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Questions and Answers
[Blank] is an expression of a liquid's resistance to flow.
[Blank] is an expression of a liquid's resistance to flow.
Viscosity
Materials are classified into Newtonian and ______ systems based on their flow behavior.
Materials are classified into Newtonian and ______ systems based on their flow behavior.
Non-Newtonian
Flow properties of Newtonian systems follow ______ law of flow.
Flow properties of Newtonian systems follow ______ law of flow.
Newton's
In Newtonian systems, the rate of shear is directly proportional to ______.
In Newtonian systems, the rate of shear is directly proportional to ______.
The viscosity (η) is measured in ______ in the CGS unite system.
The viscosity (η) is measured in ______ in the CGS unite system.
Shearing stress (F) is measured in ______.
Shearing stress (F) is measured in ______.
Rate of Shear (G) is measured in ______.
Rate of Shear (G) is measured in ______.
According to the principle of viscosity, each lower layer of liquid will move with velocity proportional to its distance from the ______.
According to the principle of viscosity, each lower layer of liquid will move with velocity proportional to its distance from the ______.
The difference in velocity (dv) between two planes of liquid separated by distance (dr) is termed ______.
The difference in velocity (dv) between two planes of liquid separated by distance (dr) is termed ______.
The force per unit area (F/A) required to bring about flow is known as ______.
The force per unit area (F/A) required to bring about flow is known as ______.
The equation η = F/G defines η as the ______ or dynamic viscosity.
The equation η = F/G defines η as the ______ or dynamic viscosity.
The shearing force required to produce a velocity of 1 cm/sec between two parallel planes of liquid each 1cm² in area and separated by a distance of 1 cm defines the ______.
The shearing force required to produce a velocity of 1 cm/sec between two parallel planes of liquid each 1cm² in area and separated by a distance of 1 cm defines the ______.
In Non-Newtonian systems, substances fail to follow ______ equation of flow.
In Non-Newtonian systems, substances fail to follow ______ equation of flow.
[Blank] flow is one of the three classes of flow included in Non-Newtonian systems.
[Blank] flow is one of the three classes of flow included in Non-Newtonian systems.
Shear thinning is also known as ______ flow.
Shear thinning is also known as ______ flow.
[Blank] flow is also known as shear thickening behavior.
[Blank] flow is also known as shear thickening behavior.
Capillary, Falling Sphere, Cup and Bob, and Cone and Plate are types of ______.
Capillary, Falling Sphere, Cup and Bob, and Cone and Plate are types of ______.
The time of flow of liquid under test is compared with time required for liquid of known viscosity (______), is the principle of Ostwald viscometer.
The time of flow of liquid under test is compared with time required for liquid of known viscosity (______), is the principle of Ostwald viscometer.
In the viscosity experiment for 2 liquids, the equation to find the viscosity is given by $η₁/η₂ = t₁ρ₁/______$
In the viscosity experiment for 2 liquids, the equation to find the viscosity is given by $η₁/η₂ = t₁ρ₁/______$
The tangential force per unit surface, known as shearing stress F and expressed in pascals is called ______.
The tangential force per unit surface, known as shearing stress F and expressed in pascals is called ______.
[Blank] is the ratio of absolute viscosity to the density of liquid
[Blank] is the ratio of absolute viscosity to the density of liquid
[Blank] measures a fluid's resistance to flow under an applied force and is expressed in pascals.
[Blank] measures a fluid's resistance to flow under an applied force and is expressed in pascals.
In the shear stress vs. shear rate graph for a Newtonian fluid, the plot is a ______ line.
In the shear stress vs. shear rate graph for a Newtonian fluid, the plot is a ______ line.
The unit of kinematic viscosity is either stock or ______.
The unit of kinematic viscosity is either stock or ______.
In the Ostwald viscometer, the time required for a liquid to pass between two marks is measured to determine its ______.
In the Ostwald viscometer, the time required for a liquid to pass between two marks is measured to determine its ______.
For Non-Newtonian materials, the relationship between shear stress and shear rate is typically ______.
For Non-Newtonian materials, the relationship between shear stress and shear rate is typically ______.
The general formula to determine viscosity involves the force (F) required for flow and the rate of ______ (G).
The general formula to determine viscosity involves the force (F) required for flow and the rate of ______ (G).
The viscosity of simple liquids such as water and milk are examples of ______ systems.
The viscosity of simple liquids such as water and milk are examples of ______ systems.
The rate of shear is typically expressed in ______.
The rate of shear is typically expressed in ______.
In the Ostwald viscometer, the liquid flows through a ______ tube due to gravity.
In the Ostwald viscometer, the liquid flows through a ______ tube due to gravity.
The parameter denoted as 'G' in viscosity equations represents the ______.
The parameter denoted as 'G' in viscosity equations represents the ______.
The term 'fluidity' is inversely proportional to the liquid's ______.
The term 'fluidity' is inversely proportional to the liquid's ______.
The determination of viscosity using an Ostwald viscometer measures the flow time between two ______.
