Introduction: Understanding Types of manometers MCQs With Answer is essential for B. Pharm students involved in process equipment, sterile environments and laboratory pressure measurements. This concise overview explains U-tube, differential, inclined, well-type, mercurial and digital manometers, their working principles, manometric fluid selection, sensitivity and common error sources. Emphasis includes pharmaceutical applications such as tablet coating chambers, lyophilizers, isolators and bioreactor pressure monitoring, plus unit conversions and interpretation of readings. It covers meniscus reading, zeroing procedures, and practical maintenance tips to prepare you for lab work and exams. ‘Now let’s test your knowledge with 50 MCQs on this topic.’
Q1. What is the basic working principle of a liquid column manometer?
- Electromagnetic induction
- Hydrostatic pressure difference as height of manometric fluid
- Capacitive change due to pressure
- Optical displacement measurement
Correct Answer: Hydrostatic pressure difference as height of manometric fluid
Q2. Which equation relates pressure difference to manometer fluid column height?
- P = mgh
- P = ρgh
- P = gh/ρ
- P = ρg/h
Correct Answer: P = ρgh
Q3. Which manometer is most suitable for measuring very small pressure differences with high sensitivity?
- Well-type manometer
- Inclined manometer
- Closed-end manometer
- Digital pressure transducer
Correct Answer: Inclined manometer
Q4. A U-tube manometer is connected to a vessel at one end and open to atmosphere at the other. This measures:
- Absolute pressure in the vessel
- Gauge pressure relative to atmosphere
- Differential pressure between two vessels
- Flow rate in the vessel
Correct Answer: Gauge pressure relative to atmosphere
Q5. Which manometric fluid gives the highest sensitivity for a given head difference?
- Mercury
- Water
- Oil with high density
- Air
Correct Answer: Water
Q6. Why is mercury traditionally used in barometers and some manometers despite toxicity concerns?
- It has low density and high volatility
- It has high density and low vapor pressure
- It wets glass making meniscus reading trivial
- It is transparent for optical measurements
Correct Answer: It has high density and low vapor pressure
Q7. In pharmaceutical labs, why might water or glycerin be preferred over mercury?
- They are denser than mercury
- Lower toxicity and easier disposal
- They vaporize easily
- They are magnetic
Correct Answer: Lower toxicity and easier disposal
Q8. What is a differential manometer primarily used for?
- Measuring atmospheric pressure only
- Measuring pressure difference between two points
- Measuring temperature
- Measuring flow velocity directly
Correct Answer: Measuring pressure difference between two points
Q9. Which error is introduced when the manometric tube is too narrow and capillarity becomes significant?
- Parallax error
- Capillary rise error altering true head
- Thermal expansion error only
- No error; narrow tubes improve accuracy
Correct Answer: Capillary rise error altering true head
Q10. For a U-tube manometer with manometric fluid density ρ, gravitational acceleration g and height difference h, pressure difference ΔP equals:
- ΔP = ρgh
- ΔP = ρg/h
- ΔP = h/ρg
- ΔP = ρg + h
Correct Answer: ΔP = ρgh
Q11. An inclined manometer increases measurable scale length for small vertical displacements by:
- Decreasing fluid density
- Tilting the tube so a small vertical change corresponds to larger along-tube length
- Using mercury exclusively
- Heating the manometric fluid
Correct Answer: Tilting the tube so a small vertical change corresponds to larger along-tube length
Q12. Which manometer type has a reservoir on one side to increase sensitivity and stability?
- Inclined manometer
- Well-type manometer
- Closed-end manometer
- Digital manometer
Correct Answer: Well-type manometer
Q13. In a closed-end manometer, the closed arm contains vacuum at zero reference. This device measures:
- Absolute pressure with direct reading from fluid displacement
- Only differential pressure between two open points
- Only relative humidity
- Temperature changes
Correct Answer: Absolute pressure with direct reading from fluid displacement
Q14. Which factor does NOT affect the reading of a liquid column manometer?
- Density of the manometric fluid
- Local gravitational acceleration
- Viscosity of the manometric fluid for static reading
- Color of the manometric fluid
Correct Answer: Color of the manometric fluid
Q15. When reading the level of transparent manometric fluids, which technique improves accuracy?
- Estimating by eye without reference
- Reading the bottom of the meniscus for mercury and top for water
- Always reading the top for all fluids
- Measuring with a ruler under the tube only
Correct Answer: Reading the bottom of the meniscus for mercury and top for water
Q16. In a two-fluid manometer (different densities), what must be accounted for in calculations?
- Only the height of heavier fluid
- Weights of the connecting pipes
- Height and density of each fluid and continuity of pressure at interfaces
- Ambient humidity only
Correct Answer: Height and density of each fluid and continuity of pressure at interfaces
Q17. Which unit is commonly used to report manometer readings in pharmaceutical settings?
