FAA Powerplant Written Practice Test

What does the viscosity of a liquid measure?

1. Its density

2. Its resistance to flow

3. Its temperature stability

4. Its electrical conductivity

The correct answer is: Its resistance to flow

Viscosity of a liquid measures its resistance to flow. This property is essential in understanding how liquids behave under different conditions and is critical for applications involving fluid dynamics. A liquid with high viscosity, such as honey, flows more slowly compared to a low-viscosity liquid like water, which flows easily. Viscosity is influenced by temperature; as temperature increases, the viscosity of most liquids decreases, allowing them to flow more freely. The other options relate to different properties of liquids. Density pertains to mass per unit volume, temperature stability refers to how well a substance maintains its properties over a range of temperatures, and electrical conductivity measures a liquid’s ability to conduct electricity, which does not relate to its flow characteristics. Understanding viscosity is crucial in fields such as engine design and fluid mechanics as it impacts lubrication, fuel delivery, and cooling systems among others.