Hydrometer, which is an instrument used to measure the density or relative density (specific gravity) of liquids.
Principle of Buoyancy: Hydrometers work based on Archimedes' principle, where the buoyant force on the instrument when placed in a liquid is equal to the weight of the liquid displaced. Construction: It typically consists of a sealed hollow glass tube with a wider bottom portion * Measurement: When placed in a liquid, the hydrometer floats at a certain depth. The point where the liquid's surface touches the stem indicates the relative density or specific gravity, which is read from the scale. * Applications: Hydrometers are used in various industries, including brewing and wine-making (to measure sugar content), the petroleum industry (for API gravity), and in battery maintenance (to check electrolyte density).