Question

Of the lubricant A and B for a machine. A has a coefficient of viscosity slightly greater than that of B. which would you prefer in summer and winter.

Answer 1

To solve this question we should know about basic term:
Viscosity: Viscosity is the resistance of a fluid (liquid or gas) to changing shape or moving adjacent sections relative to one another. The term "viscosity" refers to the resistance to flow.
So we first try to understand the relation between temperature and viscosity of a fluid.

Complete step by step solution:
Relation between temperature and viscosity: The viscosity of liquids reduces rapidly as the temperature rises, but the viscosity of gases rises as the temperature rises.
As a result, liquids flow more freely when heated, and gases flow more slowly.
Water viscosities at $27{\text{ }}^\circ C{\text{ }}\left( {81{\text{ }}^\circ F} \right)$ and $77{\text{ }}^\circ C{\text{ }}\left( {171{\text{ }}^\circ F} \right)$ are $0.85 \times {10^3}$ and $0.36 \times {10^3}$ Pascal-second, respectively, while air viscosities are $1.85 \times {10^5}$and $2.08 \times {10^5}$ Pascal-second at the same temperatures.
So, In the summer, the coefficient of viscosity of liquid reduces as the temperature rises, while in the winter, the coefficient of viscosity of liquid increases as the temperature falls. As a result, in summers, sample A with a higher viscosity coefficient is favoured, while in winters, sample B is favoured.

Note:
Lubricant: Lubrication is the application of a friction-reducing layer between moving surfaces in contact to reduce friction and wear. The lubricant can be in the form of a liquid, solid, or plastic. The application dictates which oil should be used, often known as the base oil. Synthetic oils can be effective in extreme situations. Vegetable base oils can be used where the environment is a concern.