Rheology Lecture 11, 12

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What is the meaning of the term 'Rheology'?

The science of fluid flow
The science of stress and deformation
The science of deformation of matter under the influence of stress (correct)
The study of elastic and plastic deformation

What is the primary characteristic of a Newtonian liquid?

It exhibits plastic deformation
It exhibits elastic deformation
Viscosity changes with the applied shear force
Viscosity remains constant with the applied shear force (correct)

What is the unit of viscosity equivalent to 100 centipoise?

Dyne
Newtons
Pascal
Poise (correct)

What type of deformation is reversible?

Elastic deformation (B) Signup and view all the answers

What is the relationship between the rate of shear and shearing stress in Newtonian fluids?

The rate of shear is directly proportional to the shearing stress (C) Signup and view all the answers

What is the term for the measure of a fluid's resistance to flow upon application of a certain shear stress?

Viscosity (D) Signup and view all the answers

What is the reciprocal of viscosity?

Fluidity (Ø) (C) Signup and view all the answers

What happens to the viscosity of liquids when the temperature is increased?

It decreases (C) Signup and view all the answers

What is the equation that describes the relationship between viscosity and temperature?

η=Ae^(Ev/RT) (A) Signup and view all the answers

What is the characteristic of a plastic flow rheogram?

It intersects the shearing stress axis at a point called Yield value (C) Signup and view all the answers

What type of flow does not occur until a shearing stress corresponding to the yield value is exceeded?

Plastic flow (B) Signup and view all the answers

What is the type of flow that exhibits a decrease in viscosity with an increase in shear rate?

Pseudoplastic flow (B) Signup and view all the answers

What is the characteristic of a deflocculated suspension at rest?

Closely packed particles with minimum void volume (A) Signup and view all the answers

What is the process of accelerated reformation of the gel consistency after deformation by applying gentle or regular movements?

Reopexy (A) Signup and view all the answers

Which type of viscometer is used for measuring the viscosity of non-Newtonian fluids?

Multipoint viscometer (A) Signup and view all the answers

What is the term for the time-dependent changes in the viscosity of non-Newtonian liquids at a changeable shearing stress?

Thixotropy (A) Signup and view all the answers

What is the characteristic of a dilute suspension?

Does not show dilatancy (A) Signup and view all the answers

What is the type of viscometer that uses 20-50 ml sample?

Cup and BOB viscometer (C) Signup and view all the answers

What is the effect of high shear on polymers during preparation of products?

Results in lower viscosity (A) Signup and view all the answers

What is the effect of electrolytes at high concentration on polymer viscosity?

Competes for the absorbed water leading to polymer dehydration and decreased viscosity (A) Signup and view all the answers

What is the effect of pH on some polymers?

Causes polymer precipitation (A) Signup and view all the answers

What is the effect of temperature on polymer viscosity?

Decreases polymer viscosity, except with some polymers (C) Signup and view all the answers

What is the effect of aeration on polymer viscosity?

Increases polymer viscosity, except with emulsions (B) Signup and view all the answers

What is the effect of light on some polymers?

Causes polymer decomposition and decreased viscosity (C) Signup and view all the answers

What is the percentage of aqueous Penicillin G Procaine suspension that transforms from a fluid to a compacted depot in the muscle?

40-70 % w/w (D) Signup and view all the answers

What is affected by the viscosity of creams and lotions?

Rate of diffusion through skin (B) Signup and view all the answers

What is improved in thixotropic preparations?

Stability of vitamins (A) Signup and view all the answers

What is related to the diagnosis of diseases?

Rheology of body fluids (C) Signup and view all the answers

What is minimized or eliminated by formulation of flocculated suspensions with thixotropic characters?

Sedimentation or coagulation of suspended substances (C) Signup and view all the answers