Venturimeter MCQs With Answer

Venturimeter MCQs With Answer

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Venturimeter MCQs With Answer are essential study aids for B. Pharm students focusing on fluid dynamics and pharmaceutical engineering. This concise, keyword-rich introduction covers venturi meter principles, discharge coefficient, Bernoulli’s application, pressure tapping, and flow measurement accuracy in pipelines used for liquid dosing and formulation. Understanding venturimeter design, calibration, head loss, and error sources helps in quality control, process validation, and equipment selection in pharmaceutical plants. These MCQs with answers reinforce theoretical concepts and practical problem-solving required for lab work and industrial applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What fundamental principle does a venturimeter primarily rely on to measure flow?

  • Pascal’s law
  • Archimedes’ principle
  • Bernoulli’s principle
  • Navier–Stokes equation

Correct Answer: Bernoulli’s principle

Q2. Which quantity is directly measured by the pressure taps of a venturimeter?

  • Absolute pressure at outlet
  • Differential pressure between inlet and throat
  • Total head at inlet
  • Static pressure gradient along the pipe

Correct Answer: Differential pressure between inlet and throat

Q3. The discharge coefficient (Cd) of a venturimeter accounts for which of the following?

  • Only the thermal effects in the fluid
  • Deviations from ideal flow including viscous losses and vena contracta
  • The chemical composition of the fluid
  • Variations in gravitational acceleration

Correct Answer: Deviations from ideal flow including viscous losses and vena contracta

Q4. For incompressible flow, the theoretical flow rate through a venturi (without Cd) depends on which variables?

  • Density, cross-sectional areas, and pressure difference
  • Viscosity, temperature, and pipe roughness
  • Chemical concentration and surface tension
  • Magnetic field and electric conductivity

Correct Answer: Density, cross-sectional areas, and pressure difference

Q5. What is the typical effect of increasing the beta ratio (throat diameter / inlet diameter) on the differential pressure for a given flow rate?

  • Increases differential pressure
  • Decreases differential pressure
  • No change in differential pressure
  • Differential pressure becomes negative

Correct Answer: Decreases differential pressure

Q6. Which expression best represents volumetric flow rate Q for a venturimeter including Cd?

  • Q = Cd * A1 * sqrt(2ΔP/ρ)
  • Q = Cd * A2 * sqrt(2ΔP/(ρ (1 – (A2/A1)^2)))
  • Q = Cd * (A1 + A2) * sqrt(ΔP/ρ)
  • Q = Cd * A2 * ΔP / μ

Correct Answer: Q = Cd * A2 * sqrt(2ΔP/(ρ (1 – (A2/A1)^2)))

Q7. In pharmaceutical process piping, why is a venturimeter often preferred to an orifice plate?

  • Higher permanent pressure loss
  • Lower initial cost
  • Lower head loss and reduced fouling
  • Requires more frequent recalibration

Correct Answer: Lower head loss and reduced fouling

Q8. The vena contracta in a venturi refers to:

  • The point where velocity is minimum
  • The point downstream of the throat where pressure equals atmospheric
  • The location of maximum stream contraction and often maximum velocity
  • The entrance length required for fully developed flow

Correct Answer: The location of maximum stream contraction and often maximum velocity

Q9. Which dimensionless number is most important for characterizing flow regime in a venturimeter?

  • Prandtl number
  • Froude number
  • Reynolds number
  • Biot number

Correct Answer: Reynolds number

Q10. How does Reynolds number influence the discharge coefficient Cd of a venturimeter?

  • Cd is independent of Reynolds number
  • Cd typically increases with Reynolds number until it plateaus
  • Cd decreases linearly with Reynolds number
  • Cd oscillates unpredictably with Reynolds number

Correct Answer: Cd typically increases with Reynolds number until it plateaus

Q11. Which type of manometer is commonly used to measure the differential pressure of a venturi in labs?

