Non-Newtonian systems MCQs With Answer are essential for B. Pharm students to master rheology fundamentals that impact drug formulation, processing, and stability. This concise introduction covers shear-thinning and shear-thickening behavior, yield stress, thixotropy, viscoelasticity, and common rheological models (power-law, Bingham, Herschel-Bulkley). Understanding measurement methods (rotational viscometers, cone-plate rheometers) and the role of polymers (CMC, HPMC, xanthan) in suspensions, gels, creams, and emulsions helps predict flow, syringeability, and bioavailability. These concepts link lab data to formulation performance and quality control. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What defines a non-Newtonian fluid?
- Fluid whose viscosity remains constant with shear rate
- Fluid whose viscosity changes with shear rate
- Fluid with zero viscosity
- Fluid that obeys Hooke’s law
Correct Answer: Fluid whose viscosity changes with shear rate
Q2. Which model expresses shear stress (τ) as τ = K·(γ̇)^n?
- Bingham plastic model
- Power-law (Ostwald-de Waele) model
- Newtonian model
- Casson model
Correct Answer: Power-law (Ostwald-de Waele) model
Q3. In the power-law model, what does n < 1 indicate?
- Newtonian behavior
- Pseudoplastic (shear-thinning) behavior
- Dilatant (shear-thickening) behavior
- Viscoelastic solid behavior
Correct Answer: Pseudoplastic (shear-thinning) behavior
Q4. Which rheological property represents resistance to flow?
- Elastic modulus (G’)
- Viscosity
- Surface tension
- Diffusion coefficient
Correct Answer: Viscosity
Q5. Which non-Newtonian behavior improves spreadability of topical gels?
- Dilatant behavior
- Pseudoplastic behavior
- Rigid plastic behavior
- Brittle behavior
Correct Answer: Pseudoplastic behavior
Q6. What is yield stress?
- The stress below which a material behaves as a solid
- The stress at which material melts
- The maximum stress a fluid can withstand
- The stress that decreases viscosity
Correct Answer: The stress below which a material behaves as a solid
Q7. Which model includes yield stress and power-law terms (τ = τ0 + K·γ̇^n)?
- Newtonian model
- Herschel-Bulkley model
- Stokes-Einstein model
- Arrhenius model
Correct Answer: Herschel-Bulkley model
Q8. Thixotropy is characterized by:
- Viscosity increasing with time under shear
- Viscosity decreasing with continuous shear and recovering at rest
- Immediate permanent deformation
- Elastic recovery without viscosity change
Correct Answer: Viscosity decreasing with continuous shear and recovering at rest
Q9. Which is an example of a dilatant system?
- 1% xanthan gum solution
- Concentrated cornstarch suspension
- Pure water
- Light mineral oil
Correct Answer: Concentrated cornstarch suspension
Q10. Which polymer commonly imparts pseudoplasticity in suspensions?
- Polyethylene glycol (PEG 400)
- Sodium carboxymethyl cellulose (CMC)
- Sodium chloride
- Propylene glycol
Correct Answer: Sodium carboxymethyl cellulose (CMC)
Q11. What does the consistency index K represent in the power-law model?
- Flow behavior index
- Apparent viscosity magnitude
- Shear rate
- Elastic modulus
Correct Answer: Apparent viscosity magnitude
Q12. Which instrument is best for oscillatory rheological measurements (G’ and G”)?
- Brookfield spindle viscometer
- Cone-and-plate rheometer
- Capillary viscometer
- pH meter
Correct Answer: Cone-and-plate rheometer
Q13. Viscoelastic materials exhibit which combination?
- Only viscous behavior
- Only elastic behavior
- Both viscous and elastic behavior
- No deformation under stress
Correct Answer: Both viscous and elastic behavior
Q14. G’ (storage modulus) greater than G” (loss modulus) indicates:
- Predominantly viscous behavior
- Predominantly elastic or solid-like behavior
- A Newtonian fluid
- Shear-thickening behavior
Correct Answer: Predominantly elastic or solid-like behavior
Q15. Which property is critical for syringeability of injectable suspensions?
