# DBT JRF 2022 — Question 94

Exam: DBT JRF 2022 · Section: B · Topic: Bioprocess Engineering › Fluid Rheology & Viscosity · Difficulty: Medium

## Question

For Bingham Plastics and pseudo plastic liquids, the apparent viscosity:

## Options

- **A.** Increases with increase in shear force
- **B.** Decreases with increase in shear force
- **C.** Remains constant with increase in shear force
- **D.** Changes in an unpredictable fashion with change in shear force

## Answer

Option B

## Explanation

Bingham plastic and pseudoplastic — viscosity behaviour: Non-Newtonian fluid classifications: • Pseudoplastic (shear-thinning): viscosity DECREASES with increasing shear rate. Examples: polymer solutions, many fermentation broths, blood. • Dilatant (shear-thickening): viscosity INCREASES with increasing shear rate. Examples: cornstarch slurry, some dense suspensions. • Bingham plastic: requires a yield stress before flow begins; then behaves as Newtonian (constant viscosity). Example: toothpaste, sludge. Common feature of Bingham plastic and pseudoplastic: • Both show a DECREASE in apparent viscosity with increasing applied force/shear rate (above yield stress for Bingham). This is the OPPOSITE of dilatant behaviour. Answer: Bingham plastics and pseudoplastics both show DECREASING apparent viscosity with increasing shear rate (shear-thinning behaviour).

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