Question

Why is the gravity bulb of a hydrometer for lighter liquids not made very heavy?

Answer 1

1. The basic crux of the law of floatation follows that “a body sinks in a liquid if the weight of the body exceeds the buoyant force exerted on the body by the liquid”.
2. A body that is supposed not to sink in a fluid is designed in such a way that the weight of the body does not exceed the buoyant force.
3. In the case of a hydrometer for lighter liquids, the buoyant force on the hydrometer when immersed in a lighter liquid is less because the buoyant force is directly proportional to the density of the liquid.
4. To ensure that the weight of the hydrometer is less than the buoyant force on the hydrometer, the gravity bulb of a hydrometer for lighter liquids is made lighter.

Hence, the gravity bulb of a hydrometer for lighter liquids is not made very heavy to ensure that the hydrometer does not sink into the lighter liquid.