Introduction: Understanding the types of manometers is essential for B.Pharm students involved in formulation labs, process validation, and quality control where accurate pressure measurement matters. This concise guide covers manometry basics — U-tube, differential, inclined, well-type, mercury and digital manometers — and explains principles like hydrostatic pressure, manometric fluid selection, sensitivity, and common errors. Practical examples highlight calculations using ΔP = ρgh, fluid density effects, and calibration tips relevant to pharmaceutical instrumentation. Whether measuring gas pressure in reactors or ensuring vacuum integrity, mastering manometers enhances experimental accuracy and safety. ‘Now let’s test your knowledge with 50 MCQs on this topic.’
Q1. What is the primary operating principle of a liquid manometer?
- Hydrostatic pressure balance
- Electromagnetic induction
- Piezoelectric effect
- Capacitive sensing
Correct Answer: Hydrostatic pressure balance
Q2. Which manometer type is most commonly used to measure small pressure differences with high sensitivity?
- U-tube manometer
- Inclined manometer
- Well-type manometer
- Digital manometer
Correct Answer: Inclined manometer
Q3. In a simple U-tube manometer with the same fluid on both sides, the pressure difference between the two ends is given by which expression?
- ΔP = ρ g h
- ΔP = pV/nRT
- ΔP = 2πr
- ΔP = I·R
Correct Answer: ΔP = ρ g h
Q4. Which manometric fluid is most often used when compact column heights are required?
- Water
- Glycerin
- Mercury
- Air
Correct Answer: Mercury
Q5. A differential manometer is primarily used to:
- Measure absolute pressure only
- Compare two pressures and indicate their difference
- Measure temperature variations
- Detect flow velocity directly
Correct Answer: Compare two pressures and indicate their difference
Q6. Which of the following is an advantage of an inclined manometer over a vertical U-tube?
- Lower sensitivity to small pressure changes
- Greater sensitivity and finer reading for small ΔP
- Requires larger space for installation
- Cannot use mercury as fluid
Correct Answer: Greater sensitivity and finer reading for small ΔP
Q7. In a well-type manometer, why is the reservoir made large compared to the measuring limb?
- To reduce sensitivity
- To increase sensitivity for small pressure changes
- To prevent fluid evaporation only
- To allow electrical connections
Correct Answer: To increase sensitivity for small pressure changes
Q8. Which manometer type is suitable for field, portable pressure measurements without liquid?
- Aneroid manometer
- U-tube mercury manometer
- Well-type mercury manometer
- Inclined liquid manometer
Correct Answer: Aneroid manometer
Q9. For a U-tube manometer open to atmosphere on one side and connected to a pressure P on the other, the column difference h indicates which pressure type?
- Absolute pressure Pabs
- Gauge pressure relative to atmosphere
- Temperature of the fluid
- Vacuum only
Correct Answer: Gauge pressure relative to atmosphere
Q10. If a manometric fluid has lower density, what happens to the column height for a given pressure difference?
- Column height decreases
- Column height increases
- Column height remains same
- Fluid evaporates
Correct Answer: Column height increases
Q11. Which factor does NOT affect the reading of a liquid manometer?
- Density of manometric fluid
- Ambient atmospheric pressure when measuring gauge pressure
- Acceleration due to gravity
- Electrical conductivity of the fluid
Correct Answer: Electrical conductivity of the fluid
Q12. What is the main reason mercury is avoided in some laboratory manometers despite its advantages?
- Low density
- High vapor pressure
- Toxicity and environmental hazards
- Inability to wet glass
Correct Answer: Toxicity and environmental hazards
Q13. Which expression correctly gives the hydrostatic pressure at depth h in a fluid of density ρ?
- P = ρ g h
- P = ρ / gh
- P = g / ρ h
- P = ρgh^2
Correct Answer: P = ρ g h
Q14. A U-tube manometer uses mercury (ρ ≈ 13,600 kg/m³). If the mercury column difference h = 0.05 m, what is the pressure difference ΔP (use g = 9.81 m/s²)?
- 6.67 × 10^4 Pa
- 6.67 × 10^3 Pa
- 6.67 × 10^5 Pa
- 6.67 Pa
Correct Answer: 6.67 × 10^4 Pa
Q15. For an inclined manometer, sensitivity increases because:
- The cross-sectional area increases with inclination
- A small vertical rise corresponds to a larger length along the incline
- Fluid density increases along the incline
- Temperature effects are amplified
Correct Answer: A small vertical rise corresponds to a larger length along the incline
Q16. In a differential manometer with two different manometric fluids, which approach is required to find ΔP?
