Rotameter MCQs With Answer

Rotameter MCQs With Answer is a focused study tool for B.Pharm students covering rotameter principles, construction, operation, calibration, and pharmaceutical applications. This concise introduction emphasizes variable-area flowmeters, float dynamics, taper tube design, fluid property effects (density, viscosity), and practical topics like installation, material selection, accuracy, and maintenance. Ideal for exam prep and practical lab understanding, these MCQs highlight common errors, correction factors, sanitary designs, and remote sensing options used in pharmaceutical processes. The content is tailored to reinforce both theory and applied skills important in pharmaceutical engineering and quality control. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary operating principle of a rotameter?

• Positive displacement of fluid through chambers
• Variable-area flow measurement by a free-moving float in a tapered tube
• Magnetic induction proportional to flow velocity
• Ultrasonic transit-time difference

Correct Answer: Variable-area flow measurement by a free-moving float in a tapered tube

Q2. Which two main components form a basic rotameter?

• Tapered tube and float
• Piston and cylinder
• Orifice plate and flange
• Thermocouple and display

Correct Answer: Tapered tube and float

Q3. In which orientation must a standard rotameter be installed for accurate readings?

• Horizontal with flow left to right
• Vertical with flow upwards
• Angled at 45 degrees
• Any orientation if clamped properly

Correct Answer: Vertical with flow upwards

Q4. The float in a rotameter reaches equilibrium when which forces balance?

• Magnetic and electric forces
• Upward drag force and the effective weight (weight minus buoyancy)
• Viscous shear and surface tension
• Hydrostatic pressure and capillary forces

Correct Answer: Upward drag force and the effective weight (weight minus buoyancy)

Q5. What kind of flow rate does a rotameter directly indicate?

• Mass flow rate in kg/s
• Volumetric flow rate (e.g., L/min)
• Pressure drop across a restriction
• Flow velocity in m/s only

Correct Answer: Volumetric flow rate (e.g., L/min)

Q6. How does fluid density affect a rotameter reading if the flow rate remains constant?

• Density changes do not affect float position
• Higher density increases buoyancy and raises the float
• Higher density reduces buoyancy and lowers the float
• Only viscosity affects float, not density

Correct Answer: Higher density reduces buoyancy and lowers the float

Q7. Which float shape is commonly used to provide a linear scale over a wide range?

• Spherical float
• Cylindrical or conical profiled float
• Hollow cube float
• Flat plate float

Correct Answer: Cylindrical or conical profiled float

Q8. What is a principal advantage of a rotameter in pharmaceutical applications?

• Requires no vertical space
• Simple visual reading and low maintenance
• Measures mass flow directly without correction
• Works accurately with highly pulsating flows without damping

Correct Answer: Simple visual reading and low maintenance

Q9. Which material is commonly selected for sanitary rotameters used in sterile pharmaceutical lines?

• Regular glass without protection
• Stainless steel with polished surfaces
• Plain carbon steel
• Untreated aluminum

Correct Answer: Stainless steel with polished surfaces

Q10. What is a common limitation of glass tube rotameters in industrial environments?

• Excessive electromagnetic interference
• Fragility and risk of breakage
• Inability to measure liquids
• Requires complex electronic calibration

Correct Answer: Fragility and risk of breakage

Q11. How does viscosity affect rotameter performance?

• Viscosity has no effect on float position
• Higher viscosity increases drag and can alter calibration, especially at low Reynolds numbers
• Higher viscosity always improves accuracy
• Viscosity only affects glass rotameters, not metal ones

Correct Answer: Higher viscosity increases drag and can alter calibration, especially at low Reynolds numbers

Q12. Typical accuracy of laboratory rotameters expressed as percent of full scale is approximately:

• ±50%
• ±20%
• ±1–5%
• ±0.001% (very high precision)

Correct Answer: ±1–5%

Q13. Which correction is essential when using a rotameter to measure compressed gas flow compared to calibration in liquid?

• No correction is needed; rotameter reads the same
• Density and temperature/pressure corrections to convert volumetric to standard conditions
• Only viscosity correction is required
• Switch the float to a heavier one without calculations

Correct Answer: Density and temperature/pressure corrections to convert volumetric to standard conditions

Q14. To read a rotameter correctly, where should you align your eye relative to the float?