  • Mercury U-tube manometer
  • Wind gauge
  • Thermocouple manometer
  • Optical manometer

Correct Answer: Mercury U-tube manometer

Q12. If fluid density decreases while maintaining the same differential pressure and geometry, the volumetric flow rate will:

  • Decrease
  • Remain unchanged
  • Increase
  • Become zero

Correct Answer: Increase

Q13. In compressible flow through a venturi, what additional effect must be considered at high velocities?

  • Viscous heating only
  • Compressibility and Mach number effects
  • Surface tension variations
  • Electrostatic charging

Correct Answer: Compressibility and Mach number effects

Q14. What is the primary source of error when using a venturimeter with poorly aligned pressure taps?

  • Change in chemical properties of fluid
  • Incorrect differential pressure reading leading to flow error
  • Change in gravitational acceleration
  • Variation in ambient temperature only

Correct Answer: Incorrect differential pressure reading leading to flow error

Q15. Which maintenance practice helps preserve accuracy of a venturimeter in pharmaceutical lines?

  • Regularly painting the outer surface
  • Periodic cleaning of the throat and verifying pressure taps
  • Increasing pipe roughness intentionally
  • Removing the discharge coefficient

Correct Answer: Periodic cleaning of the throat and verifying pressure taps

Q16. The beta ratio is defined as:

  • Area of throat divided by area of inlet
  • Diameter of inlet divided by diameter of throat
  • Diameter of throat divided by diameter of inlet
  • Length of venturi divided by pipe diameter

Correct Answer: Diameter of throat divided by diameter of inlet

Q17. Which of the following reduces accuracy of a venturimeter measurement?

  • Laminar, fully developed flow
  • Turbulent flow with high Reynolds number
  • Air bubbles or entrained gases
  • Properly sized pressure taps

Correct Answer: Air bubbles or entrained gases

Q18. In the Bernoulli equation applied to a venturi, which energy terms are typically considered?

  • Kinetic and potential only, neglecting pressure
  • Pressure head, velocity head, and elevation head
  • Thermal and chemical potential only
  • Electromagnetic and acoustic energy

Correct Answer: Pressure head, velocity head, and elevation head

Q19. For a venturimeter used in pharmaceutical dosing, calibration against a standard is necessary because:

  • Cd values are universal and never change
  • Real systems have losses and assembly variations affecting Cd
  • Pressure sensors are always perfectly linear
  • Viscosity does not influence flow measurement

Correct Answer: Real systems have losses and assembly variations affecting Cd

Q20. When flow is measured in vertical pipe segments, what additional factor should be included?

  • Chemical reaction rates
  • Elevation head differences between taps
  • Magnetic interference
  • Ambient humidity

Correct Answer: Elevation head differences between taps

Q21. Which pressure type is tapped at the venturi throat for differential measurement?

  • Total pressure including dynamic component only
  • Static pressure at the throat
  • Ambient atmospheric pressure only
  • Absolute vacuum pressure

Correct Answer: Static pressure at the throat

Q22. If the throat area is half of the inlet area, what is the area ratio A2/A1?

  • 2
  • 0.5
  • 1.5
  • 0.25

Correct Answer: 0.5

Q23. Which flow condition ideally yields the most repeatable Cd values for a venturimeter?

  • Highly pulsating flow
  • Steady, fully developed turbulent flow at high Re
  • Low Re laminar flow
  • Transient two-phase flow with solids

Correct Answer: Steady, fully developed turbulent flow at high Re

Q24. In pharmaceutical applications, which fluid property must be accurately known to convert differential pressure to mass flow?

  • Viscosity only
  • Density
  • Surface roughness
  • Electrical conductivity

Correct Answer: Density

Q25. What is the major hydraulic advantage of a long converging inlet in a venturi?

  • Increases turbulence at entrance
  • Reduces energy losses and flow separation
  • Causes cavitation
  • Generates additional heat

Correct Answer: Reduces energy losses and flow separation

Q26. Which instrument can be used to read very small differential pressures from a venturi for low-flow measurement?