- Simple ΔP = ρ g h irrespective of fluids
- Apply hydrostatic balance accounting for each fluid density and heights
- Use ideal gas law only
- Neglect densities and use volumetric flow
Correct Answer: Apply hydrostatic balance accounting for each fluid density and heights
Q17. Which manometer configuration is best for measuring very high pressures where liquid columns would be impractically tall?
- U-tube with water
- Aneroid gauge
- Inclined water manometer
- Simple open-tube manometer
Correct Answer: Aneroid gauge
Q18. What is the effect of temperature on manometer readings if not compensated?
- No effect at all
- Changes in fluid density alter the reading
- Only affects electronic manometers
- Causes magnetic interference
Correct Answer: Changes in fluid density alter the reading
Q19. A closed-end manometer differs from an open-end manometer because the closed end contains:
- Vacuum or trapped gas at constant pressure
- Open air at atmospheric pressure
- Moving piston
- Electrical contacts
Correct Answer: Vacuum or trapped gas at constant pressure
Q20. For measuring small vacuum (below atmospheric), which manometer type is commonly used in laboratory vacuum systems?
- U-tube open to atmosphere
- McLeod gauge or Pirani gauge
- Inclined water manometer
- Hydrostatic pressure cell
Correct Answer: McLeod gauge or Pirani gauge
Q21. In pharmaceutical labs, why is accurate manometer measurement important during tablet coating or drying?
- Pressure readings determine color of tablets
- They influence airflow and drying rates, affecting product quality
- They control tablet hardness chemically
- They are not relevant to these processes
Correct Answer: They influence airflow and drying rates, affecting product quality
Q22. Which property of manometric fluid directly affects the sensitivity and height of the column?
- Electrical conductivity
- Density
- Optical clarity
- Magnetic susceptibility
Correct Answer: Density
Q23. When connecting a manometer to measure the pressure inside a closed reactor, what precaution is essential?
- Use any random fluid regardless of chemistry
- Avoid chemical compatibility issues between fluid and process gases
- Ensure the manometer is upside down
- Seal the manometer permanently with no access
Correct Answer: Avoid chemical compatibility issues between fluid and process gases
Q24. Which manometer type provides direct reading of differential pressure between two process lines?
- Pendulum manometer
- U-tube differential manometer
- Thermocouple
- Rotameter
Correct Answer: U-tube differential manometer
Q25. Which manometer type minimizes meniscus reading errors by using a large reservoir?
- Inclined manometer
- Well-type manometer
- Aneroid manometer
- Hot-wire manometer
Correct Answer: Well-type manometer
Q26. The manometric sensitivity S is often defined as the ratio of observed column movement to pressure change. Increasing which factor increases S for a well-type manometer?
- Reservoir cross-sectional area relative to limb area
- Ambient temperature only
- Electrical supply voltage
- Length of connecting tubing only
Correct Answer: Reservoir cross-sectional area relative to limb area
Q27. For a manometer reading, the contact angle and wetting of fluid affect which reading component most directly?
- Hydrostatic pressure formula
- Meniscus formation and reading accuracy
- Gravitational acceleration
- Thermal conductivity
Correct Answer: Meniscus formation and reading accuracy
Q28. Which is a disadvantage of mercury-filled manometers in pharmaceutical labs?
- Excessively low sensitivity
- Toxicity and cleanup risk
- Inability to measure pressure
- Too volatile for closed systems
Correct Answer: Toxicity and cleanup risk
Q29. If one side of a U-tube manometer is open to atmosphere and the other is connected to a gas at lower pressure, the liquid column will:
- Rise on the open side
- Rise on the gas-connected side
- Remain level
- Evaporate
Correct Answer: Rise on the open side
Q30. Which instrument converts a pressure-induced mechanical displacement into an electrical signal often replacing liquid manometers in industrial setups?
- Piezoresistive transducer (pressure sensor)
- Mercury barometer
- Well-type manometer
- Inclined tube manometer
Correct Answer: Piezoresistive transducer (pressure sensor)
Q31. The term “gauge pressure” means pressure measured relative to:
- Absolute zero pressure
- Atmospheric pressure
- A fixed vacuum of 1 atm
- Standard temperature
Correct Answer: Atmospheric pressure
Q32. In manometry, specific gravity is used as a ratio of fluid density to which reference fluid?
- Mercury
- Air
- Water
- Alcohol
Correct Answer: Water
Q33. Which factor makes inclined manometers especially useful in laboratory experiments for small ΔP measurements?
- Larger cross-sectional area
- Longer scale length for fine resolution
- Higher fluid volatility requirement
- Requirement for electrical power
Correct Answer: Longer scale length for fine resolution
Q34. When using a manometer with a volatile manometric fluid, what error is most likely to occur?
