Question

The principal working of hydrometer is based on Archimedes’s principle.
A. True
B. False

Answer 1

Hint: This is a true/false type question so the hint for solving question should be in question itself. In this case, we must know what is Archimedes’s principle and hydrometer. We know that Archimedes’s principle states that any object immersed in liquid will experience buoyant force equal to the force of gravity on the displaced fluid. Hydrometer is an instrument based on buoyancy.

Complete step by step answer:
A hydrometer is an instrument used to determine the specific gravity of a liquid. Again Archimedes’s principle states that buoyant force on a body fully or partially submerged in a fluid, is equal to the weight of the fluid that body displaces. Now, we must see how the specific gravity is measured in a hydrometer. A hydrometer is a glass flask sealed at both ends. On one end it is filled with lead, this causes the hydrometer to float upright in a liquid. The second jar also known as a hydrometer jar is filled with liquid being measured. The hydrometer is then suspended into this liquid. On the sides of the hydrometer there are two scales indicating volume and density respectively. The hydrometer then balances itself by sinking or floating upwards in the liquid as the buoyant force and force of gravity by the hydrometer is always equal. Now readings are taken after the hydrometer is stabilized. The volume of the hydrometer submerged is measured. In a way, the amount of fluid displaced is measured and specific gravity of liquid is calculated. So, it is now clear that hydrometer works on Archimedes’s principle.

Additional Information:
While taking hydrometer readings care should be taken that the reading coinciding the liquid level is not taken but the reading just above it is considered. Also, the scale on the hydrometer should be checked as there are types of scales such as Brix scale, Baume scale, Alcohol scale, API scale.

Note:
The readings in the hydrometer may vary due to temperature or improper immersion. It should always be checked that the hydrometer is clean to avoid reading errors. The units of or scale marked on hydrometer is given by gram per cubic centimetre.