Question

Pseudo-plastic and dilatant fluid obey

• A. Fourier's law
• B. Power law
• C. Dalton's law
• D. Rault's law

Hint:

Remember the flow index (\(n\)) values:
- \(n < 1\): Pseudoplastic (Shear-thinning)
- \(n = 1\): Newtonian (Water, sugar solutions)
- \(n > 1\): Dilatant (Shear-thickening)

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In rheology, fluids are classified based on their behavior under shear stress.
Newtonian fluids show a linear relationship between shear stress and shear rate, while non-Newtonian fluids show non-linear relationships.

Step 2: Key Formula or Approach:
The Ostwald-de Waele model, commonly referred to as the Power Law, mathematically describes the behavior of pseudoplastic (shear-thinning) and dilatant (shear-thickening) non-Newtonian fluids:
\[ \tau = K \cdot \dot{\gamma}^n \]
where:
- \(\tau\) is the shear stress.
- \(K\) is the flow consistency index.
- \(\dot{\gamma}\) is the shear rate.
- \(n\) is the flow behavior index.

Step 3: Detailed Explanation:
- For pseudoplastic fluids (such as fruit purees, condensed milk, and ketchup), the viscosity decreases as shear rate increases, which corresponds to \(n < 1\).
- For dilatant fluids (such as raw starch suspensions), the viscosity increases as shear rate increases, which corresponds to \(n > 1\).
Both of these non-Newtonian fluids obey the Power Law model.

Step 4: Final Answer:
The correct option is (B).