- Kelvin
- mmHg or Pascal
- Lumen
- Mol
Correct Answer: mmHg or Pascal
Q18. How does temperature change affect manometer readings if fluid density varies significantly with temperature?
- No effect; manometers are temperature-independent
- Density change alters the height-to-pressure relation causing reading error
- Only affects digital manometers
- Only changes surface tension, not readings
Correct Answer: Density change alters the height-to-pressure relation causing reading error
Q19. For measuring negative pressures (vacuum) relative to atmosphere in a lyophilizer, which device is appropriate?
- Open U-tube with heavy fluid only
- Closed-end manometer or vacuum gauge calibrated for negative pressures
- Inclined manometer with air as fluid
- Thermometer
Correct Answer: Closed-end manometer or vacuum gauge calibrated for negative pressures
Q20. When connecting a manometer to measure pressure across a filter in a tablet press, the correct connection is:
- Both ends to the same point
- One end upstream of filter and other downstream to measure differential pressure
- Both ends open to atmosphere
- One end to the power supply
Correct Answer: One end upstream of filter and other downstream to measure differential pressure
Q21. Which manometer is easiest to sterilize and integrate into closed pharmaceutical systems?
- Open glass U-tube using mercury
- Digital electronic manometer with sanitary ports
- Inclined paper scale manometer
- Well-type open vessel manometer
Correct Answer: Digital electronic manometer with sanitary ports
Q22. Parallax error when reading a manometer can be reduced by:
- Always reading from an angle
- Using a mirror scale or aligning eye with the meniscus
- Using darker fluids only
- Increasing tube diameter
Correct Answer: Using a mirror scale or aligning eye with the meniscus
Q23. Which property of manometric fluid is most important to minimize vapor pressure inside a closed manometer?
- High color intensity
- Low vapor pressure
- High electrical conductivity
- Low viscosity only
Correct Answer: Low vapor pressure
Q24. A mercury manometer reading of 760 mmHg at sea level corresponds to approximately:
- 1 atm
- 0.5 atm
- 1000 atm
- 0 atm
Correct Answer: 1 atm
Q25. The primary safety concern when using mercury manometers in pharmaceutical labs is:
- Fire hazard
- Toxic exposure and contamination
- Explosive reactivity with oxygen
- Radioactivity
Correct Answer: Toxic exposure and contamination
Q26. To increase sensitivity of a manometer without changing the fluid, you can:
- Use a shorter tube
- Incline the tube to amplify scale length
- Replace glass with plastic
- Make the reservoir smaller
Correct Answer: Incline the tube to amplify scale length
Q27. Which phenomenon causes the meniscus of mercury to be convex while that of water is concave?
- Surface tension and wetting properties of the fluid with glass
- Difference in densities only
- Temperature variations only
- Air pressure alone
Correct Answer: Surface tension and wetting properties of the fluid with glass
Q28. A differential manometer reading is zero when:
- Both measured pressures are equal
- Both pressures are at absolute zero
- Temperature is maximum
- Fluid evaporates completely
Correct Answer: Both measured pressures are equal
Q29. Which advantage do electronic/digital manometers have over traditional liquid column manometers?
- Require mercury for operation
- Provide fast readings, data logging and easier sanitary integration
- Always more accurate in every condition
- Unaffected by fluid properties
Correct Answer: Provide fast readings, data logging and easier sanitary integration
Q30. For a manometer used to calibrate a pressure transducer, the manometer must be:
- Unstable and frequently moved
- Accurately leveled, leak-free and read with minimal parallax
- Filled with air only
- Placed in direct sunlight to warm
Correct Answer: Accurately leveled, leak-free and read with minimal parallax
Q31. Which correction may be necessary when interpreting manometer readings at high altitudes?
- No correction; manometers ignore altitude
- Convert mmHg to Pa or adjust for local atmospheric pressure differences
- Only change units to Celsius
- Change meniscus shape correction only
Correct Answer: Convert mmHg to Pa or adjust for local atmospheric pressure differences
Q32. In a pharmaceutical isolator, constant slight positive pressure relative to surrounding areas is maintained to prevent contamination. Which device is commonly used for monitoring this?
- Barometer in outside weather station
- Low-range differential or digital manometer between isolator and room
- Thermometer
- pH meter
Correct Answer: Low-range differential or digital manometer between isolator and room
Q33. If a manometer tube is not vertical, the measured vertical head must be taken as:
- The along-tube length directly
- The vertical component of the along-tube displacement
- The square of the tube angle
- Irrelevant; use any reading
Correct Answer: The vertical component of the along-tube displacement
Q34. Which common laboratory error causes false low pressure readings in an open U-tube manometer?
