Which tool is used to measure the specific gravity of the electrolyte in a wet cell battery?

The specific gravity of the electrolyte in a wet cell battery is measured using a hydrometer. This tool is specifically designed to gauge the density of liquids, allowing it to determine the concentration of sulfuric acid in the electrolyte solution of the battery. The specific gravity reading provides insights into the state of charge of the battery; a higher specific gravity indicates a fully charged state, while a lower specific gravity suggests a discharged or weak battery.

In contrast, other instruments like voltmeters are used to measure voltage, amperemeters measure electric current, and barometers measure atmospheric pressure. These tools do not provide information about the density or concentration of electrolytes, making them unsuitable for assessing battery electrolyte conditions.