the principle of buoyancy and the varying density of the sulfuric acid electrolyte.
Always remember: Specific Gravity is the ratio of density of substance to the density of water; hence it is a unitless quantity.