• From any angle; parallax is negligible
• Directly in line with the float scale at eye level to avoid parallax error
• From below the tube only
• From above at a 45° angle

Correct Answer: Directly in line with the float scale at eye level to avoid parallax error

Q15. Which property must be known or corrected for when using a rotameter calibrated for water but measuring an oil?

• Only color difference of the oil
• Density and viscosity differences relative to water
• Electrical conductivity
• Magnetic susceptibility

Correct Answer: Density and viscosity differences relative to water

Q16. What is meant by the term “variable area” in rotameter terminology?

• The cross-sectional area of the float changes during operation
• The flow area between the float and tapered tube changes with float position
• The rotameter is interchangeable with variable orifice plates
• The area of the mounting flange varies with pressure

Correct Answer: The flow area between the float and tapered tube changes with float position

Q17. Which type of rotameter can provide remote electrical output for process control?

• Standard glass only with no options
• Magnetic float rotameter with reed switches or magnetic sensors
• Piston rotameter with mechanical linkage
• Only ultrasonic rotameters can provide electrical signals

Correct Answer: Magnetic float rotameter with reed switches or magnetic sensors

Q18. For a rotameter, rangeability refers to:

• The physical height of the instrument
• The ratio between maximum and minimum measurable flows with acceptable accuracy
• The number of float designs available
• The variety of mounting positions allowed

Correct Answer: The ratio between maximum and minimum measurable flows with acceptable accuracy

Q19. Which practice improves rotameter performance with pulsating pumps in a pharmaceutical line?

• Install directly on the pump outlet without damping
• Use a flow pulsation dampener or accumulator upstream
• Replace the rotameter with a thermometer
• Operate the rotameter upside down to stabilize float

Correct Answer: Use a flow pulsation dampener or accumulator upstream

Q20. What is the effect of mounting a rotameter at an angle instead of vertical?

• No effect on reading
• Readings become inaccurate because float balance changes
• Accuracy improves due to reduced buoyancy
• Only affects magnetic sensors, not float position

Correct Answer: Readings become inaccurate because float balance changes

Q21. Which maintenance task is most important for reliable rotameter operation in pharma plants?

• Regular lubrication of the float
• Cleaning to remove deposits and ensuring the tapered tube is clear
• Replacing the glass tube weekly regardless of condition
• Painting the float to improve visibility

Correct Answer: Cleaning to remove deposits and ensuring the tapered tube is clear

Q22. Why might a metal tube rotameter be preferred over a glass tube in production?

• Metal tubes are always cheaper
• Metal tubes are shatterproof and suitable for higher pressures and temperatures
• Metal tubes provide better optical visibility
• Metal tubes do not require calibration

Correct Answer: Metal tubes are shatterproof and suitable for higher pressures and temperatures

Q23. How is a rotameter typically calibrated?

• By matching the float color to the scale
• Using a known reference flow standard of the calibration fluid and marking scale
• By measuring electrical resistance across the tube
• No calibration is required for factory instruments

Correct Answer: Using a known reference flow standard of the calibration fluid and marking scale

Q24. Which reading convention is commonly used as safe practice when interpreting float position?

• Read when the float is oscillating rapidly
• Read the steady float position after oscillations have settled
• Always read while starting flow abruptly
• Read the bottom of the float regardless of shape

Correct Answer: Read the steady float position after oscillations have settled

Q25. What additional accessory is often added to rotameters to protect glass tubes in industrial areas?

• Transparent protective shielding or metal guard
• Extra glass sleeve
• Electrical insulation wrap
• Rubber band around the float

Correct Answer: Transparent protective shielding or metal guard

Q26. In pharmaceutical dosing, why is a rotameter useful for low-to-moderate flows?

• Because it measures mass flow directly without calibration
• Because it provides a simple, continuous visual indication and good control within its range
• Because it is the only device compatible with sterile media
• Because it eliminates the need to know fluid properties

Correct Answer: Because it provides a simple, continuous visual indication and good control within its range

Q27. A rotameter scale is usually calibrated for which condition?

• Single universal fluid for all applications
• Specific calibration fluid and specified temperature/pressure
• Ambient pressure but not temperature dependent
• Only for gases, not liquids

Correct Answer: Specific calibration fluid and specified temperature/pressure

Q28. What happens to the float if flow increases beyond the maximum scale of the rotameter?