- Proper sealing of fittings
- Air bubbles trapped in the manometric fluid
- Using distilled water
- Reading at eye level
Correct Answer: Air bubbles trapped in the manometric fluid
Q35. The sensitivity of a manometer for a given fluid increases when the fluid density is:
- Decreased
- Increased
- Unchanged
- Made equal to air density
Correct Answer: Decreased
Q36. Which manometer configuration is better for rough, portable checks in manufacturing lines?
- Large well-type mercury manometer
- Handheld digital manometer
- Fixed inclined glass manometer only in lab
- Closed-end barometer only
Correct Answer: Handheld digital manometer
Q37. When using a manometer with two immiscible liquids, the pressure at the common interface depends on:
- Only the lighter liquid
- The depth and density of both liquids above that interface
- Only the temperature of the container
- Magnetic properties of the liquids
Correct Answer: The depth and density of both liquids above that interface
Q38. In manometer calculations, why is local gravitational acceleration sometimes included?
- Because g influences the hydrostatic pressure head (ρgh)
- To correct for fluid color
- To convert pressure to temperature
- It is never relevant
Correct Answer: Because g influences the hydrostatic pressure head (ρgh)
Q39. A manometer shows a 10 mm water column difference. The equivalent pressure in Pascals (approx) is:
- 98.1 Pa
- 1 Pa
- 98000 Pa
- 0.1 Pa
Correct Answer: 98.1 Pa
Q40. Why must manometers be installed vertically (unless inclined intentionally)?
- To prevent fluid from flowing
- To ensure correct hydrostatic height corresponds to pressure difference
- To make them look professional
- To increase fluid viscosity
Correct Answer: To ensure correct hydrostatic height corresponds to pressure difference
Q41. Which maintenance practice is important for long-term accuracy of liquid column manometers?
- Allowing dust to accumulate
- Removing trapped air bubbles and checking for leaks periodically
- Replacing glass with wood
- Never calibrating
Correct Answer: Removing trapped air bubbles and checking for leaks periodically
Q42. For measuring pressures in sterile isolators, a manometer fluid that is non-volatile and non-toxic is preferred. Which is a common choice?
- Mercury
- Glycerin
- Hydrochloric acid
- Liquid oxygen
Correct Answer: Glycerin
Q43. The term “gauge pressure” means:
- Pressure measured relative to absolute vacuum
- Pressure measured relative to atmospheric pressure
- Pressure measured in gauges only
- Pressure per unit mass
Correct Answer: Pressure measured relative to atmospheric pressure
Q44. In comparing mercurial and digital manometers, which statement is true for pharmaceutical QA?
- Mercurial manometers are always preferred due to safety
- Digital manometers offer safer, faster readings and data logging while avoiding mercury hazards
- Digital manometers cannot be calibrated
- Mercurial manometers are immune to contamination
Correct Answer: Digital manometers offer safer, faster readings and data logging while avoiding mercury hazards
Q45. If a manometer shows a persistent offset when both ends are open to the same pressure, this indicates:
- Proper function
- Zero error due to misleveling or trapped air or calibration drift
- That readings are more accurate
- That fluid density is infinite
Correct Answer: Zero error due to misleveling or trapped air or calibration drift
Q46. How can a manometer be used to check differential pressure across HEPA filters in cleanrooms?
- By measuring temperature across the filter
- By connecting one port upstream and one downstream and reading the head difference
- By placing it on top of the filter media
- By using it only as an absolute pressure device
Correct Answer: By connecting one port upstream and one downstream and reading the head difference
Q47. Which is a limitation of liquid column manometers in continuous manufacturing lines?
- High sample rate and easy data logging
- Slow response, bulky size and difficulty integrating sanitizable connections
- They cannot measure pressure
- They explode under normal conditions
Correct Answer: Slow response, bulky size and difficulty integrating sanitizable connections
Q48. When translating a manometer reading into process control action, what additional factor should be considered?
- Only the color of the tubing
- Instrument response time and measurement uncertainty
- How loud the manometer is
- The astrological sign of the operator
Correct Answer: Instrument response time and measurement uncertainty
Q49. Which calibration practice ensures reliable manometer-based measurements?
- Never calibrating
- Comparing readings with a reference standard and documenting adjustments periodically
- Only calibrating when device breaks
- Using random readings to estimate error
Correct Answer: Comparing readings with a reference standard and documenting adjustments periodically
Q50. For very low differential pressures in filtration tests, the recommended manometer setup is:
- High-density mercury in a short U-tube
- Low-density fluid or inclined/digital manometer to increase sensitivity
- Closed-end mercury barometer only
- Use a thermometer instead
Correct Answer: Low-density fluid or inclined/digital manometer to increase sensitivity
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