Hydrometers
Summary
HD11:50Animated video Lecture for Hydrometers
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A hydrometer is an instrument, used for measuring the relative density of a liquid directly and hence to test the purity. A hydrometer works on the principle of floatation.
The hydrometer is an instrument used to measure the relative density (specific gravity) of liquids and the purity of the liquids. It works on the principle of floatation.
While floating, the length of hydrometer immersed in a liquid is inversely proportional to the density of the liquid in which the hydro meter is placed.
Working of a Hydrometer
Float the loaded test tube first in a jar filled with water of density ρ. Note the length, l of the test tube inside the water.
Let the area of cross - section of test tube = a
Density of water in which it is floating = ρ
Volume of water displaced, V = a×l
Weight of water displaced, = a×l×ρ×g, where g = acceleration due to gravity
Accordng to the laws of floatation,
Weight of the loaded test tube = Weight of the water displaced = alρg ---------- (i