- Color distortion
- Evaporation leading to inaccurate readings
- Increased gravitational constant
- Electrical short-circuit
Correct Answer: Evaporation leading to inaccurate readings
Q35. For a two-fluid manometer with light process fluid above a heavier manometric fluid, which interface height difference relates to pressure difference?
- Height of lighter fluid only
- Height difference between the two fluid interfaces accounting for densities
- Total length of the tube
- Temperature difference only
Correct Answer: Height difference between the two fluid interfaces accounting for densities
Q36. Which manometer is best suited for measuring differential pressure across a filter in a pharmaceutical process?
- Inclined manometer for tiny differentials
- Mercury barometer
- Thermometer
- Ammeter
Correct Answer: Inclined manometer for tiny differentials
Q37. How does capillary action in narrow manometer tubes affect readings?
- No effect at all
- Causes meniscus displacement introducing small errors
- Eliminates all hydrostatic pressure
- Reverses pressure sign
Correct Answer: Causes meniscus displacement introducing small errors
Q38. For accurate readings, the connection tubing between process and manometer should be:
- Long and coiled with many restrictions
- Short, straight and free of trapped air or condensate
- Made of porous material
- Open to the environment
Correct Answer: Short, straight and free of trapped air or condensate
Q39. Which reading technique reduces parallax errors when reading a manometer scale?
- Read from a steep angle
- Keep eye level with the meniscus
- Close one eye and tilt head
- Read from far away
Correct Answer: Keep eye level with the meniscus
Q40. McLeod gauge is typically used to measure pressures in which range?
- Atmospheric to 1 atm
- High vacuum (very low pressures)
- Only above 10 atm
- Temperatures below 0°C
Correct Answer: High vacuum (very low pressures)
Q41. Which of the following is NOT a type of manometer?
- Inclined manometer
- U-tube manometer
- Well-type manometer
- Spectrophotometer
Correct Answer: Spectrophotometer
Q42. In a manometer reading, why is it important to account for the specific gravity of the manometric fluid when converting column height to pressure?
- Specific gravity affects buoyancy only
- Pressure is directly proportional to fluid density, hence specific gravity
- Specific gravity changes the gas composition
- It determines electrical resistance
Correct Answer: Pressure is directly proportional to fluid density, hence specific gravity
Q43. When comparing digital manometers to liquid manometers, a main advantage of digital models is:
- No need for calibration
- Ease of reading, data logging and portability
- Immunity to temperature and chemical effects
- Zero maintenance forever
Correct Answer: Ease of reading, data logging and portability
Q44. If ΔP = ρ g h and h is measured in meters, ρ in kg/m³ and g in m/s², the SI unit of ΔP will be:
- Pascal (Pa)
- Newton (N)
- Liter (L)
- Watt (W)
Correct Answer: Pascal (Pa)
Q45. For a manometer using oil of density 800 kg/m³, what is the qualitative effect compared to mercury for a fixed pressure difference?
- Oil gives much smaller column height than mercury
- Oil gives much larger column height than mercury
- No difference in column height
- Oil turns into gas at room temperature
Correct Answer: Oil gives much larger column height than mercury
Q46. When measuring pressure differences in a cleanroom, which manometer attribute is most critical?
- Color of the manometric fluid
- Low leakage, compatibility and cleanliness of materials
- Volume of the reservoir only
- Number of scales on the device
Correct Answer: Low leakage, compatibility and cleanliness of materials
Q47. Which error source is common when flexible tubing connects the process to the manometer and is not well supported?
- Mechanical oscillation and erroneous readings
- Change in gravitational constant
- Alteration of fluid density
- Change in atmospheric composition
Correct Answer: Mechanical oscillation and erroneous readings
Q48. A zero shift in a manometer reading after installation likely indicates:
- Correct calibration
- Air bubble, trapped fluid, or initial offset that must be corrected
- The pressure being exactly zero
- Increase in gravitational acceleration
Correct Answer: Air bubble, trapped fluid, or initial offset that must be corrected
Q49. For differential measurements across a membrane, why might one choose a U-tube manometer over an electronic sensor?
- U-tube provides a simple, inexpensive, and visual direct measure without electronics
- Electronics are always less accurate
- U-tube never needs filling
- Electronic sensors cannot measure pressure
Correct Answer: U-tube provides a simple, inexpensive, and visual direct measure without electronics
Q50. In designing a manometer setup for corrosive gases, the most important consideration is:
- Use of highly reactive metals
- Material compatibility between the manometric fluid, tube material, and process gas
- Choosing the brightest colored fluid
- Maximizing tube length only
Correct Answer: Material compatibility between the manometric fluid, tube material, and process gas
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.
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