Question

In the case of a hydrometer for lighter liquids, why is the buoyancy bulb of large volume used?

Answer 1

1. For a body not to sink in a liquid, the weight of the body must be less than the buoyant force exerted on the body by the liquid.
2. Buoyant force exerted by the liquid on the body is directly proportional to the volume of liquid displaced by the body.
3. Buoyant force in the case of lighter liquids is less because buoyant force is directly proportional to the density of the liquid.
4. Since the density of the lighter liquid is constant while using a hydrometer, the feasible way to develop appropriate buoyant force is to use a hydrometer that has a buoyancy bulb of large volume.
5. A buoyancy bulb of large volume is used in a hydrometer to ensure that there is an appropriate buoyant force on the hydrometer and the weight of the hydrometer does not exceed the buoyant force on the hydrometer.

Hence, a buoyancy bulb of large volume is used in a hydrometer for lighter liquids to ensure that the hydrometer does not sink into lighter liquids.