- Surface tension
- Viscosity and yield stress
- Optical density
- Conductivity
Correct Answer: Viscosity and yield stress
Q16. Wall slip in rheological measurements leads to:
- Overestimation of viscosity
- Underestimation of true shear stress/viscosity
- No error in measurement
- Change of sample temperature
Correct Answer: Underestimation of true shear stress/viscosity
Q17. Which rheological behavior aids sedimentation prevention in suspensions?
- Low viscosity Newtonian flow
- High yield stress and pseudoplasticity
- High shear-thinning with zero yield stress
- Shear-thickening with no structure
Correct Answer: High yield stress and pseudoplasticity
Q18. The unit of shear rate is:
- Pascal (Pa)
- Second (s)
- Reciprocal second (s⁻¹)
- Newton (N)
Correct Answer: Reciprocal second (s⁻¹)
Q19. Which method measures viscosity at a single shear rate effectively for QC?
- Rotational viscometer (single spindle), fixed speed
- Oscillatory rheometer sweep
- Capillary chromatography
- Mass spectrometry
Correct Answer: Rotational viscometer (single spindle), fixed speed
Q20. Which model is often used for Bingham plastics?
- Newtonian model
- Bingham plastic model (τ = τ0 + μp·γ̇)
- Power-law model with n=0
- Maxwell model
Correct Answer: Bingham plastic model (τ = τ0 + μp·γ̇)
Q21. Rheopexy (negative thixotropy) refers to:
- Decrease in viscosity with time under shear
- Increase in viscosity with time under shear
- Instantaneous elastic response
- Viscosity independent of shear
Correct Answer: Increase in viscosity with time under shear
Q22. Which excipient increases viscosity and stabilizes emulsions in topical creams?
- Sodium chloride
- Hydroxypropyl methylcellulose (HPMC)
- Ethanol
- Propellant gas
Correct Answer: Hydroxypropyl methylcellulose (HPMC)
Q23. Which statement about shear-thinning liquids is TRUE?
- Viscosity increases with shear rate
- Viscosity decreases with shear rate
- They always have yield stress
- They are ideal Newtonian fluids
Correct Answer: Viscosity decreases with shear rate
Q24. Which technique is preferred to study high shear processing behavior (e.g., during pumping)?
- Low-shear capillary viscometer
- Capillary rheometer
- UV-Vis spectroscopy
- DSC (Differential Scanning Calorimetry)
Correct Answer: Capillary rheometer
Q25. Which rheological change often indicates physical instability in emulsions?
- Constant viscosity over time
- Sudden increase in viscosity and gelation
- Decrease in density only
- Increase in pH without viscosity change
Correct Answer: Sudden increase in viscosity and gelation
Q26. For a pharmaceutical gel that is thixotropic, what is expected after shear stops?
- Permanent liquidification
- Gradual recovery of structure and viscosity
- Immediate crystallization
- Evaporation of solvent
Correct Answer: Gradual recovery of structure and viscosity
Q27. In oscillatory testing, the loss tangent (tan δ = G”/G’) greater than 1 indicates:
- Predominantly elastic material
- Predominantly viscous material
- Solid crystalline behavior
- Undefined rheology
Correct Answer: Predominantly viscous material
Q28. Which factor most commonly decreases viscosity of polymer solutions?
- Increasing polymer molecular weight
- Increasing temperature
- Adding cross-linking agent
- Increasing polymer concentration
Correct Answer: Increasing temperature
Q29. Which property is measured by a Brookfield viscometer?
- pH
- Apparent viscosity at specific spindle speed
- Thermal conductivity
- Surface area
Correct Answer: Apparent viscosity at specific spindle speed
Q30. Which of these formulations is likely to show shear-thickening behavior at high solids?
- Highly concentrated suspension of hard particles
- Low-viscosity oil
- Hydroalcoholic solvent
Correct Answer: Highly concentrated suspension of hard particles
Q31. Casson model is commonly applied to which type of fluid?
- Pure water
- Blood and chocolate-like suspensions
- Ideal Newtonian oils
- Gaseous mixtures
Correct Answer: Blood and chocolate-like suspensions
Q32. Why is shear history important when measuring rheology?
- Shear history never affects rheology
- Previous shear can alter structure and apparent viscosity
- Shear history only affects color
- Shear history changes chemical composition
Correct Answer: Previous shear can alter structure and apparent viscosity
Q33. Which excipient is used to create thixotropic gels in ophthalmic formulations?