  • Orifice plate
  • Micro-manometer or digital differential pressure transducer
  • Analog thermometer
  • Refractometer

Correct Answer: Micro-manometer or digital differential pressure transducer

Q27. For two geometrically similar venturi meters operating at similar Reynolds numbers, the discharge coefficients will be:

  • Very different due to size
  • Approximately equal (scale similarity)
  • Impossible to compare
  • Dependent only on fluid color

Correct Answer: Approximately equal (scale similarity)

Q28. Cavitation risk in a venturi increases when:

  • Local static pressure drops below vapor pressure of the liquid
  • Temperature drops significantly
  • Flow is very slow and laminar
  • Pipe diameter increases abruptly downstream

Correct Answer: Local static pressure drops below vapor pressure of the liquid

Q29. Which statement about energy loss across a well-designed venturi is correct?

  • Energy loss is higher than an orifice plate for same ΔP
  • Energy loss (permanent head loss) is typically lower than that of an equivalent orifice plate
  • Energy is fully recovered with zero loss
  • Energy loss depends only on ambient temperature

Correct Answer: Energy loss (permanent head loss) is typically lower than that of an equivalent orifice plate

Q30. Which factor does NOT significantly affect the discharge coefficient of a venturi?

  • Surface finish of the throat
  • Reynolds number
  • Color of the pipe paint
  • Beta ratio and geometry

Correct Answer: Color of the pipe paint

Q31. What measurement correction is required when measuring flow of a temperature-sensitive liquid with a venturi?

  • No correction needed for temperature effects
  • Correct density and possibly viscosity for temperature to compute flow accurately
  • Increase beta ratio as temperature increases
  • Replace the venturi with an orifice plate

Correct Answer: Correct density and possibly viscosity for temperature to compute flow accurately

Q32. When calibrating a venturimeter, which reference method is commonly used?

  • Gravimetric (weighing collected fluid) or volumetric tank method
  • Estimating visually
  • Using pH measurement
  • Magnetic resonance imaging

Correct Answer: Gravimetric (weighing collected fluid) or volumetric tank method

Q33. In two-phase flow (liquid with entrained gas), venturi readings typically:

  • Remain perfectly accurate
  • Underestimate or overestimate flow due to density and pressure distortions
  • Only depend on fluid color
  • Become independent of discharge coefficient

Correct Answer: Underestimate or overestimate flow due to density and pressure distortions

Q34. Which geometric feature of venturi minimizes disturbances and provides stable readings?

  • Sharp corners at inlet
  • Gradual converging and smooth throat profile
  • Multiple abrupt expansions
  • Flat plate obstructions upstream

Correct Answer: Gradual converging and smooth throat profile

Q35. Which of the following is a correct way to reduce measurement noise from pressure transducers on a venturi?

  • Install pulsation dampeners or use averaging electronics
  • Remove the transducer filter
  • Paint the transducer body
  • Increase pipe vibrations intentionally

Correct Answer: Install pulsation dampeners or use averaging electronics

Q36. The throat Reynolds number is based on:

  • Pipe length only
  • Throat diameter, fluid density, velocity, and viscosity
  • Only fluid temperature
  • Ambient pressure exclusively

Correct Answer: Throat diameter, fluid density, velocity, and viscosity

Q37. In designing a venturi for low flow pharmaceutical streams, which strategy is useful?

  • Maximize beta ratio to approach unity
  • Choose a smaller throat to increase differential pressure while controlling head loss
  • Remove converging section
  • Operate near vapor pressure

Correct Answer: Choose a smaller throat to increase differential pressure while controlling head loss

Q38. Which statement about pressure recovery in the diverging section of a venturi is true?

  • All dynamic pressure is converted back to static without loss
  • Some dynamic pressure is recovered, but viscous losses prevent full recovery
  • Pressure always decreases further in the diverging section
  • Pressure recovery is independent of the divergence angle

Correct Answer: Some dynamic pressure is recovered, but viscous losses prevent full recovery

Q39. Which parameter is crucial when comparing venturi performance across different fluids?

