Question

For an ideal fluid, viscosity is

• A. Unity
• B. Zero
• C. Infinity
• D. Finite but small

Answer 1

The correct option is B

Zero

Ideal fluid: A fluid with no resistance to the shear stress between the layers is called as an ideal fluid.

Viscosity: It is defined as the resistance a fluid offers to deformation.

Explanation for the correct option:

Option B:

1. As there is no resistance, the viscosity of an ideal fluid will be zero.
2. Hence, this is the correct option.

Explanation for the incorrect option:

Option A:

1. As there is no resistance, the viscosity of an ideal fluid cannot be unity.
2. Hence, this is not the correct option.

Option C:

1. A fluid with infinite viscosity will have infinite resistance.
2. But an ideal fluid has no resistance.
3. Hence, this is not the correct option.

Option D:

1. The viscosity of an ideal fluid is zero.
2. Even a small finite amount of viscosity will lead to it not being an ideal fluid anymore.
3. Hence, this is not the correct option.

Hence, option B is the correct option.