- Xanthan gum
- Sucrose
- Sodium chloride
- Isopropyl myristate
Correct Answer: Xanthan gum
Q34. A formulation with high G’ and low tan δ is best described as:
- Viscous liquid
- Gel-like or solid-like
- Newtonian fluid
- Highly dilatant liquid
Correct Answer: Gel-like or solid-like
Q35. Which factor does NOT typically influence rheology of suspensions?
- Particle size and shape
- Continuous phase viscosity
- Particle concentration
- Color of particles
Correct Answer: Color of particles
Q36. Which procedure helps avoid wall slip during rotational rheometry?
- Use smooth parallel plates
- Use roughened fixtures or serrated plates
- Increase temperature drastically
- Measure at extremely low speeds only
Correct Answer: Use roughened fixtures or serrated plates
Q37. Which is the primary reason for adding polymers to oral syrups?
- To increase drug potency
- To adjust rheology for mouthfeel and stability
- To change API molecular structure
- To make syrup volatile
Correct Answer: To adjust rheology for mouthfeel and stability
Q38. Which rheological test helps determine recovery after shear?
- Shear rate sweep only
- Three-interval thixotropy test (thixotropic loop or recovery test)
- pH titration
- Melting point determination
Correct Answer: Three-interval thixotropy test (thixotropic loop or recovery test)
Q39. In pharmaceutical extrusion-coating processes, why is rheology important?
- Rheology dictates color only
- Rheology affects flow, film thickness, and coating uniformity
- Rheology controls API potency chemically
- Rheology is irrelevant for coating
Correct Answer: Rheology affects flow, film thickness, and coating uniformity
Q40. Which behavior best facilitates easy pouring but prevents rapid sedimentation?
- High Newtonian viscosity that never changes
- Pseudoplasticity with appropriate yield stress
- Ionic conductivity
- Shear-thickening without yield stress
Correct Answer: Pseudoplasticity with appropriate yield stress
Q41. Which polymer is known for producing highly viscous, shear-thinning solutions at low concentrations?
- Polyvinyl chloride (PVC)
- Xanthan gum
- Sodium chloride
- Glycerin
Correct Answer: Xanthan gum
Q42. Which term describes a time-dependent increase in viscosity on standing?
- Thixotropy
- Syneresis
- Gellation or aging
- Rheopexy
Correct Answer: Gellation or aging
Q43. Which outcome is expected when temperature rises for most liquids?
- Viscosity increases
- Viscosity decreases
- Viscosity remains unchanged
- Material becomes solid
Correct Answer: Viscosity decreases
Q44. Which rheological parameter is particularly critical for topical cream spreadability?
- Electrical conductivity
- Yield stress and shear-thinning index
- Melting point only
- Refractive index
Correct Answer: Yield stress and shear-thinning index
Q45. In a rheogram (shear stress vs shear rate), Newtonian fluids show:
- Linear relation passing through origin
- Curved non-linear relation
- Horizontal line
- Vertical line
Correct Answer: Linear relation passing through origin
Q46. Which measurement helps predict sedimentation velocity in suspensions?
- Viscosity of continuous phase
- Color of suspension
- Optical rotation
- Boiling point
Correct Answer: Viscosity of continuous phase
Q47. Which phenomenon reduces apparent viscosity at high shear in polymer solutions?
- Polymer chain alignment and disentanglement
- Polymer crosslinking
- Polymer oxidation
- Polymer precipitation
Correct Answer: Polymer chain alignment and disentanglement
Q48. Which rheological model is simplest for Newtonian liquids?
- τ = μ·γ̇
- τ = τ0 + K·γ̇^n
- τ = K·γ̇^n
- G’ = G”
Correct Answer: τ = μ·γ̇
Q49. During formulation development, why measure rheology at multiple temperatures?
- Temperature has no effect on rheology
- To understand performance during storage and use conditions
- To change chemical identity of API
- To sterilize the formulation
Correct Answer: To understand performance during storage and use conditions
Q50. Which practice improves reproducibility of rheological measurements?
- Ignoring sample conditioning
- Standardizing shear history, temperature, and geometry
- Using different instruments each time
- Measuring at random times
Correct Answer: Standardizing shear history, temperature, and geometry
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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