• The float will stick to the bottom
• The float may seat at the top, be launched out, or cause inaccurate reading
• The float splits into two
• The float converts volumetric to mass flow automatically

Correct Answer: The float may seat at the top, be launched out, or cause inaccurate reading

Q29. Which statement best describes the pressure drop across a rotameter compared to an orifice plate?

• Rotameters typically have higher pressure drop than orifice plates
• Rotameters typically have lower pressure drop than orifice plates for similar flows
• Both always have identical pressure drops
• Pressure drop is irrelevant for rotameters

Correct Answer: Rotameters typically have lower pressure drop than orifice plates for similar flows

Q30. For which of these fluids is a rotameter generally NOT ideal without modification?

• Clean, low-viscosity liquids
• Highly viscous, abrasive slurries or fluids with heavy particulates
• Compressed dry gases
• Solvents with moderate viscosity

Correct Answer: Highly viscous, abrasive slurries or fluids with heavy particulates

Q31. What is the typical effect of temperature increase on a rotameter reading for a liquid if density decreases?

• Float position rises because lower density reduces buoyancy
• Float position lowers due to increased buoyancy
• Temperature has no effect on rotameter readings
• Float will be unaffected but scale shifts automatically

Correct Answer: Float position rises because lower density reduces buoyancy

Q32. How is a rotameter commonly protected for use with hazardous or high-pressure gases?

• By painting the tube with lead paint
• Using metal tube construction, pressure-rated fittings and protective guards
• No protection needed for gases
• By removing the float

Correct Answer: Using metal tube construction, pressure-rated fittings and protective guards

Q33. Which measurement correction method is used when changing from one calibration fluid to another?

• Apply a correction factor based on fluid density and sometimes viscosity
• Only change the mounting orientation
• Replace the float with an identical weight float
• No correction; rely on operator judgment

Correct Answer: Apply a correction factor based on fluid density and sometimes viscosity

Q34. Which installation practice can minimize turbulence affecting rotameter readings?

• Mount the rotameter immediately after a 90° elbow
• Provide adequate straight inlet piping length upstream of the rotameter
• Install directly downstream of a pump discharge with no straight run
• Use the largest possible pipe size to create turbulence

Correct Answer: Provide adequate straight inlet piping length upstream of the rotameter

Q35. Which application in pharmaceutical manufacturing commonly uses rotameters?

• As final sterile filtration membranes
• Monitoring and controlling liquid dosing, reagent feeds and gas purge flows
• As exact mass balances for batch reporting without correction
• To measure particle size distribution in suspensions

Correct Answer: Monitoring and controlling liquid dosing, reagent feeds and gas purge flows

Q36. What is the typical recommended action if you observe persistent float sticking?

• Increase flow until it dislodges the float
• Isolate, clean or replace the float/tube and inspect for deposits or mechanical damage
• Heat the tube until the deposit dissolves in-situ
• Invert the rotameter to free the float

Correct Answer: Isolate, clean or replace the float/tube and inspect for deposits or mechanical damage

Q37. How does a tapered tube’s geometry affect rotameter calibration?

• Tube taper and internal profile define the relationship between float position and flow
• Taper has no effect; only the float matters
• Taper is only decorative
• A larger taper always reduces sensitivity

Correct Answer: Tube taper and internal profile define the relationship between float position and flow

Q38. Which type of float provides magnetic coupling for switch or transmitter options?

• Non-magnetic ceramic float only
• Floats with embedded magnets (magnetic floats)
• Hollow glass floats without magnetic parts
• Lead balls glued to the float

Correct Answer: Floats with embedded magnets (magnetic floats)

Q39. Why is it important to specify the process temperature when ordering a rotameter?

• Because temperature determines the color of glass needed
• Because material compatibility, tube and float selection, and calibration can depend on temperature
• Because rotameters do not work above 20°C
• Temperature only matters for electrical instruments, not rotameters

Correct Answer: Because material compatibility, tube and float selection, and calibration can depend on temperature

Q40. What is a common accuracy-related error when using a rotameter with multiphase fluids?