The determination of viscosity using an Ostwald viscometer measures the flow time between two ______.
The equation $F = ηG$ relates force, viscosity, and ______ in Newtonian fluids.
The equation $F = ηG$ relates force, viscosity, and ______ in Newtonian fluids.
For a shear-thinning fluid, the viscosity decreases as the shear rate ______.
For a shear-thinning fluid, the viscosity decreases as the shear rate ______.
A liquid with high viscosity has greater ______ to flow.
A liquid with high viscosity has greater ______ to flow.
A ______ fluid does not experience a change in viscosity regardless of the amount of shear stress applied
A ______ fluid does not experience a change in viscosity regardless of the amount of shear stress applied
All types of ______ cab be used to determine the viscosity of Newtonian systems.
All types of ______ cab be used to determine the viscosity of Newtonian systems.
Kinematic viscosity is equal to absolute viscosity divided by the ______ of liquid
Kinematic viscosity is equal to absolute viscosity divided by the ______ of liquid
Liquids that exhibit a decrease in viscosity with time under a constant shear rate display ______ behavior.
Liquids that exhibit a decrease in viscosity with time under a constant shear rate display ______ behavior.
Flashcards
Viscosity
Viscosity
The expression of a liquid's resistance to flow.
Newtonian Systems
Newtonian Systems
Systems where flow properties follow Newton's law of flow.
Shearing Stress (F)
Shearing Stress (F)
The force per unit area needed to cause flow.
Poise
Poise
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Non-Newtonian Systems
Non-Newtonian Systems
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Ostwald Viscometer
Ostwald Viscometer
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Dynamic viscosity (η)
Dynamic viscosity (η)
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Kinematic viscosity (v)
Kinematic viscosity (v)
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Study Notes
- Viscosity expresses a liquid's resistance to flow.
- Higher viscosity means greater resistance.
Material Classification by Flow Type
- Materials may be classified into Newtonian systems or Non-Newtonian systems based on flow.
Newtonian Systems
- Follow Newton's law of flow where the rate of shear is directly proportional to shearing stress
- Viscosity (η) is measured in Poise (dyne.sec/cm²).
- Shearing stress (F) is measured in dyne/cm².
- Rate of Shear (G) is measured in sec⁻¹.
- Simple liquids like water and milk are examples.
Newtonian System Principle
- Imagine a liquid block comprised of parallel molecule plates
- If the top plate moves at a constant velocity, each lower layer moves with velocity proportional to its distance from the stationary bottom layer
- The velocity gradient (rate of shear) = dv/dr, where dv is the velocity difference between two liquid planes separated by distance dr
- Shearing stress (F) refers to the force per unit area (F/A) needed to initiate flow
- Higher viscosity leads to higher shear stress required for a certain shear rate
- Viscosity coefficient or viscosity (dynamic or absolute viscosity) can be expressed as η = F/G.
Viscosity Measurement
- The shearing force needed to produce a 1 cm/sec velocity between two parallel liquid planes each 1cm² in area separated by 1 cm.
- Measured as dyne/cm² = poise * cm/sec/cm.
- 1 Poise equals dyne. Sec/cm².
- 1 centiPoise (Cp) equals 0.01 poise.
Non-Newtonian Systems
- These substances deviate from Newton's flow equation
- Includes plastic flow, pseudoplastic flow (shear thinning), and dilatant flow (shear thickening)
Viscosity Determination
- Viscometers can ascertain the viscosity of Newtonian systems
- Examples include:
- Capillary Viscometer (e.g., Ostwald Viscometer)
- Falling Sphere Viscometer
- Cup and Bob Viscometer
- Cone and Plate Viscometer
Ostwald Viscometer (Capillary Viscometer)
- The time is measured for a liquid to pass between two marks, flowing by gravity via a vertical capillary tube
- It involves comparing the flow time of a test liquid against a liquid with known viscosity (e.g., water).
Viscosity Measurement for Two Liquids
- η₁/η₂ = t₁ρ₁/t₂ρ₂, where:
- t = time
- ρ = density
Procedure for Viscosity Measurement
- Introduce 10 mL of water into the cylindrical tube, and raise it to the upper mark
- Measure the time water takes to pass between the two marks (t₁) with a stopwatch
- Replace water with sample (A), then sample (B), and repeat the procedure to measure (t₂) for sample A, and (t₃) for sample B
- Repeat the prior procedure three times for each sample
- Determine η₂ for sample (A) and η₃ for sample (B)
- The following relationships hold:
- η₁/η₂ = t₁/t₂
- ρ₁ = ρ₂ (constant)
- η₁ (water) = 1 cp
Results
- η₁/η₂ = t₁/t₂
Types of Viscosity
Dynamic Viscosity (η)
- Represents the tangential force per unit surface (shearing stress F, in pascals).
- dv/dx ratio is a speed gradient, indicating shear rate G, measured in reciprocal seconds (s⁻¹).
Kinematic Viscosity (ν)
- Calculated as absolute viscosity divided by liquid density (η/ρ).
- Measured in stokes or centistokes (cs).
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