  • Fluid density and viscosity (rheology)
  • Color and odor
  • Ambient light level
  • Pipe manufacturer name

Correct Answer: Fluid density and viscosity (rheology)

Q40. What is the effect of roughness inside the venturi throat on the discharge coefficient?

  • Increases Cd significantly for polished surfaces
  • Roughness generally reduces Cd by increasing energy losses
  • Has no effect at all
  • Makes Cd infinite

Correct Answer: Roughness generally reduces Cd by increasing energy losses

Q41. In venturi theory, the continuity equation ensures:

  • Mass flow rate is conserved between sections
  • Pressure is the same everywhere
  • Temperature remains constant
  • Energy is created at the throat

Correct Answer: Mass flow rate is conserved between sections

Q42. Which installation practice upstream of a venturi is recommended to ensure accurate readings?

  • Place a valve with high turbulence immediately upstream
  • Provide sufficient straight length of pipe to develop steady flow
  • Install a sharp elbow close to the venturi inlet
  • Place a pump directly at the throat

Correct Answer: Provide sufficient straight length of pipe to develop steady flow

Q43. For liquid flow measurement, why might a three-tube venturi be used instead of a two-tube venturi?

  • To increase head loss intentionally
  • To measure multiple differential pressures for improved averaging and accuracy
  • To introduce more turbulence
  • To heat the liquid

Correct Answer: To measure multiple differential pressures for improved averaging and accuracy

Q44. Which is a common unit for expressing differential pressure from a venturimeter?

  • Meters of head (m H2O) or Pascals (Pa)
  • Liters per mole
  • Degrees Celsius
  • Candela

Correct Answer: Meters of head (m H2O) or Pascals (Pa)

Q45. In pharmaceutical liquid dosing, why is traceability of venturi calibration important?

  • To ensure measurements are auditable and meet regulatory quality standards
  • Because calibration never drifts
  • It is not important at all
  • Only aesthetics matter for piping

Correct Answer: To ensure measurements are auditable and meet regulatory quality standards

Q46. If the measured ΔP is zero, what is the likely flow state in the venturi?

  • Maximum flow
  • No flow or equal pressures due to blockage or sensor fault
  • Cavitation occurring
  • Throat choking

Correct Answer: No flow or equal pressures due to blockage or sensor fault

Q47. When converting volumetric flow rate to mass flow for process control, which relation is used?

  • Mass flow = Volumetric flow × Pressure
  • Mass flow = Volumetric flow × Density
  • Mass flow = Volumetric flow / Temperature
  • Mass flow equals discharge coefficient

Correct Answer: Mass flow = Volumetric flow × Density

Q48. Which advantage does a venturimeter offer for sterile pharmaceutical lines?

  • Large permanent dead zones that trap contaminants
  • Smooth profile and minimal obstruction reduce trapping and ease cleaning
  • Requires frequent disassembly for cleaning
  • Incompatible with clean-in-place systems

Correct Answer: Smooth profile and minimal obstruction reduce trapping and ease cleaning

Q49. What is the recommended action if the venturi shows a sudden unexplained change in Cd during routine checks?

  • Ignore it and continue operation
  • Inspect for fouling, damaged taps, leaks, and recalibrate if necessary
  • Replace fluid with air
  • Paint the venturi throat

Correct Answer: Inspect for fouling, damaged taps, leaks, and recalibrate if necessary

Q50. For accurate design and selection of a venturimeter in pharmaceutical systems, which combined data set is most essential?

  • Fluid properties (density, viscosity), flow range, pipe size, and allowable head loss
  • Only the color and smell of the fluid
  • Number of operators in the plant
  • Brand of the pumps used

Correct Answer: Fluid properties (density, viscosity), flow range, pipe size, and allowable head loss

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