• Rotameters automatically separate phases so there is no error
• Presence of bubbles or entrained gas causes unstable readings and large errors
• Multiphase fluids improve linearity
• Only temperature affects multiphase readings

Correct Answer: Presence of bubbles or entrained gas causes unstable readings and large errors

Q41. How can a rotameter be adapted to measure very low flows accurately?

• Use a larger float and tube
• Use a rotameter designed for low-flow range with finer taper and matched float
• Operate it upside down to slow the float
• Remove the float to increase sensitivity

Correct Answer: Use a rotameter designed for low-flow range with finer taper and matched float

Q42. Which standard operating precaution is essential when cleaning a rotameter used for active pharmaceutical ingredients (APIs)?

• Use any household cleaner for speed
• Follow validated cleaning procedures, compatible solvents, and documentation for cross-contamination control
• Autoclave every cleaning without validation
• Always disassemble the rotameter entirely before cleaning

Correct Answer: Follow validated cleaning procedures, compatible solvents, and documentation for cross-contamination control

Q43. What feature distinguishes a variable-area flowmeter with multiple scales?

• It can display both volumetric and mass flow simultaneously without correction
• It has separate scale markings for different fluids or conditions to allow direct reading after selecting appropriate scale
• It uses multiple floats stacked on top of each other
• It requires an external calculator to read the flow

Correct Answer: It has separate scale markings for different fluids or conditions to allow direct reading after selecting appropriate scale

Q44. Which is a safe practice when choosing rotameter materials for corrosive pharmaceutical liquids?

• Assume glass is always compatible with all chemicals
• Consult chemical compatibility charts and select appropriate alloys or lined tubes
• Choose the cheapest available material
• Only consider aesthetics, not compatibility

Correct Answer: Consult chemical compatibility charts and select appropriate alloys or lined tubes

Q45. How does a magnetic-coupled transmitter attached to a rotameter generate an electrical signal?

• By measuring pressure directly from the float
• The magnetic float’s position actuates reed switches or a linear magnetic sensor to produce pulses or analog signal proportional to flow
• By sensing fluid color change near the float
• By detecting float mass using strain gauges

Correct Answer: The magnetic float’s position actuates reed switches or a linear magnetic sensor to produce pulses or analog signal proportional to flow

Q46. What is the expected action when scale markings are provided for multiple fluids on the same rotameter?

• Ignore the markings; choose any fluid scale
• Select the scale corresponding to your fluid and process conditions to read directly or apply correction
• Always use the water scale regardless of fluid
• Only use the gas scale for liquids

Correct Answer: Select the scale corresponding to your fluid and process conditions to read directly or apply correction

Q47. Which installation detail helps prevent trapping of air bubbles in liquid rotameters?

• Mounting the rotameter horizontally
• Installing rotameter with venting or purge provisions and vertical orientation allowing bubbles to escape upward
• Placing the rotameter below the sump so bubbles collect there
• Mounting the rotameter backwards relative to flow

Correct Answer: Installing rotameter with venting or purge provisions and vertical orientation allowing bubbles to escape upward

Q48. Which parameter is most directly affected by float mass when selecting a rotameter?

• Electrical conductivity
• Range and sensitivity because float weight determines balance with drag and buoyancy
• Color of the fluid being measured
• Pipe flange size only

Correct Answer: Range and sensitivity because float weight determines balance with drag and buoyancy

Q49. In comparing rotameters and mass flowmeters (e.g., Coriolis), which statement is true?

• Rotameters measure mass flow directly, while Coriolis measures volumetric flow
• Rotameters measure volumetric flow and require fluid-property corrections for mass flow; Coriolis measures mass flow directly
• Both devices always give identical readings for any fluid
• Mass flowmeters cannot be used for liquids

Correct Answer: Rotameters measure volumetric flow and require fluid-property corrections for mass flow; Coriolis measures mass flow directly

Q50. Which troubleshooting step should be taken if a rotameter shows intermittent high readings not consistent with process changes?

• Assume instrument is fine and ignore variations
• Check for entrained gas, pulsation, loose fittings, sensor faults (if magnetic output), and clean tube/float
• Replace the entire process line immediately
• Paint the float a different color to improve reading

Correct Answer: Check for entrained gas, pulsation, loose fittings, sensor faults (if magnetic output), and clean tube/float

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com